# SHOULD the P39 have been able to handle the Zero? Was it training or performance?



## pinsog (May 4, 2013)

The P39 had an unspectacular record against Japanese fighters. Was it an issue of pilot training against an unfamilier enemy aircraft? Or was the performance of the Zero the P39's undoing? The P39 had a 30 or 40 mph speed advantage over the Zero, about the same as a Spitfire, so why couldn't the P39 use this speed and dive advantage to beat the Zero like the Hellcat did?


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## varsity078740 (May 5, 2013)

The Hellcat had a 2,000 HP two stage, two speed engine that provided superior performance over the Zero at all altitudes despite weighing much more. What ever speed advantage the P-39 had over the Zero was at low altitude and degraded rapidly at altitudes greater than 12,000 ft. which was the rated altitude for the single speed, single stage Allison.

Duane


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## davebender (May 5, 2013)

Engine power per se isn't what matters. You want a high power to weight ratio. P-39 power to weight ratio is similiar to F6F.

Data from Wikipedia.
.....F6F5. 2,000hp. 12,598 lbs loaded weight. 6.3 lbs per hp.
.....P39Q. 1,200hp. 7,379 lbs loaded weight. 6.15 lbs per hp.


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## tomo pauk (May 5, 2013)

The P-39 (among many Allied airplanes) have had several issues that were hampering it's better score vs. Zero.
The crucial thing could easily be the lack of dependable early warning systems in areas where the P-39s were operating during 1942. As seen in ww2 in all theaters, the fighters, no matter how good, need sufficient time to warm-up, take off and climb to the suitable altitude. 
Next thing would be the pilot's tactics experience - P-39 should flatly lose the vs. Zero in turning fight, and Zero's pilots were the best in the world in 1942. 
Then we go to the engine limitations: the single speed V-1710 was, during the 1st half of the war, a dog above 15000 ft. The airframe issue would be the loopsided layout of the engine intake, much reducing the ram effect. That should steal couple of thousands HP/feet from the already low engine power/altitude. The Japanese bombing runs were conducted at higher altitudes, and their Zeros have had two-speed superchargers, so the Zeros would be the ones to dive at P-39s, not vice versa. Another airframe issue would be the low fuel quantity, giving the P-39 pilot two uneasy choices:
- drop the tank and engage what is close (and that might be the Zero coming to get him), leaving it without fuel to chase speedy Japanese bombers
- leave the drop tank on, and risk to be shot down since one is slow unviedly with the DT
Having the DT attached also lowers the rate of climb, not a good thing if the bombers Zeros are close.

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## CobberKane (May 5, 2013)

The P-39s altitude performance sucked. At Guadalcanal the Japanese pilots were so used to seeing the P-39s at a serious height disadvantage they thought they were being used as bait to give the higher flying Wildcats a free shot.


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## davebender (May 5, 2013)

Not every fighter aircraft needs to be a high altitude interceptor.

What about below 10,000 feet where A-20s and B-25s are performing low altitude attacks?


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## altsym (May 5, 2013)

Speaking of low altitude performance.. I believe Chuck Yeager said, ' at 100 feet, nothing can outfly the P-39 '.

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## Francis marliere (May 6, 2013)

As far as I know, P-39 37 mm cannon almost always jammed (according to pilots), and machineguns frequently did. A plane can't be succesfull if it can't fire ...

At Guadalcanal, the early planes were P-400 (export version with 20 mm cannon) which used British oxygen bottles which were not available there. Hence the planes were limited to low altitude and performed ground attack missions.


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## VBF-13 (May 6, 2013)

pinsog said:


> The P39 had an unspectacular record against Japanese fighters. Was it an issue of pilot training against an unfamilier enemy aircraft? Or was the performance of the Zero the P39's undoing? The P39 had a 30 or 40 mph speed advantage over the Zero, about the same as a Spitfire, so why couldn't the P39 use this speed and dive advantage to beat the Zero like the Hellcat did?


Pinsog, I'd have to throw that off on the aircraft. The F4Fs had trouble, too. Everything else being equal, they were outclassed. Of course, disclaimer, everything else is never equal.


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## pinsog (May 6, 2013)

VBF-13 said:


> Pinsog, I'd have to throw that off on the aircraft. The F4Fs had trouble, too. Everything else being equal, they were outclassed. Of course, disclaimer, everything else is never equal.



I agree the P39 had flaws, but it was much faster then the Zero and could easily out dive the Zero. The F4F had nothing on the Zero except being tougher and yet it fought the Zero to about a draw while the P39 didn't do as well. How can that be explained?


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## davebender (May 6, 2013)

P-40 was faster then Japanese fighter aircraft used in Philippine invasion and FEAF had over 100 yet they accomplished little. I suspect early war P-39s had the same problem - poor U.S. Army Air Corps training and leadership.

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## FLYBOYJ (May 6, 2013)

"You don't dig a hole with a rake."

I think the biggest problem with the P-39 was its misuse by the USAAF. It was pretty obvious that about 15,000 feet the aircraft would be useless, but given its handicap it performed well. Go look at the Air Force Historical Research site and check out the claims/ losses during early and mid 1942. The P-39 (and P-40) were scoring about a 1:1/ 1:2 against the Japanese through out the Pacific. There was only one P-39 ace, Lt. William Fiedler Jr., but look how many P-38 aces achieved their first kills in the P-39.

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## pinsog (May 6, 2013)

FLYBOYJ said:


> "You don't dig a hole with a rake."
> 
> I think the biggest problem with the P-39 was its misuse by the USAAF. It was pretty obvious that about 15,000 feet the aircraft would be useless, but given its handicap it performed well. Go look at the Air Force Historical Research site and check out the claims/ losses during early and mid 1942. The P-39 (and P-40) were scoring about a 1:1/ 1:2 against the Japanese through out the Pacific. There was only one P-39 ace, Lt. William Fiedler Jr., but look how many P-39 aces achieved their first kills in the P-39.



Would you be suggesting that the reputation of the P39 vs the Zero has been unfairly maligned over the years? 
How many US or other pilots had good things to say about the P39 vs the Zero?


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## FLYBOYJ (May 6, 2013)

pinsog said:


> Would you be suggesting that the reputation of the P39 vs the Zero has been unfairly maligned over the years?


Yes - and in many cases the F4F as well.



pinsog said:


> How many US or other pilots had good things to say about the P39 vs the Zero?



AFAIK not many, but then again, many P-39 drivers wound up in the P-38, so of course the P-39 is going to be scorned.

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## Piper106 (May 6, 2013)

There have been several discussions in this forum on how to build a 'better' P-39. 

The P-39C had two 50 cal and two 30 cal machine guns firing syncronized thru the propeller, but in the P-39D and later models the nose 30 cals were removed to make room for additional 37mm cannon ammo. Hindsight says keeping the P-39C armament but replacing the 37 mm with a hub mounted 50 cal would have been a better arrangement against the Japanese. Even better, trade the two syncronized 30 cals for another syncronized 50caliber (one thru thru the prop hub and a new total of three syncronized). Then use the space in the wing formerly devoted to ammunition storage for additional internal fuel capacity.

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## pinsog (May 6, 2013)

Piper106 said:


> There have been several discussions in this forum on how to build a 'better' P-39.
> 
> The P-39C had two 50 cal and two 30 cal machine guns firing syncronized thru the propeller, but in the P-39D and later models the nose 30 cals were removed to make room for additional 37mm cannon ammo. Hindsight says keeping the P-39C armament but replacing the 37 mm with a hub mounted 50 cal would have been a better arrangement against the Japanese. Even better, trade the two syncronized 30 cals for another syncronized 50caliber (one thru thru the prop hub and a new total of three syncronized). Then use the space in the wing formerly devoted to ammunition storage for additional internal fuel capacity.



Or go with 2 50's, a 20mm through the hub, wet wings with no guns and hopefully a bit of weight savings.


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## pinsog (May 6, 2013)

FLYBOYJ said:


> Yes - and in many cases the F4F as well.
> 
> 
> 
> AFAIK not many, but then again, many P-39 drivers wound up in the P-38, so of course the P-39 is going to be scorned.



I would like to see a head to head comparison of the F4F vs the P39 and see how they matched up with each other. My guess is the P39 would win everything but turning. Your thoughts?


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## FLYBOYJ (May 6, 2013)

pinsog said:


> I would like to see a head to head comparison of the F4F vs the P39 and see how they matched up with each other. My guess is the P39 would win everything but turning. Your thoughts?


 Agree - providing this match up was under 10/ 15,000'. Then the F4F would take all.

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## pinsog (May 6, 2013)

FLYBOYJ said:


> Agree - providing this match up was under 10/ 15,000'. Then the F4F would take all.



Best guess at what altitude they would be dead even at? Wouldn't the P39 be faster than an F4F even at 20,000 feet?


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## Piper106 (May 6, 2013)

pinsog said:


> Or go with 2 50's, a 20mm through the hub, wet wings with no guns and hopefully a bit of weight savings.



Three comments. First the mixed armament thing, trying to deal with two different trajectories when deflection shooting. That is why I suggested an all 50 cal armament package. Second, history tells us the most US versions of the 20mm Hispano cannon had almost as much trouble with jams/un-reliability early in the war as the 37mm. Another point for staying with just Browning 50 cal guns. Finally, as far as I know, during WW2 'wet wings' implied unprotected fuel tanks. I am suggesting adding self-sealing rubber bag tanks as per other American fighters.

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## pinsog (May 6, 2013)

Piper106 said:


> Three comments. First the mixed armament thing, trying to deal with two different trajectories when deflection shooting. That is why I suggested an all 50 cal armament package. Second, history tells us the most US versions of the 20mm Hispano cannon had almost as much trouble with jams/un-reliability early in the war as the 37mm. Another point for staying with just Browning 50 cal guns. Finally, as far as I know, during WW2 'wet wings' implied unprotected fuel tanks. I am suggesting adding self-sealing rubber bag tanks as per other American fighters.



I am a big fan of the 50 so an all 50 arrangement, especially against the Japanese, with their limited protection, would be fine with me. Agreed on the self sealing wing tanks, when I said wet wings I meant self sealing wing tanks, OR standard wing tanks and a CO2 purge system might work just as well and provide more fuel and still provide good protection.


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## davebender (May 6, 2013)

> history tells us the most US versions of the 20mm Hispano cannon had almost as much trouble with jams/un-reliability early in the war as the 37mm


Problem is real world people don't get the benefit of hindsight.

If U.S. 20mm cannon had worked as advertised it would have been far superior to .50cal MG. Which btw also had problems with jams in early war P-40s. I wouldn't be surprised if .50cal MGs in P-39 jammed also. 

If all your weapons tend to jam it's understandable that early war P-39s would have a tough time in combat.


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## pinsog (May 6, 2013)

davebender said:


> Problem is real world people don't get the benefit of hindsight.
> 
> If U.S. 20mm cannon had worked as advertised it would have been far superior to .50cal MG. Which btw also had problems with jams in early war P-40s. I wouldn't be surprised if .50cal MGs in P-39 jammed also.
> 
> If all your weapons tend to jam it's understandable that early war P-39s would have a tough time in combat.



Wasn't the P38 20mm much more reliable than the other 20mm mounted on other US aircraft?


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## Shortround6 (May 7, 2013)

Not sure about the P-39 but the P-38 20mm was pretty good. Gun was mounted in a heavy cradle. Early P-39s had terrible trouble with the 37mm, it often fired just two rounds and jammed, solved by altering the ejection port/chute. Early 20mm didn't have to very good to beat that. 
Early .50 cal guns were very slow firing when synchronized, between 450-500rpm, I am not sure if they ever got faster.


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## CobberKane (May 7, 2013)

That's fine - employ the P-39 at at an altitude where it works best, say 10,000 feet. All we have do do now is assume that the Japanese fighters won't be so unsporting as to use their superior altitude performance to position themselves for an attack from above.
If the P-39 was going to make an impression against the Zero or Oscar in the kind of situations typical of the early to mid PTO it would need to have been able to tackle them at or above 15000 feet, but it couldn't and it didn't. Being a good performer at low altitude isn't much use if the opposition can climb faster, fly higher and has the opportunity to do so. Under those circumstances the superiority in speed and dive don't confer competitiveness, they just give you a chance for escape.
I suggested somewhere else that the two most important performance characteristics in air to air combat are speed and climb/altitude performance, on the grounds that I can't think of any fighter that significantly lacked both of these characteristics relative to the opposition and still proved superior overall, irrespective of other qualities. Compared to the Zero, the P-39 was faster but badly lacking in altitude capability. As covered by Tomo earlier, the tactical situation in the PTO meant that thenJapanese fighters could therefore usually engage from above. The Wildcat was somewhat slower than the zero but like the P-39 it could outlive the Japanese fighters, and it's much better altitude performance gave it the chance of using that advantage offensively as well as defensively.
Like a lot of people, I think the P-39 was a missed opportunity for the USAF. At a time when pretty much all other US single engine fighter designs were sound but uninspired, it was genuinely forward thinking. Pity the same couldn't be said of the Air Force theoreticians who neutered it.


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## Shortround6 (May 7, 2013)

CobberK said:


> Like a lot of people, I think the P-39 was a missed opportunity for the USAF. At a time when pretty much all other US single engine fighter designs were sound but uninspired, it was genuinely forward thinking. Pity the same couldn't be said of the Air Force theoreticians who neutered it.



Neutered how? 

And if not neutered when would it have entered large scale squadron service?


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## michaelmaltby (May 7, 2013)

".... I think the P-39 was a missed opportunity for the USAF. At a time when pretty much all other US single engine fighter designs were sound but uninspired, it was genuinely forward thinking."

Agree.

MM


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## FLYBOYJ (May 7, 2013)

CobberKane said:


> That's fine - employ the P-39 at at an altitude where it works best, say 10,000 feet. All we have do do now is assume that the Japanese fighters won't be so unsporting as to use their superior altitude performance to position themselves for an attack from above.
> If the P-39 was going to make an impression against the Zero or Oscar in the kind of situations typical of the early to mid PTO it would need to have been able to tackle them at or above 15000 feet, but it couldn't and it didn't. Being a good performer at low altitude isn't much use if the opposition can climb faster, fly higher and has the opportunity to do so. Under those circumstances the superiority in speed and dive don't confer competitiveness, they just give you a chance for escape.
> I suggested somewhere else that the two most important performance characteristics in air to air combat are speed and climb/altitude performance, on the grounds that I can't think of any fighter that significantly lacked both of these characteristics relative to the opposition and still proved superior overall, irrespective of other qualities. Compared to the Zero, the P-39 was faster but badly lacking in altitude capability. As covered by Tomo earlier, the tactical situation in the PTO meant that thenJapanese fighters could therefore usually engage from above. The Wildcat was somewhat slower than the zero but like the P-39 it could outlive the Japanese fighters, and it's much better altitude performance gave it the chance of using that advantage offensively as well as defensively.
> Like a lot of people, I think the P-39 was a missed opportunity for the USAF. At a time when pretty much all other US single engine fighter designs were sound but uninspired, it was genuinely forward thinking. Pity the same couldn't be said of the Air Force theoreticians who neutered it.



Some US pilots were able to engage the Japanese at altitudes where the P-39 was able to put up a fight. "Buzz" Wagner was one of the first US aces and scrored kills in both P-40 and P-39. He led several low level raids that were quite successful before being sent back to the US with 8 credits. He was later killed in a P-40 crash stateside.

Pittsburgh Post-Gazette - Google News Archive Search


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## drgondog (May 7, 2013)

pinsog said:


> Best guess at what altitude they would be dead even at? Wouldn't the P39 be faster than an F4F even at 20,000 feet?



It might, but the excess power available to the P-39 is probably less and that would reduce climb as well as sustained turn as well as acceleration


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## drgondog (May 7, 2013)

CobberKane said:


> That's fine - employ the P-39 at at an altitude where it works best, say 10,000 feet. All we have do do now is assume that the Japanese fighters won't be so unsporting as to use their superior altitude performance to position themselves for an attack from above.
> 
> If the P-39 was going to make an impression against the Zero or Oscar in the kind of situations typical of the early to mid PTO it would need to have been able to tackle them at or above 15000 feet, but it couldn't and it didn't. Being a good performer at low altitude isn't much use if the opposition can climb faster, fly higher and has the opportunity to do so. Under those circumstances the superiority in speed and dive don't confer competitiveness, they just give you a chance for escape.
> I suggested somewhere else that the two most important performance characteristics in air to air combat are speed and climb/altitude performance, on the grounds that I can't think of any fighter that significantly lacked both of these characteristics relative to the opposition and still proved superior overall, irrespective of other qualities. Compared to the Zero, the P-39 was faster but badly lacking in altitude capability. As covered by Tomo earlier, the tactical situation in the PTO meant that thenJapanese fighters could therefore usually engage from above. The Wildcat was somewhat slower than the zero but like the P-39 it could outlive the Japanese fighters, and it's much better altitude performance gave it the chance of using that advantage offensively as well as defensively.
> Like a lot of people, I think the P-39 was a missed opportunity for the USAF. At a time when pretty much all other US single engine fighter designs were sound but uninspired, it was genuinely forward thinking. Pity the same couldn't be said of the Air Force theoreticians who neutered it.



It is hard to argue for the P-39 in PTO, MTO and ETO where its primary opponents could all out perform it with respect to high altitude performance and overall combat agility. The 37mm cannon was the eternal nightmare. It had wicked and often fatal spin characteristics, relatively short range.

In late 1941, if you had been sitting on a USAAF Review Board, why would you single the P-39 as a fighter to invest in for the future when both the P-47 and P-38 were faster, more heavily armed and a much greater performance vs altitude bandwidth.

Had Allison been capable of a two stage supercharger then, the story would be different. The P-63 was much better but too late for USAAF. Only the P-38 and P-63 survived the war with Allisons as the powerplant of choice for US Fighters.


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## vinnye (May 7, 2013)

Did they ever try to fit a Merlin into the P39?
It worked quite well in the P51 - so why not the P39?


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## drgondog (May 7, 2013)

Major CG issues re-locating 1600 pounds from behind cockpit to in front. Total re-design almost with no common parts.


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## Shortround6 (May 7, 2013)

Why was the P-39 so zippy at low altitudes on limited power?

_ Because it was small_

Why didn't they fit bigger superchargers, inter-coolers and larger engines in the P-39?

_ Because it was small_

Simple really.

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## tomo pauk (May 7, 2013)

To be fair, there were Merlins that were roughly sized as P-39's V-1710 (complete with supercharger), and required no inter-coolers. Made in the USA, never the less.


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## michaelmaltby (May 7, 2013)

"... Neutered how? 

And if not neutered when would it have entered large scale squadron service?"

The USAAF had no engagements that in any way replicated the totality of the Eastern Front where the Soviets were able to utilize the P-39 as an under 11,000 ' down to the deck dogfighter, supporting Sturmoviks .... but, that said, during Guadalcanal, the P-39 was an effective fire support platform over land and sea. The 20 mm canon from the British rejects and later the 37 mm Olds canon, were good at barge busting. The AC was less vulnerable to ground fire than the P-40 due to the engine location. Range wa less an issue in this theatre, and the idea of accepting that the P-39 was not ever going to be a high altitude interceptor and hence getting on with using the AC for its strengths, seems obvious to me. It was a flawed concept in 1941-42 but by 1944 the Q model was very good and the P-63 took the best and made it better. The Soviets certainly benefitted, and those American who mastered the P-39, like Chuck Yeager, knew it had sass.

MM

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## michaelmaltby (May 7, 2013)

".. Only the P-38 and P-63 survived the war with Allisons as the powerplant of choice for US Fighters."

And the Twin Mustang ...

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## CobberKane (May 7, 2013)

drgondog said:


> In late 1941, if you had been sitting on a USAAF Review Board, why would you single the P-39 as a fighter to invest in for the future when both the P-47 and P-38 were faster, more heavily armed and a much greater performance vs altitude bandwidth.
> 
> Had Allison been capable of a two stage supercharger then, the story would be different. The P-63 was much better but too late for USAAF. Only the P-38 and P-63 survived the war with Allisons as the powerplant of choice for US Fighters.



That's pretty much what I meant by the P-39 being neutered. The pre-war thinking of the time was that the bomber would always get through, so altitude performance for fighters was not a major concern. If it had been, and if Alison had incentive to develop their engine accordingly, maybe the P-39 would have been available for the PTO in a form that allowed it to use it's speed and dive superiority for something other than running for home. Unfortunately it didn't happen, and and pilots who managed to make effective use of the P-39 against zeros and Oscars were very much in the minority. As noted in a Japanese training manual of the time: "Altitude is worth more than a brave heart."


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## bobbysocks (May 7, 2013)

people get sentimental about a plane they like...and wish it could be or could have been upgraded and improved to perform like all the aircraft that had been designed around new ground breaking technology. i am sure somewhere there is a guy sitting and thinking with a few tweeks the kingfisher could have been made into a top notch fighter.


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## drgondog (May 7, 2013)

Actually the P-82B was Merlin driven with 1650-9 and 11. Its downfall as a top high performance a/c is when the Sec'y Air Force dictated the Allison -143 and -145 for the P-82E ordered in Dec 1945.

Edgar Schmeud and his team solved the constant backfire issues but Allison wouldn't listen and NAA wasn't able to fire the GM owned Allison.


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## drgondog (May 7, 2013)

michaelmaltby said:


> "... Neutered how?
> 
> And if not neutered when would it have entered large scale squadron service?"
> 
> ...



Chuck is often quoted as being willing to soldier on in the P-39 - but he didn't mean it for ETO. He would have had his ass handed to him by perhaps inferior pilots had they flown to 109 and 190 strengths rather than try low altitude turning fight. Escorting B-17s at 25000 feet would have resulted in extremely high losses. The Brits figured that out in 1941 and sent all of theirs to USSR.

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## drgondog (May 7, 2013)

True but a.) weighed 400 pounds more and b.) needed twice the radiator surface area to cool it.

Can we whisper 'unrecoverable aft cg issues' after ammo gone?


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## bobbysocks (May 7, 2013)

"she'll tumble and spin and soon auger in
give me a P39"

and dont forget the lovely aroma of exhaust and cordite in the cockpit....

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## michaelmaltby (May 7, 2013)

".. Chuck is often quoted as being willing to soldier on in the P-39 - but he didn't mean it for ETO. He would have had his ass handed to him by perhaps inferior pilots had they flown to 109 and 190 strengths rather than try low altitude turning fight. Escorting B-17s at 25000 feet would have resulted in extremely high losses. The Brits figured that out in 1941 and sent all of theirs to USSR."

All granted ....


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## bobbysocks (May 7, 2013)

as much as chuck liked it....William "Obee" O'Brien who was in his FG had a slightly different opinion:

*HOW WAS FLYING THE P-39?

I could write a book about this, but thank God someone else did. The book is "Nanette" by a man named Park. He, like me, thinks the damn thing had a soul. The P-39 was undoubtedly the worst airplane the Air Corps had in its inventory. But if a pilot could accumulate about 150 hours, he should be awarded a medal, as he is well on his way to being a fighter pilot. That particular airplane was absolutely unforgiving and aerodynamically unstable. It was so bad that many service pilots did not, or more likely, would not fly it. Tactical units had members sent to the manufacturers to fly P-39s to their units. I know this because I was one of the lucky ones who got to do this type of work.*

357th FG Interview

here's a story of Bill Overstreet's experience in a 39 from joey maddox's book the great rat race...go up to page 116.

http://books.google.com/books?id=1f...wBw#v=onepage&q=357th Fg P 39 stories&f=false


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## davebender (May 7, 2013)

Did P-63 clean up the aerodynamics in addition to providing a better engine?


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## Jabberwocky (May 7, 2013)

michaelmaltby said:


> ".. Only the P-38 and P-63 survived the war with Allisons as the powerplant of choice for US Fighters."
> 
> And the Twin Mustang ...


 
The Merlin was the powerplant of choice for the Twin Mustang. The switch to Allisons was forced by Rolls-Royce insisting that once the war ended their royalty payments be resumed.


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## drgondog (May 7, 2013)

Jabberwocky said:


> The Merlin was the powerplant of choice for the Twin Mustang. The switch to Allisons was forced by Rolls-Royce insisting that once the war ended their royalty payments be resumed.



The Air Force was delighted to pay royalties for a better engine. NAA Hated the ALLIson and Schmeud was bitter till his dying day that the Sec'y of the Air Force forced the Allisons onto the P-82E in order to get the contract.


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## wuzak (May 7, 2013)

drgondog said:


> Major CG issues re-locating 1600 pounds from behind cockpit to in front. Total re-design almost with no common parts.





Shortround6 said:


> Why was the P-39 so zippy at low altitudes on limited power?
> 
> _ Because it was small_
> 
> ...





tomo pauk said:


> To be fair, there were Merlins that were roughly sized as P-39's V-1710 (complete with supercharger), and required no inter-coolers. Made in the USA, never the less.





drgondog said:


> True but a.) weighed 400 pounds more and b.) needed twice the radiator surface area to cool it.
> 
> Can we whisper 'unrecoverable aft cg issues' after ammo gone?




I think what Tomo suggests is the V-1650-1. Sure it doesn't have the altitude performance of the 60-series, but it does have much better altitude performance than the V-1710 in the P-39. 

It is also only about 100lbs heavier and doesn't need that much more cooling, if any. Certainly doesn't need an intercooler and associated radiator. 

The V-1650-1 was significantly shorter than the two stage versions, and should be shorter than the V-1710. So that may help in balancing the CoG issues.

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## wuzak (May 7, 2013)

michaelmaltby said:


> "... Neutered how?
> 
> And if not neutered when would it have entered large scale squadron service?"
> 
> ...



Some would say that the removal of the turbo after the XP-39 would count as "neutering".


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## Shortround6 (May 7, 2013)

Well, considering that the original turbo installation didn't work for sour apples and after the NACA issued a report AFTER testing it in a full sized wind tunnel that offered little hope of it EVER reaching the predicted performance one wonders how it was "Neutered". 

There were 939 P-39s delivered by the end of 1941, if they had waited to solve the turbo problems (if they could be fixed) how many hundreds of fewer P-39s would have been available in the spring/summer of 1942? 

AS near as can be figured out the *CLAIMED* 390mph at 20,000ft and fast climb were not only never achieved but never attempted. Not only were there chronic cooling problems with the XP-39 but there was a problem with the original drive shaft and the early flights were restricted to 2600 engine RPM, not the full 3000rpm until AFTER the plane came back from the wind tunnel. 

Can you neuter something that was impotent to begin with?


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## wuzak (May 7, 2013)

Shortround6 said:


> Well, considering that the original turbo installation didn't work for sour apples and after the NACA issued a report AFTER testing it in a full sized wind tunnel that offered little hope of it EVER reaching the predicted performance one wonders how it was "Neutered".
> 
> There were 939 P-39s delivered by the end of 1941, if they had waited to solve the turbo problems (if they could be fixed) how many hundreds of fewer P-39s would have been available in the spring/summer of 1942?
> 
> ...



I certainly wouldn't say the USAAF neutered the P-39. Just that I know some people would.

Was there ever any danger that Allison would develop a 2 speed drive for their supercharger or, considering how they went with the 2 stage design, a variable speed supercharger?


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## CobberKane (May 8, 2013)

Oh boy, I can feel a new thread coming on. In fact I think I'll go back and post it myself...


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## drgondog (May 8, 2013)

Wuzak - I was referring the the 1650-3 (and associated changes to cooling system) when i flipped out the 400 pound comment. IIRC it was closer to 350 for just the engine comparison...

As to cooling, the figure of 2x was extrapolated directly from the P-51A/Allison to P-51B/1650-3 experience encountered by NAA. In my mind I was being charitable as the P-39 was plagued by cooling issues in 1941-1942.


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## wuzak (May 8, 2013)

drgondog said:


> Wuzak - I was referring the the 1650-3 (and associated changes to cooling system) when i flipped out the 400 pound comment. IIRC it was closer to 350 for just the engine comparison...



Of this I was aware.

The Merlin doesn't have to be the 1650-3. The V-1650-1 could give a useful altitude performance gain without much weight penalty, and it shouldn't require the massive increase in cooling capacity for the -3.

Though Packard didn't make them, I wonder how a Merlin 45 would have gone in the P-39. Obviously low down performance would suffer, but there should be some gain at higher altitudes (the 45 having a higher FTH than the Allison).


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## Shortround6 (May 8, 2013)

Actually not by that much once the later Allisons with 9.60 gears showed up. Critical height the Merlin 45 may be 3-4,000ft higher than a late model P-39 which would be a help but not solve the problem. The Late Allisons sort of split the difference between an early Allison and the Merlin 45. 

A big problem is the weight, A P-39D clean is about 1000lbs heavier than a Spit V clean or almost 15%. Put together with the smaller wing and the wing loading was about 30% higher. At altitude the P-39 has to fly faster just to keep from stalling leaving that much less power for climb and maneuver. 

Then you have a take-off problem. Early P-39s had 1150hp for take-off, late model Ds, Ks and Ls had 1325hp for take-off and the late versions had 1200hp for take-off. Merlin 45 had 1230hp for take-off at 12 lb boost. While the Allison was rated for 5 minutes CLIMBING at take-off or Military Power the Merlin was not so rated, what they did in the squadrons I don't know. We do know that Allisons tolerated over-boost abuse fairly well at low altitudes.

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## krieghund (May 8, 2013)

This is taken from the NACA report about the P-39 with the turbo and a single stage blower. The single stage is better lower to the deck.

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## krieghund (May 8, 2013)

tomo pauk said:


> and their Zeros have had two-speed superchargers



The first year of the war the P-39 was engaged against the A6M2 with the Sakae 12 engine which was single stage with a critical of about 14,600 feet, albeit about 2000 feet higher that the V1710-35.


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## pinsog (May 8, 2013)

Ok. So the Zero has better performance up high than the P39, the Zero also had better performance than the F4F up high, in the middle and down low. At least the P39 had a significant advantage down low. 

How did the P39's performance compare with the F4F up high?


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## krieghund (May 8, 2013)

I guess about like this

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## pinsog (May 8, 2013)

krieghund said:


> I guess about like this



Thank you for the graph.

This seems to show that the P39 will outperform the F4F up to 24,000 feet or so. I'm having a hard time believing that it was the P39's performance as much as it was a training issue considering the F4F was around 1 to 1 against the Zero. I think if I was given the choice, I would choose the P39, at least I had the option of running if things didn't work in my favor.


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## tomo pauk (May 8, 2013)

wuzak said:


> Of this I was aware.
> 
> The Merlin doesn't have to be the 1650-3. The V-1650-1 could give a useful altitude performance gain without much weight penalty, and it shouldn't require the massive increase in cooling capacity for the -3.
> 
> Though Packard didn't make them, I wonder how a Merlin 45 would have gone in the P-39. Obviously low down performance would suffer, but there should be some gain at higher altitudes (the 45 having a higher FTH than the Allison).


 


Shortround6 said:


> Actually not by that much once the later Allisons with 9.60 gears showed up. Critical height the Merlin 45 may be 3-4,000ft higher than a late model P-39 which would be a help but not solve the problem. The Late Allisons sort of split the difference between an early Allison and the Merlin 45.
> 
> A big problem is the weight, A P-39D clean is about 1000lbs heavier than a Spit V clean or almost 15%. Put together with the smaller wing and the wing loading was about 30% higher. At altitude the P-39 has to fly faster just to keep from stalling leaving that much less power for climb and maneuver.
> 
> Then you have a take-off problem. Early P-39s had 1150hp for take-off, late model Ds, Ks and Ls had 1325hp for take-off and the late versions had 1200hp for take-off. Merlin 45 had 1230hp for take-off at 12 lb boost. While the Allison was rated for 5 minutes CLIMBING at take-off or Military Power the Merlin was not so rated, what they did in the squadrons I don't know. We do know that Allisons tolerated over-boost abuse fairly well at low altitudes.



Indeed, I was thinking about V-1650-1 (note to self - next time be direct, instead of being cryptic).
That engine was able to outperform single stage V-1710 at every altitude, and it was available earlier than the '9.60 V-1710s' show up. Installation of that engine would've dictated also the relocation of (now longer) engine intake into a place not hampered from having the canopy ahead itself, should help to better use of ram effect.
The main problem to get V-1650-1 in P-39 would've been the low availability; also, IIRC the reduction gear was integral with crankcase - not compatible with P-39 power-plant installation.

BTW, the grpah kindly posted by krieghund neatly describes the single-stage V-1710 as an 'altitude rated engine'


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## krieghund (May 8, 2013)

Well climb and speed are only a few of the factors involved in determining maneuverability. It would appear at face value that the P-39 has the advantage but I would suspect the F4F is the more nimble due to a lower wing loading and able to easily out turn the P-39. The P-39 probably bleeds energy faster than the F4F as well. Remember later in the war the USN used the F4F (FM-2) to simulate the Zero in dissimilar aerial combat training. The P-39 would have to employ AVG tactics against the F4F.


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## krieghund (May 8, 2013)

Here's a comparison of the engine charts from the flight manuals. The military power recommended duration on the V1710 is 15 minutes and the V1650 is 5 minutes. A clear advantage of the V1650 in military is an increase in critical altitude by over 6000 feet. Of course the V1710 is the without ram. With ram it approaches 14,900 feet


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## tomo pauk (May 8, 2013)

The table for the V-1650-1 lists the critical altitudes in the wrong column, under 'with ram', instead under 'no ram'.


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## wuzak (May 8, 2013)

tomo pauk said:


> The main problem to get V-1650-1 in P-39 would've been the low availability; also, IIRC the reduction gear was integral with crankcase - not compatible with P-39 power-plant installation.



I don't think that the reduction gear was a big issue, tbh. Just needs a new casing with bearing and output shaft, as Rolls-Royce did with the Griffon for the Flying Test Bed (FTB). They could also use a torque tube, as was done in the FTB.

The main issues with the Merlin was the updraft carburettor. A downdraft carby would make fitting easier, but not sure how easy it was to convert. 

The V-1650-1 should be a little shorter than the V-1710.

http://www.airpages.ru/draw/merlin25.gif


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## krieghund (May 8, 2013)

tomo pauk said:


> The table for the V-1650-1 lists the critical altitudes in the wrong column, under 'with ram', instead under 'no ram'.



Would you have a source that has the correct information?


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## varsity078740 (May 9, 2013)

FLYBOYJ said:


> Some US pilots were able to engage the Japanese at altitudes where the P-39 was able to put up a fight. "Buzz" Wagner was one of the first US aces and scrored kills in both P-40 and P-39. He led several low level raids that were quite successful before being sent back to the US with 8 credits. He was later killed in a P-40 crash stateside.
> 
> Pittsburgh Post-Gazette - Google News Archive Search



There's more than a little doubt about the 3 kills attributed to Wagner on that mission.

Duane


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## pinsog (May 9, 2013)

varsity078740 said:


> There's more than a little doubt about the 3 kills attributed to Wagner on that mission.
> 
> Duane



Do you have any details? Could you please explain what the other side of the story is?


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## varsity078740 (May 9, 2013)

pinsog said:


> Do you have any details? Could you please explain what the other side of the story is?



Officially he's credited with 3 Zeros although contemporary records vary from one to three. None of the narratives from other pilots mention Zeros shot down by Wagner. A total of 4 claims were made for the mission. Until recently, available Japanese records shed no light on the mission, but recent research by Michael Claringbould shows one loss, FPO2c Izumi Hideo. He may have been shot down by George Greene who claimed hits on a Zero that he thought fell to the water.

Duane


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## FLYBOYJ (May 9, 2013)

varsity078740 said:


> There's more than a little doubt about the 3 kills attributed to Wagner on that mission.
> 
> Duane



Bottom line, Wagner and his pilots successfully brought the fight to the Japanese and did show the P-39 could at least hold its own uncer the right circumstances.

We could also re-write history and take 3 credits away from one of the first US Aces...


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## tomo pauk (May 9, 2013)

krieghund said:


> Would you have a source that has the correct information?



The part of the document encompassing the US airplane engines (open the picture in separate tab for hi-res):






Whole document:

http://www.enginehistory.org/ModDesig/SecI.pdf

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## varsity078740 (May 9, 2013)

FLYBOYJ said:


> Bottom line, Wagner and his pilots successfully brought the fight to the Japanese and did show the P-39 could at least hold its own uncer the right circumstances.
> 
> We could also re-write history and take 3 credits away from one of the first US Aces...



I don't think that history needs to be rewritten and I'm not saying for certain that he didn't shoot down the 3 Zeros. But it remains a controversial topic as noted in the 8th Fighter Groups history Attack and Conquer. Nevertheless The Air Force
and the American Aces Association both credit him with 8 victories which includes the 3 from the Lae Mission. But, it's no secret that alot of the stories that came out of the Pacific during the first 6 months of the war were pure propaganda. Witness the variety of stories about Colin Kelly. When the legend becomes fact, print the legend. As far as the merits of the P-39 vs. the Zero goes, Wagner's written report on it after the Lae mission is very informative.

Duane


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## FLYBOYJ (May 9, 2013)

varsity078740 said:


> I don't think that history needs to be rewritten and I'm not saying for certain that he didn't shoot down the 3 Zeros. But it remains a controversial topic as noted in the 8th Fighter Groups history Attack and Conquer. Nevertheless The Air Force
> and the American Aces Association both credit him with 8 victories which includes the 3 from the Lae Mission. But, it's no secret that alot of the stories that came out of the Pacific during the first 6 months of the war were pure propaganda. Witness the variety of stories about Colin Kelly. When the legend becomes fact, print the legend. As far as the merits of the P-39 vs. the Zero goes, Wagner's written report on it after the Lae mission is very informative.
> 
> Duane



And that mission also gave a big boost to the 8FG, it really showed that the USAAF WAS capable of taking on the Japanese even with P-39s and P-40s.


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## pinsog (May 9, 2013)

Down on the deck, one on one with a Zero, what would you guys want to be in, a P39, an F4F or a P40? Personally, I would take the P39 because it is alot faster and has a very good climb rate down low. Of course, hind sight 20/20, I would also want all the wing guns removed to dump a few hundred pounds of extra weight and I would want the 20mm cannon and not the 37mm cannon.


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## Conslaw (May 10, 2013)

Pinsog, I have noticed the same thing - the charts show the P-39 as faster than the F4F to 24,000 feet, and if we overlaid a A6M-2 chart, the P-39 would likely have a similar paper advantage over the Zero. So why did the P-39 have the reputation of being such a dog at much lower altitudes, sometimes 12,000 to 15,000 feet? I can understand that the Guadalcanal P-400s didn't have oxygen. That's a good excuse, but the New Guinea P-39s had the reputation of being dogs both to the American and the Japanese pilots, and they were U.S. spec.


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## Glider (May 10, 2013)

pinsog said:


> Down on the deck, one on one with a Zero, what would you guys want to be in, a P39, an F4F or a P40? Personally, I would take the P39 because it is alot faster and has a very good climb rate down low. Of course, hind sight 20/20, I would also want all the wing guns removed to dump a few hundred pounds of extra weight and I would want the 20mm cannon and not the 37mm cannon.



Personally I would take the Zero


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## varsity078740 (May 10, 2013)

Conslaw said:


> Pinsog, I have noticed the same thing - the charts show the P-39 as faster than the F4F to 24,000 feet, and if we overlaid a A6M-2 chart, the P-39 would likely have a similar paper advantage over the Zero. So why did the P-39 have the reputation of being such a dog at much lower altitudes, sometimes 12,000 to 15,000 feet? I can understand that the Guadalcanal P-400s didn't have oxygen. That's a good excuse, but the New Guinea P-39s had the reputation of being dogs both to the American and the Japanese pilots, and they were U.S. spec.



The P-39 was not a "dog" at 12,000 feet but at 24,000 it needed full throttle to keep from stalling. In the early part of the New Guinea campaign, the P-39 was used as an interceptor against bombers with escorts coming over the target at altitudes over 20,000. They never were able to attain an altitude advantage during attempted intercepts and were constantly bounced by escorts coming down on them from higher altitudes. The 8th Pursuit(fighter)Group was decimated. At Guadalcanal lack of oxygen for P-400s was a mute point. They couldn't get to the same height as the F4Fs with or without oxygen.

Duane


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## Shortround6 (May 10, 2013)

The performance charts are all corrected to stand air pressure and _sometimes_ standard temperature. Temperature is usually 59 or 60 degrees F or 15 degrees C. _BUT NOT ALWAYS_.

See: 






Please note that for THIS chart take-off distance and time for climb are figured for 0 degrees C or 32 degrees F and need 15% added to them just to bring them TO STANDARD. 

Now adjust for 90-100 degree tropical heat on some days and the climb rate IN THEATER can take a real beating compared to the test results at factory or test center. And no, the air temp at 20,000ft is not the same world over.


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## Conslaw (May 10, 2013)

Wouldn't the performance of all aircraft be negatively affected by the high density-altitudes caused by the high temperatures? Why the p-39 more than the P-40? the navy got loaded TBDs over the Owen Stanleys for Pete's sake. When WWII pilots refer to altitude, are they generally talking about density altitude, or actual distance over sea level?


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## Njaco (May 10, 2013)

isn't this for a P-47?


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## Shortround6 (May 10, 2013)

It is, the P-39 chart at Zeno's doesn't have the percentages filled in but we know it can't be zero 

Just pointing out that test results don't always reflect service results, especially in very different climate conditions. ALL planes are going to be degraded somewhat, some may be degraded more than others.

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## krieghund (May 11, 2013)

tomo pauk said:


> The part of the document encompassing the US airplane engines (open the picture in separate tab for hi-res):
> 
> View attachment 233020
> 
> ...



Is there something that indicates the altitudes are with or without RAM?


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## Shortround6 (May 11, 2013)

As a check try the Hurricane II test report;

Hurricane II Z-3564 Trials Report

That _particular_ test machine held 8.8lb boost to 20,800ft in level flight at 3000rpm.

While climbing at 2850 rpm the full throttle height was 15,700ft for 9.4lbs and 16,500ft for the same 8.8lbs used in level flight. A problem with the pressure control or normal tolerance?

In another test of the Merlin XX in a Hurricane reported in the a book on the Merlin by the Rolls Royce Heritage trust the "9lbs" boost was held to over 20,000ft in level flight.


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## wuzak (May 11, 2013)

Shortround6 said:


> As a check try the Hurricane II test report;
> 
> Hurricane II Z-3564 Trials Report
> 
> ...



What are you saying SR?

The FTH was 20,800ft in FS gear.


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## Shortround6 (May 11, 2013)

With RAM, in level flight _at full speed _and in the Hurricane II......YES. 

Since the _amount_ of RAM is dependent on speed the 20,800 ft altitude ONLY works for the INTAKE of the Hurricane AT 246mph ASI. 

Going to a hypothetical Spitfire with a Merlin XX you have a different air scoop, inlet duct which may affect things, for good or bad. You also have extra speed which should give an even higher FTH . 

Dropping to climb speed of 142 mph ASI for the Hurricane is what drops the FTH in climb. 

Sticking the Merlin XX in a Mosquito will give different results as will sticking it in Lancaster. 

Different air scoops/inlet ducts and different speeds. 

This is why the _engine makers_ rarely included RAM altitudes in their specification sheets.

Also please note that if the plane was cruising at 20,800ft at 170mph ASI and opened the throttle to accelerate, it would not have 8.8-9lb boost available UNTIL it had accelerated _to_ 246 mph ASI. 

and any maneuver, even a 1.5 "G" turn that bled speed would also cause the manifold pressure to drop.


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## wuzak (May 11, 2013)

Ok, understood.


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## tomo pauk (May 11, 2013)

krieghund said:


> Is there something that indicates the altitudes are with or without RAM?



Yep, click on the 'Introduction' link posted here.


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## krieghund (May 11, 2013)

Here's the charts for the P-39D with two engine options


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## P-39 Expert (Mar 12, 2018)

Correct on the lack of EW, they didn't have radar in New Guinea until August 1942. Hard to intercept Bettys at 22000' if you don't know they are coming. 
Regarding P-39 drop tanks, most used the 110 gallon external tank. Made fuel management easy, you had 120 gallons internal and 110 external, so when you ran your drop tank dry it was time to head back to base. If you encountered combat and dropped your external tank, you headed for home after that combat.


tomo pauk said:


> The P-39 (among many Allied airplanes) have had several issues that were hampering it's better score vs. Zero.
> The crucial thing could easily be the lack of dependable early warning systems in areas where the P-39s were operating during 1942. As seen in ww2 in all theaters, the fighters, no matter how good, need sufficient time to warm-up, take off and climb to the suitable altitude.
> Next thing would be the pilot's tactics experience - P-39 should flatly lose the vs. Zero in turning fight, and Zero's pilots were the best in the world in 1942.
> Then we go to the engine limitations: the single speed V-1710 was, during the 1st half of the war, a dog above 15000 ft. The airframe issue would be the loopsided layout of the engine intake, much reducing the ram effect. That should steal couple of thousands HP/feet from the already low engine power/altitude. The Japanese bombing runs were conducted at higher altitudes, and their Zeros have had two-speed superchargers, so the Zeros would be the ones to dive at P-39s, not vice versa. Another airframe issue would be the low fuel quantity, giving the P-39 pilot two uneasy choices:
> ...


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## P-39 Expert (Mar 12, 2018)

pinsog said:


> I agree the P39 had flaws, but it was much faster then the Zero and could easily out dive the Zero. The F4F had nothing on the Zero except being tougher and yet it fought the Zero to about a draw while the P39 didn't do as well. How can that be explained?


Navy pilots were better right out of flight training. They had 600 hours of pilot training where the Army pilots graduated with only 200. All that "landing on a ship", navigation, etc. Those Navy pilots were living proof that the better pilot wins over the better plane, because there wasn't much worse a plane during that period than the F4F. Barely the same top speed as a Zero but abysmal climb and turn, and a very narrow landing gear. They beat the Zero with boom and zoom tactics, if you were above the Zero you made a diving pass and then converted your dive speed to altitude by climbing back up above. If the Zero was above you, you dove away and when out of range climbed back up above and made a diving pass. No turning with the amazingly maneuverable Zero, ever. Just dive away, your Wildcat was stressed to take it, the Zero was not. By the way, the Army pilots caught up with the Navy pilots as they gained more experience, but right out of flight school ( and almost all Army pilots were) the Navy was better.

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## P-39 Expert (Mar 12, 2018)

tomo pauk said:


> The table for the V-1650-1 lists the critical altitudes in the wrong column, under 'with ram', instead under 'no ram'.


The columns are correct, the two figures are for low and high gear. You took off in low and shifted to high at about 11500' for military (full) power. The Allison had a single speed supercharger so there was no shifting. Two speeds was not better than the Allison single speed. Low gear was a safety measure simply to keep the pilot from overboosting the engine at take off. Allison just told the pilot not to exceed a certain amount of boost at takeoff and the throttle had a "take off" stop about halfway up. Just set the throttle at the takeoff stop and it was the same as "low gear" in a two speed. Then as you climbed you gradually opened the throttle above the "take off" stop to maintain power as the air got gradually thinner the higher you went. Then when you reached critical altitude (12000' in the early engines, 15000' in the later) power gradually declined up to the ceiling, just like every other engine.


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## P-39 Expert (Mar 12, 2018)

pinsog said:


> Thank you for the graph.
> 
> This seems to show that the P39 will outperform the F4F up to 24,000 feet or so. I'm having a hard time believing that it was the P39's performance as much as it was a training issue considering the F4F was around 1 to 1 against the Zero. I think if I was given the choice, I would choose the P39, at least I had the option of running if things didn't work in my favor.


The graphs are correct except the early P-39 was about 10mph faster than shown. So it was faster than the F4F at all altitudes. And keep in mind that not much combat took place above about 26000' (8000 meters) in either the Pacific or European theater. B-17s and B-24s flew at 25000' so you needed about another 1000' or so to intercept or escort them. Specialized reconnaissance planes flew higher, but combat planes didn't much go over 26000'.


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## P-39 Expert (Mar 12, 2018)

varsity078740 said:


> The P-39 was not a "dog" at 12,000 feet but at 24,000 it needed full throttle to keep from stalling. In the early part of the New Guinea campaign, the P-39 was used as an interceptor against bombers with escorts coming over the target at altitudes over 20,000. They never were able to attain an altitude advantage during attempted intercepts and were constantly bounced by escorts coming down on them from higher altitudes. The 8th Pursuit(fighter)Group was decimated. At Guadalcanal lack of oxygen for P-400s was a mute point. They couldn't get to the same height as the F4Fs with or without oxygen.
> 
> Duane


Beg to differ. The P-39s (couple of squadrons) were all that stood between the Japanese and Port Moresby in May/June/July of 1942. The Japs flew multiple bombing missions daily (weather permitting) trying to knock out the P-39 bases and the P-39s kept them out. Problem was the early P-39 (carrying a drop tank) could only reach up to about 18000' before it's climb rate fell below 1000'/minute, and in combat that was excruciatingly slow. The Japanese Navy Betty bombers came in between 18000' and 22000'. There was no long range radar until August at Milne Bay. So these boys had to fly patrols or wait on the ground. And those patrols were at 22000' so it took a long time to get there, but they could do it. And flying around waiting for your opponent when you had no idea if he was even coming or not was wasting already incredibly scarce resources. After the radar arrived in August these pilots could perform the more conventional method of interception, getting a call from the radar station with altitude and direction of the incoming force with time to take off and climb above them to attack. Results (and the pilot's nerves) were much better with radar. Even with all these disadvantages the Army pilots were able to maintain a 1:1 kill ratio. Tough, smart kids.

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## tomo pauk (Mar 12, 2018)

Welcome to the forum.



P-39 Expert said:


> ...
> Regarding P-39 drop tanks, most used the 110 gallon external tank.
> ...



I'd politely ask for the source for that statement.



P-39 Expert said:


> ...
> Those Navy pilots were living proof that the better pilot wins over the better plane, because there wasn't much worse a plane during that period than the F4F. Barely the same top speed as a Zero but abysmal climb and turn, and a very narrow landing gear. They beat the Zero with boom and zoom tactics, if you were above the Zero you made a diving pass and then converted your dive speed to altitude by climbing back up above
> ...



There was Buffalo and P-36 around, plus the CW 21. Hurricane was no better than better versions of the F4F - F4Fs weren't all the same in 1941/42. 
F4F hardly beat Zeros by a wide margin.



P-39 Expert said:


> The columns are correct, the two figures are for low and high gear. You took off in low and shifted to high at about 11500' for military (full) power.



The figures for the rated altitude were in the wrong cloumn. See for your self - there is a firm ~7500 ft worth of altitude advantage the V-1650-1 had over the early V-1710s. Or, more than 200 HP difference at 20000 ft, a 25% power more for the V-1650-1 there.
Granted, later V-1710s cut that difference in power to 15-20% above 15000 ft.








> The Allison had a single speed supercharger so there was no shifting. Two speeds was not better than the Allison single speed. Low gear was a safety measure simply to keep the pilot from overboosting the engine at take off. Allison just told the pilot not to exceed a certain amount of boost at takeoff and the throttle had a "take off" stop about halfway up. Just set the throttle at the takeoff stop and it was the same as "low gear" in a two speed. Then as you climbed you gradually opened the throttle above the "take off" stop to maintain power as the air got gradually thinner the higher you went. Then when you reached critical altitude (12000' in the early engines, 15000' in the later) power gradually declined up to the ceiling, just like every other engine.



Let's not make advantage from a shortcoming. There was a reason why people all around the world were installing 2- , 3- or variable-speed drives for the superchargers on their engines when possible, despite the higher cost and more resources and manufacturing time needed. BTW - US pilots were listening to the USN/USMC/USAAC/AAF, not Allison or other engine maker.
Low gear enabled to the engine to have good power at low level, while retaining good power at high altitude. That, combined with bigger S/C on the V-1610, meant that it produced more power at most of altitude bands than any 1-stage V-1710.


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## Stig1207 (Mar 13, 2018)

P-39 Expert said:


> Even with all these disadvantages the Army pilots were able to maintain a 1:1 kill ratio.


Is that 1:1 ratio against all enemy aircraft types?


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## Shortround6 (Mar 13, 2018)

I would note that a lot of people used single stage single speed superchargers and used some sort of restriction on the throttle for take-off and low altitude even if it was just watching the boost gauge (the British actual fitted a boost control mechanism, set the boost to 6lbs and the mechanism would hold that boost or at least not exceed it now matter how the pilot climbed and dived below full throttle height).
However since the problems in the engine with a single speed supercharger are that 
1. you don't have the throttle plate/s fully open so there are "pumping losses".
2. The fast spinning impeller takes more power to drive.
3. The fast spinning impeller heats the intake charge more making it less dense and the higher temperature pushes it nearer to the detonation limit.

All put together the single speed engine is making much less power at low altitude than a two speed engine. 
Sorry, not having to shift supercharger gears or saving on manufacturing costs is a bogus argument. 
For the Merlin running on 87 octane gas the Merlin III with an 8.588 supercharger gear take off was 880hp at 3000rpm at 6 1/4 lb boost.
a Prototype engine with 7.32 supercharger gear was rated at 1000hp for take-off at 3000rpm and 6lbs boost and this was superseded by the Merlin VIII
using a 6.313 supercharger gear and rated at 1080hp at 3000rpm at 5 3/4 lbs boost. 
Now the low gear MK VIII was using about 55% of the power to drive it's supercharger compared to the MK III Merlin and was also heating the intake charge proportionally less, throttle plate/s were also much closer to fully open.

overboosting engines well beyond manufactures recommendations was done, but usually only at the cost of shorter engine life. In fact the Flying Tigers started to pick up on the fact that while a severely over boosted engine often made it home it also showed a very noticeable tendency to fail on either the next flight or the one after. 

Please note that early Allison engines (the long nose) used a crankshaft that did not have the heat treatment/surface treatments of later Allison crankshafts and would not tolerate severe abuse for any where near as long even if they would give hundreds if not thousands of hours of service if stress levels were kept to more moderate levels.

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## P-39 Expert (Mar 13, 2018)

Stig1207 said:


> Is that 1:1 ratio against all enemy aircraft types?


Yes, all aircraft types. A twin engined bomber and an observation plane each counted one victory. Not all victories were against Zeros.


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## P-39 Expert (Mar 13, 2018)

tomo pauk said:


> Welcome to the forum.
> 
> 
> 
> ...


Couple of things, not arguing that the 1650-1 made more power than the Allison, it did because it had a larger diameter impeller (supercharger). That is a fact.
But the two figures listed in the "Engine Ratings" column (below the Takeoff rating) are for low gear (1240hp/3000rpm/11500') and high gear (1120hp/3000rpm/18500'). Takeoff was in low gear (to not overboost the engine at low altitude where the air is thicker) and then manually shifted to high gear at 11500' with critical altitude being 18500' to draw in more of the thinner air at higher altitudes.
And the single speed Allison was in no way a disadvantage. Later models (starting with the 1325hp V-1710-63) were equipped with an automatic boost control or automatic manifold pressure regulator (same thing). The maximum boost (or manifold pressure) for the engine was preset and this gizmo mounted on the carburetor limited boost to at or below that preset amount. In other words you couldn't blow up (overboost) the engine at ANY throttle setting. This eliminated the need for two speeds, manual shifting or automatic shifting. And this device apparently worked very well and was very dependable since it was used on most all the engines Allison manufactured thereafter.
So, with no throttle management the pilot could set the boost control, firewall the throttle and not overboost the engine at any altitude. This eliminated a lot of pilot workload.
Back to the two speed supercharger, the disadvantage was that in low gear power started to decline almost right away as the plane gained altitude and the air began to get thinner, so by the time you reached the shift point (11500') power was lower. Then you shifted into high and power steadily increased up to the critical altitude (18500') when it began to fall off again (just like low gear). This resulted in a sawtooth performance curve for both the engine and airplane. The Allison didn't have that problem (especially with the auto boost control) as it made 1325HP at takeoff and maintained that figure up to 8000' where it began to decline due to the thinner air. 
Only real problem with the Allison was that the Army insisted on designing planes around it that just weighed too darn much. The P-39 weighed around 7650#, the P-40 weighed 8400# and the P-51A weighed about that also. 8400# divided by 1150HP is 7.3 pounds/HP. The Me109G6 weighed 6800# with a 1475HP engine or 4.6 pounds/HP. You can see the problem.


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## P-39 Expert (Mar 13, 2018)

Since we are talking about the P-39, lets clear up a few inaccuracies that have perpetuated over the decades:
1. The XP-39 was not ruined by deleting the turbocharger. Turbo was deleted to get the P-39 and P-40 ready in time for WWII. Turbo was new and was the main reason that the similarly turbocharged P-38 didn't enter combat until the end of 1942. And the intercooler and oil cooler arrangements were not adjustable to let in more or less air as needed so they would not have worked in combat. Allison was coming out with engines that had higher critical altitudes and even one with a second stage supercharger that ended up going into the P-63.
2. The rejection of the P-39 and P-400 (export P-39) by the British was solely political and economic. They ordered those planes in 1940 when Hitler was about to invade France expecting a long war and needing more airplane production. They cancelled the order in late 1941 after France had fallen and the Battle of Britain was over. They no longer needed these planes since their own fighter production (Spitfire and Typhoon) was adequate with no threat of Nazi invasion. But the main reason for cancellation was these original orders were hard money purchase contracts and they no longer had the money to pay for them, and in the meantime Lend Lease had been enacted that would send them all the planes they wanted/needed for free. Why spend $millions on a plane when they were now free. So the British specified much more armament and weight on these P-39s so that performance suffered and they could weasel out of the contract.


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## varsity07840 (Mar 13, 2018)

tomo pauk said:


> The P-39 (among many Allied airplanes) have had several issues that were hampering it's better score vs. Zero.
> The crucial thing could easily be the lack of dependable early warning systems in areas where the P-39s were operating during 1942. As seen in ww2 in all theaters, the fighters, no matter how good, need sufficient time to warm-up, take off and climb to the suitable altitude.
> Next thing would be the pilot's tactics experience - P-39 should flatly lose the vs. Zero in turning fight, and Zero's pilots were the best in the world in 1942.
> Then we go to the engine limitations: the single speed V-1710 was, during the 1st half of the war, a dog above 15000 ft. The airframe issue would be the loopsided layout of the engine intake, much reducing the ram effect. That should steal couple of thousands HP/feet from the already low engine power/altitude. The Japanese bombing runs were conducted at higher altitudes, and their Zeros have had two-speed superchargers, so the Zeros would be the ones to dive at P-39s, not vice versa. Another airframe issue would be the low fuel quantity, giving the P-39 pilot two uneasy choices:
> ...



The A6M2 Model 21 Zero encountered by the P-39 in New Guinea did not have a 2 speed engine. That was introduced on the A6M3.


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## varsity07840 (Mar 13, 2018)

P-39 Expert said:


> Since we are talking about the P-39, lets clear up a few inaccuracies that have perpetuated over the decades:
> 1. The XP-39 was not ruined by deleting the turbocharger. Turbo was deleted to get the P-39 and P-40 ready in time for WWII. Turbo was new and was the main reason that the similarly turbocharged P-38 didn't enter combat until the end of 1942. And the intercooler and oil cooler arrangements were not adjustable to let in more or less air as needed so they would not have worked in combat. Allison was coming out with engines that had higher critical altitudes and even one with a second stage supercharger that ended up going into the P-63.
> 2. The rejection of the P-39 and P-400 (export P-39) by the British was solely political and economic. They ordered those planes in 1940 when Hitler was about to invade France expecting a long war and needing more airplane production. They cancelled the order in late 1941 after France had fallen and the Battle of Britain was over. They no longer needed these planes since their own fighter production (Spitfire and Typhoon) was adequate with no threat of Nazi invasion. But the main reason for cancellation was these original orders were hard money purchase contracts and they no longer had the money to pay for them, and in the meantime Lend Lease had been enacted that would send them all the planes they wanted/needed for free. Why spend $millions on a plane when they were now free. So the British specified much more armament and weight on these P-39s so that performance suffered and they could weasel out of the contract.

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## Shortround6 (Mar 13, 2018)

P-39 Expert said:


> Couple of things, not arguing that the 1650-1 made more power than the Allison, it did because it had a larger diameter impeller (supercharger). That is a fact.
> But the two figures listed in the "Engine Ratings" column (below the Takeoff rating) are for low gear (1240hp/3000rpm/11500') and high gear (1120hp/3000rpm/18500'). Takeoff was in low gear (to not overboost the engine at low altitude where the air is thicker) and then manually shifted to high gear at 11500' with critical altitude being 18500' to draw in more of the thinner air at higher altitudes.
> And the single speed Allison was in no way a disadvantage. Later models (starting with the 1325hp V-1710-63) were equipped with an automatic boost control or automatic manifold pressure regulator (same thing). The maximum boost (or manifold pressure) for the engine was preset and this gizmo mounted on the carburetor limited boost to at or below that preset amount. In other words you couldn't blow up (overboost) the engine at ANY throttle setting. This eliminated the need for two speeds, manual shifting or automatic shifting. And this device apparently worked very well and was very dependable since it was used on most all the engines Allison manufactured thereafter.
> So, with no throttle management the pilot could set the boost control, firewall the throttle and not overboost the engine at any altitude. This eliminated a lot of pilot workload.
> ...




Ah, the British had the pretty much the same device on the Merlin so the need for a two speed supercharger was NOT as you state. 
The Merlin as used in the P-40F shows this pretty clearly
1300hp for take-off at at 12lbs boost (54 in) and could hold 1240hp to 11500ft (including ram?) 
in high gear it could hold 1120hp to 18,500ft. 
The V-1710-63 engine you reference was good for 1150hp at 11,800ft with no ram. 
The difference shows up with the V-1710-83 engine with the 9.60 supercharger gear. the 1150hp point was moved to 15,500ft *but at the cost *of lowering the take-off power to 1200hp from the 1325hp. 
At a given point in time ( engine materials, cooling and fuel) the two speed supercharger allowed for more power at both sea level and at altitude without having to compromise one or the other.

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## Shortround6 (Mar 13, 2018)

P-39 Expert said:


> The rejection of the P-39 and P-400 (export P-39) by the British was solely political and economic. They ordered those planes in 1940 when Hitler was about to invade France expecting a long war and needing more airplane production. They cancelled the order in late 1941 after France had fallen and the Battle of Britain was over. They no longer needed these planes since their own fighter production (Spitfire and Typhoon) was adequate with no threat of Nazi invasion. But the main reason for cancellation was these original orders were hard money purchase contracts and they no longer had the money to pay for them, and in the meantime Lend Lease had been enacted that would send them all the planes they wanted/needed for free. Why spend $millions on a plane when they were now free. So the *British specified much more armament and weight* on these P-39s so that performance suffered and *they could weasel out of the contract*.



Got any proof?
The 20mm Hispano gun weighed about 100-110lbs less than the 37mm for one thing and since 37mm ammo weighs roughly 3 times per round what 20mm ammo does even with the drum the ammo load for the 20mm gun was less than 30 rounds of 37mm ammo?
four British .303 guns weigh more than four american .30 cal guns?

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## Stig1207 (Mar 13, 2018)

P-39 Expert said:


> Yes, all aircraft types. A twin engined bomber and an observation plane each counted one victory. Not all victories were against Zeros.



A 1:1 ratio against all types would not indicate a good ratio against Zeros or other fighters; most air-to-air losses are likely to be to fighters. So a 1:1 ratio for the P-39 against all types may well mean a 1:2, 1:3, 1:4....and so on, against enemy fighters.


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## varsity07840 (Mar 13, 2018)

pinsog said:


> I agree the P39 had flaws, but it was much faster then the Zero and could easily out dive the Zero. The F4F had nothing on the Zero except being tougher and yet it fought the Zero to about a draw while the P39 didn't do as well. How can that be explained?


The F4F had a much higher ceiling.


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## varsity07840 (Mar 13, 2018)

pinsog said:


> Wasn't the P38 20mm much more reliable than the other 20mm mounted on other US aircraft?


same gun.


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## tomo pauk (Mar 13, 2018)

P-39 Expert said:


> Couple of things, not arguing that the 1650-1 made more power than the Allison, it did because it had a larger diameter impeller (supercharger). That is a fact.



Indeed, the bigger impeller was one of key ingredients of Merlin's power. ANother is that compression ratio was low, some 10% lower than on the V-1710, and 10-25% lower than on the DB-601/605 - that meant the Merlin took overboosting very well, more boost = more power in linear fashion. On 100 oct fuel Merlin III was factory aprooved by factory to make up to +12 psi boost (54 in Hg, around 1.9 ata) by 1939, with some subsequent types quickly going to +18 psi (67 in Hg, ) by early 1942. By time 130 grade fuel was available (~mid 1942?), better Merlins went to + 21 psi (~73 in Hg). 



> But the two figures listed in the "Engine Ratings" column (below the Takeoff rating) are for low gear (1240hp/3000rpm/11500') and high gear (1120hp/3000rpm/18500'). Takeoff was in low gear (to not overboost the engine at low altitude where the air is thicker) and then manually shifted to high gear at 11500' with critical altitude being 18500' to draw in more of the thinner air at higher altitudes.
> And the single speed Allison was in no way a disadvantage. Later models (starting with the 1325hp V-1710-63) were equipped with an automatic boost control or automatic manifold pressure regulator (same thing). The maximum boost (or manifold pressure) for the engine was preset and this gizmo mounted on the carburetor limited boost to at or below that preset amount. In other words you couldn't blow up (overboost) the engine at ANY throttle setting. This eliminated the need for two speeds, manual shifting or automatic shifting. And this device apparently worked very well and was very dependable since it was used on most all the engines Allison manufactured thereafter.
> So, with no throttle management the pilot could set the boost control, firewall the throttle and not overboost the engine at any altitude. This eliminated a lot of pilot workload.



I'm not sure how you can say at face value that 1-speed V-1710 was not in disadvantage vs. 2-speed engine, particulary vs. V-1650-1.
Later models of V-1710 are exactly that - later models. They lagged behind the V-1650-1 by 8-10 months, meaning that engines powering the P-40s and P-39s in 1942 were making 20% less power at altitude than V-1650-1. I will say that having less power = being in disadvantage. 
Automatic manifold pressure regulators were not endemic to the V-1710.



> Back to the two speed supercharger, the disadvantage was that in low gear power started to decline almost right away as the plane gained altitude and the air began to get thinner, so by the time you reached the shift point (11500') power was lower. Then you shifted into high and power steadily increased up to the critical altitude (18500') when it began to fall off again (just like low gear). This resulted in a sawtooth performance curve for both the engine and airplane. The Allison didn't have that problem (especially with the auto boost control) as it made 1325HP at takeoff and maintained that figure up to 8000' where it began to decline due to the thinner air.



Please, take a look at the tables. At 11500 ft, the V-1650-1 makes 1240 HP, vs. V1710-39 making 1160-1170 there. Or, at 11800-12000 ft, the difference is some 70-80 HP, while above 15000 ft we have the V-1650-1 making 25% more power. Sawtooth or not, nowhere where mattered the V-1710-39 and similar were not matching the power of V-1650-1. The V-1650-1 was making 1325 HP up to 9000 ft. And again at ~15000 ft due to having another S/C speed and a sizable S/C, despite the thinner air.
The Merlin 20 series from 1943 on were good for 1600 HP for take off, vs. 1200 HP on the 1-stage V-1710s from same time. take a look



> Only real problem with the Allison was that the Army insisted on designing planes around it that just weighed too darn much. The P-39 weighed around 7650#, the P-40 weighed 8400# and the P-51A weighed about that also. 8400# divided by 1150HP is 7.3 pounds/HP. The Me109G6 weighed 6800# with a 1475HP engine or 4.6 pounds/HP. You can see the problem.



Granted, the US fighters were over weight. However, Allison have had lagging too much with introduction of more powerful engines when compared with RR and DB, they managed by late 1942 to equal altitude performance of the Merlin III from 1937. Let's recall that every important US engine in 1944 was with 2-, 3- or variable-speed drive, unless a turbocharger was involved.
BTW - the P-51A have had 1480 HP max, the Bf 109G6 around 1550 PS (fully rated) or 1400 PS (restricted from mid-1942 to Oct 1943). Sure enough, the G6 have had better altitude power.

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## Shortround6 (Mar 13, 2018)

varsity07840 said:


> same gun.


The 20mm gun in the P-38 was mounted in a substantial cradle which _helped. _The gun being originally designed to mounted *on an engine block,*
How much more relaible I don't know.

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## tomo pauk (Mar 13, 2018)

P-39 Expert said:


> Since we are talking about the P-39, lets clear up a few inaccuracies that have perpetuated over the decades:
> 1. The XP-39 was not ruined by deleting the turbocharger. Turbo was deleted to get the P-39 and P-40 ready in time for WWII. Turbo was new and was the main reason that the similarly turbocharged P-38 didn't enter combat until the end of 1942. And the intercooler and oil cooler arrangements were not adjustable to let in more or less air as needed so they would not have worked in combat. Allison was coming out with engines that had higher critical altitudes and even one with a second stage supercharger that ended up going into the P-63.
> 2. The rejection of the P-39 and P-400 (export P-39) by the British was solely political and economic. They ordered those planes in 1940 when Hitler was about to invade France expecting a long war and needing more airplane production. They cancelled the order in late 1941 after France had fallen and the Battle of Britain was over. They no longer needed these planes since their own fighter production (Spitfire and Typhoon) was adequate with no threat of Nazi invasion. But the main reason for cancellation was these original orders were hard money purchase contracts and they no longer had the money to pay for them, and in the meantime Lend Lease had been enacted that would send them all the planes they wanted/needed for free. Why spend $millions on a plane when they were now free. So the British specified much more armament and weight on these P-39s so that performance suffered and they could weasel out of the contract.



1. Allison was lagging with engines that have had higher critical altitudes by perhaps 2 years after the RR and DB. Original XP-39 installation of turbo, intercoolers, radiators etc was aerodynamically apalling, with top speed barely exceeding 340 mph above 20000ft, without any armament, protection or radio antennae protruding. The P-43, with radial engine and guns, was faster.
2. A good idea might be not to throw mud on people that don't deserve it. It tends to fly backwards.

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## Shortround6 (Mar 13, 2018)

I would note that the British got 3 P-39Cs from the USAAF order of 20 and these made it to England in June/July of 1941 with test flying starting July 6th 1941, the first Aircobra I showed up July 30th. The P-39Cs had no self sealing fuel tanks even though they have armor glass behind windscreen. amount of armor in other places I don't know. 
The P-400 weighed 5550lbs empty (no guns, no armor, oxygen etc) while a P-39D weighed 5523lbs and a P39D-2 weighed 5658lbs. 20-30 lbs could be the production variation, 100lbs starts to stretch it.
Basic weight (guns, armor, Oxygen, radios etc) added in has the P-400 at 6328.6lbs and the P-39D at 6290lbs and the P-39D-2 at 6431.5.
This is no fuel, no ammo, no oil except what is left in the systems and so on.

Just where did those perfidious men from Albion stick all that weight in order to get out of the contracts? 
Please note that when the first AirCobras get to England the British have the Spitfire Vb in squadron service with two 20mm cannon and four .303 machineguns so asking for one 20mm, two .50s and four .303s hardly seems like they are deliberately loading down the plane.

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## Glider (Mar 13, 2018)

P-39 Expert said:


> 2. The rejection of the P-39 and P-400 (export P-39) by the British was solely political and economic. They ordered those planes in 1940 when Hitler was about to invade France expecting a long war and needing more airplane production. They cancelled the order in late 1941 after France had fallen and the Battle of Britain was over. They no longer needed these planes since their own fighter production (Spitfire and Typhoon) was adequate with no threat of Nazi invasion. But the main reason for cancellation was these original orders were hard money purchase contracts and they no longer had the money to pay for them, and in the meantime Lend Lease had been enacted that would send them all the planes they wanted/needed for free. Why spend $millions on a plane when they were now free. So the British specified much more armament and weight on these P-39s so that performance suffered and they could weasel out of the contract.


I am sorry but this isn't close to being accurate. For use in Europe the P39 was no match for the Luftwaffe or as good as the RAF fighters, it was also totally unfit for combat when the RAF first tried to use them in the autumn of 1941. As for the change in weapons as others have pointed out the 20mm was lighter and better for air to air combat.

At low altitude the P39 was better but the war in Europe tended to be fought at higher altitudes. Had the cost been an issue, the RAF could simply have taken the US P39 at no cost under lend lease and made changes in the UK. Nearly all the lend lease aircraft came to the UK and had to be modified for RAF service.


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## P-39 Expert (Mar 13, 2018)

tomo pauk said:


> 1. Allison was lagging with engines that have had higher critical altitudes by perhaps 2 years after the RR and DB. Original XP-39 installation of turbo, intercoolers, radiators etc was aerodynamically apalling, with top speed barely exceeding 340 mph above 20000ft, without any armament, protection or radio antennae protruding. The P-43, with radial engine and guns, was faster.
> 2. A good idea might be not to throw mud on people that don't deserve it. It tends to fly backwards.


Please accept my apology if you think I threw mud on you. Message boards are for debate and everyone always doesn't agree with everyone else. I'm just trying to explain to you what the numbers on the engine chart mean.


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## P-39 Expert (Mar 13, 2018)

Shortround6 said:


> Ah, the British had the pretty much the same device on the Merlin so the need for a two speed supercharger was NOT as you state.
> The Merlin as used in the P-40F shows this pretty clearly
> 1300hp for take-off at at 12lbs boost (54 in) and could hold 1240hp to 11500ft (including ram?)
> in high gear it could hold 1120hp to 18,500ft.
> ...


I don't see how a single stage supercharger could compromise on power, all the power the engine could generate was available at every altitude subject to governance of the auto boost control below the critical altitude. The two speed supercharger by definition limited power at takeoff/low altitude. Both systems worked effectively.


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## P-39 Expert (Mar 13, 2018)

Stig1207 said:


> A 1:1 ratio against all types would not indicate a good ratio against Zeros or other fighters; most air-to-air losses are likely to be to fighters. So a 1:1 ratio for the P-39 against all types may well mean a 1:2, 1:3, 1:4....and so on, against enemy fighters.


Correct. Same for all combatants, your fighters are not just shooting down opposition fighters, your main goal is to get by the escorting fighters to knock down the higher value targets like bombers or cargo planes.


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## P-39 Expert (Mar 13, 2018)

Shortround6 said:


> I would note that the British got 3 P-39Cs from the USAAF order of 20 and these made it to England in June/July of 1941 with test flying starting July 6th 1941, the first Aircobra I showed up July 30th. The P-39Cs had no self sealing fuel tanks even though they have armor glass behind windscreen. amount of armor in other places I don't know.
> The P-400 weighed 5550lbs empty (no guns, no armor, oxygen etc) while a P-39D weighed 5523lbs and a P39D-2 weighed 5658lbs. 20-30 lbs could be the production variation, 100lbs starts to stretch it.
> Basic weight (guns, armor, Oxygen, radios etc) added in has the P-400 at 6328.6lbs and the P-39D at 6290lbs and the P-39D-2 at 6431.5.
> This is no fuel, no ammo, no oil except what is left in the systems and so on.
> ...


All that weight was in the form of the useless 4 .30 caliber machine guns in the wings that weighed almost 400# (including gun mounts, ammo, ammo boxes and gun chargers) and and other such items as a cockpit heater that was fueled by kerosene when the P-39 already had probably the best cockpit climate control system of any American fighter that simply ducted hot air from the radiator. Reduce the weight of the P-400 by almost 500# and you have a plane very competitive with the Spitfire V.


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## P-39 Expert (Mar 13, 2018)

Glider said:


> I am sorry but this isn't close to being accurate. For use in Europe the P39 was no match for the Luftwaffe or as good as the RAF fighters, it was also totally unfit for combat when the RAF first tried to use them in the autumn of 1941. As for the change in weapons as others have pointed out the 20mm was lighter and better for air to air combat.
> 
> At low altitude the P39 was better but the war in Europe tended to be fought at higher altitudes. Had the cost been an issue, the RAF could simply have taken the US P39 at no cost under lend lease and made changes in the UK. Nearly all the lend lease aircraft came to the UK and had to be modified for RAF service.


Cost was the big issue, especially for the British. They had stood alone against Germany since the fall of France and they were dead broke. They had to order those planes before France fell not knowing how long the war would run. After they were safely past the Battle of Britain and a German invasion was no longer possible, they moved to cut their losses and weasel out of not only the P-39 contract but a similar contract for P-38s that were ordered without turbochargers. Those were hard money contracts and payment was demanded. The British knew that if the Battle of Britain had not gone their way and they needed the P-39s that they could have quickly stripped the excess weight (.30 cal MGs, heater, unnecessary radio equipment) from those planes to make them competitive.


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## Shortround6 (Mar 13, 2018)

You don't understand how the supercharger works. 

See my post #96.

It takes power to drive the supercharger, the power needed goes up with the square of the speed. a given impeller, inlet and diffuser set up will need twice the power if driven by a set of 10.0 gears than if driven by a set of 7.0 gears. Of course the peak pressure will be much lower with the 7.0 gears. I will get back to this.

of the power going into the supercharger, a good supercharger in 1939-41 used about 70% power to actually compress the air. The extra 30% was pretty much wasted in churning the air around without actually compressing it, however this "wasted" power did not simply go away. The extra churning created friction between the air and the impeller and the housing/diffuser and this friction turned into heat. Basically if you had 100hp driving the supercharger input shaft you were doing good if you got 70hp worth of compression of the air. Now simply compressing the air will heat it, ask anybody who has grabbed a bicycle tire pump after it has seen some use. The extra 30hp turned pretty much into pure heat. Your intake charge could go from 60-70 degrees f to several hundred degrees very easily. 
SInce there is a limit to the amount of boost you can use with a given fuel that also depends of the temperature of the air/fuel before it gets to the cylinder there is a problem with using a high gear at low altitude. 
at sea level the air, rounded off is at 15lbs/sq in so if we want 44in of manifold pressure (7lbs of boost) we only need to compress the air 1.46 times. However at 12,000f the air pressure 9.5 lbs so if we still want 44in we need to compress the air 2.3 times. at 18,000ft we need to compress the air 2.93 times. 

Now if we use a single gear set and we chose a set that will give us 44in of manifold pressure at high altitude (14-18,000ft) we are spinning way faster than we need at low altitude. we are using up power form the crankshaft that could be going to the propeller, we are over heating the intake charge at low altitude and our fancy auto boost control simply closes off the the throttle plate and restricts the air flow entering the supercharger. It doesn't solve any of these problems. 

The two speed supercharger spins the impeller slower, uses less power from the crankshaft, heats the intake charge less meaning that at a give pressure the air is denser, and the lower temperature means we can use more pressure if we so desire. Of course at the slower speed the supercharger cannot compress the air enough to give the desired manifold pressure at higher altitudes. 
During the 1930s many engines came with different supercharger gears for their single speed superchargers to suit them to the expected duty. Many transports/flying boats getting engines with high take-off power but low altitude performance while engines intended for fighters or fast bombers sacrificed take-off power for power at altitude (12-15,000ft) 
The coming of high octane fuel allowed for higher temperatures in the intake charge and higher boost without detonation setting and wrecking the engine.


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## P-39 Expert (Mar 13, 2018)

Glider said:


> I am sorry but this isn't close to being accurate. For use in Europe the P39 was no match for the Luftwaffe or as good as the RAF fighters, it was also totally unfit for combat when the RAF first tried to use them in the autumn of 1941. As for the change in weapons as others have pointed out the 20mm was lighter and better for air to air combat.
> 
> At low altitude the P39 was better but the war in Europe tended to be fought at higher altitudes. Had the cost been an issue, the RAF could simply have taken the US P39 at no cost under lend lease and made changes in the UK. Nearly all the lend lease aircraft came to the UK and had to be modified for RAF service.


Just which Luftwaffe plane(s) were so superior to the P-39?
Regarding lend lease, how could the British take the P-39 under lend lease when they had so publicly derided them as inferior under the hard money contract? "Oh these P-39s suck, but we'll take them for free"? They no longer needed them after winning the BoB and their internal fighter production was then adequate. They didn't need them and couldn't pay for them. Bell had the last laugh though. They got a $2million cash advance from the British in the original order. Bell was a relatively new company struggling under depression era economics and although $2mil doesn't sound like much today, in 1940 dollars it was a fortune and put them in the black for the rest of the war. And the Army took over the British order and had P-39s available from 1941 on.


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## Shortround6 (Mar 13, 2018)

P-39 Expert said:


> All that weight was in the form of the useless 4 .30 caliber machine guns in the wings that weighed almost 400# (including gun mounts, ammo, ammo boxes and gun chargers) and and other such items as a cockpit heater that was fueled by kerosene when the P-39 already had probably the best cockpit climate control system of any American fighter that simply ducted hot air from the radiator. Reduce the weight of the P-400 by almost 500# and you have a plane very competitive with the Spitfire V.


 Not even close. 
I asked where the British *added *weight to get out off the contract. They took out over 100lbs compared to an American P-39 with 37mm gun. The P-39c had a pair of 30 cal guns in the fuselage 





weight figures may be suspect. The speed sure is, British got 359mph out of the ones they got. 
Basically Larry Bell sold the British and French an imaginary aircraft. When the British took delivery it would not come close to meeting the promised performance. The XP-39 when delivered to Wright field in 1939 was 10% overweight and the prototype had no guns let alone armor or self sealing tanks.
Yanking a cabin heater wasn't going to save it. 
Nobody says you have to fill the ammo boxes completely full.

Spitfire Vb went a bit over 6500lbs, cutting 500lbs out of an Aircobra still leaves you over 500lbs heavy and several hundred hp short.

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## P-39 Expert (Mar 14, 2018)

Shortround6 said:


> You don't understand how the supercharger works.
> 
> See my post #96.
> 
> ...


Sorry I don't understand how a supercharger works. I thought it compressed intake air to provide more power to the engine. Whether the power is reduced at lower altitudes because of a lower gear or because of a lower throttle setting on a single gear seems irrelevant to me. The sole purpose of low gear is to keep from overboosting the engine at takeoff. The same protection against overboosting at takeoff in a single speed engine is provided by reduced throttle. The Allison's single speed was high gear, it didn't have a low gear. It reduced boost at takeoff and low altitude by reduced throttle. Simple operation, lighter weight, more reliable.


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## Shortround6 (Mar 14, 2018)

P-39 Expert said:


> Just which Luftwaffe plane(s) were so superior to the P-39?
> Regarding lend lease, how could the British take the P-39 under lend lease when they had so publicly derided them as inferior under the hard money contract? "Oh these P-39s suck, but we'll take them for free"? They no longer needed them after winning the BoB and their internal fighter production was then adequate. They didn't need them and couldn't pay for them. Bell had the last laugh though. They got a $2million cash advance from the British in the original order. Bell was a relatively new company struggling under depression era economics and although $2mil doesn't sound like much today, in 1940 dollars it was a fortune and put them in the black for the rest of the war. And the Army took over the British order and had P-39s available from 1941 on.



Oh boy........
The British took delivery of 80 P-39s. The US took over 179. 212 are sent to Russia and 53 are lost at sea en-route. The British _may _have sent some of their P-39s on to Russia. This all takes some time and it takes until June 30th 1942 to get 93 P-400s to the Russians, this may be different than Aircobra Is

British P-39s had lethal concentrations of carbon monoxide in the cockpit after the nose guns fired. Firing the nose guns knocked the compass out of action. There were other faults.


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## Shortround6 (Mar 14, 2018)

P-39 Expert said:


> Sorry I don't understand how a supercharger works. I thought it compressed intake air to provide more power to the engine. Whether the power is reduced at lower altitudes because of a lower gear or because of a lower throttle setting on a single gear seems irrelevant to me. The sole purpose of low gear is to keep from overboosting the engine at takeoff. The same protection against overboosting at takeoff in a single speed engine is provided by reduced throttle. The Allison's single speed was high gear, it didn't have a low gear. It reduced boost at takeoff and low altitude by reduced throttle. Simple operation, lighter weight, more reliable.


 try reading it again. use of a lower gear meant better fuel economy at low altitude, it meant less of a cooling problem, it meant lower stress on the whole engine. 
The advantages of a lower gear are not just for take-off but at any time the plane is operating at pretty much under 10,000ft.

I would note that Wright built 2 speed R-1820s, 2 speed R-2600s, 2 speed R-3350s. Pratt and Whitney built 2 speed R-1830s, two speed R-2800s and they even built a few 2 speed R-4360s and some variable speed ones.
Rolls-royce built a lot ot two speed Merlins and Bristol built 2 speed Pegasus engines and 2 speed Hercules and 2 speed Centaurus engines.

Allison built a few two speed prototypes at the end of the war or just after. 

I guess they were all wrong along with the Russian, German and Japanese engine builders who all built 2 speed or variable speed superchargers.


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## P-39 Expert (Mar 14, 2018)

Shortround6 said:


> Not even close.
> I asked where the British *added *weight to get out off the contract. They took out over 100lbs compared to an American P-39 with 37mm gun. The P-39c had a pair of 30 cal guns in the fuselage
> View attachment 485844
> 
> ...


Okay, look at your photo of the P-39C. Says it weighed 7075# and made 379mph at 13000'. The British only got 359mph from theirs because they weighed 7850#. That's 775# lighter. But the real performance gain was in climb. That little P-39C at 7075# would climb at 3720fpm up to 12000'. How fast would the SpitV climb at that altitude? About 3000fpm or 750fpm less. The P-39C was faster and climbed faster than the SpitV. 
Now, that P-39C didn't have self sealing tanks or armor plate/glass necessary for combat. The tanks added 260# and the armor added 240# so now we're up to 7575#. But wait, we can deduct 300# because the self sealing tanks reduced fuel capacity by 50 gallons, 100# by removing the two .30 caliber MGs in the nose and another 100# by deleting the nose armor (too far from pilot for protection) leaving us back at the original 7075# that gave the 379mph/3700'climb. Now the P-39C is faster than the SpitV, climbs faster, carries 20 gallons more gas, easier to land and is heavily armed/armored. This plane was available from July 1941 and was the plane the Army should have purchased.

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## P-39 Expert (Mar 14, 2018)

Shortround6 said:


> try reading it again. use of a lower gear meant better fuel economy at low altitude, it meant less of a cooling problem, it meant lower stress on the whole engine.
> The advantages of a lower gear are not just for take-off but at any time the plane is operating at pretty much under 10,000ft.
> 
> I would note that Wright built 2 speed R-1820s, 2 speed R-2600s, 2 speed R-3350s. Pratt and Whitney built 2 speed R-1830s, two speed R-2800s and they even built a few 2 speed R-4360s and some variable speed ones.
> ...


I think that having to operate in single stage, two stage turbo (P-38) and two stage mechanical (P-63) may have had something to do with keeping the single speed for simplicity. But I still maintain it was no disadvantage vs. the two speed.


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## Graeme (Mar 14, 2018)

Shortround6 said:


> Basically Larry Bell sold the British and French an imaginary aircraft. When the British took delivery it would not come close to meeting the promised performance.



I've read (Ray Wagner) Bell promised the RAF the Model 14 (Airacobra I) to have a top speed of 383 mph at 14,400 ft, an altitude that should have been reached in 5 minutes 30 seconds. The American support group could not explain the speed loss and believed the company had greatly exaggerated their product's virtues. 

Other authors deride the British for believing Bell - knowing the turbo-supercharger had now been removed.

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## tomo pauk (Mar 14, 2018)

P-39 Expert said:


> Please accept my apology if you think I threw mud on you. Message boards are for debate and everyone always doesn't agree with everyone else. I'm just trying to explain to you what the numbers on the engine chart mean.



I'm from Croatia, not from UK, the country that was trying to 'weasel out' from P-39 contract, per your words. The term can mean " To back out of some situation or commitment in a selfish or sly manner:" by this on-line dictionary.
It is one thing to debate and discuss about numbers, that above was not about the numbers.


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## pbehn (Mar 14, 2018)

The British operated almost every major type of aircraft made by the USA, they operated the P-39 on one mission of four aircraft, if the P-39 was any use they would have taken it, many were ordered and diverted under lend lease. By the time the P-39 was operational in UK the FW-190 was on the other side of the channel, the British needed something superior to the MkV both in UK (for offense) and Malta (for defence) and the P-39 wasn't, if it had been it would have been put into service with begging letters for more as happened with the P51A (Mustang I).

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## P-39 Expert (Mar 14, 2018)

Graeme said:


> I've read (Ray Wagner) Bell promised the RAF the Model 14 (Airacobra I) to have a top speed of 383 mph at 14,400 ft, an altitude that should have been reached in 5 minutes 30 seconds. The American support group could not explain the speed loss and believed the company had greatly exaggerated their product's virtues.
> 
> Other authors deride the British for believing Bell - knowing the turbo-supercharger had now been removed.
> 
> View attachment 485848


Look at your SpitV speed of 364mph. Now look at the photo in post #119. P-39C speed of 379mph. Weight was the issue.


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## pbehn (Mar 14, 2018)

P-39 Expert said:


> Look at your SpitV speed of 364mph. Now look at the photo in post #119. P-39C speed of 379mph. Weight was the issue.


There were many issues, most of them embodied in the FW190.


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## Graeme (Mar 14, 2018)

P-39 Expert said:


> Look at your SpitV speed of 364mph. Now look at the photo in post #119. P-39C speed of 379mph. Weight was the issue.



Yes, post No.119 shows the P-39C with 379mph.
As I understand it the British received only 3 P-39C versions in July 1941 - but under test were capable of only 359 mph. Why?
However the bulk of the order were for the export version - the Airacobra I which according to Wagner was promised to the British as capable of 383 mph and their was even a claim that 392 mph had been attained on April 29 1941.
I get the weight issue - but then why were Bell telling the British speeds that weren't attainable?

In the end this is what they got...

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## Peter Gunn (Mar 14, 2018)

P-39 Expert said:


> Just which Luftwaffe plane(s) were so superior to the P-39?
> 
> *SNIP*


I'll venture to say the Bf-109 and the Fw-190 to name just two. I'd wager the Bf-110 and the Ju-87 and 88 would be tough nuts to crack. I'm a dyed in the wool lover of the P-39, mostly for it's looks and the whole tricycle landing gear forward thinking behind it, but in no way do I ever think it was going to be competitive anywhere but low down and overboosting the engine like the VVS pilots used it.

Visually for me, it's one great looking ship, right next to the Mustang, Macchi 202, Reggiane 2005, the Ki-61 just to name a few.

Unfortunately, no matter how good I think it looks, it still doesn't help it's real world performance.

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## Graeme (Mar 14, 2018)

A 1943 assessment - British of course....

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## Elmas (Mar 14, 2018)

Problems with the airplanes with central engines were the same in the world over: see

Piaggio P-119


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## P-39 Expert (Mar 14, 2018)

Peter Gunn said:


> I'll venture to say the Bf-109 and the Fw-190 to name just two. I'd wager the Bf-110 and the Ju-87 and 88 would be tough nuts to crack. I'm a dyed in the wool lover of the P-39, mostly for it's looks and the whole tricycle landing gear forward thinking behind it, but in no way do I ever think it was going to be competitive anywhere but low down and overboosting the engine like the VVS pilots used it.
> 
> Visually for me, it's one great looking ship, right next to the Mustang, Macchi 202, Reggiane 2005, the Ki-61 just to name a few.
> 
> Unfortunately, no matter how good I think it looks, it still doesn't help it's real world performance.


Okay, pick one. FW190 or Me109. Either one. Which version of each so we know we are comparing the correct version of the P-39.


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## drgondog (Mar 14, 2018)

P-39 Expert said:


> Cost was the big issue, especially for the British. They had stood alone against Germany since the fall of France and they were dead broke. They had to order those planes before France fell not knowing how long the war would run. After they were safely past the Battle of Britain and a German invasion was no longer possible, they moved to cut their losses and weasel out of not only the P-39 contract but a similar contract for P-38s that were ordered without turbochargers. Those were hard money contracts and payment was demanded. The British knew that if the Battle of Britain had not gone their way and they needed the P-39s that they could have quickly stripped the excess weight (.30 cal MGs, heater, unnecessary radio equipment) from those planes to make them competitive.



Where in the world are you drawing facts from?

The Brits were desperate to augment their own production capacity with aircraft equal to, or better than their own. The NA-73/Mustang I was accepted because it promised And Delivered the performance estimates NAA provided and it was better than the P-40 (and P-39) and P-38 at the altitudes RAF engaged in for most ops.

The P-39C was Not Ever competitive in combat ops because they did not come equipped with Required modifications such as self sealing tanks, etc. It was not even better than the Hurricane, certainly not as good as Mk 5 Spit or A6M or FW 190A-1 introduced into Operations 9/41. There was a reason the P-39D and subsequent were relegated to CAS as quickly as P-40E and P-38F could replace the P-400 in SWP and Africa. The AAF thought so much of the P-39, that the P-39 trained 52nd and 31st FG sent pilots only to England to be replaced by Spit V on reverse Lend Lease. The P-39D and subsequent, when stripped of wing armament & 20mm (mostly) replacing the 37mm, were 'almost' competitive at low altitude but still suffered appalling losses to BF 109F and FW 190A-2 and -3.

You will Never find a US or Commonwealth survivor of the Iron Dog experience against A6M, Tony, 109 or 190 that wished they could get the P-39 after they graduated to P-40F/N or 38E/F or P-47C/D.

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## P-39 Expert (Mar 14, 2018)

Graeme said:


> Yes, post No.119 shows the P-39C with 379mph.
> As I understand it the British received only 3 P-39C versions in July 1941 - but under test were capable of only 359 mph. Why?
> However the bulk of the order were for the export version - the Airacobra I which according to Wagner was promised to the British as capable of 383 mph and their was even a claim that 392 mph had been attained on April 29 1941.
> I get the weight issue - but then why were Bell telling the British speeds that weren't attainable?
> ...


THE REASON WAS WEIGHT. WEIGHT per your photo says the P-400 gross weight was 7845#. The P-39C weighed 7075#, that extra 770# is the difference in the 355mph vs the 379mph. Everything about the P-39C and the P-400 was exactly the same (engine, propeller, aerodynamics) except the additional 770#. To put this in perspective, you know the performance benefits of dropping your external tank for combat, it is quite substantial or the pilots would not have dropped them. A 75 gallon external tank only weighed 500# FULL OF FUEL. We're talking about 770# here. This is the same reason that the Russian P-39s outperformed the Luftwaffe, they discarded the useless 30 caliber wing guns and one of the radios (didn't use their frequency) and got much better performance.

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## buffnut453 (Mar 14, 2018)

P-39 Expert said:


> THE REASON WAS WEIGHT. WEIGHT per your photo says the P-400 gross weight was 7845#. The P-39C weighed 7075#, that extra 770# is the difference in the 355mph vs the 379mph. Everything about the P-39C and the P-400 was exactly the same (engine, propeller, aerodynamics) except the additional 770#. To put this in perspective, you know the performance benefits of dropping your external tank for combat, it is quite substantial or the pilots would not have dropped them. A 75 gallon external tank only weighed 500# FULL OF FUEL. We're talking about 770# here. This is the same reason that the Russian P-39s outperformed the Luftwaffe, they discarded the useless 30 caliber wing guns and one of the radios (didn't use their frequency) and got much better performance.



And where did much of that extra weight come from? Armour plating probably made up a fair amount of it. Per Shortround6's Post #110, the P-39C did not have armour plating. Given that armour was considered vital in ALL combat aircraft engaged in operations from mid-1940 onwards, we cannot consider the P-39C to be a truly combat-capable platform.

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## Shortround6 (Mar 14, 2018)

The P-39C did have armor, at least some and had BP glass, it didn't have self sealing tanks.
I would not use the Ray Wagner figures as gospel however. I used the photo to show the British aircraft only had 2 more RCMGs than the P-39C.

SOme of the disparity in figures come from different test conditions. 
http://www.wwiiaircraftperformance.org/P-39/P-39C_40-2988.pdf
A P-39C that did do 379mph, however it was at 6689lbs, roughly 400lbs lighter than the figure Ray Wagner used. One wonders what was left out, ammo or fuel? A bit of both?
Please note the comments where under no circumstance was the oil cooling satisfactory to USAAF standards and in both high speed level flight and in climb both oil and prestone cooling did not meet USAAF standards. 
Please note that Larry Bell & company were promising a LOT more than they could deliver.
Company performance chart.
http://www.wwiiaircraftperformance.org/P-39/P-39C_Chart-Bell_Aircraft-1400.jpg
Dated feb of 1940 which is well before the YP-39s flew.
I would note that the British had 675 Aircobras on order about 4 months before the first YP-39 flew let alone any P-39Cs 

British test
http://www.wwiiaircraftperformance.org/P-39/AH573.pdf

I would note that while the US tested climb at 3000rpm for the first 5 minutes the British used 2600rpm for the entire climb but this was British procedure. ALL british climb figures are done at max continuous or a 30 minute rating and not at a 5 minute rating.

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## pbehn (Mar 14, 2018)

Where did the USA use the P-39 with any success? Wiki states it was good at ground straffing and recon,


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## drgondog (Mar 14, 2018)

P-39 Expert said:


> Okay, pick one. FW190 or Me109. Either one. Which version of each so we know we are comparing the correct version of the P-39.


 
The P-39D-2 was operational as the first 'combat ready' P-39 (self sealing tanks/uprated engine) and introduced into combat ops in Spring 1942. 

Combat experience shows that they are ineffectual at interception (the original design Purpose) at altitudes at or above 20,000 feet against Japanese. It was so bad that the P-39 and P-400 are relegated to CAS as USMC Wildcats take over air defense until P-38F arrive. At MP, the P-39D-2 climb rate = max at 2400fpm at 7,000 feet, declines to 1900 fpm at 15000 at GW=7631 # (ref A100K by Dean, pg 191 Top speed at MP= 371mp at ~12K, at SL = 310mph.

The P-40E had peak ROC at 2400fpm @15,000 ft, Top speed at 310mp at SL/365 at 15K at 8,400# and MP w/200 hp less.(than 39-D-2).

The Bf 109F-2/G-1 at same period had 3,427 fpm at SL; 2,644 at 19,000 feet; Top speed 314mph at SL; 391mph 22,000 feet -----------> at all altitudes a better climb rate and top speed than the P-39 and P-40.

The FW 190A-2 earlier - Digging now for same reference data, but greater in all respects except turn rate vs Spit V.

For the A-5, Peak ROC at SL=2950fpm; 2000fm @20,000. Top speed = 352mph; 408mph @21000.

The question is" what 1st line fighter - US, RAF, LW, IJN was Not superior combat a/c than any P-39?

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## drgondog (Mar 14, 2018)

P-39 Expert said:


> THE REASON WAS WEIGHT. WEIGHT per your photo says the P-400 gross weight was 7845#. The P-39C weighed 7075#, that extra 770# is the difference in the 355mph vs the 379mph. Everything about the P-39C and the P-400 was exactly the same (engine, propeller, aerodynamics) except the additional 770#. To put this in perspective, you know the performance benefits of dropping your external tank for combat, it is quite substantial or the pilots would not have dropped them. A 75 gallon external tank only weighed 500# FULL OF FUEL. We're talking about 770# here. This is the same reason that the Russian P-39s outperformed the Luftwaffe, they discarded the useless 30 caliber wing guns and one of the radios (didn't use their frequency) and got much better performance.



It was what it was. Weight is an integral part of the design philosophy of the company making the aircraft as well as the standards of the purchasing agency. The AAF required slightly higher Limit and Ultimate Load factors than Brits. The P-39 was designed to AAF standards for Structural considerations (8G Limit and 12G Ultimate) for original design combat gross weight. The YP-39 was designed at a much lower weight than ultimately included by the time combat mods were applied -As Required - it only had one path, namely to grow in Gross weight based on combat operational requirements. The P-39 had less range than a Spit and a 109, it peaked out on ROC at 7K, then petered out - making it useful close to front lines at low altitude. It was slaughtered in air to air combat versus A6M and Ki-43 and -61, it was hammered versus FW 190 A-3/A-5 and Bf 109F and G in North Africa. The Russians Claimed 'success' but not reflected in eyes of LW which considered it our (US made) 'poorest fighter'. By the time Bell learned from the mistakes and designed the P-63, it was useful for Russia but too late for US/Commonwealth operations by a year. The comparable period a/c for P-63 included Spit IX, Tempest, P-51B, P-47D, P-38H, Yak 3. Useful to Russians, but not necessary in contrast to Yak and Laag's coming on line.

The P-39C did not have self sealing tanks, oxygen equipment. The P-400 arrived in SWP with No oxygen equipment (VVS didn't need the O2).

The P-39D-2 had the more powerful engine and STILL couldn't climb past 20,000 feet (in less than 15 minutes) to intercept incoming Japanese bombers at Guadalcanal, even with O2 equipment - simply because that Allison peaked out between 12K and 14K

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## Peter Gunn (Mar 14, 2018)

P-39 Expert said:


> Okay, pick one. FW190 or Me109. Either one. Which version of each so we know we are comparing the correct version of the P-39.


I think drgondog has answered this more expertly than I could, my short answer would be "any marque of either v any marque P-39".

NAA promised a plane better than the P-40 and boy did they deliver.

Bell promises? Allow me to quote John Wayne... "I"ve been promised a posse, which I suspect will be Looong on promise and short on posse". I think you get my drift.

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## P-39 Expert (Mar 14, 2018)

Shortround6 said:


> The P-39C did have armor, at least some and had BP glass, it didn't have self sealing tanks.
> I would not use the Ray Wagner figures as gospel however. I used the photo to show the British aircraft only had 2 more RCMGs than the P-39C.
> 
> SOme of the disparity in figures come from different test conditions.
> ...


Glad you are sourcing wwiiaircraftperformance, that is the source of most of my radical theories on the P-39. Please indulge me, print the P-39K performance chart. Then take a pencil and chart the performance figures of the A6M2, SpitV, Me109G1 and maybe the Wildcat over the P-39K lines. Then chart the P-39C figures in your report above. This will clearly show the performance of the P-39C as compared to the other planes. Couple of observations, the 6689# figure is with "mean fuel" which is roughly half the tank capacity. Add back half the fuel 360# and you get approximately your 7075# gross weight. Virtually all the American fighter tests used this "half fuel" figure for gross weight, since you couldn't fight your enemy full of fuel since you would still be on the runway and you couldn't fight with no fuel for obvious reasons so for calculations they used mean fuel.
Now when you graph the P-39C climb take one thing into account: see that little curved line starting at 12500' lowering the climb figure? The engine was at that time limited to 5 minutes at maximum power. So these tests had the pilot climb at full power (3000rpm) for the 5 minutes and then reduce rpm to 2600 (maximum continuous or max cruise) for the remainder of the climb. Check the P-38, P-40 and P-47 tests before August 1942 and they all reduced power from max power to their respective maximum cruise power in climb at the 5 minute mark per regs. The Army changed the 5 minute maximum to 15 minutes maximum RETROACTIVE during mid year 1942 for virtually all their fighter combat engines (V-1710, R-2800, etc.). Now all these planes could climb at full power (3000rpm for the V-1710) for the full 15 minutes which greatly increased their climb rates. Give the P-39C the same benefit of 3000rpm for 15 minutes. Take the rate of climb at 5 minutes (3700fpm) and from that point draw your climb rate line up diagonally to a ceiling of about 37000' and you have the climb rate for the P-39C at 15 minute full power. Full power (3000) for 15 minutes in climb makes a huge difference over full power for 5 minutes then reducing power to max continuous/max cruise (2600rpm). Once you graph all these lines on the same graph it is easy to see the performance of each plane at every altitude.

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## Shortround6 (Mar 14, 2018)

The US use of the Aircrobra was also handicapped by climate. They usually try to adjust or correct performance figures to a "standard" day of 59 degrees F or 15 degrees C. and standard air pressure. Operating at temperatures much higher reduce performance due to less lift from the wing, less power form the engine (even at the same pressure) and less 'bite' from the propeller. 
For some weird reason the US sometimes gave pilots charts that used a base line of 32 degrees F (0 degrees C) and the P-39 is one of those planes that use the point of freezing as a base line with notes to increase the take off distance and the time to hight by 10% for every 20 degrees F (or 10 degrees C) above the baseline. SO on a 92 Degree F day on a pacific Island or in North Africa the P-39 will need 30% longer runways and take 30% more time to make it to 15,000ft than the charts say. Other planes also suffered a similar loss of performance but if they started with a 59 degree base then they might only be around 15% below book figures. You can have hot days in Russia but a lot of their use would have been on days without such a large difference from the book figures. 
P-39 had one of the higher wing loadings of the early fighters and one of the worst power loadings. (Not counting WEP) and may be affected even more by extreme heat.

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## Elmas (Mar 14, 2018)

_“Omnia in mensura et numero et pondere disposuisti.”_

Thou hast ordered all things in measure, and number, and weight.

Book of Wisdom, 11:21.

I had my M.of Sc. in Structural Engineering in 1979, so numbers have been, and still are, a very important part of my life. But, IMHO of an humble technician, sheer numbers are not at all the best way to evaluate the overall performance of an airplane, let alone to compare two or more.

In an airplane there are many other parameters to evaluate, not all susceptible to numerical evaluation: the design of an airplane is the result of many compromises, and the best airplane it is not the one that has the best numbers, but the one wich is a better compromise. And often this compromise depends on the circumstances: best compromise for PTO can be totally different for ETO.

At the end of the ‘60s, in Tobruk, Lybia, I had long conversations with a Gentleman who had served as Navigator in Lancasters and was ending his career in the RAF commanding the Rescue Service at El Adem airport. At my question wich one was better, if Spitfire or Me 109 ( I was very young, then…) he replied _“Oh, they were pretty equal. One had some slight advantages, Spitfire turned better, 109 was a little bit faster… the difference was made by a better training of the average pilot of the RAF than the average pilot of the Luftwaffe…”_ So his words.

Btw, P-39, as already said in many other posts, was hated by Italian Pilots who received this aeroplane in the Cobelligerent Air Force. It was assigned to the 4° Stormo, the spearhead of Regia Aeronautica, with Pilots seasoned with years of war. They accepted to fly it just for discipline and accidents were numerous.

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## Shortround6 (Mar 14, 2018)

P-39 Expert said:


> The Army changed the 5 minute maximum to 15 minutes maximum RETROACTIVE during mid year 1942 for virtually all their fighter combat engines (V-1710, R-2800, etc.). Now all these planes could climb at full power (3000rpm for the V-1710) for the full 15 minutes which greatly increased their climb rates. Give the P-39C the same benefit of 3000rpm for 15 minutes.



That might lead to a lot wrecked engines. I would double check your source on that.

The V-1710 went through 3 different crankshafts by Early 1942. The 3rd crankshaft stayed unchanged until the very late war 12 counterbalance cranks. 
The first crankshafts were plain steel, by that I mean no special surface finish. the Next crankshaft was shot peened and had a much improved resistance to stress. It would operate practically forever at a level that would destroy the plain crankshaft in fairly short order. This was followed by a crankshaft that was both shot peened and nitrided. This crank would operate forever at stress levels that would destroy the shot peened crankshaft in short order. 

Allowing full combat power for 15 minutes at a time was going to significantly shorten the life of the older crankshafts. The new crankshafts could be dropped into an old engine at overhaul time. Without some regard for the older engines this would be a very poor blanket policy. I don't know when the shot peened cranks were introduced but obviously the P-39C and the majority of the Ds and P-400s did not have the nitrided crankshafts. 

You may also have a cooling problem, use of military power was always dependent on coolant and oil temperatures. If the temperature limit/s were exceed the engine had to be throttled back regardless of the number of minutes that been spent at that power level. If the P-39 was exhibiting marginal cooling in 5 minutes or under (although it can get pretty hot in Ohio in the summer) then pushing the engine for 15 minutes may not be a good idea. 

I have no idea what, if anything, they did to address the cooling issues of the P-39C. One hopes they did something because if you are having cooling issues at 1150hp then with 1325hp engines or operating at WEP settings things are going into the red zone real quick.

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## drgondog (Mar 14, 2018)

P-39 Expert said:


> Glad you are sourcing wwiiaircraftperformance, that is the source of most of my radical theories on the P-39. Please indulge me, print the P-39K performance chart. Then take a pencil and chart the performance figures of the A6M2, SpitV, Me109G1 and maybe the Wildcat over the P-39K lines. Then chart the P-39C figures in your report above. This will clearly show the performance of the P-39C as compared to the other planes. Couple of observations, the 6689# figure is with "mean fuel" which is roughly half the tank capacity. Add back half the fuel 360# and you get approximately your 7075# gross weight. Virtually all the American fighter tests used this "half fuel" figure for gross weight, since you couldn't fight your enemy full of fuel since you would still be on the runway and you couldn't fight with no fuel for obvious reasons so for calculations they used mean fuel.
> Now when you graph the P-39C climb take one thing into account: see that little curved line starting at 12500' lowering the climb figure? The engine was at that time limited to 5 minutes at maximum power. So these tests had the pilot climb at full power (3000rpm) for the 5 minutes and then reduce rpm to 2600 (maximum continuous or max cruise) for the remainder of the climb. Check the P-38, P-40 and P-47 tests before August 1942 and they all reduced power from max power to their respective maximum cruise power in climb at the 5 minute mark per regs. The Army changed the 5 minute maximum to 15 minutes maximum RETROACTIVE during mid year 1942 for virtually all their fighter combat engines (V-1710, R-2800, etc.). Now all these planes could climb at full power (3000rpm for the V-1710) for the full 15 minutes which greatly increased their climb rates. Give the P-39C the same benefit of 3000rpm for 15 minutes. Take the rate of climb at 5 minutes (3700fpm) and from that point draw your climb rate line up diagonally to a ceiling of about 37000' and you have the climb rate for the P-39C at 15 minute full power. Full power (3000) for 15 minutes in climb makes a huge difference over full power for 5 minutes then reducing power to max continuous/max cruise (2600rpm). Once you graph all these lines on the same graph it is easy to see the performance of each plane at every altitude.


Got a better idea for you. Compare 'Period P-39 vs Period 'whatever' at the rated Hp and Boost and combat weight for each?

The P-38C was in same period as the Bf 109F-1 and Spit Vb, delivered in January, 1941 with 20th completed in March 1941, None of the three P-39C's were close to meeting Bell claims for performance, nor were the production P-39D-1 and -2 delivered at the same time as the FW 190A-1. It was a hazard to life and limb without self sealing tanks and O2.

The P-39Q, introduced in Spring 1943 was first to achieve reliable 3200 fpm in Combat Power at S/L but reducing to ~ 3000 fm at 12000 and dropping to about 2000fpm at 20K. . Performance tests flown at design Combat load of 7570 #, but only included 87 gallons of fuel. With 33 gallon fuselage kit, the fuel load jumped to 120 gallons and 200 more pounds. It reached US combat zone with 332nd FG in February 1944 but were quickly swapped for P-40, then P-51B by June 1944.

So the P-39Q period to period has to compete with P-51B/C, P-38J-15, Spit XIV, FW 190A-7 and A-8, Bf 109G-6 - all of which climb faster at rated Combat Power (available with 150 grade fuel for example for the P-51B), are faster in level flight - at all altitudes- and roll with or better than the P-39Q. The Q would normally outturn all the above fighters except the Spitfire and the P-38J with boosted ailerons and skilled use of throttles. It has the shortest combat radius, is a sad sack above 20,000 feet and can't find a fighter to fight on even terms except for the occasional LW fighter flying low and medium fast where the P-39Q performs well... The ETO banished them to Bomb Squadrons in the 12th AF for close air support, the 9th/15th and 8th AF rejected them from operating in THEIR airspace, the SWP relegated them to CAS and then got rid of them as fast as P-40/P-38/P-47 and P-51s arrived.

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## P-39 Expert (Mar 14, 2018)

Here you go boys, the vaunted FW190A6 vs. P-39N is attached. Looks like the little Cobra is faster below 5km, and the same combat speed at 8km (26000'). A little slower than the FW190's emergency maximum good for one minute with liquid injectant. US war emergency was good for 5 minutes and the engine had to be torn down and inspected after every use. Bet that German emergency maximum was an engine destroyer. Second page is rate of climb. The P-39N climbs significantly faster at all altitudes, period. A whole hell of a lot faster below 6km (20000') and about 65% faster at 8km (26000'). Personally, give me the best climb rate.


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## Hansie Bloeckmann (Mar 14, 2018)

Piper106 said:


> Three comments. First the mixed armament thing, trying to deal with two different trajectories when deflection shooting. That is why I suggested an all 50 cal armament package. Second, history tells us the most US versions of the 20mm Hispano cannon had almost as much trouble with jams/un-reliability early in the war as the 37mm. Another point for staying with just Browning 50 cal guns. Finally, as far as I know, during WW2 'wet wings' implied unprotected fuel tanks. I am suggesting adding self-sealing rubber bag tanks as per other American fighters.


I'm with the school of thought that endorses all MG's- whether wing, cowl or through the prop hub be the Browning M-2 in .50 cal. Much more reliable than the 37 mm cannon, and as General Patton once remarked: "In combat, a gun that won't fire reliably is as useful as a pecker on a Pope" I like the prop hub mounting, when feasible, as then, where the nose is pointed, the rounds go--Hansie


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## pbehn (Mar 14, 2018)

P-39 Expert said:


> Here you go boys, the vaunted FW190A6 vs. P-39N is attached. Looks like the little Cobra is faster below 5km, and the same combat speed at 8km (26000'). A little slower than the FW190's emergency maximum good for one minute with liquid injectant. US war emergency was good for 5 minutes and the engine had to be torn down and inspected after every use. Bet that German emergency maximum was an engine destroyer. Second page is rate of climb. The P-39N climbs significantly faster at all altitudes, period. A whole hell of a lot faster below 6km (20000') and about 65% faster at 8km (26000'). Personally, give me the best climb rate.


Is this a wind up? Are you saying that if the RAF and US air forces had been given the correct graph and data then the P-39 would have been a winner in service? 601 squadron changed from Hurricane Mk IIs to P39s flew one mission with it then changed to Spitfire Mk Vb and went to Malta. The P 39 would have been no use at all in Malta. In the UK the FW 190 was superior to the Spitfire MkV forcing the Typhoon into service early. When the P51A arrived it was used because at low / medium altitudes it was a top performer, liked by all who flew it. As soon as the P 51 arrived people started figuring out how to put a Merlin in it because its only problem was altitude performance. Merlins were also put in P-40s for the same reason. Did anyone ever suggest putting a Merlin in a P-39?

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## buffnut453 (Mar 14, 2018)

Hansie Bloeckmann said:


> I'm with the school of thought that endorses all MG's- whether wing, cowl or through the prop hub be the Browning M-2 in .50 cal. Much more reliable than the 37 mm cannon, and as General Patton once remarked: "In combat, a gun that won't fire reliably is as useful as a pecker on a Pope" I like the prop hub mounting, when feasible, as then, where the nose is pointed, the rounds go--Hansie



Depends on the timeframe you're talking about. The 50cal only became an effective weapon in wing installations in 1942 which wouldn't be much use to the RAF in the Battle of Britain.

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## tomo pauk (Mar 14, 2018)

buffnut453 said:


> Depends on the timeframe you're talking about. The 50cal only became an effective weapon in wing installations in 1942 which wouldn't be much use to the RAF in the Battle of Britain.



Buy the heavy machine guns in Belgium or Italy in the second half of 1930s if the US types were not up the task with 600 rpm.



Hansie Bloeckmann said:


> I'm with the school of thought that endorses all MG's- whether wing, cowl or through the prop hub be the Browning M-2 in .50 cal. Much more reliable than the 37 mm cannon, and as General Patton once remarked: "In combat, a gun that won't fire reliably is as useful as a pecker on a Pope" I like the prop hub mounting, when feasible, as then, where the nose is pointed, the rounds go--Hansie



Having 3 synchroised .50s under the cowl of the P-39 and 4th firing through the prop, with wing guns deleted, would've made the P-39 lighter and would've also shaved some drag. I'd also remove one of radio sets, and replace the rear-most armor with duraluminium deflection plate.

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## Glider (Mar 14, 2018)

Taking the points one at a time.


P-39 Expert said:


> Just which Luftwaffe plane(s) were so superior to the P-39?


The P39 arrived in Aug 1941 roughly when the Fw 190 entered service with the Luftwaffe and the Me109F was the standard fighter both of which had clear advantages over the P39. 


> Regarding lend lease, how could the British take the P-39 under lend lease when they had so publicly derided them as inferior under the hard money contract? "Oh these P-39s suck, but we'll take them for free"? They no longer needed them after winning the BoB and their internal fighter production was then adequate. They didn't need them and couldn't pay for them. Bell had the last laugh though. They got a $2million cash advance from the British in the original order. Bell was a relatively new company struggling under depression era economics and although $2mil doesn't sound like much today, in 1940 dollars it was a fortune and put them in the black for the rest of the war. And the Army took over the British order and had P-39s available from 1941 on.


The RAF didn't need the P39 because it was so far behind the performance of contemporary fighters and your right, production was more than sufficient. The point behind the comment on lend lease was if and I repeat if, the RAF had needed them then they could have been supplied via lend lease.
Your observation on Bell being saved by the UK financially also applied to Curtis. They had huge orders from Europe for the P40 and almost none from the USA (or UK). They spent a lot of money expanding the productions lines but when Europe fell there was no money coming in and the UK taking up the cost of all those orders saved them. Had we not done so its an interesting what if, what would the USAAF look like in late 1941 without Bell or Curtis as politically its unlikely that the US authorities would have spent the money.


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## Glider (Mar 14, 2018)

Apologies to one and all as I hadn't seen this posting when I replied to the other response. 


P-39 Expert said:


> Cost was the big issue, especially for the British. They had stood alone against Germany since the fall of France and they were dead broke. They had to order those planes before France fell not knowing how long the war would run. After they were safely past the Battle of Britain and a German invasion was no longer possible, they moved to cut their losses and weasel out of not only the P-39 contract but a similar contract for P-38s that were ordered without turbochargers. Those were hard money contracts and payment was demanded. The British knew that if the Battle of Britain had not gone their way and they needed the P-39s that they could have quickly stripped the excess weight (.30 cal MGs, heater, unnecessary radio equipment) from those planes to make them competitive.


I am sorry but this is total rubbish. The P39's were ordered by the UK in September 1940 when it was already clear that the BOB had been won and of course France had fallen some time before. As a result it wasn't a case of cutting losses, or weaseling out of a contract (not a fan of the UK are you) it was because the P39 wasn't a match for the latest fighters and wasn't combat ready for Ground attack, a role it could have been very useful in. We did what we did with later Hurricanes, send them to Russia or somewhere else anywhere apart from Europe. 
Just a thought did the UK pay for the P400's used by the USAAF?

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## pbehn (Mar 14, 2018)

The British were desperate for fighters in 1941 as Russia was desperate for the British to put pressure on Germany. However those fighters had to be superior in every respect to the Spitfire MkV, some fighter sweeps over France with Mk Vs resulted in no aircraft returning home. Being equal to the MkV was of no use at all because that was in no way good enough. To be any use at all the P39 had to be the equal of the P51A and Spitfire MkIX and it wasn't.


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## Hansie Bloeckmann (Mar 14, 2018)

buffnut453 said:


> Depends on the timeframe you're talking about. The 50cal only became an effective weapon in wing installations in 1942 which wouldn't be much use to the RAF in the Battle of Britain.


Yes, and didn't Browning chamber the .30 cal. 1919 MG for the British .303 cal. round?? Not sure, but seems likely to me. Thanks


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## Hansie Bloeckmann (Mar 14, 2018)

tomo pauk said:


> Buy the heavy machine guns in Belgium or Italy in the second half of 1930s if the US types were not up the task with 600 rpm.
> 
> 
> 
> Having 3 synchroised .50s under the cowl of the P-39 and 4th firing through the prop, with wing guns deleted, would've made the P-39 lighter and would've also shaved some drag. I'd also remove one of radio sets, and replace the rear-most armor with duraluminium deflection plate.


Agree, the weight of 4 .50 Brownings in the wings, fully loaded and mounted properly would most assuredly have increased the drag..

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## pbehn (Mar 14, 2018)

Glider said:


> Apologies to one and all as I hadn't seen this posting when I replied to the other response.
> 
> I am sorry but this is total rubbish. The P39's were ordered by the UK in September 1940 when it was already clear that the BOB had been won and of course France had fallen some time before. As a result it wasn't a case of cutting losses, or weaseling out of a contract (not a fan of the UK are you) it was because the P39 wasn't a match for the latest fighters and wasn't combat ready for Ground attack, a role it could have been very useful in. We did what we did with later Hurricanes, send them to Russia or somewhere else anywhere apart from Europe.
> Just a thought did the UK pay for the P400's used by the USAAF?


Not only did the British order 675 P39s named as "Caribou" in 1940, there were also another 150 ordered under lend lease in 1941. When they arrived they were tested and tried out, found to be not good enough so all were sent or diverted to Russia.


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## buffnut453 (Mar 14, 2018)

tomo pauk said:


> Buy the heavy machine guns in Belgium or Italy in the second half of 1930s if the US types were not up the task with 600 rpm.



The problem there is that you're applying the retrospectroscope. In the mid-1930s, pretty much every fighter in the world was armed with 2 or 4 rifle-calbre machine guns. Even the early P-40s carried a mix of 30cal and 50cal weapons as late as 1941. I think it's asking a bit much for the crystal ball to foresee that 50cal weapons would be the preferable option in time to impact the Battle of Britain...and that's before we consider the other logistical issues. 

Additionally, the main problem with the US 50cal in wing mounts seems to have been with the guns jamming due to mis-feeds. Now that can be blamed on poor/non-representative testing, but the simple fact remains that every US fighter with wing-mounted 50cals suffered stoppages right through until the latter half of 1942: P-40, F4F, F2A and the P-51.


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## Shortround6 (Mar 14, 2018)

tomo pauk said:


> Buy the heavy machine guns in Belgium or Italy in the second half of 1930s if the US types were not up the task with 600 rpm.



The Breda 12.7 machine gun was just about as heavy as the US Browning.50. and was rated at 700rpm instead of 600. perhaps the fact that the bolt only had to move 79% as far due to the shorter ammo has something to do with the 16-17% higher rate of fire  

I also have serious doubts about the Belgian guns rate of fire. Like how long they could keep it up. I have no idea how close in contact the FN factory was with Colt although they seemed to co-operate on other things but it took the US 3 1/2 to 4 years to get the .50 cal up to the rate of fire of the Belgian guns _with an acceptable degree of reliability. _That is an acceptable number of jams and broken parts per 1000 rounds fired. Perhaps the US standards were too high? 





> Having 3 synchroised .50s under the cowl of the P-39 and 4th firing through the prop, with wing guns deleted, would've made the P-39 lighter and would've also shaved some drag. I'd also remove one of radio sets, and replace the rear-most armor with duraluminium deflection plate.



Other things in the nose of the P-39 include an oil tank for the reduction gear box, a glycol tank (not to be confused with the Prestone tank). the aircraft battery,
any oxygen tanks for the pilot. P-39s carried 200rpg for the .50 cal 
I would note that 30 rounds of 37mm ammo weighs about the same as 200 rounds of .50 cal ammo. Yanking one 238lb gun and 60 lbs of ammo (298lbs) and replacing it with two guns weighing 138lbs and using 120lbs of ammo (258lbs) isn't really going to turn the P-39 into rocket plane. 
Just use skinny pilots 

This is only half jest. Early weight tables called for 160lb allowance for the pilot. later tables increased the weight to the more standard 200lbs although the 200lbs includes parachute. Not sure if the 160lb figure does. 

Some units may have flown the P-39 with only 300rpg for the wing .30 cal but this saves about 165lbs. 
30 rounds of 37 is less than 15 seconds firing time.
200 rounds of .50 cal is around 20 seconds assuming you can get the synchronized guns up to 600rpm. 
300 rounds of .30 is about 15 seconds for the wing guns. 1000 rounds is ridiculous. 
Under wing .50s had 300rpg and that is good for around 23 seconds at 780rpm.

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## parsifal (Mar 14, 2018)

RAF was very unhappy with the p-39s it received. it is not exaggerating to say they basically wanted to return them and get their money back. This is despite the generally favourable combat comparisons carried out at Duxford

One needs to remember the old axiom has it that the bombers deterimine the altitude at which fighters must fight. In the SWPA, the Japanese sent their bombers over generally at between 18,000 and 22,000 ft., sometimes substantially higher, seldom much lower. The air was generally very humid and heavy but with high levels of turbulence due to the frequent presence of large mountains. While the P-39 could get that high, it took it a long time to do so, so the and the opportunities for high altitude intercepts were few. Effectively, it was all done by about 17,000 ft. It was at its best below about 12,000 ft. Considering that the mountains in New Guinea rose to over 14,000 ft., and in the early days of the conflict both sides were going back and forth over those mountains to get at each other, the P-39 was at an instant disadvantage. Despite some rather fantastic claims by the USAAC units defending Port Morseby after March 1942, IJAAF losses to Cobra equipped units have been shown post war to be largely unsubstantiated.
.
The VVS was the other major user of the type. Soviets fought over terrain much like that of Iowa, were based close to the enemy, and the Germans chose to send their bombers over at medium and low altitudes. So none of the factors that worked against the P-39 in New Guinea were present on the Eastern Front.

Also worth noting. An RAF Duxford comparison test of a captured Me 109E and P-39C showed the Bell outperforming the 109 in every category except rate of climb when below 15,000 ft. The P-39 could easily out-turn the 109--it took the 'Cobra less than 720 degrees to get on the tail of an Me that was planted on its tail. So the P-39 should have had no trouble dealing with the 109 at the altitudes common in the East. But this assumes the 109 would accept a full turning fight, which was seldom the case. In the SWPA, however, the P-39 units again opted for manouvre fighting, but this time they were up against an aircraft that excelled at horizontal manouvre. Not only were the P-39s forced to fight at altitudes above where they were competitive, it had to contend with fighters that were much, much more maneuverable than it was. P-39 squadrons routinely stripped off the wing guns to get more performance, and some even ripped out the armor plating (which weighed about 750 pounds) to get yet more performance, preferring to reduce their susceptibility to battle damage (as the Japanese did) at the expense of vulnerability to it.

That said, the P-39 was not a complete failure in New Guinea. The two groups equipped with it--the 8th and 35th--performed quite effectively, but their victory claims are so dicey as to be not worth much consideration. . The two squadrons of the 8FG that relieved RAAF 75 Squadron at Port Moresby at the end of March, 1942, were the only fighter force available to stop the Japanese air onslaught. This they did, although at great cost.

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## Shortround6 (Mar 15, 2018)

I would note that by the time the P39 was coming into service (fall of 1941) the 109E was on the way out and the 109F was equiping more squadrons every month. WHile the 109F may not have turned any tighter than the 109E it could sustain height or speed in a turn much better than the 109E. 

I also have doubts about pulling 750lbs of armor out of a P-39. according to the weight tables there wasn't over 275lbs to begin with. Not to mention that an empty P-39D-2/P-400 weighed about 5550-5600lbs, basic weight (empty equipped) with guns, armor, radio, and oxygen was 6330-6420lbs. 

Now _perhaps _you could save 750lbs (or close to it) by taking out the four wing guns (and their ammo) the armor *and *about another 100-130 worth of _stuff _(no oxygen over the Owen Stanleys? No radio? leave out 20 gallons of gas?) 
I have no doubt that the pilots and crews did strip stuff out of the planes, however the weight saved by stripping the armor seems to be abut as exaggerated as the some of the air to air victories.


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## Peter Gunn (Mar 15, 2018)

pbehn said:


> Is this a wind up?
> 
> *SNIP*


My vote is an unequivocal "Yes".


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## Hansie Bloeckmann (Mar 15, 2018)

Shortround6 said:


> The Breda 12.7 machine gun was just about as heavy as the US Browning.50. and was rated at 700rpm instead of 600. perhaps the fact that the bolt only had to move 79% as far due to the shorter ammo has something to do with the 16-17% higher rate of fire
> 
> I also have serious doubts about the Belgian guns rate of fire. Like how long they could keep it up. I have no idea how close in contact the FN factory was with Colt although they seemed to co-operate on other things but it took the US 3 1/2 to 4 years to get the .50 cal up to the rate of fire of the Belgian guns _with an acceptable degree of reliability. _That is an acceptable number of jams and broken parts per 1000 rounds fired. Perhaps the US standards were too high?
> 
> ...


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## Hansie Bloeckmann (Mar 15, 2018)

Shortround6 said:


> The Breda 12.7 machine gun was just about as heavy as the US Browning.50. and was rated at 700rpm instead of 600. perhaps the fact that the bolt only had to move 79% as far due to the shorter ammo has something to do with the 16-17% higher rate of fire
> 
> I also have serious doubts about the Belgian guns rate of fire. Like how long they could keep it up. I have no idea how close in contact the FN factory was with Colt although they seemed to co-operate on other things but it took the US 3 1/2 to 4 years to get the .50 cal up to the rate of fire of the Belgian guns _with an acceptable degree of reliability. _That is an acceptable number of jams and broken parts per 1000 rounds fired. Perhaps the US standards were too high?
> 
> ...


I understood that the Germans took over the FN arms factories in Liegte, when they occupied Belgium in 1940--thus cutting off any ties with American gun companies (Colt) and designers (Browning)--I doubt the US standards for MG's, whether for aircraft, naval vessels or ground and armor troops were set too high--IMO anyway. Hansie


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## Timppa (Mar 15, 2018)

parsifal said:


> Also worth noting. An RAF Duxford comparison test of a captured Me 109E and P-39C showed the Bell outperforming the 109 in every category except rate of climb when below 15,000 ft. The P-39 could easily out-turn the 109--it took the 'Cobra less than 720 degrees to get on the tail of an Me that was planted on its tail. So the P-39 should have had no trouble dealing with the 109 at the altitudes common in the East. ...ripped out the armor plating (which weighed about 750 pounds)



Also worth noting, P-39D was the first mass produced variant, about 650lb heavier than the -C. In the Eastern Front, about 1942 it (-D)was against the Bf109F rather than E, a completely better beast. 750 lb armour is not correct. It doesn't pass my BS meter even without checking.

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## P-39 Expert (Mar 15, 2018)

drgondog said:


> Got a better idea for you. Compare 'Period P-39 vs Period 'whatever' at the rated Hp and Boost and combat weight for each?
> 
> The P-38C was in same period as the Bf 109F-1 and Spit Vb, delivered in January, 1941 with 20th completed in March 1941, None of the three P-39C's were close to meeting Bell claims for performance, nor were the production P-39D-1 and -2 delivered at the same time as the FW 190A-1. It was a hazard to life and limb without self sealing tanks and O2.
> 
> ...


See post #148 for the facts.


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## buffnut453 (Mar 15, 2018)

P-39 Expert said:


> See post #148 for the facts.



Ok, this is really starting to look like a wind-up. Post #148 makes no mention of self-sealing fuel tanks or O2. You may well think that your pretty graphs make your point but they still miss the fundamental issue that the P-39C was NOT combat capable. The P-39D was the first truly combat-ready variant but it was a much heavier beast...with consequent loss of performance.

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## Peter Gunn (Mar 15, 2018)

P-39 Expert said:


> See post *#163* for the facts.


Fixed that for ya.


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## P-39 Expert (Mar 15, 2018)

buffnut453 said:


> Ok, this is really starting to look like a wind-up. Post #148 makes no mention of self-sealing fuel tanks or O2. You may well think that your pretty graphs make your point but they still miss the fundamental issue that the P-39C was NOT combat capable. The P-39D was a much heavier beast...with consequent loss of performance.


Pls explain "wind up"?


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## buffnut453 (Mar 15, 2018)

Wind-up: a joke meant to deceive someone (eg "He's winding you up" meaning "he's pulling your leg" or "he's kidding you").

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## P-39 Expert (Mar 15, 2018)

Shortround6 said:


> That might lead to a lot wrecked engines. I would double check your source on that.
> 
> The V-1710 went through 3 different crankshafts by Early 1942. The 3rd crankshaft stayed unchanged until the very late war 12 counterbalance cranks.
> The first crankshafts were plain steel, by that I mean no special surface finish. the Next crankshaft was shot peened and had a much improved resistance to stress. It would operate practically forever at a level that would destroy the plain crankshaft in fairly short order. This was followed by a crankshaft that was both shot peened and nitrided. This crank would operate forever at stress levels that would destroy the shot peened crankshaft in short order.
> ...


You are truly an expert on crankshafts. My source for the 15 minutes is wwiiaircraftperformance.net. The actual government performance docs. Check them if you like.


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## P-39 Expert (Mar 15, 2018)

buffnut453 said:


> Wind-up: a joke meant to deceive someone (eg "He's winding you up" meaning "he's pulling your leg" or "he's kidding you").


Thanks, I had never heard that.


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## Shortround6 (Mar 15, 2018)

P-39 Expert said:


> You are truly an expert on crankshafts. My source for the 15 minutes is wwiiaircraftperformance.net. The actual government performance docs. Check them if you like.


 I have looked at some and have no desire to waste any more time, If you have a link to a specific document that says *ALL V-1710 *engines regardless of model or date of manufacture was cleared to use 15 minutes military power please post it. 
I am not disputing that the standard was changed in the summer of 1942, Or that some V-1710 engines manufactured prior to that date were included in the order. But some is not all.


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## P-39 Expert (Mar 15, 2018)

buffnut453 said:


> Ok, this is really starting to look like a wind-up. Post #148 makes no mention of self-sealing fuel tanks or O2. You may well think that your pretty graphs make your point but they still miss the fundamental issue that the P-39C was NOT combat capable. The P-39D was the first truly combat-ready variant but it was a much heavier beast...with consequent loss of performance.


#148 is talking about the P-39N, not the P-39C. The N was produced from December 1942 and was in action almost immediately. The FW190A6 was produced from June 1943 and was actually newer than the N. The P-39C was 7075#. It did not have self sealing tanks and armor plate/glass, but would have weighed the same because the self sealing tanks reduced fuel capacity by 50gallons or 300# and we were deleting the 2 .30caliber MGs in the nose so we could increase the 37mm cannon armament to the full 30 rounds. This was not the P-39C that was actually produced, just "what could have been". The P-39N/FW190A6 comparison was straight from the government performance tests.


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## P-39 Expert (Mar 15, 2018)

Shortround6 said:


> The US use of the Aircrobra was also handicapped by climate. They usually try to adjust or correct performance figures to a "standard" day of 59 degrees F or 15 degrees C. and standard air pressure. Operating at temperatures much higher reduce performance due to less lift from the wing, less power form the engine (even at the same pressure) and less 'bite' from the propeller.
> For some weird reason the US sometimes gave pilots charts that used a base line of 32 degrees F (0 degrees C) and the P-39 is one of those planes that use the point of freezing as a base line with notes to increase the take off distance and the time to hight by 10% for every 20 degrees F (or 10 degrees C) above the baseline. SO on a 92 Degree F day on a pacific Island or in North Africa the P-39 will need 30% longer runways and take 30% more time to make it to 15,000ft than the charts say. Other planes also suffered a similar loss of performance but if they started with a 59 degree base then they might only be around 15% below book figures. You can have hot days in Russia but a lot of their use would have been on days without such a large difference from the book figures.
> P-39 had one of the higher wing loadings of the early fighters and one of the worst power loadings. (Not counting WEP) and may be affected even more by extreme heat.


Every other plane in that theater would have to adjust their performance figures too.

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## pbehn (Mar 15, 2018)

buffnut453 said:


> Wind-up: a joke meant to deceive someone (eg "He's winding you up" meaning "he's pulling your leg" or "he's kidding you").


Wind up, comes from the old clockwork toys, a person being wound up and set off in a particular direction for amusement like a toy. This is definitely a wind up, when you discuss removing armour, radios, fuel and guns to show how effective a plane could be the conversation borders on surreal.

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## tomo pauk (Mar 15, 2018)

buffnut453 said:


> The problem there is that you're applying the retrospectroscope. In the mid-1930s, pretty much every fighter in the world was armed with 2 or 4 rifle-calbre machine guns. Even the early P-40s carried a mix of 30cal and 50cal weapons as late as 1941. I think it's asking a bit much for the crystal ball to foresee that 50cal weapons would be the preferable option in time to impact the Battle of Britain...and that's before we consider the other logistical issues.
> ...



Hurricane was not ordered with 2 or 4 RCMGs, but with 8. Ordering them with 4 HMGs instead does not rock the boat.
The CR.32 fighter, perhaps the last of the fighters with un-supercharged engines, was armed with two HMGs, with option for two 7.7mm MGs. French fighters, like the D.510, were armed with cannon + LMGs. Polish P.24 was armed with two cannons. COmpared with these 3 types, having 4 HMGs on a fighter with supercharged engine is nothing outrageous.
Both Italian and Belgian guns are in roduction much before ww2 started, ie. once can have them for Hurricane and Spitfire from the get go.



Shortround6 said:


> I also have serious doubts about the Belgian guns rate of fire. Like how long they could keep it up. I have no idea how close in contact the FN factory was with Colt although they seemed to co-operate on other things but it took the US 3 1/2 to 4 years to get the .50 cal up to the rate of fire of the Belgian guns _with an acceptable degree of reliability. _That is an acceptable number of jams and broken parts per 1000 rounds fired. Perhaps the US standards were too high?



Or perhaps Belgian technicians/gunners/engineers got to the solution earlier?
At any rate, one can buy earlier, 600-800 rpm models.


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## buffnut453 (Mar 15, 2018)

tomo pauk said:


> Hurricane was not ordered with 2 or 4 RCMGs, but with 8. Ordering them with 4 HMGs instead does not rock the boat.
> The CR.32 fighter, perhaps the last of the fighters with un-supercharged engines, was armed with two HMGs, with option for two 7.7mm MGs. French fighters, like the D.510, were armed with cannon + LMGs. Polish P.24 was armed with two cannons. COmpared with these 3 types, having 4 HMGs on a fighter with supercharged engine is nothing outrageous.
> Both Italian and Belgian guns are in roduction much before ww2 started, ie. once can have them for Hurricane and Spitfire from the get go.



Per my earlier post, the problem with US 50cals appears to have been belt-fed wing installations. The CR32 carried guns in the fuselage while the P.24 cannons were drum fed. 

Having a workable HMG is one thing. Having an operationally viable belt-fed wing installation in the latest generation of 300+mph fighters is something else. If installing multiple HMGs in the wings of high-speed fighters was so straightforward, why did it take the US until late 1942 to get it right?


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## Elmas (Mar 15, 2018)

Regia Aeronautica tried experimentally to install two MG in the wings of C.R. 32 but the wings did vibrate so much that shooting with some accuracy was impossible. This was the reason why the following Italian fighters, M.C. 200 and G. 50 had MGs in the fuselage.
Ing. Trojani, designer of A.U.T. 18, more or less contemporary of M.C. 200 and G. 50, had to insist with Gen. Cebrelli, Chief of Technical Services, to install MG in the wings of his aeroplane. But wings of C.R. 32 were maybe 12 cm thick, A.U.T. 18 were 37 cm at the Mg bays.
Chiefs of Technical services in the late 30s were still suspicious about the strenght of monoplane wings with D-boxes and stressed skin.


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## Shortround6 (Mar 15, 2018)

tomo pauk said:


> Or perhaps Belgian technicians/gunners/engineers got to the solution earlier?
> At any rate, one can buy earlier, 600-800 rpm models.



Maybe they did but something seems off. The US got the M2 up to 800rpm without much difficulty. The problem was going to 1000-1200rpm.
Look at Chinn for the number of projects and companies involved and some of the failures. The fast firing M3 had almost no interchangeable parts with the M2.
You can't even take an M2 and convert it to an M3 with a parts kit. 

I would note that the Belgian 12.7mm gun saw little or no actual service? 

as for the Italian gun, think of a machine gun like a piston engine. If you shorten the stroke (length of bolt travel/length of cartridge) you can raise the revolutions per minute or the rounds fired per minute while keeping the piston speed (bolt speed) about the same. 
Taking the Italian gun and trying to get it fire American 12.7 ammo wich was 29mm longer than the Italian ammo wasn't going to give you a high rate of fire machine gun. Not without breaking things and figuring out how to move an heavier belt. 
Try increasing the stroke on an engine 26% and turning the same max rpm?


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## tomo pauk (Mar 15, 2018)

buffnut453 said:


> Per my earlier post, the problem with US 50cals appears to have been belt-fed wing installations. The CR32 carried guns in the fuselage while the P.24 cannons were drum fed.
> 
> Having a workable HMG is one thing. Having an operationally viable belt-fed wing installation in the latest generation of 300+mph fighters is something else. If installing multiple HMGs in the wings of high-speed fighters was so straightforward, why did it take the US until late 1942 to get it right?



Were the US wing installations of the .50 that problematic in all of the listed A/C? The P-51, once the 4 HMG set-up was the norm, yes - it was problematic due to the canted attitude of guns. OTOH, I don't believe that P-40D/E and F4F-3 was let down by their guns in 1941-42.
If there was a decision for the Hurricane to be outfitted with HMGs from the get go, there is 4 years to refine the installations before BoB.



Shortround6 said:


> Maybe they did but something seems off. The US got the M2 up to 800rpm without much difficulty. The problem was going to 1000-1200rpm.
> Look at Chinn for the number of projects and companies involved and some of the failures. The fast firing M3 had almost no interchangeable parts with the M2.
> You can't even take an M2 and convert it to an M3 with a parts kit.
> 
> ...



In caliber of 13.2mm, the model 39 was installed on the FFVS J-22.
Let's not think of the US gunsmiths and techinicians designing the airborne guns of ww2 as if they were given by Good, ie. if they needed 10 years to go from 600 rpm to 1000-1200 rpm, that every other designer team will also need 10 years. We know that even the Soviet and German gunsmiths, some of them with actual record of succesful airborne guns, sometimes went in wrong direction.

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## Shortround6 (Mar 15, 2018)

US had at least three teams trying to improve the M2. As I said perhaps the standards were too high. The Russians were fully prepared to junk an entire gun after it fired enough rounds for the US to allow it 6-8 jams and one or two broken parts. If the US had allowed more malfunctions/parts breakage per 1000 rounds fired (2-3 complete firings of ammunition supply in most fighters) they may have gotten a high rate of fire gun into service much quicker.


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## Hansie Bloeckmann (Mar 15, 2018)

buffnut453 said:


> Wind-up: a joke meant to deceive someone (eg "He's winding you up" meaning "he's pulling your leg" or "he's kidding you").


Another way of saying: "He's jerking your chain".. Anyone know where that saying had its origin?? Like- Okey-Dokey??


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## parsifal (Mar 15, 2018)

Thanks for the correction regarding weight savings on armour. I misread my source. it should be 250lbs.


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## P-39 Expert (Mar 15, 2018)

pbehn said:


> Is this a wind up? Are you saying that if the RAF and US air forces had been given the correct graph and data then the P-39 would have been a winner in service? 601 squadron changed from Hurricane Mk IIs to P39s flew one mission with it then changed to Spitfire Mk Vb and went to Malta. The P 39 would have been no use at all in Malta. In the UK the FW 190 was superior to the Spitfire MkV forcing the Typhoon into service early. When the P51A arrived it was used because at low / medium altitudes it was a top performer, liked by all who flew it. As soon as the P 51 arrived people started figuring out how to put a Merlin in it because its only problem was altitude performance. Merlins were also put in P-40s for the same reason. Did anyone ever suggest putting a Merlin in a P-39?


No Merlin for the P-39, different mount, different attachment points, the Merlin would have had to be redesigned with a remote reduction gear, basically no. Regarding P-51, any true comparison between P-51A and P-39N with the same engines and propellers had the P-51A about 10mph faster at all altitudes, but the P-39N climbed much faster so basically a trade off. P-51 was endurance champ for sure.


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## P-39 Expert (Mar 15, 2018)

Glider said:


> Apologies to one and all as I hadn't seen this posting when I replied to the other response.
> 
> I am sorry but this is total rubbish. The P39's were ordered by the UK in September 1940 when it was already clear that the BOB had been won and of course France had fallen some time before. As a result it wasn't a case of cutting losses, or weaseling out of a contract (not a fan of the UK are you) it was because the P39 wasn't a match for the latest fighters and wasn't combat ready for Ground attack, a role it could have been very useful in. We did what we did with later Hurricanes, send them to Russia or somewhere else anywhere apart from Europe.
> Just a thought did the UK pay for the P400's used by the USAAF?


The original order for P-400s by the French was March 1940, before France had fallen and well before the BOB. British added to the order and ended up assuming the whole order after France fell. Then in the fall they won the BOB and at that point invasion of Britain was impossible. Now they really don't need the planes they ordered, because their own Spit and Typhoon production is plenty with no threat of invasion. And they sure don't want to pay for them because Lend Lease was enacted the following February and they would now get any US plane they want for free (at the time). So they specified an overweight plane that if necessary they could strip (like Russia) and have a nice plane. At the time the P-39/P-400 was delivered in mid 1941 they didn't need them and didn't want to pay for them. So big stink about the plane, blah blah, was okay because the US Army desperately needed them after December 1941.

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## tomo pauk (Mar 15, 2018)

P-39 Expert said:


> No Merlin for the P-39, different mount, different attachment points, the Merlin would have had to be redesigned with a remote reduction gear, basically no. Regarding P-51, any true comparison between P-51A and P-39N with the same engines and propellers had the P-51A about 10mph faster at all altitudes, but the P-39N climbed much faster so basically a trade off. P-51 was endurance champ for sure.



Talk about ~20 mph difference P-51A vs. P-39N - 385-398 mph vs 409-415. Kinda points out how unfortunate it was that Allison didn't managed to put the reliable version of the V-1710 with 9.60:1 drive for supercharger. Here is the gun-less, well prepared P-39C with the 'faster' S/C making 406 mph: link.
The P-39Q, sans gun pods, was supposedly able to beat 400 mph. Sometimes the -85 engine was stated as with rated altitude at 15500 ft, no ram. We know that P-39s were succesful in post-war racing, despite some of competitors boasting twice the horsepower.

BTW - the comparison between the Fw 190A and P-39 is a tricky thing. We know that, in winter of 1941/42, the Fw 190A1 and A2 were good for 400+ mph at 17000-18000 ft, with full weapon set up and protection for both pilot, fuel and oil system. P-39C will not cut it performance-wise, it's protection is also lacking. It will pass another 10 months before the P-39M can do 375 mph at 15000 ft, by what time the Fw 190A3 makes 410 mph at 20000 ft. Where the P-39 shines is between sea leavel and 10000 ft.


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## tomo pauk (Mar 15, 2018)

P-39 Expert said:


> The original order for P-400s by the French was March 1940, before France had fallen and well before the BOB. British added to the order and ended up assuming the whole order after France fell. Then in the fall they won the BOB and at that point invasion of Britain was impossible. Now they really don't need the planes they ordered, because their own Spit and Typhoon production is plenty with no threat of invasion. And they sure don't want to pay for them because Lend Lease was enacted the following February and they would now get any US plane they want for free (at the time). *So they specified an overweight plane that if necessary they could strip (like Russia) and have a nice plane. * At the time the P-39/P-400 was delivered in mid 1941 they didn't need them and didn't want to pay for them. So big stink about the plane, blah blah, was okay because the US Army desperately needed them after December 1941.



Why push an agenda without proof? British specifying a lighter cannon in order to make fighter overweight? Typhoon prodction is plenty once BoB is finnished?Do you have facsimiles of the original documents that can prove the agenda?

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## Shortround6 (Mar 15, 2018)

parsifal said:


> Thanks for the correction regarding weight savings on armour. I misread my source. it should be 250lbs.


No worries,

I have misquoted and most certainly mistyped plenty of times.

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## pbehn (Mar 15, 2018)

P-39 Expert said:


> The original order for P-400s by the French was March 1940, before France had fallen and well before the BOB. British added to the order and ended up assuming the whole order after France fell. Then in the fall they won the BOB and at that point invasion of Britain was impossible. Now they really don't need the planes they ordered, because their own Spit and Typhoon production is plenty with no threat of invasion. And they sure don't want to pay for them because Lend Lease was enacted the following February and they would now get any US plane they want for free (at the time). .


The British ordered what became called "P400"s because they were told it did 400 MPH, additional planes were ordered under lend lease in 1941. When they arrived they didn't do anything like 400, as you say it was slower than the P51A and that didn't do 400MPH either. The British and the USA wanted top class fighters. If as you say, the British could have any US plane for free why wouldn't they choose the P-39 if it was as good as you say it was? As previously requested please advise what role the USA used the P-39 in and for how long?

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## CORSNING (Mar 15, 2018)

pinsog said:


> The P39 had an unspectacular record against Japanese fighters. Was it an issue of pilot training against an unfamilier enemy aircraft?
> 
> *YES.
> *
> ...



*Before November 1942 it just did not have the engine to make it happen.*
.
*I apologize to everyone. I have just now stumbled across this thread and not had time
to read all post yet.*


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## Glider (Mar 15, 2018)

P-39 Expert said:


> The original order for P-400s by the French was March 1940, before France had fallen and well before the BOB. British added to the order and ended up assuming the whole order after France fell. Then in the fall they won the BOB and at that point invasion of Britain was impossible. Now they really don't need the planes they ordered, because their own Spit and Typhoon production is plenty with no threat of invasion. And they sure don't want to pay for them because Lend Lease was enacted the following February and they would now get any US plane they want for free (at the time). So they specified an overweight plane that if necessary they could strip (like Russia) and have a nice plane. At the time the P-39/P-400 was delivered in mid 1941 they didn't need them and didn't want to pay for them. So big stink about the plane, blah blah, was okay because the US Army desperately needed them after December 1941.



I am afraid that you are simply digging a bigger hole for yourself. 
a) What the French ordered isn't the point, the point is that the British didn't order any P39's until the BOB was effectively over in September. To pretend that we were trying to cancel an order at the sane time as we ordered them is foolish
b) You seem to believe that Typhoon production was 'plenty' in 1940, I strongly recommend you check that as the second prototype didn't fly until May 1941 entering service in late 1941
c) The UK took over all the aircraft ordered by France from the USA irrespective of type when France fell. Some such as the P36 Mohawk and the Martin Maryland were used in combat but most either did nothing or were used in third line duties such as target towing or training. The fact that the P39 was taken theoretically into RAF care in May 1940 doesn't mean that we wanted or liked them. Indeed the fact that they were not used in combat when some as mentioned earlier were speaks volumes about how poorly they were thought of
d) As far as I am aware the UK paid all it's bills for all the aircraft taken over from the fall of France even if they just rotted away on a backend airfield, there was nothing special in the way the P39 was treated. As for the claim 'So they specified an overweight plane'. Others have pointed out to you that armour to protect the pilot, self sealing fuel tanks to stop them turning into torches isn't specifying an overweight aircraft. Its the bare minimum for making them combat worthy.

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## Shortround6 (Mar 15, 2018)

Even the US had decided back in 1940 that planes without armor and self sealing tanks would not be counted as combat worthy. 
I would also note that by the time the British had built 150 Typhoons Bell had built over 900 Aircobras (end of 1941) which makes trying to get out the P-39 contract in late 1940 or early 1941 by "specifying" an overweight plane a very risky business. The British already having been burned by the Botha, the Lerwick, the Beaufort/Taurus problem and perhaps a few other programs where drawing board or prototype aircraft failed rather miserably. Deliberately screwing up 
"insurance/back up" aircraft would be the height of folly.


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## pbehn (Mar 15, 2018)

Shortround6 said:


> Even the US had decided back in 1940 that planes without armor and self sealing tanks would not be counted as combat worthy.
> I would also note that by the time the British had built 150 Typhoons Bell had built over 900 Aircobras (end of 1941) which makes trying to get out the P-39 contract in late 1940 or early 1941 by "specifying" an overweight plane a very risky business. The British already having been burned by the Botha, the Lerwick, the Beaufort/Taurus problem and perhaps a few other programs where drawing board or prototype aircraft failed rather miserably. Deliberately screwing up
> "insurance/back up" aircraft would be the height of folly.


I just realised that the pesky British screwed up that other winner the Brewster Buffalo, and they used exactly the same sneaky methods.

Facing a shortage of combat aircraft in January 1940, the British government established the British Purchasing Commission to acquire U.S. aircraft that would help supplement domestic production. Among the U.S. fighter aircraft that caught the Commission's attention was the Brewster. The remaining 32 B-339 aircraft ordered by the Belgians, suspended at the fall of France, were passed on to the United Kingdom.[44] Appraisal by Royal Air Force acceptance personnel criticized it on numerous points including inadequate armament and lack of pilot armor, poor high-altitude performance, engine overheating, maintenance issues, and cockpit controls, while it was praised for its handling, roomy cockpit, and visibility.[11] With a top speed of about 323 mph (520 km/h) at 21,000 ft (6,400 m), but with fuel starvation issues over 15,000 ft (4,600 m), it was considered unfit for duty in western Europe.[11] Still desperately in need of fighter aircraft in the Pacific and Asia for British and Commonwealth air forces, the UK ordered an additional 170 aircraft under the type specification *B-339E*.[45] The aircraft were sent to Royal Australian Air Force, RAF and Royal New Zealand Air Force fighter squadrons in Singapore, Malaya and Burma, shortly before the outbreak of war with Japan.


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## Shortround6 (Mar 15, 2018)

Contracts were often complicated documents with performance spelled out and even weights spelled out with penalties (reductions in price) for failing to meet performance or weight requirements, usually a certain margin was allowed. Some US contracts allowed up to 3%. at some point a short fall in performance (each plane was test flown on one or more acceptance flights) would result in that particular plane being rejected until it was brought up to standard.

Curtiss for example lost over 10,000 dollars on the 2nd XP-46 when it failed to get close to promised performance.

No manufacturer was going to accept change orders from a customer that would severely impact performance without renegotiating the contract weights and performance. TO do otherwise could result in bankruptcy.


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## Juha2 (Mar 15, 2018)

This is how comrades saw things
I don't have Fw 190 A-6 figures but A-5


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## buffnut453 (Mar 15, 2018)

tomo pauk said:


> Were the US wing installations of the .50 that problematic in all of the listed A/C? The P-51, once the 4 HMG set-up was the norm, yes - it was problematic due to the canted attitude of guns. OTOH, I don't believe that P-40D/E and F4F-3 was let down by their guns in 1941-42.



Yes, the problems were very real in all the types mentioned. Read Bill Bartsch's "Doomed at the Start" for accounts of the P-40s in the Philippines for the number of times gun stoppages prevented engagements. On the USN side of things, Lundstrom's "The First Team" makes it clear that the problems with the F4F's gun installation were not fully resolved until the latter half of 1942 (which makes the F4F's successes in combat prior to that point even more remarkable, IMHO).




tomo pauk said:


> If there was a decision for the Hurricane to be outfitted with HMGs from the get go, there is 4 years to refine the installations before BoB.



But that's applying hindsight again. When the Hurricane was ordered, the British didn't KNOW that they had 4 years' breathing room. They had to be ready for combat ASAP. Attempting to re-arm the entire Fighter Command force with HMGs when war was expected imminently would not be a sensible move, and a partial re-armament of only certain units would introduce significant logistical challenges under combat conditions. Note that cannons were only rolled out in any numbers AFTER the Battle of Britain was effectively won.


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## buffnut453 (Mar 15, 2018)

pbehn said:


> The aircraft were sent to Royal Australian Air Force, RAF and Royal New Zealand Air Force fighter squadrons in Singapore, Malaya and Burma, shortly before the outbreak of war with Japan.



Just a slight bit of pedantry but most Buffalo squadrons were officially RAF units, the only exception being 21 Sqn RAAF. There were 2 Article XV squadrons, 453 and 488 which later became RAAF and RNZAF units respectively but, at the time of Buffalo usage, were still strictly speaking RAF units manned with Australian and New Zealand personnel. Like I said...pedantry!

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## wuzak (Mar 15, 2018)

P-39 Expert said:


> You are truly an expert on crankshafts. My source for the 15 minutes is wwiiaircraftperformance.net. The actual government performance docs. Check them if you like.



The 15 minute rating may have been for 3000rpm at lower boost than combat power.


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## wuzak (Mar 15, 2018)

P-39 Expert said:


> Okay, look at your photo of the P-39C. Says it weighed 7075# and made 379mph at 13000'. The British only got 359mph from theirs because they weighed 7850#. That's 775# lighter. But the real performance gain was in climb. That little P-39C at 7075# would climb at 3720fpm up to 12000'. How fast would the SpitV climb at that altitude? About 3000fpm or 750fpm less. The P-39C was faster and climbed faster than the SpitV.
> Now, that P-39C didn't have self sealing tanks or armor plate/glass necessary for combat. The tanks added 260# and the armor added 240# so now we're up to 7575#. But wait, we can deduct 300# because the self sealing tanks reduced fuel capacity by 50 gallons, 100# by removing the two .30 caliber MGs in the nose and another 100# by deleting the nose armor (too far from pilot for protection) leaving us back at the original 7075# that gave the 379mph/3700'climb. Now the P-39C is faster than the SpitV, climbs faster, carries 20 gallons more gas, easier to land and is heavily armed/armored. This plane was available from July 1941 and was the plane the Army should have purchased.



You need to be careful when comparing fuel capacities of UK and US aircraft in gallons. That is because the UK quoted in UKG and the US quoted in USG, the UKG being 20% greater in volume than the USG.

Note also that British tests generally corrected their flight test results back to 95% of normal take-off weight (ie, normal ammo and fuel load, etc., not overload).


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## wuzak (Mar 15, 2018)

P-39 Expert said:


> Back to the two speed supercharger, the disadvantage was that in low gear power started to decline almost right away as the plane gained altitude and the air began to get thinner, so by the time you reached the shift point (11500') power was lower. Then you shifted into high and power steadily increased up to the critical altitude (18500') when it began to fall off again (just like low gear). This resulted in a sawtooth performance curve for both the engine and airplane. The Allison didn't have that problem (especially with the auto boost control) as it made 1325HP at takeoff and maintained that figure up to 8000' where it began to decline due to the thinner air.



The single stage V-1710's power curve follows the same shape as the V-1650-1, but without the second gear.

The reason for this is that the throttle causes a pressure loss and a reduction in efficiency of the supercharger. So the power *rises* as altitude increases, the throttle progressively opening to maintain the required boost level, until the critical altitude/full throttle height where the engine makes its peak rated power. The power then, pretty much, falls off a cliff.

The difference for the V-1650-1 is that when the power begins to fall off, another gear can be engaged. Note that the change point is determined by when the high gear has the same power as the low gear. Once in high gear the throttle has to be closed again, to prevent overboosting, and is, again, progressively opened until critical altitude/full throttle height. Hence the sawtooth shape.

The advantage in the 2nd speed can be seen in the Merlin XX (of which the V-1650-1 was a derivative) and Merlin 45. They were essentially the same, except for the supercharger drive. The XX had the 2 speed drive, low speed (Medium Supercharged gear or MS, in British jargon) had a lower ratio than the 45's single gear and high speed (Fully Supercharged, or FS, gear) had a higher ratio than the 45. Thus the XX had more power at low altitudes and high altitudes, with the 45 basically having the advantage around its full throttle height (~18,000ft).


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## P-39 Expert (Mar 16, 2018)

wuzak said:


> You need to be careful when comparing fuel capacities of UK and US aircraft in gallons. That is because the UK quoted in UKG and the US quoted in USG, the UKG being 20% greater in volume than the USG.
> 
> Note also that British tests generally corrected their flight test results back to 95% of normal take-off weight (ie, normal ammo and fuel load, etc., not overload).


Right, the Spit held 100 American gallons and the P-39 held 120 American gallons.


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## P-39 Expert (Mar 16, 2018)

pbehn said:


> The British were desperate for fighters in 1941 as Russia was desperate for the British to put pressure on Germany. However those fighters had to be superior in every respect to the Spitfire MkV, some fighter sweeps over France with Mk Vs resulted in no aircraft returning home. Being equal to the MkV was of no use at all because that was in no way good enough. To be any use at all the P39 had to be the equal of the P51A and Spitfire MkIX and it wasn't.


The British sure accepted a lot of P-40s, and they were in no way comparable to the SpitV or P-51A.

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## P-39 Expert (Mar 16, 2018)

Shortround6 said:


> I would note that by the time the P39 was coming into service (fall of 1941) the 109E was on the way out and the 109F was equiping more squadrons every month. WHile the 109F may not have turned any tighter than the 109E it could sustain height or speed in a turn much better than the 109E.
> 
> I also have doubts about pulling 750lbs of armor out of a P-39. according to the weight tables there wasn't over 275lbs to begin with. Not to mention that an empty P-39D-2/P-400 weighed about 5550-5600lbs, basic weight (empty equipped) with guns, armor, radio, and oxygen was 6330-6420lbs.
> 
> ...


There was only 240# of armor in the P-39, but 100# of that could have been saved by removing the nose armor. Pilot was still protected by armor plate and glass right in frot of him.


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## P-39 Expert (Mar 16, 2018)

tomo pauk said:


> Talk about ~20 mph difference P-51A vs. P-39N - 385-398 mph vs 409-415. Kinda points out how unfortunate it was that Allison didn't managed to put the reliable version of the V-1710 with 9.60:1 drive for supercharger. Here is the gun-less, well prepared P-39C with the 'faster' S/C making 406 mph: link.
> The P-39Q, sans gun pods, was supposedly able to beat 400 mph. Sometimes the -85 engine was stated as with rated altitude at 15500 ft, no ram. We know that P-39s were succesful in post-war racing, despite some of competitors boasting twice the horsepower.
> 
> BTW - the comparison between the Fw 190A and P-39 is a tricky thing. We know that, in winter of 1941/42, the Fw 190A1 and A2 were good for 400+ mph at 17000-18000 ft, with full weapon set up and protection for both pilot, fuel and oil system. P-39C will not cut it performance-wise, it's protection is also lacking. It will pass another 10 months before the P-39M can do 375 mph at 15000 ft, by what time the Fw 190A3 makes 410 mph at 20000 ft. Where the P-39 shines is between sea leavel and 10000 ft.


The "faster" supercharger with 9.6 gears was installed in the P-39N, N and Q. Comparison with the FW190A and P-39M is in post #148. Official German govt document with official US govt figures on P-39N superimposed. Official govt docs, not 70 years of heresay.


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## tomo pauk (Mar 16, 2018)

P-39 Expert said:


> The British sure accepted a lot of P-40s, and they were in no way comparable to the SpitV or P-51A.



P-40 was available earlier and in greater quantities than the P-39, let alone the P-51A that entered the service with RAF by June 1943.
The P-40 was a better fighter than Hurricane, thus it was no wonder the P-40s ended up in North Africa. Not in UK by any meanigful numbers, though.



P-39 Expert said:


> The "faster" supercharger with 9.6 gears was installed in the P-39N, N and Q. Comparison with the FW190A and P-39M is in post #148. Official German govt document with official US govt figures on P-39N superimposed. Official govt docs, not 70 years of heresay.



People are frying you exactly because you endeavoured in heresay when claiming that British were trying to weasel out from P-39 situation.
I know that M, N and Q versions got the 9.60:1 drive for the S/C. Unfortunately, that S/C drive was 10 months too late.
My point is/was that P-39 managed to best the Fw 190 a year too late in the altitude band that was well suited for the Eastern front, but couldn't do it in the ETO where a good performance at altitude was needed. On the other hand, the Fw 190As from mid-1943 were able to use greater manifold pressure = more power = more speed, the P-39N/Q from that time is a very 'niche' fighter.
Post #148 does not contain a comparison, comparisons include much more than speed figures.

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## pbehn (Mar 16, 2018)

P-39 Expert said:


> The British sure accepted a lot of P-40s, and they were in no way comparable to the SpitV or P-51A.


Yes, and after the first shipment all P-40s were delivered with armour and BP glass. The P-40 was not used as a fighter from UK but in recon and then only for 29 sorties. The P-40 was in service in North Africa and replaced the Hurricane. The P-39 was more of the same and arrived much later with serviceability issues. The P-40 as Tomahawk and Kittyhawks remained in service until tropicalized Spitfires started to replace them in 1942, but this is just after the P-39 started to arrive in UK. 

Most of your "case" is just a trick with time lines. A comparison with the Bf 109E may give some information but the Bf 109F was arriving in service from October 1940. By the time any P-39s could have been in service in any numbers the Spitfire was being tropicalised and replacing the P-40 in Africa. Similarly you bring the time line of the Typhoon forward to make a political point about the British not needing the P39. In 1941 to 43 the British and the Americans needed front line fighters, no one gave a stuff who made them or what they were called but they had to do the job. While the Hurricane could remain in service to the end of the war in ground attack, in terms of taking on front line fighters it was obsolete in 1940, the P39 was pretty much the same.


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## Shortround6 (Mar 16, 2018)

P-39 Expert said:


> There was only 240# of armor in the P-39, but 100# of that could have been saved by removing the nose armor. Pilot was still protected by armor plate and glass right in frot of him








Perhaps you are right, on the other hand




British could have saved weight on the Whirlwind by getting rid of the armor in front of the ammo drums for the 20mm cannon.
Many British fighters had a piece of armor in front of their 20mm belt boxes and heavy dural behind and or on top of the belt boxes.

Just _maybe_ the the gearbox armor was doing double duty and not only protecting the gear box but keeping small bullets out of 37mm ammo?

one of the 37mm shells going off inside the feed way could ruin your whole day.

Not to mention the the P-39 had a few issues with center of gravity. Like not supposed to be flown without ammo for the nose guns unless ballast was carried?
Yanking the nose armor without yanking a similar weight from the rear of the plane at an equal distance is going to increase your accident rate.

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## P-39 Expert (Mar 16, 2018)

Shortround6 said:


> View attachment 486062
> 
> Perhaps you are right, on the other hand
> View attachment 486063
> ...


Exactly what I was saying, all that armor plate and glass weighed 240# but that gear box armor in the nose was 100# of that. No other fighters had armor there (unless there was a liquid tank there), and it really didn't protect the pilot much since he already had the forward armor plate and the windshield armor glass directly in front of him. It would have been a CG/balance issue though, but that could have been offset by moving the radio equipment from the tail cone up to right behind the pilot above the engine. Look closely and lots of P-39s have moved the radio equipment there.


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## P-39 Expert (Mar 16, 2018)

pbehn said:


> Yes, and after the first shipment all P-40s were delivered with armour and BP glass. The P-40 was not used as a fighter from UK but in recon and then only for 29 sorties. The P-40 was in service in North Africa and replaced the Hurricane. The P-39 was more of the same and arrived much later with serviceability issues. The P-40 as Tomahawk and Kittyhawks remained in service until tropicalized Spitfires started to replace them in 1942, but this is just after the P-39 started to arrive in UK.
> 
> Most of your "case" is just a trick with time lines. A comparison with the Bf 109E may give some information but the Bf 109F was arriving in service from October 1940. By the time any P-39s could have been in service in any numbers the Spitfire was being tropicalised and replacing the P-40 in Africa. Similarly you bring the time line of the Typhoon forward to make a political point about the British not needing the P39. In 1941 to 43 the British and the Americans needed front line fighters, no one gave a stuff who made them or what they were called but they had to do the job. While the Hurricane could remain in service to the end of the war in ground attack, in terms of taking on front line fighters it was obsolete in 1940, the P39 was pretty much the same.


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## P-39 Expert (Mar 16, 2018)

No trick time lines. Different planes. Two different P39s, the older ones with the 8.8 supercharger gears (P-39D, F, K and L) and the later ones with the 9.6 gears (P-39M, N and Q). The 9.6 gears gave an additional 100HP at all altitudes. The improved 9.6 gears were available in production P-39s starting with the M in November 1942. Over 7000 were the improved M, N & Q of the 9500 total produced. The N and Q were the primary models supplied to the Russians. The charts in post #148 compare the N introduced in Dec 1942 with the FW190A6 introduced in June 1943. Apples to apples time-wise, both fully loaded, these are the official Luftwaffe charts for speed and climb with the official US Army figures for the P-39N superimposed. The FW was a little faster above 5km altitude in override boost with C3 injection (war emergency) for one minute, but the P-39N was just as fast as the FW's "combat" rating which is column #2. The climb chart shows the P-39N substantially outclimbed the FW AT ALL ALTITUDES. Pretty much a wash vs the Luftwaffe's premier fighter. 
And below 5km altitude (16500') the P-39Ns advantage in both speed and climb is huge. Now, please let me hear from all you "two speed" and crankshaft experts about how big an advantage low gear is. As you can see from the charts the two speed supercharger results in a "sawtooth" speed and climb curve while the single speed P-39N develops its maximum power at 3km (10000') and then gradually declines from there up to the combat ceiling. Most historians would have you believe that the Allison engine fell off the mounts and the plane tumbled to earth after crossing 12000'. This was a much better plane than history gives credit for.


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## Peter Gunn (Mar 16, 2018)

P-39 Expert said:


> *SNIP*
> 
> This was a much better plane than history gives credit for.


That's why there are so many P-39 aces in the USAAF and RAF...
Sure, over the steppes of Russia at low altitude and overboosting the engine, VVS pilots did well with it. Again, a niche fighter, the Germans on the western front and the Japanese were no so obliging to stick to low altitude combat.

Wasn't it George Welch that supposedly said the best thing about the P-39 was the twelve hundred pounds of pilot armor behind him?

I think in this instance, history has given credit where it is due.

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## pbehn (Mar 16, 2018)

P-39 Expert said:


> No trick time lines. Different planes. Two different P39s, the older ones with the 8.8 supercharger gears (P-39D, F, K and L) and the later ones with the 9.6 gears (P-39M, N and Q). The 9.6 gears gave an additional 100HP at all altitudes. The improved 9.6 gears were available in production P-39s starting with the M in November 1942. Over 7000 were the improved M, N & Q of the 9500 total produced. The N and Q were the primary models supplied to the Russians. The charts in post #148 compare the N introduced in Dec 1942 with the FW190A6 introduced in June 1943. Apples to apples time-wise, both fully loaded, these are the official Luftwaffe charts for speed and climb with the official US Army figures for the P-39N superimposed. The FW was a little faster above 5km altitude in override boost with C3 injection (war emergency) for one minute, but the P-39N was just as fast as the FW's "combat" rating which is column #2. The climb chart shows the P-39N substantially outclimbed the FW AT ALL ALTITUDES. Pretty much a wash vs the Luftwaffe's premier fighter.
> And below 5km altitude (16500') the P-39Ns advantage in both speed and climb is huge. Now, please let me hear from all you "two speed" and crankshaft experts about how big an advantage low gear is. As you can see from the charts the two speed supercharger results in a "sawtooth" speed and climb curve while the single speed P-39N develops its maximum power at 3km (10000') and then gradually declines from there up to the combat ceiling. Most historians would have you believe that the Allison engine fell off the mounts and the plane tumbled to earth after crossing 12000'. This was a much better plane than history gives credit for.


You are still doing exactly the same thing. By December 1942 the RAF had the Spitfire Mk IX Typhoon and the Mustang Mk 1 in service in numbers, they were used at Dieppe. The P-39N may have been something in UK arriving in numbers in UK in 1939, by the end of 1942 in addition to the RAF aircraft the USA was introducing the P-47 and P -38 the time had passed.

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## P-39 Expert (Mar 16, 2018)

pbehn said:


> You are still doing exactly the same thing. By December 1942 the RAF had the Spitfire Mk IX Typhoon and the Mustang Mk 1 in service in numbers, they were used at Dieppe. The P-39N may have been something in UK arriving in numbers in UK in 1939, by the end of 1942 in addition to the RAF aircraft the USA was introducing the P-47 and P -38 the time had passed.


P-39N was comparable to the Typhoon in speed and superior to the Typhoon in climb. The Spitfire IX had a two stage engine (two superchargers) for it's high altitude capability. I never said the P-39N was comparable to the SpitIX. Would have been superior to the SpitIX with the Allison V-1710-93 mechanical two stage engine that went into the P-63. The -93 was in series production from March 1943 and the first P-63 wasn't ready until October, so that -93 should have been installed in the P-39 immediately in March. 1800HP WEP at 22000' compared very favorably with the Merlin 61 in the SpitIX and P-51B. 
P-38 didn't enter combat until December 1942 in the older and less capable F and G models and the P-47 didn't enter combat until May 1943 with the 8th Air Force in England. These new turbocharged "superplanes" weren't without their faults. The P-47 couldn't climb and the P-38 couldn't dive. Neither could maneuver with a FW or Messer, much less a P-39N.

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## Elmas (Mar 16, 2018)

I’m always puzzled how some posters in this forum refer only to maximum speed, climb rate, manifold pressures and so on and of an airplane completely ignore things like (from Wiki, just for a quick reference)

Angular momentum - Wikipedia

Moment of inertia - Wikipedia

that are_ essential_ to judge the behaviour of a plane.

I can imagine the behaviour of a P-39, all ammunition spent, when a Pilot had to pull energetically the stick to come out from a dive, one or two Me-109 on his tail. I know that some Italian Pilots described the experience as hair raising, and some British too, I can imagine, from the use the RAF did of the plane. Russian Pilots I don’t know, but probably they were used to things like Russian Roulette…


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## Peter Gunn (Mar 16, 2018)

One might ask oneself if the V-1710-93 with attending supercharger setup would fit in the P-39. The P-63 is two feet longer after all. But in reality, you're going off into flights of fancy to prove an un-provable point.

Cheers.

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## pbehn (Mar 16, 2018)

P-39 Expert said:


> P-39N was comparable to the Typhoon in speed and superior to the Typhoon in climb. The Spitfire IX had a two stage engine (two superchargers) for it's high altitude capability. I never said the P-39N was comparable to the SpitIX. Would have been superior to the SpitIX with the Allison V-1710-93 mechanical two stage engine that went into the P-63. The -93 was in series production from March 1943 and the first P-63 wasn't ready until October, so that -93 should have been installed in the P-39 immediately in March. 1800HP WEP at 22000' compared very favorably with the Merlin 61 in the SpitIX and P-51B.
> P-38 didn't enter combat until December 1942 in the older and less capable F and G models and the P-47 didn't enter combat until May 1943 with the 8th Air Force in England. These new turbocharged "superplanes" weren't without their faults. The P-47 couldn't climb and the P-38 couldn't dive. Neither could maneuver with a FW or Messer, much less a P-39N.


And again the same thing, pushing the time line back for one aircraft but not another. By the end of 1943 the P51B/C is in service, you are a few months away from the Tempest being in service. The P 47 arrived in January, it takes months to get into service, that is also true for any engine produced in USA as you quoted, they must be made, shipped, installed, tested shipped and tested again. Both the P47 and P-38 whatever their faults could fight at range and altitude which is where the combat would be in the near future. The Spitfire MkXII with Griffon engine was superior by 14MPH to the Mk IX at low level but found targets hard to find. The LW would just climb away above 20,000ft where it ran out of lungs, it needed a two speed two stage supercharger the first of which flew in Jan 1943.

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## tomo pauk (Mar 16, 2018)

P-39 Expert said:


> No trick time lines. Different planes. Two different P39s, the older ones with the 8.8 supercharger gears (P-39D, F, K and L) and the later ones with the 9.6 gears (P-39M, N and Q). The 9.6 gears gave an additional 100HP at all altitudes. The improved 9.6 gears were available in production P-39s starting with the M in November 1942. Over 7000 were the improved M, N & Q of the 9500 total produced. The N and Q were the primary models supplied to the Russians. The charts in post #148 compare the N introduced in Dec 1942 with the FW190A6 introduced in June 1943. Apples to apples time-wise, both fully loaded, these are the official Luftwaffe charts for speed and climb with the official US Army figures for the P-39N superimposed. The FW was a little faster above 5km altitude in override boost with C3 injection (war emergency) for one minute, but the P-39N was just as fast as the FW's "combat" rating which is column #2. The climb chart shows the P-39N substantially outclimbed the FW AT ALL ALTITUDES. Pretty much a wash vs the Luftwaffe's premier fighter.



Fw 190 was probably LW's premiere fighter, the Bf 109F/G climbed better, though.
Please note that P-39N that can out-climb the Fw 190As was the model with less fuel, 87 US gals (72.44 imp gals), so the weight was down by 200 lbs vs. the models with 120 US glas. The C3 injection override boost was allowed for 10 minutes, and was option at lower altitudes, typically 3000 ft and lower. The 'simple' overboost was allowed for both supercharger gears, on the other hand.



> And below 5km altitude (16500') the P-39Ns advantage in both speed and climb is huge. Now, please let me hear from all you "two speed" and crankshaft experts about how big an advantage low gear is. As you can see from the charts the two speed supercharger results in a "sawtooth" speed and climb curve while the single speed P-39N develops its maximum power at 3km (10000') and then gradually declines from there up to the combat ceiling. Most historians would have you believe that the Allison engine fell off the mounts and the plane tumbled to earth after crossing 12000'. This was a much better plane than history gives credit for.



P-39 usualy does not receive a bad rap here. Like every other A/C, it have had it's good and bad sides.
Let's imagine for a moment that P-39 is outfitted with a 2-speed drive for the S/C. We'll use a brand new gearing, with, say, 10:1 drive for high gear, and 8:1 for low gear. Should be making military power of 1100 HP at 17000 ft, and 1200 HP at ~10500 ft? WER of 1400 HP at 11000 ft, and 1600 HP at 2000 ft; take off 1400 HP. Net result 400 mph with 120 gals and full wepon set up, with increase in climb rate at all altitudes and shorter take off distance.



P-39 Expert said:


> P-39N was comparable to the Typhoon in speed and superior to the Typhoon in climb. The Spitfire IX had a two stage engine (two superchargers) for it's high altitude capability. I never said the P-39N was comparable to the SpitIX. Would have been superior to the SpitIX with the Allison V-1710-93 mechanical two stage engine that went into the P-63. The -93 was in series production from March 1943 and the first P-63 wasn't ready until October, so that -93 should have been installed in the P-39 immediately in March. 1800HP WEP at 22000' compared very favorably with the Merlin 61 in the SpitIX and P-51B.
> P-38 didn't enter combat until December 1942 in the older and less capable F and G models and the P-47 didn't enter combat until May 1943 with the 8th Air Force in England. These new turbocharged "superplanes" weren't without their faults. The P-47 couldn't climb and the P-38 couldn't dive. Neither could maneuver with a FW or Messer, much less a P-39N.



Typhoon was faster at most altitudes.
P-39 + 2-stage V-1710 is a non-starter, unless the fuselage internals are reworked. Let's recall that even the post-war racing P-39s were still outfitted with 1-stage engines, despite the potential for much greater power offered by 2-stage versions.
2-stage V-1710s installed on P-63 were good for 1120-1300 HP at 22000 ft (no ram) 1800-1850 was available at low level. chart
Too much 2-stage V-1710s gathering dust inn 1943? Install them on the P-51s, those at least can bring war to the enemy.
Nobody will put the P-38 or P-47 in the box tagged 'perfect fighters', even if they were much more useful than P-39s or P-40s.

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## Shortround6 (Mar 16, 2018)

We also have the flight of Fancy in which the engines with 9.60 gears get an extra 100np at all altitudes.
They did not. For take-off and military power they were limited to 1200hp instead of 1325hp. And WEP was also dropped. Strong warnings were issued about exceeding the book boost limits as the 9.60 gears heated the intake charge more than the 8.80 gears and at the same pressure level was actually skating much closer to the detonation limit.
This is the classic trade off a single speed supercharger makes that the automatic boost control can do nothing about.

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## parsifal (Mar 16, 2018)

buffnut453 said:


> Just a slight bit of pedantry but most Buffalo squadrons were officially RAF units, the only exception being 21 Sqn RAAF. There were 2 Article XV squadrons, 453 and 488 which later became RAAF and RNZAF units respectively but, at the time of Buffalo usage, were still strictly speaking RAF units manned with Australian and New Zealand personnel. Like I said...pedantry!



That is technically true,but it is indeed being very pedantic about the issue. Imperial defence of Malaya was being bankrolled by the dominions in the main from about fenruary 1941. After Japan signed her military ten year pact with Germany and Italy 27 September,1940, there were a series of meetings with the dominions that reappraised the air defence needs of the far east and PTO. It was determined that a minimum of 1404 a/c were required for imperial defence,but the british more or less immediately conceded that they lacked both the manpower and the financial depth to meet those commitments. Part of the response was to train and equip Australian airforce formations using british equipment, but Australian personnel in the main.

In July 1940, the RAAFs first operational bomber sqn,with modern equipment (Hudons),no 1 GRU was sent to singapore. a month later it was followed by No 8 sqn. these aircraft were part of the British "Cash and carry" purchases so they too were technically British aircraft (though I do note these hudsons were given Australian serialisations). technically. they had been paid for by the Australian govt, were fully manned by Australian personnel, so referring to them as "british aircraft" is more than a bit rich!!!

The conferences that followed the Axis September pacts led to the formation of firstly ABD and later ABDA. Part of the commitment to boost the Malayan defences was a commitment to send two Australian fighter squadrons to singapore. This presented a problem however. what fighters we did have were all obsolete (Gloster Gauntlets mainly) which we had been given to the RAAF in the middle east. the home based squadrons were all obsolete (Hawker demons I think). The three organisation within Australia building aircraft were contracted by the british to build types like the Beaufort , or were committed to building training a/c like the moth or the Wackett. The Wirraway was built as a GP a/c, with the RAAF believing the british delusions about how obsolete the JAAF was and deluding itself into believing the CA6 was good enough for front line service. It was in that climate of self delusion and downright baloney being fed to us by the British war organisation at the time that convinced the Australian govt that it could continue with Beaufort development (which by this stage was being deliberately stifled by the british with their embargo on the export of engine technologies. it would take until October 1941 for a substitute US engine production line to be founded),

With no domestic fighters in production, and existing resources otherwise committed, the Australian commitment to send two fighter sqadrons to Malaya was utterly dependant on the british supplying aircraft. At the time this deployment was being discussed (Fenruary 1941), menzies had wanted the units to be equipped with hurricanes, but was told that in the interests of standardisation the buffalo would need to do. It was stated at the time that the Brewster was more than adequate to deal with the IJAAF. In this period two units were so equipped.....453 and 21 sqns. both were officially RAAF units. both were manned, in the main by Australians. their deployment to Malaya required approval of the Australian Govt.. the aircraft supplied to them were British owned, but I have never, until now, heard any claim these formations were british formations. it is, indeed, a very big stretch to say that. if for some reason, the Australians had insisted those squadrons return home , they would have done so with those a/c on strength and available, as indeed survivor Buffaloes did (I know of at least two airframes that did, A51-10 and A51-11).

Some buffaloes eventually were serialised using Australian registration codes, though I believe they were ex-Dutch A51-1 to A-51-17 were all registered as Ä"series registered aircraft. this places them firmly under australian control.

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## parsifal (Mar 16, 2018)

Thought this link on P-39s in Australia might be helpful

http://www.adf-serials.com.au/research/Airacobra.pdf

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## Glider (Mar 16, 2018)

One aspect not mentioned is payload. The Typhoon and the P47 and P38 could carry a serious amount of bombs/rockets and were normally used as GA aircraft. The P39 wasn't even close in this area. If you commanded an air force you want flexibility and this the P39 didn't give you. It lacked payload and armour for GA work

I also like the others believe you are almost ignoring the difficulties that weight give you The P39's center of gravity problems were grave

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## pbehn (Mar 16, 2018)

Glider said:


> One aspect not mentioned is payload. The Typhoon and the P47 and P38 could carry a serious amount of bombs/rockets and were normally used as GA aircraft. The P39 wasn't even close in this area. If you commanded an air force you want flexibility and this the P39 didn't give you. It lacked payload and armour for GA work
> 
> I also like the others believe you are almost ignoring the difficulties that weight give you The P39's center of gravity problems were grave


As a fighter bomber the Typhoon had 350Kg of armour added around the radiator and under/ beside the pilot.


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## Elmas (Mar 16, 2018)

_"He remembers having a Japanese bomber in his gunsight and the cannon rounds from the P-39 falling short. “
“It was also the only American fighter that didn’t have a fan club.”
"P-400? A P-39 with a Zero on his tail..."_

It seems that among American Pilots P-39 was not a beloved plane...

https://www.defensemedianetwork.com...39-airacobra-in-the-pacific-posed-challenges/

Bell P-39 Airacobra

WWII Planes: The P-39 Airacobra “Peashooter”

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## Glider (Mar 16, 2018)

pbehn said:


> As a fighter bomber the Typhoon had 350Kg of armour added around the radiator and under/ beside the pilot.


I agree now lets see what happens to a P39 with that much armour and the 2,000lb of bombs


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## pbehn (Mar 16, 2018)

Glider said:


> I agree now lets see what happens to a P39 with that much armour and the 2,000lb of bombs


That 2000Ib bomb load is approximately the same as a Do-17 a few years before without the armour, but the Typhoon is a very competent and potent fighter when they have been dropped. That indication of how quickly things changed in WW2 which is what I find irksome in this discussion.


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## CORSNING (Mar 17, 2018)

pinsog said:


> The P39 had an unspectacular record against Japanese fighters. Was it an issue of pilot training against an unfamilier enemy aircraft
> 
> *Yes!, use altitude.
> *
> ...



*The Airacobras of the period did not have the altitude performance to get above the Zero
to do so, as has been pointed out by several others.


The overall performance of later P-39 actually increased dramatically IMO. The
overall performance of the later Zeros did not. But by the time the late 1942 
P-39N appeared the reputation damage had been done. At this time the A6M3
Model 32 had been in service since April 1942.
*

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## Shortround6 (Mar 18, 2018)

P-39 Expert said:


> And below 5km altitude (16500') the P-39Ns advantage in both speed and climb is huge. Now, please let me hear from all you "two speed" and crankshaft experts about how big an advantage low gear is. As you can see from the charts the two speed supercharger results in a "sawtooth" speed and climb curve while the single speed P-39N develops its maximum power at 3km (10000') and then gradually declines from there up to the combat ceiling. Most historians would have you believe that the Allison engine fell off the mounts and the plane tumbled to earth after crossing 12000'. This was a much better plane than history gives credit for.



Oh, boy. 
There were basically 3 different engines used mass produced P-39s.

The E4, used in the P-39C, the P-400, the P-39D and the P-39F (different propeller)
These engines were rated at 1150hp for take-off, and would hold 1150hp from sea level to 12,000ft (42inMAP) no ram. after that power fell off, at 15,000ft you had 1020 hp, at 20,000ft you had about 830hp. 
WEP was 1490hp (56in MAP) which is certainly a nice boost, _HOWEVER, _this was only good till 4,300ft at which point power declines to meet the 1150hp at 12,000ft, for instance power at 8000ft is about 1325hp. There is no _tweaking _of the boost control. The supercharger simply is maxed out and cannot supply any more air at that altitude and engine rpm. *ANY *over boosting above 56in requires the ram effect from forward speed, *OR* over revving the engine beyond 3000rpm, *OR* being below 4,300ft or a combination of the above. 

The E6 engine was used in the P-39K and L, about 460 of these P-39s were built so they are not common. The engine got some stronger parts ( and a different reduction gear to the propeller)and was uprated to 1325hp for take-off (using 51in MAP) , but since it used the same supercharger gear and pretty much the same basic supercharger (minor details/improvements) it was still rated at 1150hp (42in MAP) at 12,000ft. No improvement in altitude performance. WEP was allowed to go to 1580hp at 60in of MAP but this was only good to 2500ft at which point power declined with altitude until........._surprise_....... it was making 1490hp at 4300ft and then on to the 1150hp at 12,000ft. Over boosting above the 60in limit was limited to the three conditions already mentioned _*except*_ the lower altitude limit.

3rd engine was the E18/19, only around 240 planes were built with E-18 (P-39Ms) and the primary difference was the reduction gear ratio to the propeller so both can be considered together. This is were the 9.60 gears show up.

The engine was rated at 1200hp for take-off (50.5in MAP) and with a bit fudging with the numbers, 1125hp at 15,500 (42in MAP). I say fudging because 1150hp probably fell on some odd number rather than a multiple of 500. Now you do have about 100hp more at 15,000 feet or so and at any higher altitudes, HOWEVER, you do NOT have more power at lower altitudes. 
WEP was limited to 1410hp at 57in MAP. at very low levels (under 2500-3500ft) using MAP you have 80 hp less than the early engines and 170hp less than the scarce intermediate engines. 
Allison was, as I have said, issuing stron warnings about over boosting this later engines. 
Now, for all those people who think the automatic boost limiter was a gift from the aircraft gods and rendered 2 speed superchargers so much overweight junk lets take another look at the numbers.
The engines with the 9.60 gears made 125hp less for take-off using *0.5lbs *_less boost_ than the engines using 8.80 gears. *WHY?*
Because the higher gear ratio took more power to drive, 40-50hp? you had less power to the prop. You also had more heat going to the intake mixture and the air was less dense. Fewer pounds of air 10,000 cubic feet even at the same pressure. Please note the 3in drop in max pressure used for WEP power rating. A direct result of the high temperature in the supercharger/intake manifold due the faster spinning impeller. Over boosting beyond the approved 57in was coming closer to wrecking the engine that over boosting beyond 60 in on the older engines. 

I would note that without RAM the Allison engines using 9.60 gears were rated at about 950hp at 20,000ft with about 37in of MAP (3 1/2 /bs boost) available at 3000rpm and no amount of "magic" from an automatic boost limiter is going to fix that. 

The Allison with 9.60 gears was good for about 1020hp at 18,500ft compared to the Merlin V-1650-1 in the P-40 having 1120hp at 18,500ft. 
In Low gear it had 1240hp at 11,500ft, both at 9lbs boost (roughly 48in MAP) 
It had 1300hp for take-off. 
Pretty much seems like a 100hp advantage for the 2 speed engine at may altitudes and I would be very careful about bringing up the WEP settings for the Allison as those HP ratings for the Merlin are Military ratings, not WEP and an overboosted Merlin can also have several hundred hp more on tap. 

I would note that the Russian M-105 engines were also pretty crappy much above 12,000ft so the Russians don't have a lot to compare to. 
The ASh-82 was also set up with low gear maxing out around 5400-6600ft and high gear maxing out around 13-15000ft(?) so altitude performance wasn't that great either. But then Russian gas wasn't that good so allowable boost was limited.

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## RCAFson (Mar 18, 2018)

Zero versus P39:

http://www.wwiiaircraftperformance.org/japan/intelsum85-dec42.pdf

note the boost levels used on the P39.


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## tomo pauk (Mar 18, 2018)

Shortround6 said:


> Oh, boy.
> There were basically 3 different engines used mass produced P-39s.
> 
> The E4, used in the P-39C, the P-400, the P-39D and the P-39F (different propeller)
> ...



Seems like the -35 and -37 engines from late 1941 were not capable to make 1150 HP at 11800-12000 ft, but at just 11200 ft. Or 1090 HP at 12500 ft. (doc attached)
Coupled with 'shaded' ram air intake, the altitude performance is not going to cut it. BTW - late V-1710s on the P-39Q were making 1410-1420 HP on 57 in Hg and 3000 rpm, vs. 1480 on same boost and rpm on the P-40N and P-51A.



> I would note that the Russian M-105 engines were also pretty crappy much above 12,000ft so the Russians don't have a lot to compare to.
> The ASh-82 was also set up with low gear maxing out around 5400-6600ft and high gear maxing out around 13-15000ft(?) so altitude performance wasn't that great either. But then Russian gas wasn't that good so allowable boost was limited.



They have had AM-35A that made 1200 CV at 19700 ft in 1941, that will take V-1710 with 2-stage supercharger from late 1943 to beat.
Altitude performance of the ASh-82 was again 1200 CV at 20000 ft, again it will take a V-1710 with 2-stage S/C to best it. Boost figures of both of Soviet engines were hampered due to high compression ratio, 7:1.

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## Shortround6 (Mar 18, 2018)

Figures for early Allisons are all over the place due to different standards and minor equipement like backfire screens (more than one type) and intake manifolds (again, more than one type), while production engines may have been more standardized, prototype or early test samples sometimes differed from production examples.

Not at all helped in 1940-41 by the changes in fuel specifications. American 100 octane, American 100/125, British 100 octane and joint 100/130.
A number of Allisons were developed and tested using the 100/125 that was never (?) shipped overseas. 


Point about the Russian engines is that the majority of Russian engines didn't have very good altitude performance. The AM-35 aside and since there were only a few thousand of them out of tens of thousands (hundred thousand?) of engines, most Russian pilots and air commanders had little or no experience with them. 
SO by comparison the P-39s didn't look all that bad.

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## Shortround6 (Mar 18, 2018)

RCAFson said:


> Zero versus P39:
> 
> http://www.wwiiaircraftperformance.org/japan/intelsum85-dec42.pdf
> 
> note the boost levels used on the P39.



Note that 70inches, which other sources claim could barely be reached at sea level, caused detonation and could not be used in the test. The US of 52-55in of MAP is firmly in WEP range. NO note is made of when the P-39 dropped down in the mid to low 40in pressure range due to altitude.


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## P-39 Expert (Mar 18, 2018)

tomo pauk said:


> Seems like the -35 and -37 engines from late 1941 were not capable to make 1150 HP at 11800-12000 ft, but at just 11200 ft. Or 1090 HP at 12500 ft. (doc attached)
> Coupled with 'shaded' ram air intake, the altitude performance is not going to cut it. BTW - late V-1710s on the P-39Q were making 1410-1420 HP on 57 in Hg and 3000 rpm, vs. 1480 on same boost and rpm on the P-40N and P-51A.
> 
> 
> ...


Notice on the Temporary Specific Operating Instructions Chart in the upper left hand corner it says "Engine-V-1710-35 (with backfire screens) meaning the screens were still in the intake ports causing reduced MP and excess maintenance. These were removed from the engine permanently in mid 1942 about the same time that takeoff power was increased from 5 minutes to 15 minutes. Without the screens the -35 developed it's full 1150hp at 12000'.

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## P-39 Expert (Mar 18, 2018)

Shortround6 said:


> Oh, boy.
> There were basically 3 different engines used mass produced P-39s.
> 
> The E4, used in the P-39C, the P-400, the P-39D and the P-39F (different propeller)
> ...


The Merlin made more power. I'm comparing the performance of the FW190A6 to the P-39N. With the Allison engine. P-39 was almost as fast but climbed much better, right? And it didn't have a two speed blower, like the FW, right?


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## Shortround6 (Mar 18, 2018)

You are comparing two different airframes, that differed in weight by 1800lbs with different types of engine, using different fuel and trying to draw a conclusion about the type of supercharger????

Lets try to compare apples to apples and not apples to brussel sprouts.


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## parsifal (Mar 18, 2018)

_Lets try to compare apples to apples and not apples to brussel sprouts_.

Fruit to vegetables. Looks more like reality to fantasy to me.


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## wuzak (Mar 19, 2018)

P-39 Expert said:


> Right, the Spit held 100 American gallons and the P-39 held 120 American gallons.





> After completion of the first 166 P-39Ns, the USAAF requested that four fuel cells be removed in order to reduce the internal fuel capacity from 120 to 87 US gallons, and so to reduce the maximum permissible gross weight from 9100 lbs to 8750 lbs. This kept weight down, but unfortunately it also restricted range.


Bell P-39N Airacobra

It seems that the bulk of the P-39Ns had only 87USG from the factory, though they could be brought back up to 120USG in the field.

Depending on the supvariant, it looks like the P-39Q could have between 87USG and 120USG.
Bell P-39Q Airacobra


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## pbehn (Mar 19, 2018)

P-39 Expert said:


> The Merlin made more power. I'm comparing the performance of the FW190A6 to the P-39N. With the Allison engine. P-39 was almost as fast but climbed much better, right? And it didn't have a two speed blower, like the FW, right?


As has been stated many times the problem of the FW190 was solved by the Spitfire MkIX at all altitudes before the P-39-N arrived. By the time the P-39N was available the F4-U and P47 were coming into service.

In operations from UK being slower than your opponent is not a minor issue, the minimum distance to France is 21 miles but it quickly increases to over 100, you cannot sneak in over water, at low level you are seen and in range of every man with a rifle or machine gun. You cannot disengage by climbing and if you are slower you cant run away.


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## tomo pauk (Mar 19, 2018)

P-39 Expert said:


> Notice on the Temporary Specific Operating Instructions Chart in the upper left hand corner it says "Engine-V-1710-35 (with backfire screens) meaning the screens were still in the intake ports causing reduced MP and excess maintenance. These were removed from the engine permanently in mid 1942 about the same time that takeoff power was increased from 5 minutes to 15 minutes. Without the screens the -35 developed it's full 1150hp at 12000'.



Military power duration went to 15 minutes, both take off ans WER were set at 5 min duration (though that duration was many times exceeded in heat of combat).
Thing with backfire screens removed in mid 1942 is that it does not help the RAF in 1941 or in 1st half of 1942. The P-39D even with engines making 1150 HP at 12000 ft will not cut it against the LW opposition, while P-39M/N is too late to matter for ETO.



P-39 Expert said:


> The Merlin made more power. I'm comparing the performance of the FW190A6 to the P-39N. With the Allison engine. P-39 was almost as fast but climbed much better, right? And it didn't have a two speed blower, like the FW, right?



Fw 190 was capable to take off with much greater extenal load, almost 4000 lb total, due to having plenty of power for take off. Having the low speed S/C to choose from was worth 400-600 HP for take off. That also meant that it was capable to make 1900 HP at low level from mid-1943 on, time to climb to 26000 ft was reduced to just 8.5 min on 2700 rpm, speed went to 400+ mph above 13000 ft. link

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## michaelmaltby (Mar 19, 2018)

It is noteworthy that the Soviets used P-39Qs for photo reconnaissance ... I did not know that .... but makes great sense ... based immediately behind the front ... Qs could fly short range tactical missions. Removing belly tanks to enable this was a shrewd trade-off, IMO. Never under-estimate the Soviets.


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## P-39 Expert (Mar 19, 2018)

Shortround6 said:


> You are comparing two different airframes, that differed in weight by 1800lbs with different types of engine, using different fuel and trying to draw a conclusion about the type of supercharger????
> 
> Lets try to compare apples to apples and not apples to brussel sprouts.


I'm comparing the performance of two fighter planes that were used at the same time in WWII, the FW190A6 and P-39N. They had different weights and different engines, mainly because they were manufactured by different countries and opposed each other in battle. P-39N was as good (at least) as the FW190A6. Government performance figures prove this.

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## P-39 Expert (Mar 19, 2018)

tomo pauk said:


> Military power duration went to 15 minutes, both take off ans WER were set at 5 min duration (though that duration was many times exceeded in heat of combat).
> Thing with backfire screens removed in mid 1942 is that it does not help the RAF in 1941 or in 1st half of 1942. The P-39D even with engines making 1150 HP at 12000 ft will not cut it against the LW opposition, while P-39M/N is too late to matter for ETO.
> 
> 
> ...


P-39N came out in December 1942, how is that too late for the ETO? 
Check your date on the linked document in the upper right corner, 12/13/1943. The air war for fighters would be basically over three months later in March 1944. Plenty of bombing and ground attack missions yet to go, but if you even saw a Luftwaffe or Japanese plane after then you were the hit of the officers club that evening. So the FW190 would have this performance for about 3 months. I'll stick with my figures for the FW190A6.


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## Peter Gunn (Mar 19, 2018)

It doesn't matter if your vaunted N "came out" in December '42, it's not too late for the ETO, it's too useless for the ETO. Range is unsuitable for 8th AF escort ops, performance is useless for 8th AF escort ops at bomber altitudes, payload and range is useless for 9th AF tactical ops, no climb performance above 10,000 ft for interception duties, and on top of all that, it's too GD slow for the theater as a whole.
Not argumentative, just fact.

Also, after March of 1944 Luftwaffe fighters were so scare that just to see one made you a hit at the O club? Riiiight. Might want to rethink that gem.

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## pbehn (Mar 19, 2018)

Peter Gunn said:


> It doesn't matter if your vaunted N "came out" in December '42, it's not too late for the ETO, it's too useless for the ETO. Range is unsuitable for 8th AF escort ops, performance is useless for 8th AF escort ops at bomber altitudes, payload and range is useless for 9th AF tactical ops,* no climb performance above 10,000 ft* for interception duties, and on top of all that, it's too GD slow for the theater as a whole.
> Not argumentative, just fact.
> 
> Also, after March of 1944 Luftwaffe fighters were so scare that just to see one made you a hit at the O club? Riiiight. Might want to rethink that gem.


If a plane has no performance above 10,000ft then if your enemy has, he just climbs straight to 10,000ft. and looks down at you laughing. This happened to early Griffon Spitfires.

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## tomo pauk (Mar 19, 2018)

P-39 Expert said:


> P-39N came out in December 1942, how is that too late for the ETO?



It does not add anything to two main tasks the day fighters were doing in the ETO from late 1942 - bomber escort at 20000-30000 ft as far as possible, and fighter-bomber duties involving a good-sized load of bombs or rockets. P-39N for ETO is a solution looking for a problem.



> Check your date on the linked document in the upper right corner, 12/13/1943. The air war for fighters would be basically over three months later in March 1944. Plenty of bombing and ground attack missions yet to go, but if you even saw a Luftwaffe or Japanese plane after then you were the hit of the officers club that evening. So the FW190 would have this performance for about 3 months. I'll stick with my figures for the FW190A6.



I have no problems with you sticking with any set of numbers you prefer. LW was flying fighter missions in 1945, let alone in 1944.
The P-39M/N/Q will be fine fighters for altitudes under 15000 ft where long range is not required - talk Eastern front. As-is, they have nothing to add in ETO, Asia/Pacific and, possibly, MTO.

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## Shortround6 (Mar 19, 2018)

P-39 Expert said:


> I'm comparing the performance of two fighter planes that were used at the same time in WWII, the FW190A6 and P-39N. They had different weights and different engines, mainly because they were manufactured by different countries and opposed each other in battle. P-39N was as good (at least) as the FW190A6. Government performance figures prove this.





P-39 Expert said:


> And below 5km altitude (16500') the P-39Ns advantage in both speed and climb is huge. *Now, please let me hear from all you "two speed" and crankshaft experts about how big an advantage low gear is.* As you can see from the charts the two speed supercharger results in a "sawtooth" speed and climb curve while the single speed P-39N develops its maximum power at 3km (10000') and then gradually declines from there up to the combat ceiling.



You wanted to hear from us about the advantage of the low gear, you did, you just don't *want *to hear about it or you want to ignore it if it conflicts with your pet theory. 
You remind me of an old fire captain I had, didn't know squat about hydraulics and thought if you screwed a magic nozzle on the end of the hose it did away with all the friction loss and calculations needed for different setups (different distances from pump to nozzle) .

You ignore what you don't want hear and try to change the argument. 

It isn't hard to figure out that a 7300lb aircraft is going to outclimb a 9100lb aircraft. The 9100lb aircraft needs about 25% more power than the 7300lb aircraft just for starters. The FW 190 didn't have it regardless of the type of supercharger it had. 
You have proved nothing about the types or advantages of superchargers.

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## pbehn (Mar 19, 2018)

The Spitfire doubled in weight from first to last versions, I cant remember anyone suggesting it would have been a better plane with less guns, armour thinner skin covering etc, possibly because it was a bit of a lightweight next to a "Jug".


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## Glider (Mar 19, 2018)

pbehn said:


> The Spitfire doubled in weight from first to last versions, I cant remember anyone suggesting it would have been a better plane with less guns, armour thinner skin covering etc, possibly because it was a bit of a lightweight next to a "Jug".


The special thing about the Spitfire was it did increase its weight, power firepower but it was as good as the best of the opposition, the P39 never was and was always trying to play catchup. The Spitfire didn't need to lose weight to match with the opposition
In 1940 the two best fighters in the world were the 109E and the Spitfire. When the Fw190 entered service it was the best until the Mk IX arrived on the scene. Even late war The Mk XIV was a fighter that could take on the best.
It wasn't perfect but few would deny that range was the one big problem from start to finish. That said the specialised PR versions were arguably the best PR aircraft of the war with an almost astonishing range. It wasn't a great GA aircraft but carried up to a 1000lb of bombs and some (I think) up to 1,500Lb.

The important part of this posting was* it (the Spitfire) was as good as the best of the opposition, the P39 never was and was always trying to play catchup. *

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## P-39 Expert (Mar 19, 2018)

Peter Gunn said:


> It doesn't matter if your vaunted N "came out" in December '42, it's not too late for the ETO, it's too useless for the ETO. Range is unsuitable for 8th AF escort ops, performance is useless for 8th AF escort ops at bomber altitudes, payload and range is useless for 9th AF tactical ops, no climb performance above 10,000 ft for interception duties, and on top of all that, it's too GD slow for the theater as a whole.
> Not argumentative, just fact.
> 
> Also, after March of 1944 Luftwaffe fighters were so scare that just to see one made you a hit at the O club? Riiiight. Might want to rethink that gem.


Did you look at the graphs? P-39N performance was about the same as the FW190A6 except the P-39 climbed a lot better. No climb performance above 10000'? Did you look at the charts, post #148? Plenty of climb at all altitudes.
And yes, German and Japanese fighters were extremely scarce (or inept) after March 1944. Air superiority had been won clearing the way for the D-Day invasion in June. The Great Marianas Turkey Shoot that same June proved the Japanese were beaten when the Navy shot down 350 Japanese planes for the loss of 30 some odd Hellcats. The Axis were beaten in the air, everybody knew it and sightings of opposing fighters was indeed rare.


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## P-39 Expert (Mar 19, 2018)

Glider said:


> The special thing about the Spitfire was it did increase its weight, power firepower but it was as good as the best of the opposition, the P39 never was and was always trying to play catchup. The Spitfire didn't need to lose weight to match with the opposition
> In 1940 the two best fighters in the world were the 109E and the Spitfire. When the Fw190 entered service it was the best until the Mk IX arrived on the scene. Even late war The Mk XIV was a fighter that could take on the best.
> It wasn't perfect but few would deny that range was the one big problem from start to finish. That said the specialised PR versions were arguably the best PR aircraft of the war with an almost astonishing range. It wasn't a great GA aircraft but carried up to a 1000lb of bombs and some (I think) up to 1,500Lb.
> 
> The important part of this posting was* it (the Spitfire) was as good as the best of the opposition, the P39 never was and was always trying to play catchup. *


Continuing to disagree with you, go to wwiiaircraftperformance.org. Their latest update to the P-39 was in 2012, fairly recent for research. All the other WWII fighters are there (except Russia) with the official government docs for performance. Compare the performance graphs head to head and chronologically. You will find that the German and Japanese planes were not super planes. The P-39 had surprisingly good performance especially after all the negative propaganda you have heard about them for the last 70 years. Fascinating reading and no editorial license, just facts.


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## pbehn (Mar 19, 2018)

P-39 Expert said:


> Did you look at the graphs? P-39N performance was about the same as the FW190A6 except the P-39 climbed a lot better. No climb performance above 10000'? Did you look at the charts, post #148? Plenty of climb at all altitudes.
> And yes, German and Japanese fighters were extremely scarce (or inept) after March 1944. Air superiority had been won clearing the way for the D-Day invasion in June. The Great Marianas Turkey Shoot that same June proved the Japanese were beaten when the Navy shot down 350 Japanese planes for the loss of 30 some odd Hellcats. The Axis were beaten in the air, everybody knew it and sightings of opposing fighters was indeed rare.


Oh for goodness sake, we have now entered 1944 with the P-39-N, put your performance figures against the Tempest, Spitfire Mk XIV, P51-B, Corsair and Hellcat.
It needs to escort a bomber formation, shoot down a V1 or be good at ground attack as well as just fight with an FW 190 at your chosen altitude.

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## P-39 Expert (Mar 19, 2018)

tomo pauk said:


> Military power duration went to 15 minutes, both take off ans WER were set at 5 min duration (though that duration was many times exceeded in heat of combat).
> Thing with backfire screens removed in mid 1942 is that it does not help the RAF in 1941 or in 1st half of 1942. The P-39D even with engines making 1150 HP at 12000 ft will not cut it against the LW opposition, while P-39M/N is too late to matter for ETO.
> 
> 
> ...


Your link to the FW190 is interesting in that it is dated December 1, 1943 and in the first paragraph says that this investigation is to increase boost in the FW190A8 which began production in Feb 1944. A FW190A5 was used as test bed since they had the same engine. These increases in boost were obviously never put into service as the performance graphs for the A6 and A8 (both later models) do not reflect these performance increases. Go to the site that your link is from, wwiiaircraftperformance.org and look up the FW190A8.


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## fubar57 (Mar 19, 2018)



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## Milosh (Mar 19, 2018)

Starting from July 1944 all Fw 190 A-8 aircraft will be equipped with "increased emergency". By overridding the supercharger boost regulator, boost pressures are increased at take-off and emergency power in low supercharger setting from *1,42 ata to 1,58 ata* and at the high supercharger setting from 1*,42 to 1,65 ata*.


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## drgondog (Mar 19, 2018)

P-39 Expert said:


> Did you look at the graphs? P-39N performance was about the same as the FW190A6 except the P-39 climbed a lot better. No climb performance above 10000'? Did you look at the charts, post #148? Plenty of climb at all altitudes.
> And yes, German and Japanese fighters were extremely scarce (or inept) after March 1944. Air superiority had been won clearing the way for the D-Day invasion in June. The Great Marianas Turkey Shoot that same June proved the Japanese were beaten when the Navy shot down 350 Japanese planes for the loss of 30 some odd Hellcats. The Axis were beaten in the air, everybody knew it and sightings of opposing fighters was indeed rare.



You might have missed the memo


P-39 Expert said:


> P-39N came out in December 1942, how is that too late for the ETO?
> Check your date on the linked document in the upper right corner, 12/13/1943. The air war for fighters would be basically over three months later in March 1944. Plenty of bombing and ground attack missions yet to go, but if you even saw a Luftwaffe or Japanese plane after then you were the hit of the officers club that evening. So the FW190 would have this performance for about 3 months. I'll stick with my figures for the FW190A6.



You have an 'interesting' view of the air war in the ETO. You are also seemingly clueless regarding 'gestation period' to introduce a new model, produce it in quantity and deploy it in Group level strength. AFAIK, four US Fighter Groups Began receiving P-39N for combat deployment in Q3/1943 - the 354th, 357th & 363rd destined for 9th AF CAS role for ETO in November-December 1943. The 332nd FG destined for 12th AF and also CAS role went to MTO in November 1943. The decision was made that the ETO bound FG's would convert immediately as the first combat deployed P-51B-1 and prepare for CAS role leading up and through D-Day. The 332nd also left the P-39Ns in the States, and converted to P-40N upon arrival, then P-47D, then P-51B/C in June 1944.

Deployment of P-39s to SWP also stopped in fall 1943. The NET-NET is that despite improved low and mid altitude performance equivalent performance against Bf 109/FW 190 the incredibly stupid leaders of the AAF came to the following convictions in mid 1943:

1.) there was no clear cut role for the P-39M/N/Q or P-63 for Any mission ranging from CAS to middle altitude escort to Recon to long range escort in which either the P-51B, the P-47D or P-38H/J was not superior - range, top speed, load carrying capability being dominant. The P-39 was very limited in range and even moreso when bombs replaced external fuel tanks. The beneficial mid altitude performance didn't matter as our bases were not close to front lines except for North Africa and SWP - and the P-39 was clobbered by the Japanese and German aircraft engaged in those timeframes.

2.) the Russians very much wanted them because their air/ground mission and tactics were entirely different and suitable for the P-39. That said the Yak 3 and Laag 7 quickly replaced the P-39s in the Guards units tasked with interceptor/air superiority role. 

So, it was an easy decision by stupid leaders aware of the US Mission doctrine to decide to let Bell continue production for Russians - but quit buying Bell for AAF.

And, NO the air war in the ETO was 'not over' in March, 1944 when only four ETO FG (2-9thAF 2-8th AF) were flying Mustangs, and 3 P-38 FG, for LR Escort and just in the early phase of taking out the LW capability of inflicting unacceptable losses on 8th BC.

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## DarrenW (Mar 19, 2018)

This is probably one of the most interesting and enlightening threads that I have had the pleasure NOT to be a part of......

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## Glider (Mar 19, 2018)

P-39 Expert said:


> Continuing to disagree with you, go to wwiiaircraftperformance.org. Their latest update to the P-39 was in 2012, fairly recent for research. All the other WWII fighters are there (except Russia) with the official government docs for performance. Compare the performance graphs head to head and chronologically. You will find that the German and Japanese planes were not super planes. The P-39 had surprisingly good performance especially after all the negative propaganda you have heard about them for the last 70 years. Fascinating reading and no editorial license, just facts.


I have done and must have missed something - can you point out to me where the P39 matches the 440 mph of the Spit XIV because I cannot find it, in fact I cannot find where is matches the 413mph of the Spit IX.
Or to make it easier for you, where does the P39 match the Spitfire IX climb rate at sea level of 4,700 ft/min at 7,000ft, I can only find 4,000 ft/min for the P39N. If we wish we can look at altitude but the best I can find for the P39 is 15,000 ft where I can find 3,230 ft/min. The Spit was climbing at 3,480 ft/min at approx. 25,000 ft where the P39N seems to max out at 1,940 ft/min which isn't good.
If you want to compare the P39D against a Spit V feel free.

As you say its just facts.

Edit - As a low altitude aircraft in Europe GA missions are certain. Can you tell us how the P39 compares to other aircraft in this role. I honestly have no idea of the GA capability of the P39 but suspect its little if any apart from the guns.

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## Shortround6 (Mar 19, 2018)

Glider said:


> Edit - As a low altitude aircraft in Europe GA missions are certain. Can you tell us how the P39 compares to other aircraft in this role. I honestly have no idea of the GA capability of the P39 but suspect its little if any apart from the guns.



Most/all could carry one 500lb (or 600lb) bomb where the drop tank went. None were ever fitted for underwing loads in service. 
I would guess that smaller bombs could be carried (singly) and the 600lb bomb was a pre-war/early war bomb that surprisingly showed up in combat reports of B-17s after you would have thought it disappeared. 
Late model P-40s were turned into bomb trucks (up to three 500lbs and they rigged racks to take multiple 250s under the wings) which _may _help explain their use after they were outmoded as fighters, using pretty much the same basic engine as the P-39.

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## Shortround6 (Mar 19, 2018)

Photo of a model that illustrates the Problem of a P-39 as a bomb truck




There is only so much room between the wheel doors for stores carried on the center line




Not a lot of room for big single stores. The wing never got beefed up (nor were controls fitted) to take under wing loads except for the .50 cal gun pods. 
P-63s were fitted with under wing racks for drop tanks, bombs and even rockets, the triple "bazooka" style.

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## wuzak (Mar 19, 2018)

pbehn said:


> If a plane has no performance above 10,000ft then if your enemy has, he just climbs straight to 10,000ft. and looks down at you laughing. This happened to early Griffon Spitfires.



I think what Spitfire XII pilots found is that the Germans could not really distinguish between a Spitfire V, a Spitfire IX and a Spitfire XII at distance.

The 109 and 190s in service at that time could comfortable handle a V, the IX was a handful for them, particularly at higher altitudes, and the XII would span them at low altitudes. 

Not being able to clearly identify which version of Spitfire was in the area, the Luftwaffe would be reluctant to engage.

PS: Not sure if Spitfire Vs remained in service in the ETO in early 1943, when the XII was deployed.

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## pbehn (Mar 19, 2018)

wuzak said:


> I think what Spitfire XII pilots found is that the Germans could not really distinguish between a Spitfire V, a Spitfire IX and a Spitfire XII at distance.
> 
> The 109 and 190s in service at that time could comfortable handle a V, the IX was a handful for them, particularly at higher altitudes, and the XII would span them at low altitudes.
> 
> ...


I just read it a few days ago, production Mk XIIs all had clipped wings so perhaps not so difficult to tell at a distance.


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## Shortround6 (Mar 19, 2018)

A fair number of MK Vs had clipped wings.

MK Vs with cropped impeller engines had some rather startling climb rates even if top speed was a bit low. 

I have thought of another reason that P-39s weren't used as bomb trucks.
This is speculation but the P-39 was a ground loving airplane. 
A P-39L with the 1325hp take-off power engine needed 1600ft of runway at 7800lbs, Zero head wind and at 0 degrees C. This weight would be without bomb or drop tank. Other models needed just a bit more. 
A P-40E with an 1150hp engine needs the same 1600ft at 8700lbs. That is with drop tank or 500lb with slightly reduced fuel or ammo. 
The only US fighters to need significantly more runway to take-off clean, at sea level, were the P-47 and P-61.

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## P-39 Expert (Mar 20, 2018)

Milosh said:


> Starting from July 1944 all Fw 190 A-8 aircraft will be equipped with "increased emergency". By overridding the supercharger boost regulator, boost pressures are increased at take-off and emergency power in low supercharger setting from *1,42 ata to 1,58 ata* and at the high supercharger setting from 1*,42 to 1,65 ata*.


Nothing on the FW190A8 performance charts shows any boost setting over 1.42. And by July 1944 the air war was truly lost for the Luftwaffe, so too little too late.


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## Elmas (Mar 20, 2018)

Could have been this plane the best fighter of WWII?






Just add somewhere in the airframe a couple of MGs...

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## P-39 Expert (Mar 20, 2018)

Glider said:


> I have done and must have missed something - can you point out to me where the P39 matches the 440 mph of the Spit XIV because I cannot find it, in fact I cannot find where is matches the 413mph of the Spit IX.
> Or to make it easier for you, where does the P39 match the Spitfire IX climb rate at sea level of 4,700 ft/min at 7,000ft, I can only find 4,000 ft/min for the P39N. If we wish we can look at altitude but the best I can find for the P39 is 15,000 ft where I can find 3,230 ft/min. The Spit was climbing at 3,480 ft/min at approx. 25,000 ft where the P39N seems to max out at 1,940 ft/min which isn't good.
> If you want to compare the P39D against a Spit V feel free.
> 
> ...


Just the facts, Spit XIV production was started in late 1943 and operational service was mainly from 1944. P-51B entered combat in 1944 (Dec. 1943). P-39N was in service from Dec. '42, a full year earlier. 
And no, N could not climb with the Spit IX, but then nothing could. N could substantially outclimb a FW190 at all altitudes.


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## wuzak (Mar 20, 2018)

P-39 Expert said:


> Just the facts, Spit XIV production was started in late 1943 and operational service was mainly from 1944. P-51B entered combat in 1944 (Dec. 1943). P-39N was in service from Dec. '42, a full year earlier.



Deliveries of P-39Ns started in December 1942. They weren't in service in 1942.

From an earlier post:



drgondog said:


> You have an 'interesting' view of the air war in the ETO. You are also seemingly clueless regarding 'gestation period' to introduce a new model, produce it in quantity and deploy it in Group level strength. AFAIK, *four US Fighter Groups Began receiving P-39N for combat deployment in Q3/1943* - the 354th, 357th & 363rd destined for 9th AF CAS role for ETO in November-December 1943. The 332nd FG destined for 12th AF and also CAS role went to MTO in *November 1943*. The decision was made that the ETO bound FG's would convert immediately as the first combat deployed P-51B-1 and prepare for CAS role leading up and through D-Day. The 332nd also left the P-39Ns in the States, and converted to P-40N upon arrival, then P-47D, then P-51B/C in June 1944.


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## wuzak (Mar 20, 2018)

P-39 Expert said:


> And no, N could not climb with the Spit IX, but then nothing could. N could substantially outclimb a FW190 at all altitudes.



Not much could. But I believe some versions of the Bf109G at around the same time could. Bearing in mind that the IX gained power over its life as it went from the standard F.IX with Merlin 63 to the HF.IX with Merlin 70 and the LF.IX with Merlin 66. It was the latter whose climb statistics are normally quoted. Prototypes of the HF.IX were testing in late 1942, so probably stated appearing in mid to late 1943.

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## pbehn (Mar 20, 2018)

P-39 Expert said:


> Just the facts, Spit XIV production was started in late 1943 and operational service was mainly from 1944. P-51B entered combat in 1944 (Dec. 1943). P-39N was in service from Dec. '42, a full year earlier.
> And no, N could not climb with the Spit IX, but then nothing could. N could substantially outclimb a FW190 at all altitudes.


The Spitfire of course was in service at the start of the war, the prototype for the Mk IX flew in September 1941, the first test aircraft in Feb 1942 and production started in June 1942. The first Griffon Spitfire the Mk XII outperformed the Mk IX up to 20,000 ft and entered service in Feb 1943.

Please note the RAF were not tasked with the single problem of the FW190 over France. They had to also halt high level German recon planes and low level tip and run raids. Additionally they needed to perform high and low level recon themselves against improving opposition and cope with (x) the unknown. Since the USA was producing 2000BHP+ radials and RR were producing 2,000BHP+ water cooled "V"s there was nothing to stop another shock like the FW190 appearing, as it did with the V1 and Me 262.

In all of the above the P39 was either not up to the job at all or about a year behind the curve.

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## Peter Gunn (Mar 20, 2018)

P-39 Expert said:


> Did you look at the graphs? P-39N performance was about the same as the FW190A6 except the P-39 climbed a lot better. No climb performance above 10000'? Did you look at the charts, post #148? Plenty of climb at all altitudes.
> *And yes, German and Japanese fighters were extremely scarce (or inept) after March 1944. Air superiority had been won clearing the way for the D-Day invasion in June. The Great Marianas Turkey Shoot that same June proved the Japanese were beaten when the Navy shot down 350 Japanese planes for the loss of 30 some odd Hellcats. The Axis were beaten in the air, everybody knew it and sightings of opposing fighters was indeed rare*.



Look, you seem like an intelligent and well read guy, I suggest you read drgondogs post #256 carefully and take it to heart. As I've said, I think the P-39 is one of the best looking fighters of WWII, and I believe that low down over the steppes of Russia it found its niche. But as literally ANYTHING else it was next to useless.

As I stated ( and others as well ), it DID NOT have the performance needed to escort 8th AF bombers ( Range, Speed, Climb, Firepower were all lacking ( dreadfully so ) ) so it was useless to 8th FC.

It DID NOT have the ability to be a bomb truck so it was useless to the 9th AF as its inability to haul any type of useful load any distance squashed that idea.

It DID NOT have the ability to serve as an interceptor regardless of your claims of its outstanding rate of climb ( which seems to have escaped the attention of all the silly pilots that actually flew ( and hated ) the plane ).

As I said earlier, no argument, just fact.

Lastly, referencing the bold type above, I REALLY think you need to catch up on the history of the air war in WWII, because that kind of statement can totally undermine any other argument ( no matter how good ) you bring to the table.

As I said, I think you're an intelligent and well read guy, I hope you'll stick around and learn from some of the most knowledgeable folks on WWII aircraft on the net. ( myself excluded )

Cheers.

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## Milosh (Mar 20, 2018)

P-39 Expert said:


> Nothing on the FW190A8 performance charts shows any boost setting over 1.42. And by July 1944 the air war was truly lost for the Luftwaffe, so too little too late.



Is that so?

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## Shortround6 (Mar 20, 2018)

We seem to be getting into arguing over a one trick pony.

There is no doubt, based on _selected facts, _that certain models of the P-39 could climb at high rate.

This high rate of climb was achieved using WEP and while the Alison was rather justly noted for tolerating abuse this interpretation of the ability of the P-39 needs a bit closer examination. WEP is, War _Emergency _power, not climb to intercept altitude power. Most of the time WEP was limited to 5 minutes but yes, in combat you sometimes have to do what you have to do. HOWEVER, *ANY USE *of WEP had to be noted in logbooks, Crew chiefs and engineering officers made decisions about more frequent spark plug changes and oil changes and repeated use of WEP could affect how soon the engine was pulled for overhaul.
Tests were sometimes run, like the one for the P-39N in which the time limit was considerably exceeded, however such tests were done at air bases/test facilities in non combat zones and within easy access to spare engines/aircraft. The test gave them a good idea what the aircraft was capable of in actual combat, not as an indicator of how quick it could climb to altitude XXX to intercept an incoming force.
As the war went on WEP settings were used a bit more and on occasion were used for getting heavily loaded aircraft out of short runways but that was not the original intention and you had better be pretty sure of your support system to do such things on a regular basis ( not cleaning and re-installing used spark plugs like was done in the Pacific in the early part of the war).

I would note that the British did a few tests of Spitfire Vs using combat ratings for the full climb instead of the "normal" rating and got some rather impressive results. Especially considering that they used full fuel tanks on take-off and not 1/2 filled tanks. In one case they used a Vc that had two cannon and four machine guns but was ballasted to represent a four cannon version. 


The later P-39s, for the American and British forces, it didn't bring a lot to the table.
Other aircraft had showed up that could do more different jobs and devoting the pilots, ground crews, and logistic support to a fighter of limited capability didn't make sense.

For the Russians the equations were a bit different. Or a lot different. The Russian fighters were lightly armed, you could pull guns from the P-39 and still be comparable. The Russian engines were notoriously short lived. You could beat up on the Allisons until they crapped out at 1/2 the hours the US and British wanted and they still lasted longer than most Russian engines. almost all air combat in Russian was at very low altitudes. Russian planes (well over 90%) had engines that were crap much above 12-15000ft so the P-39 fit right in. Russian single engine fighters had crap for bomb loads so the P-39 didn't look bad that way either.
The Russians could allocate the same number of pilots, ground crew and logistic support ( fuel, fuel transport, ammo supply, food and shelter for ground crews, etc) to a P-39 squadron/group and have a very similar combat capability as the same effort devoted to a squadron/group of their own planes. One can argue if it was better or worse than certain Russian planes but the differences are not all that great.

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## pbehn (Mar 20, 2018)

The conflict in Russia was completely asymmetric, at the start of operation Bagration the Germans had 1,000-1300 aircraft while the Russians had 7-8,000 this on a front of over 1000 miles. The German aces may have made big scores where they operated but there were huge areas where they didn't and even where they did they were simply out numbered.


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## michaelmaltby (Mar 20, 2018)

" ... For the Russians the equations were a bit different. Or a lot different. The Russian fighters were lightly armed, you could pull guns from the P-39 and still be comparable. The Russian engines were notoriously short lived. You could beat up on the Allisons until they crapped out at 1/2 the hours the US and British wanted and they still lasted longer than most Russian engines. almost all air combat in Russian was at very low altitudes. Russian planes (well over 90%) had engines that were crap much above 12-15000ft so the P-39 fit right in. Russian single engine fighters had crap for bomb loads so the P-39 didn't look bad that way either.
The Russians could allocate the same number of pilots, ground crew and logistic support ( fuel, fuel transport, ammo supply, food and shelter for ground crews, etc) to a P-39 squadron/group and have a very similar combat capability as the same effort devoted to a squadron/group of their own planes. One can argue if it was better or worse than certain Russian planes but the differences are not all that great."

The Eastern Front was a battleground like none other ... if the P-39 was effective there, _that_ in itself is a tribute to the machine and to Larry Bell.

The P-39s in the USSR were well-supplied from the US ... replacement engines were regularly supplied along with octane boost ... crew chiefs regularly checked engine oil for metal .. and pilots in Guards Squadrons flew the P-39 very aggressively and used combat power regularly. [Dmitriy Loza: Attack of the Airacobras: Soviet Aces American P-39s & The Air War Against Germany]

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## P-39 Expert (Mar 20, 2018)

wuzak said:


> Deliveries of P-39Ns started in December 1942. They weren't in service in 1942.
> 
> From an earlier post:


Dec. '42 to Dec '43 is one year.
Regarding the "gestation period" for a new model, the P-39N was a mature model with the main difference from prior models being a newer version of the same engine (V-1710). "Gestation" was very short, production began in December '42 and P-39Ns were serving that same month in New Guinea. "Gestation" for this model consisted of transporting them to New Guinea. Now I will admit gestation for a new fighter can take an agonizingly long time. The first P-47 Thunderbolt was built in 1941 but first combat was April 1943.


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## P-39 Expert (Mar 20, 2018)

wuzak said:


> Not much could. But I believe some versions of the Bf109G at around the same time could. Bearing in mind that the IX gained power over its life as it went from the standard F.IX with Merlin 63 to the HF.IX with Merlin 70 and the LF.IX with Merlin 66. It was the latter whose climb statistics are normally quoted. Prototypes of the HF.IX were testing in late 1942, so probably stated appearing in mid to late 1943.


Nothing could climb with a SpitIX. A two stage engine mated with a 7500# airframe will get you some climb. P-39N outclimbed the FW190 at all altitudes. P-39N outclimbed the Me109G substantially to 20000' and then climbed with the G ti their ceiling.


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## P-39 Expert (Mar 20, 2018)

Peter Gunn said:


> Look, you seem like an intelligent and well read guy, I suggest you read drgondogs post #256 carefully and take it to heart. As I've said, I think the P-39 is one of the best looking fighters of WWII, and I believe that low down over the steppes of Russia it found its niche. But as literally ANYTHING else it was next to useless.
> 
> As I stated ( and others as well ), it DID NOT have the performance needed to escort 8th AF bombers ( Range, Speed, Climb, Firepower were all lacking ( dreadfully so ) ) so it was useless to 8th FC.
> 
> ...


Thanks for your comments.
Regarding post #256, please read my reply in post #275 "Gestation Period".
P-39s did at times escort 8th AF heavies. 
Was an excellent dive bomber with a 500# bomb, in New Guinea squadrons went on dive bombing missions with no special training and got excellent results. Also had the 37mm cannon to make short work of trucks.
Wasn't an interceptor? N would climb to 25000' in 8 minutes, better than any contemporary (1943) Mustang, Thunderbolt or Lightning and had a 37mm cannon.
And yes, the air war FOR FIGHTERS was pretty much over after March '44. Still tons of bombing missions but escort fighters were instructed to attack ground targets because they had already gained air superiority. The D-Day invasion in June was successful because the Luftwaffe was defeated and couldn't attack the invasion beaches. Truly, just sighting an enemy plane was very rare after March 1944. 
Thanks for the compliment. Obviously I have done a ton of research on the P-39. A lot of new information has come from the Russians since the fall of Gorbachev that sheds new light on this. And the official performance docs on the P-39 in wwiiaircraftperformance came out in 2012. The P-39 was a lot more capable than we have been led to believe for the last 60 years. You know, like the Russians used the P-39 for ground attack, no power above 12000', low ceiling, poor rate of climb, the 37mm cannon wouldn't work, all Russian work was at low altitude, blah blah. If you chart the performance right on top of the FW190 and Me109 graphs, the P-39N comes off much better than people think. The Russians didn't defeat the Luftwaffe by flying around at 10000' and waiting for the Germans to dive on them. But 60 years of lies has buried this plane.

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## Hansie Bloeckmann (Mar 20, 2018)

P-39 Expert said:


> The British sure accepted a lot of P-40s, and they were in no way comparable to the SpitV or P-51A.


They also accepted quite a few WW1 destroyers under Lend-Lease--I'll omit the rest, and save it for a more fitting thread, should someone start one. My apologies, gents, I intended no offense to Britain-they were a strong Ally then, are remain so now. Hansie

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## buffnut453 (Mar 20, 2018)

P-39 Expert said:


> The air war for fighters would be basically over three months later in March 1944.



There is a former B-17 crewman who frequents this forum whom, I suspect, would disagree with you.


Hansie Bloeckmann said:


> They also accepted quite a few WW1 destroyers under Lend-Lease- what did we get: (1) a few islands we didn't need, and (2), a chance, once again ( ala Woody Wilson in 1917) for England to be indebted to America for bailing out the Brits, again. Why FDR felt the US should be involved in another European conflict that would cost many American lives and gain us nothing (Stalin carved up the post-WW2 real estate) is beyond belief.



I don't think I've ever seen a more partial perspective on WW2. America gained nothing from WW2? Really? Apart from becoming a global superpower, a role that it has maintained in the intervening 70+ since 1945. 

As for "bailing out Britain", please remember that Britain had already ensured its own security in the summer of 1940. It's also worth pointing out that, had Britain not prevailed, America would have been surrounded by totalitarian regimes, with virtually the entire globe being carved up between Hitler, Stalin and Tojo. How would America have fared under those circumstances without the ability to influence world affairs and with no launching point for any liberation of Europe?

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## Peter Gunn (Mar 20, 2018)

P-39 Expert said:


> Thanks for your comments.
> Regarding post #256, please read my reply in post #275 "Gestation Period".
> P-39s did at times escort 8th AF heavies.
> Was an excellent dive bomber with a 500# bomb, in New Guinea squadrons went on dive bombing missions with no special training and got excellent results. Also had the 37mm cannon to make short work of trucks.
> ...


First off, you're welcome, no harm no foul, hope you don't take offense to anything I type, it's not intended to belittle or insult.

Uh, there are guys here far more able than I to address some of your points above. Actually, I think they already have but YMMV.

Again though, a P-39 ( any ) able to climb faster than say a P-38 to 25,000'? If that were so why weren't they used in New Guinea for that purpose? Or Guadalcanal?

As for the air war being over for fighters by March of '44... Perhaps drgondog or bobbysocks can enlighten you on that a bit, seeing as how their fathers were Mustang pilots at the time.

Lt. Runnels can set you straight on that as well.

I will unequivocally call bollocks on your contention of this myself as my uncle on my mothers side ( her brother ) was there at the time in Mustangs as well, if he were still alive I believe he'd have quite a good laugh ( or scoff ) at that statement.

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## Elmas (Mar 20, 2018)

Peter Gunn said:


> Look, you seem like an intelligent and well read guy, I suggest you read drgondogs post #256 carefully and take it to heart. As I've said, I think the P-39 is one of the best looking fighters of WWII, and I believe that low down over the steppes of Russia it found its niche. But as literally ANYTHING else it was next to useless.
> 
> As I stated ( and others as well ), it DID NOT have the performance needed to escort 8th AF bombers ( Range, Speed, Climb, Firepower were all lacking ( dreadfully so ) ) so it was useless to 8th FC.
> 
> ...


And I dare add:
IT COULD HAVE BEEN (WAS) under some circumstances of the flight envelope, very dangerous, exactly for the distibution of weights that was chosen ( I repeat: for things related to moment of inertia and angular momentum, that some people here seem to ignore and probably believe void of significance in the design of an aeroplane). And to cure that there was no increase of manifold pressure or other tricks that could change things: just to change an unsuccesful design, as the American airplane industry rightly did.
Of course every aeroplane must be treated with the utmost respect, but it is much much different to handle a Spitfire or a Macchi 202 and to handle a P-39: in all videos about P-39 the "Instructor" always tell his pupils "to handle it carefully".
To the Russians, who never were too worried for the lives of their pilots, this did not seem to have been of particular importance, but for the American, British, Australian, Italian pilots, that were particularly attached to their skins, it was...

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## Hansie Bloeckmann (Mar 20, 2018)

buffnut453 said:


> There is a former B-17 crewman who frequents this forum whom, I suspect, would disagree with you.
> 
> 
> I don't think I've ever seen a more partial perspective on WW2. America gained nothing from WW2? Really? Apart from becoming a global superpower, a role that it has maintained in the intervening 70+ since 1945.
> ...



I beg to differ, gentleman, based on 2 factors, all British-- I have little trust or faith in a Nation who gave the world: (1) Neville Chamberlain, who bent over backwards to Hitler in the Czech "Peace In Our Time" scenario--(2) Churchill, who proved his military prowess in WW1 at Gallipoli-a major FUBAR, later repeated at Dieppe! .

I am not saying we should have Not been involved in WW2- but only against the Japanese, Pearl Harbor nonwithstanding. If we had all our resources that went to Churchill and the ETO marshalled in the PTO--we might have defeated Japan earlier, and hopefully with less loss of American lives.

I have 2 uncles who flew in WW2- one was a Naval aviator, flew Corsair F-4U aircraft in the PTO in 1944-1945, and survived, one who few on a B-17 crew in the ETO-- bailed out on a Polesti oil field mission, and spent 13 months in a Luftwaffe run Stalag (Stockade) POW camp. He survived also.

Did we become a "World Power"-- yes. But remember, "absolute power corrupts, absolutely!"

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## buffnut453 (Mar 20, 2018)

Hansie Bloeckmann said:


> I beg to differ, gentleman, based on 3 factors, all British-- I have little trust or faith in a Nation who gave the world: (1) Neviile Chamberlain, who bent over backwards to Hitler in the Czech "Peace In Our Time" scenario--(2) Fat old cigar chomper Winnie Churchill, who proved his military prowess in WW1 at Gallipoli-a major FUBAR, later repeated at Dieppe, although that fiasco was Not Winnie's planning- (2) A King who didn't want the job-- Bertie Windsor was King because his older brother David Windsor passed up a Coronation for some cheap American floozie, who was twice divorced-- Not proper form, Davey-Boy-not proper form at all.
> 
> I am not saying we should have Not been involved in WW2- but only against the Japanese, Pearl Harbor nonwithstanding. If we had all our resources that went to Churchill and the ETO marshalled in the PTO--we might have defeated Japan earlier, and hopefully with less loss of American lives.
> 
> ...



This clearly needs another thread so this will be my last post on this topic, although I'm bemused at your blaming Britain (or, at least, certain Britons) for all ills and yet not admitting to any American mistakes...and that in a post that also mentions Vietnam. The irony couldn't be more amusing. 

Before I go, however, please note that it was Hitler who declared war on America, not the other way around. America didn't choose to enter the European war because Hitler brought it to America.

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## tomo pauk (Mar 20, 2018)

P-39 Expert said:


> Your link to the FW190 is interesting in that it is dated December 1, 1943 and in the first paragraph says that this investigation is to increase boost in the FW190A8 which began production in Feb 1944. A FW190A5 was used as test bed since they had the same engine. These increases in boost were obviously never put into service as the performance graphs for the A6 and A8 (both later models) do not reflect these performance increases. Go to the site that your link is from, wwiiaircraftperformance.org and look up the FW190A8.



The increased boost was certainly used on the Fw 190A8, going from previous limit of 1.42 ata to 1.58 or 1.65. Against the previous climbs done at 2400 rpm, the climb at 2700 rpm using as much of the boost as possible reduced time to 8 km by more than 1/4. Shaded areas on the speed & climb graph show performance when over-boost ('Erhoehte Notleistung') was used. Text also notes that overboost via C3 injection was allowed for both S/C speeds, allowed up to 10 minutes. Hopefuly your German is up to the speed, if not the 3rd pic is the translated perf graph:

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## Elmas (Mar 20, 2018)

Hansie Bloeckmann said:


> I beg to differ, gentleman, based on 3 factors, all British-- I have little trust or faith in a Nation who gave the world: (1) Neviile Chamberlain, who bent over backwards to Hitler in the Czech "Peace In Our Time" scenario--
> Omissis



MODE O.T. ON
Note that the bombing of Guernica (April 26, 1937) had been a year and a few months before the Munich Conference (September 1938). The bombing of Guernica was extremely publicized and overrated in negative by the Western Powers, which pointed out the high number of deaths






Guernica, by Pablo Picasso, oil on canvas, 351x782 cm, 1937

and overvalued positively by the Axis, which were eager to show an air power that they did not actually possess in 1938.
And this were times where the people thought _" the bomber always will pass"._
How many Squadrons of modern fighters did exist in Great Britain in September 1938?
From September 1938, after the return homeland of Chamberlain, the letters of the British Air Ministry to Supermarine to get the new fighter became almost threatening: everyone knew that the war would be there, and Chamberlain bought time at the expense of Czechoslovakia.
MODE O.T: OFF

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## Elmas (Mar 20, 2018)

A question, please:
Wing profiles of P-39, root and tip? Wash-out?
Thanks!


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## pbehn (Mar 20, 2018)

Hansie Bloeckmann said:


> I beg to differ, gentleman, based on 3 factors, all British-- I have little trust or faith in a Nation who gave the world: (1) Neviile Chamberlain, who bent over backwards to Hitler in the Czech "Peace In Our Time" scenario--(2) Fat old cigar chomper Winnie Churchill, who proved his military prowess in WW1 at Gallipoli-a major FUBAR, later repeated at Dieppe, although that fiasco was Not Winnie's planning- (2) A King who didn't want the job-- Bertie Windsor was King because his older brother David Windsor passed up a Coronation for some cheap American floozie, who was twice divorced-- Not proper form, Davey-Boy-not proper form at all.
> 
> I am not saying we should have Not been involved in WW2- but only against the Japanese, Pearl Harbor nonwithstanding. If we had all our resources that went to Churchill and the ETO marshalled in the PTO--we might have defeated Japan earlier, and hopefully with less loss of American lives.
> 
> ...


In 1939 we had the choice of fighting and winning, fighting and losing or forming a cosy agreement to carve up Europe which would have had the USA facing Japanese German British French and Italian forces at sea. Chamberlain did the only thing anyone could do about Czecholslovakia, bluster and re- arm what did or could the USA have done? Churchill for all his faults, by the time he became PM had experience running the navy, serving in the army and more importantly working in the ministry of munitions. That's my bit......start a new thread if you like, this is way off topic here.

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## Hansie Bloeckmann (Mar 20, 2018)

buffnut453 said:


> This clearly needs another thread so this will be my last post on this topic, although I'm bemused at your blaming Britain (or, at least, certain Britons) for all ills and yet not admitting to any American mistakes...and that in a post that also mentions Vietnam. The irony couldn't be more amusing.
> 
> Before I go, however, please note that it was Hitler who declared war on America, not the other way around. America didn't choose to enter the European war because Hitler brought it to America.


Yes, I am aware that Hitler, on Dec 11th 1941, declared war on America. As we declared war on Japan on Dec 7th 1941. The question to me is, when and if would America have declared war on Germany, following the Pearl Harbor fiasco/-or, would we have waited for Herr Hitler to make the first move towards World aggression on 2 TO's??

I am Not Blaming Britain for America's involvement in either WW1 or WW2- Wilson and FDR and the Democrats allowed America to become involved- due to trade and economic policy. Wars are often fought for territory- both Japan to add to her much needed importing of needed raw materials not found in Japan, Germany to satisfy Hitler's twin policies; the myth of Aryan superiority, and the Lebensraum (living space) he wanted for the expanding Aryan population he had planned for the "1000 year Reich" program.

But Both Wilson and later, FDR, allowed Britain open trade access to her needed wartime material needs, as long as her ships crossed the Atlantic and docked in American ports and harbors. WW2 and trade with Britain and later, Russia, brought American employment back from the depths of the unemployment status from 1929 through 1939-- And, to some extent, so did our sale of oil and scrap metal to Japan, until FDR cut it off and froze Japanese held assets, in 1941.

In support of England, I will say that both in WW1 and WW2 in Europe, and in Asia in WW2, England most likely saw more of her upper class families losing their sons (Sandringham, etc.) than possibly in America, where our class system enabled the sons of the rich to either escape combat scenarios, or the draft entirely. Our current POTUS was deferred I believe 5 times from service in Vietnam, due to "bone spurs" in his feet. A previous POTUS served in the Texas ANG as a "week-end warrior pilot", possibly saving Nieman-Marcus from air attacks from "Uncle Ho's AF"-- And although his upper crusted father (Yale, Skull & Bones) did fly in combat in WW2 as a Naval aviator, when he was the first Bush POTUS, he picked a rich young draft dodger from Indiana, whose family's $ and "connections" allowed "Danny" to serve in the NG.

To the best of my knowledge, few if any of the USA's Reserve forces were called up by


Elmas said:


> MODE O.T. ON
> Note that the bombing of Guernica (April 26, 1937) had been a year and a few months before the Munich Conference (September 1938). The bombing of Guernica was extremely publicized and overrated in negative by the Western Powers, which pointed out the high number of deaths
> 
> View attachment 486649
> ...





Elmas said:


> MODE O.T. ON
> Note that the bombing of Guernica (April 26, 1937) had been a year and a few months before the Munich Conference (September 1938). The bombing of Guernica was extremely publicized and overrated in negative by the Western Powers, which pointed out the high number of deaths
> 
> View attachment 486649
> ...





buffnut453 said:


> This clearly needs another thread so this will be my last post on this topic, although I'm bemused at your blaming Britain (or, at least, certain Britons) for all ills and yet not admitting to any American mistakes...and that in a post that also mentions Vietnam. The irony couldn't be more amusing.
> 
> Before I go, however, please note that it was Hitler who declared war on America, not the other way around. America didn't choose to enter the European war because Hitler brought it to America.


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## tomo pauk (Mar 20, 2018)

Elmas said:


> A question, please:
> Wing profiles of P-39, root and tip? Wash-out?
> Thanks!



Root: NACA 0015, tip: NACA 23009, no washout (2 deg constant incindence).

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## Shortround6 (Mar 20, 2018)

Nobody is saying the P-39 didn't do good work, However this attempt to rewrite history is getting a bit tiresome.
P-40s also did a lot of bombing attacks with single 500lb bombs, later P-40s could and did carry three 500lb, there are photos of them with six 250lb bombs,




There was at least one instance in Italy of P-40s carrying a pair of 1000lbs, not one plane but one or more squadrons attacking one target. Granted it was only about 30-40 miles from the airfield.
While the 37mm was nice you don't need a 37mm to kill a truck. You also have to hit the truck in order to kill it. You need about 4 seconds to fire ten 37mm shells and a 300mph airplane covers over 500yds in 4 seconds, making aiming and hitting a single target with such a gun a bit of problem, spectacular when it does hit but actual number of hits?
Most trucks don't take well to even rifle caliber bullets let alone .50 cal bullets, punctured fuel tanks, punctured radiators, holes in the cooling jacket of the engine block, holes in the transmission and final drive casings, punctured tires. Multiple machine guns batteries certainly missed a lot but had a higher chance of getting some hits.

You are also taking one test of a lightly loaded P-39 and trying to extrapolate from it. Many other tests were done at full load clean.
like one for a P-51B using 67in of MAP,
"High speed and climb performances have been completed on this airplane at a take-off weight of 9205 lbs. This loading corresponds to the average P-51B combat weight with full oil, 180 gallons of fuel and specified armament and ammunition."
P-51B Performance Test
Climb to 25,500ft in 8.28 minutes.

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## Elmas (Mar 20, 2018)

tomo pauk said:


> Root: NACA 0015, tip: NACA 23009, no washout (2 deg constant incindence).



Thanks!


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## Hansie Bloeckmann (Mar 20, 2018)

buffnut453 said:


> There is a former B-17 crewman who frequents this forum whom, I suspect, would disagree with you.
> 
> 
> I don't think I've ever seen a more partial perspective on WW2. America gained nothing from WW2? Really? Apart from becoming a global superpower, a role that it has maintained in the intervening 70+ since 1945.
> ...


We can only guess- in my mind, one of the great parts of studying World history is the "What If's?" No chance to chance the outcome, but the questions can be interesting.


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## Hansie Bloeckmann (Mar 20, 2018)

Elmas said:


> MODE O.T. ON
> Note that the bombing of Guernica (April 26, 1937) had been a year and a few months before the Munich Conference (September 1938). The bombing of Guernica was extremely publicized and overrated in negative by the Western Powers, which pointed out the high number of deaths
> 
> View attachment 486649
> ...


Re-reading Hemingway's novel- "For Whom The Bell Tolls" shows the air power above the Spanish skies-and Picasso's 1937 shows the tragic results of war. One of his finer works, IMO. Not certain if Spanish artist Juan Gris was still alive and working in 1937- would have liked to have seen his "take" on this tragic event.


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## Hansie Bloeckmann (Mar 20, 2018)

pbehn said:


> In 1939 we had the choice of fighting and winning, fighting and losing or forming a cosy agreement to carve up Europe which would have had the USA facing Japanese German British French and Italian forces at sea. Chamberlain did the only thing anyone could do about Czecholslovakia, bluster and re- arm what did or could the USA have done? Churchill for all his faults, by the time he became PM had experience running the navy, serving in the army and more importantly working in the ministry of munitions. That's my bit......start a new thread if you like, this is way off topic here.


Thanks- I agree-mea culpa- The questions I raised about how and why we were involved in WW2 belong in another thread. I'll shall wait for someone else to start such, as I am a "rookie" here, and if my comments have offended, please accept my apologies. I study World history extensively, 1900 to present date, but have little understanding of the "ruling classes" in Europe and England. Watching "Downton Abbey" does not make one an expert of the British upper classes, n'ces pas??


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## tomo pauk (Mar 20, 2018)

Hansie Bloeckmann said:


> Thanks- I agree-mea culpa- The questions I raised about how and why we were involved in WW2 belong in another thread. I'll shall wait for someone else to start such, as I am a "rookie" here, and if my comments have offended, please accept my apologies.



I don't think that you were involved in the ww2.
At any rate, you as a member of the board are very much allowed to start a thread.

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## pbehn (Mar 20, 2018)

Hansie Bloeckmann said:


> Thanks- I agree-mea culpa- The questions I raised about how and why we were involved in WW2 belong in another thread. I'll shall wait for someone else to start such, as I am a "rookie" here, and if my comments have offended, please accept my apologies. I study World history extensively, 1900 to present date, but have little understanding of the "ruling classes" in Europe and England. Watching "Downton Abbey" does not make one an expert of the British upper classes, n'ces pas??


I am not offended apart from by complete inaccurate nonsense and flag waving. In 1939 the British had the chain home and chain home low radar and CCC system installed and operational. We had the Spitfire and Hurricane in production with the new Castle Bromwich factory under construction, at the start of the Battle of Britain we still had enough (just) fighters to defend the UK from the LW. The designs which were to become the Halifax and Lancaster were accepted in 1937. All this was done while Chamberlain was Prime Minister. When Churchill became PM he appointed Beaverbrook (a newspaper magnate) as minister of aircraft production. This was an unusual choice, possibly one that could only be made by a Prime Minister who had worked as minister of munitions, he knew what was needed to increase production quickly. As a result of this UK fighter production was approximately twice that of Germany during the BoB. Now consider what the USA had in service in 1939 and also explain how Pearl Harbor happened in 1941 in an age of integrated radar defences?
You don't have to start a thread just find an old one on the subject and add to it, but please stop discussing "England" it is British and Commonwealth and the government is that of the U.K.


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## Glider (Mar 20, 2018)

P-39 Expert said:


> Just the facts, Spit XIV production was started in late 1943 and operational service was mainly from 1944. P-51B entered combat in 1944 (Dec. 1943). P-39N was in service from Dec. '42, a full year earlier.
> And no, N could not climb with the Spit IX, but then nothing could. N could substantially outclimb a FW190 at all altitudes.


As you said just the facts and I thank you for reminding me about the Spit XII which entered production before the P39N and service about the same time.


Hansie Bloeckmann said:


> I beg to differ, gentleman, based on 2 factors, all British-- I have little trust or faith in a Nation who gave the world: (1) Neville Chamberlain, who bent over backwards to Hitler in the Czech "Peace In Our Time" scenario--


 True it was humiliating, but it did buy us a precious 12 months to get our preparations in hand for when war came. 



> (2) Churchill, who proved his military prowess in WW1 at Gallipoli-a major FUBAR, later repeated at Dieppe! .


 Again true to a point but he got a lot more right than he got wrong in WW2. If you want to look at mismanagement and poor leadership the USA was far from blameless. Anzio and post war, Cuba the Bay of Pigs and Vietnam spring to mind.


> I am not saying we should have Not been involved in WW2- but only against the Japanese, Pearl Harbor nonwithstanding. If we had all our resources that went to Churchill and the ETO marshalled in the PTO--we might have defeated Japan earlier, and hopefully with less loss of American lives.


 Without the UK the USA would have had a lot of problems. It was mentioned earlier that the UK saved Curtis and Bell financially, with what would you have fought the Japanese? Also remember the technical information we gave the USA such as Radar an area where the Germans and Britain were well ahead of the world. Add to this the fact that Japan and Germany were in a pact and if the Japanese had more German technology, Japanese forces with Modern Radar well ahead of the USA would have been a nightmare.


> Did we become a "World Power"-- yes. But remember, "absolute power corrupts, absolutely!"


 Am I the only one who see's a certain amount of Irony in this

This ends my first and only posting of this nature

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## parsifal (Mar 20, 2018)

No Hansie, you are sadly misinformed about why the US gave its support in the ETO and became involved there.

The US entered the war in the ETO for a number of reasons. Its concern to prop up the british was one of them, but wasn’t even the main reason why it became embroiled in the conflict. 

The US was set on a collision course with both Japan and the European Axis because of fundamental differences on world trade. 

The US above all other considerations, favoured open door policies for trade. Basically a level playing field as far as access to markets. They wanted to be able to sell their goods on an open market unfettered by trade restrictions. 

This set the US on a direct path of disagreement with the tripartite powers. All of them wanted to set up spheres of influence, with restricted and closed markets, based on the principals of “most favoured nation” within those areas. Closed market systems are inherently inefficient and grossly unfair, and absolutely diametrically opposed to the US ideas of a free and open market system.

All of the axis powers in the lead up to war pursued policies to close off the markets they wanted to control. In the Pacific, the Japanese took strong steps to close the ports of entry into China, occupying territories like French Indochina and forcing the closure of the Burma Road and other measures that incensed the Americans and made war against Japan more or less inevitable.

A very similar situation arose in the ETO, though the means of achieving that closure of access to the European markets was very different.

At the beginning of the war, up until April 1940, the US as a neutral power enjoyed considerable access to the neutrals for the sale of her goods. Neutral shipping was meant to be protected if it displayed certain painted images on the hull, remained illuminated at all times and did not transmit position details when being stopped and searched. German attacks on shipping were meant to be restricted to a “declared area”, which was progressively expanded and then totally abandoned altogether. By august 1940 the Germans were advising that all shipping regardless of nationality was a legitimate target, in any ocean of the world, from any nationality and with no warning given. Any nationality was fair game. At least 4 Italian flagged blockade runners were attacked and sunk (or damaged) 1941, and at least 1 german blockade runner also attacked. These were axis controlled ships, not allied. And of course these indiscriminate attacks included attacks on US controlled shipping.

This unrestricted and uncontrolled warfare did not go down well with the US. They had over 120 WWI DDs mothballed at the time, but lacked the trained manpower or the bases to use them all effectively. Conversely, the RN was offering escort protection in her transatlantic convoys not only for shipping working for the allies but also for any neutral shipping making the hazardous passage across the Atlantic. Many nations received protection for their shipping fleets including nations such as Spain, Sweden, Finland, and the Soviets. Such nations if travelling through any of the declared areas were made to submit to british contraband/quota searches (to prevent any being passed to the axis) and this did cause angst with the americans. That angst evaporated when faced with the alternative of being sunk without warning by the KM.

The bases given in exchange were far from useless to the US. From the beginning, the US needed to protect oil shipping from the Gulf of mexico and central America as well as protecting her vital interests in Panama. The bases were used as an insurance, should the germans seek to interfere with any of those interests. At the time it seemed like a wise and beneficial move to exchange 50 DDs surplus to needs that would protect US shipping anyway, and with only remote chances of getting to sea in the foreseeable future, for bases that looked like they would be needed and if needed might help defend vital US interests.

The final reason I should mention is that the US relied on British controlled shipping to keep her economy afloat in those lead up years. The British controlled 26 million tons of shipping to the US 9 million, of which nearly 2million tons was reflagged anyway and effectively controlled by the British. More importantly the Americans were even more short of tankers than the brtish were in 1939. Guess what, by various means, the two big tanker fleets of the world, the Dutch and the Norwegians both came under British control before those countries were overrun. It was the Norwegian tanker fleet that drove the british on to the otherwise futile campaign in Norway. By the British making the sacrifices they did, as juxtaposed to the abysmal behaviours of the KM in Norway, virtually every Norwegian tanker willingly came under British control. For the Dutch the decision was more circumspect. Most of its 3 million tons of tankers were passed to the NEI, but then, to receive support from the British in that TO, they began to haul fuel worldwide for the Allies and the neutrals (including the US), but only with british approval.

If the US had opted for a more strictly neutral policy, they would have risked access to markets and also risked doing real damage to their economy due to shortages of strategic imports. It was in their interests to side with the british and give them the support they needed

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## drgondog (Mar 20, 2018)

P-39 Expert said:


> Dec. '42 to Dec '43 is one year.
> Regarding the "gestation period" for a new model, the P-39N was a mature model with the main difference from prior models being a newer version of the same engine (V-1710). "Gestation" was very short, production began in December '42 and P-39Ns were serving that same month in New Guinea. "Gestation" for this model consisted of transporting them to New Guinea. Now I will admit gestation for a new fighter can take an agonizingly long time. The first P-47 Thunderbolt was built in 1941 but first combat was April 1943.



Sources for squadron level deployment of P-39N in New Guinea? Specifically, the deployment of the N to SWP vs to 354, 357, 363 destined for ETO and 332nd for MTO? The latter required approximately 300 P-39Ns in summer of 1943. Which other FGs would you cite as recipients of the P-39N other than French and Russians in mid 1943? The first operational deployment for US FG that I can find is 18th FG in June-July 1943 as CAS. P-38s assume role of interceptors.

When the 15th AF was formed, basically all P-39s, all types, relegated to 5th Bomb Wing. 350th FG flying P-39Q, 332nd FG arrives with P-39Q. All P-39s in US FG's replaced with P-47s in January/February 1944 and P-39s go to French and Italian Air Force. P-40N replaces SWP P-39/P-400 in the Groups still tasked for CAS and the Recon squadrons receive P-39N until P-51B/C arrive in April-June 1944. June 1944 P-39 Productions ceases.

The 31st FG trained in P-39s but left them in US in June 1942, pilots go to UK and a/c replaced by Brit Spit V. 52nd FG trained in P-39s but leave them in US and equipped w/Spit V in UK. The 81st and 350th in UK fly P-400 and P-39D-1 destined for Russia, but move to Africa in Jan 1943 - assigned to strafing, convoy escort and recon role due to insufficient performance as fighter/interceptor in contrast to Spit V. The 81st moves to CBI and converts to P-40 in early 1944.

The P-39 Never flew an escort mission for 8th AF. The spotty occasions in the MTO when it flew escort for medium and light attack bombers were because nothing better (P-40/Spit V/P-38) were available at the time. 

The combat radius for the P-39N on internal fuel was approximately 60% of the P-40K/F/M/N. The Max range of the P-39 Q with kit raising total fuel to 120 internal and 175 external (ferry tank only - not self sealing) was about 1000 miles. That is equivalent to a Mustang I with Only 170 gallons of internal fuel. 

In contrast the P-51B-1 in first flight tests at 8600 pounds made 25K in 7 min, at full internal combat load of 9200 (269 gal internal fuel) pounds ~ 8min. The P-51B/C with 2x1000 pound bombs, internal fuel only at 269 gal had a Combat Radius more than P-39N clean

The P-39N with 87 gallons at 7600 pounds took ~ 10 min for 25K.

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## rochie (Mar 20, 2018)

Hansie Bloeckmann said:


> I beg to differ, gentleman, based on 2 factors, all British-- I have little trust or faith in a Nation who gave the world: (1) Neville Chamberlain, who bent over backwards to Hitler in the Czech "Peace In Our Time" scenario--(2) Churchill, who proved his military prowess in WW1 at Gallipoli-a major FUBAR, later repeated at Dieppe! .
> 
> I am not saying we should have Not been involved in WW2- but only against the Japanese, Pearl Harbor nonwithstanding. If we had all our resources that went to Churchill and the ETO marshalled in the PTO--we might have defeated Japan earlier, and hopefully with less loss of American lives.
> 
> ...







Think i made a mistake coming back !
Shame really

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## pbehn (Mar 20, 2018)

rochie said:


> View attachment 486693
> 
> Think i made a mistake coming back !
> Shame really


Its just one post from one poster, have a Parmo and relax.

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## wuzak (Mar 20, 2018)

wuzak said:


> The single stage V-1710's power curve follows the same shape as the V-1650-1, but without the second gear.
> 
> The reason for this is that the throttle causes a pressure loss and a reduction in efficiency of the supercharger. So the power *rises* as altitude increases, the throttle progressively opening to maintain the required boost level, until the critical altitude/full throttle height where the engine makes its peak rated power. The power then, pretty much, falls off a cliff.
> 
> ...



Just going back to the single speed s 2 speed supercharger discussion for a moment, this is what I would expect the power curve of the V-1710 to look like, though the peak power will be at lower altitudes, for some versions, than shown for the Merlin 45 and 46.

Only for a small altitude band around the single speed engine's peak will it have any marked advantage over the 2 speed engine, and then only if that corresponds to the gap between FTH in low gear and FTH in high gear. If the 2 speed engine had a low speed gear ratio the same as the single speed engine, the performance would be identical as the single speed engine until the supercharger was changed into high gear, after which the 2 speed engine would be vastly superior.


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## Shortround6 (Mar 20, 2018)

Actually you may have the reverse. The Merlin 46 & 47 having about the best performance at altitude of _any_ single stage supercharger. to get 9lbs of MAP (48 in?) it was compressing the ambient air at 22,000ft 3.8 times. Which is about as good as it got for a single stage compressor in service in WW II, even for jets. 

A second gear was often used to increase the power available at lower altitudes and for take-off. Less power to drive the supercharger, less heating of the intake charge, throttle plates open wider.

For example a Wright R-2600 was limited to about 1450hp in high gear, anywhere from 8000ft to 12,000ft (or higher?) using a 10.0 gear set to drive the supercharger.
Using a 7.0 gear set in low gear they had 1700hp from 0 to 3000ft and did it at about 2 1/2 less inches of MAP.
I would note that the two _speed_ drive to the supercharger on the R-2600 increase the weight by about 25-35lbs over a single speed engine.


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## wuzak (Mar 21, 2018)

Shortround6 said:


> Actually you may have the reverse. The Merlin 46 & 47 having about the best performance at altitude of _any_ single stage supercharger. to get 9lbs of MAP (48 in?) it was compressing the ambient air at 22,000ft 3.8 times. Which is about as good as it got for a single stage compressor in service in WW II, even for jets.



I wasn't suggesting that the V-1710 was as good as those, just that the shape of the curve will be similar.

The peak altitude (for similar boost) will be at a lower altitude, but I would expect the power to climb to the FTH, as the throttle would cause power loss until it is fully open.




Shortround6 said:


> A second gear was often used to increase the power available at lower altitudes and for take-off. Less power to drive the supercharger, less heating of the intake charge, throttle plates open wider.



I realise this.

I was just point out that if the first gear on the 2 speed engine is the same as the gear ratio on the single stage engine, the performance would be the same between the two. A few thousand feet above the FTH of the first gear the high gear will be engaged, giving the 2 speed an advantage over the single stage.

It is also true that the high gear could be the same as the single stage engine's supercharger ratio. That would mean the same altitude performance, but enhanced low altitude performance.

In the case of the Merlin XX compared to the 45, the low gear ratio was lower than the 45's single, and the high gear ratio was higher.

IIRC, the 46 had a larger impeller, which gave improved altitude performance, at the cost of low altitude performance.


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## Shortround6 (Mar 21, 2018)

You are correct and have been around long enough to have been through a number of these supercharger discussions and you may well have known most of this already. 
We always seem to get new members who think you can just up the gear ratio and get even higher altitude performance and don't realize that each compressor had a limit at which it couldn't deliver more air regardless of how fast the impeller was spun. 

On the Allison the "curve" was actually pretty much flat from take-off to rated altitude, then sloped down. 
There was a slight rise from sea level to rated altitude but nowhere near what the Merlin often shows. 
This _may _be because the Allison supercharger was smaller and required less power to drive (it also delivered less volume and pressure) and the slight difference in engine displacement and compression _may _also enter into it. 

The Merlin 46 could make about the same power in WEP as the Allison but do it 5000ft higher up.


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## pbehn (Mar 21, 2018)

Shortround6 said:


> Nobody is saying the P-39 didn't do good work, However this attempt to rewrite history is getting a bit tiresome.
> P-40s also did a lot of bombing attacks with single 500lb bombs, later P-40s could and did carry three 500lb, there are photos of them with six 250lb bombs,
> View attachment 486662
> 
> ...


Interesting S/R, I don't know when the final decision was made on D-Day but after the Dieppe raid I think the idea of taking a channel port was abandoned. The straight line distance between Portsmouth and Caen is 125 miles.


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## pbehn (Mar 21, 2018)

Shortround6 said:


> You are correct and have been around long enough to have been through a number of these supercharger discussions and you may well have known most of this already.
> * We always seem to get new members who think you can just up the gear ratio and get even higher altitude performance and don't realize that each compressor had a limit at which it couldn't deliver more air regardless of how fast the impeller was spun.*
> 
> On the Allison the "curve" was actually pretty much flat from take-off to rated altitude, then sloped down.
> ...



Isnt the part now in bold what Stanley Hooker brought to the RR Merlin, noticing the compressor was stalled he boosted maximum performance, or am I barking up the wrong tree?


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## Hansie Bloeckmann (Mar 21, 2018)

rochie said:


> View attachment 486693
> 
> Think i made a mistake coming back !
> Shame really


F.U.C.K.-- goes back to the days of King Henry V111- Fornication Under Consent (of the) King-overused in today's parlance, IMO..


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## Hansie Bloeckmann (Mar 21, 2018)

pbehn said:


> Its just one post from one poster, have a Parmo and relax.[/QUOT


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## Shortround6 (Mar 21, 2018)

Sort of, He did notice fairly quickly that actual results did not match the formulas/assumptions used in design. Then he went looking for why.
First big change was "simply" a change in the curve in the inlet between the carburetor and the impeller. 
A 90 degree bend right before the inlet is not a good idea but a more gentle radius (and a bigger cross section?) can make a large difference. Not only in airflow through the bend but in getting an even airflow hitting the impeller instead of more air hitting one side than the other. 
SInce the inlet bend had been cast in one piece with the front supercharger cover getting different castings to try wasn't all that simple. 
Picture of model





On the Merlin XX series engines (and 45s) it was like this

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## pbehn (Mar 21, 2018)

Hansie Bloeckmann said:


> Parmo-- same as our "Bromo-Selter" in The Colonies??


No, it is a local dish, and you are seriously pushing my buttons. Now start your thread, I suggest the following title. "Is the Kings Speech" the best source of information on the build up to WW2 because its the only thing I know". or "Are Hollywood dramas better than books as a source of information". Now get back on topic.


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## Hansie Bloeckmann (Mar 21, 2018)

tomo pauk said:


> I don't think that you were involved in the ww2.
> At any rate, you as a member of the board are very much allowed to start a thread.


Correct-I was born some years later- My main source of information came from the Allied side of things, with two uncles who flew in Combat, one in the PTO, and one in the ETO--I had no family that served in the ground forces. Thanks for the clarification, and just how does one start a thread here? Hansie


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## Hansie Bloeckmann (Mar 21, 2018)

pbehn said:


> No, it is a local dish, and you are seriously pushing my buttons. Now start your thread, I suggest the following title. "Is the Kings Speech" the best source of information on the build up to WW2 because its the only thing I know". or "Are Hollywood dramas better than books as a source of information". Now get back on topic.


Thank you, and please forgive my "faux pas" regarding the Parmo- as that word has the number of letters as Bromo, I took a "WAG"- looks like I missed the mark. The only English dishes I have heard of, besides beef Wellington, are steak and kidney pie, and bangers and mash.


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## tomo pauk (Mar 21, 2018)

Hansie Bloeckmann said:


> Thanks for the clarification, and just how does one start a thread here? Hansie



Hit the 'Post new thread' button, you can see it when checking out the topics listed in a (sub-)forum. The button is roughly at top right.

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## pbehn (Mar 21, 2018)

Hansie Bloeckmann said:


> Thank you, and please forgive my "faux pas" regarding the Parmo- as that word has the number of letters as Bromo, I took a "WAG"- looks like I missed the mark. The only English dishes I have heard of, besides beef Wellington, are steak and kidney pie, and bangers and mash- all from movies. I haven't yet seen "The King's Speech" as of yet, shall remedy that deficit post haste.


Strange because it was not commonly known that Elizabeth called her husband Bertie until the film was shown I didn't know, you are educated by Hollywood. That whole post acts as a summary of the movie, the director would be proud.

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## Peter Gunn (Mar 21, 2018)

I was looking over the P-51B performance data referenced in SR6's post earlier: P-51B Mustang
( Not that I'd obsess over a Mustang performance chart or anything... )

But about two thirds the way down in chart "C Cruise Data", there's this little gem:
RPM Hg. Mix Setting Mix Temp BHP True Speed MPH
2400 42.5 AR 45.5 937 349.0
2250 37.0 AL 38.5 763 *624.0*
1950 35.0 AL 26.5 650 302.0
_Suck on THAT Me 262!_

Utilizing P-39N logic, I have found the fastest piston engine fighter of WWII. Because there's NO WAY that's a typographical error... 

I might be forced to continually cite this reference in future debates, which I categorically declare myself the winner of based on the data stated above. /sarc.

*edit* stupid editor messed up my formatting, sorry about that, it was supposed to be in a nice little table.


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## Shortround6 (Mar 21, 2018)

I think some of us need a Pimm's or two after that interchange

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## wuzak (Mar 21, 2018)

Was just reading part of _America's Hundred Thousand_ in the pilots' comments about the P-39.

It says:


> A pilot report that in North Africa P-39s doing low level strafing missions were considered quite resistant to ground fire. However another said "In North Africa the German 109s shot them down almost at will."





> The Russians liked the P-39 even though German fighters on the Eastern Front were reported to have picked them off with ease.





> German pilots reported on the Russian front they knocked P-39s down almost at will, and in North Africa they reported they were always looking down at P-39s, which gave them no trouble.


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## Peter Gunn (Mar 21, 2018)

wuzak said:


> Was just reading part of _America's Hundred Thousand_ in the pilots' comments about the P-39.
> 
> It says:
> 
> ...


But... but... HOW can that be SO? We have data that PROVES the P-39 was superior, especially in climb, to the the Fw-190!!!


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## Shortround6 (Mar 21, 2018)

Peter Gunn said:


> But... but... HOW can that be SO? We have data that PROVES the P-39 was superior, especially in climb, to the the Fw-190!!!


Germans were using Bf-109s???

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## pbehn (Mar 21, 2018)

Peter Gunn said:


> But... but... HOW can that be SO? We have data that PROVES the P-39 was superior, especially in climb, to the the Fw-190!!!


It is quite possible for all the opinions to be correct. When you outnumber the enemy by 7 to 1 its possible you rarely see them and so proceed unmolested enjoying the controls and radio. When you meet the enemy late in the conflict and he has only a few hours training maybe you do have the upper hand. In other circumstances meeting a trained pilot on a 1 to 1 basis you are in a very bad position.

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## buffnut453 (Mar 21, 2018)

Hansie Bloeckmann said:


> Just how does one start a thread here?



If you click on the top banner and scroll down below the "Recent Posts" you'll find a list of the available forums. Click on the one that best suits your needs (in this case, probably "WW2 General"). At the top right, you should find a button allowing you to create a new thread. Click that, add a title and write your message.

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## Hansie Bloeckmann (Mar 21, 2018)

buffnut453 said:


> If you click on the top banner and scroll down below the "Recent Posts" you'll find a list of the available forums. Click on the one that best suits your needs (in this case, probably "WW2 General"). At the top right, you should find a button allowing you to create a new thread. Click that, add a title and write your message.


Thanks--Hansie


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## Hansie Bloeckmann (Mar 21, 2018)

Shortround6 said:


> I think some of us need a Pimm's or two after that interchange


Pimm's Cup-- OK, the first round is on me--I wonder if the late Queen Victoria called her husband Albert "Bertie"-- I read somewhere that she preferred that German be spoken in her family, as well as English.. Any truth to that??


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## CORSNING (Mar 21, 2018)

wuzak said:


> Deliveries of P-39Ns started in December 1942. They weren't in service in 1942.
> 
> *Deliveries of the P-39N Airacobra to the USAAF began in November 1942.*


*The French in North Africa were supplied with P-39Ns in April 1943.
The P-39N first became operational with the USAAF in June 1943 at Guadalcanal. It is 
entirely possible that it entered operational service immediately with the French.
*


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## CORSNING (Mar 21, 2018)

tomo pauk said:


> P-40 was available earlier and in greater quantities than the P-39, let alone* the P-51A that entered the service with RAF by June 1943.*
> 
> *Tomo,
> Where did you get this information? The first deliveries of the P-51A that I am aware of
> were in September 1943 to the 23rd Fighter Group of the 9th Air Force...?*


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## Shortround6 (Mar 21, 2018)

And here we hit "what is a delivery"?

Test flown and signed off as accepted in Buffalo New York is a long way from any combat zone. 
You have two basic ways of getting P-39s to combat zones, knocked down and crated for rail transport to a seaport.
Flown to airfield near seaport and towed to dock and cocooned for sea transport.
For Russia you can fly them to Alaska and then over the Bering strait. 
For Britain, The Med and for the Pacific they went by ship. 
And for the most part, had to reassembled or de-cocooned and test flown before being placed in service. 
Getting P-39Ns into service in the SWP in Dec of 1942 seems just about impossible.

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## tomo pauk (Mar 21, 2018)

CORSNING said:


> Tomo,
> Where did you get this information? The first deliveries of the P-51A that I am aware of
> were in September 1943 to the 23rd Fighter Group of the 9th Air Force...?



From 'America's hundred thousand', pg. 332. It says that 50 Mustang II and one A-36 join the RAF in June 1943.

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## Peter Gunn (Mar 21, 2018)

Shortround6 said:


> Germans were using Bf-109s???


Smarty pants...

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## Peter Gunn (Mar 21, 2018)

Shortround6 said:


> And here we hit "what is a delivery"?
> 
> Test flown and signed off as accepted in Buffalo New York is a long way from any combat zone.
> You have two basic ways of getting P-39s to combat zones, knocked down and crated for rail transport to a seaport.
> ...



Agreed, which is why I have a hard time with Mr. P-39's assertion of:
_*"*"Gestation" was very short, production began in December '42 and P-39Ns were serving that same month in New Guinea.*"*_

I don't see how they could get from Buffalo to New Guinea in like, two weeks?

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## Hansie Bloeckmann (Mar 21, 2018)

pbehn said:


> Strange because it was not commonly known that Elizabeth called her husband Bertie until the film was shown I didn't know, you are educated by Hollywood. That whole post acts as a summary of the movie, the director would be proud.


Actually, I looked up the Royal families on Wikipedia- Albert, later King George V1- was called "Bertie" by his family members, his wife was named Elizabeth, as was their oldest of two daughters, now the present Monarch- but apparently was called "Libideth" by her loving father, Albert.


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## pbehn (Mar 21, 2018)

Hansie Bloeckmann said:


> Actually, I looked up the Royal families on Wikipedia- Albert, later King George V1- was called "Bertie" by his family members, his wife was named Elizabeth, as was their oldest of two daughters, now the present Monarch- but apparently was called "Libideth" by her loving father, Albert.


Thanks for the information, always nice to know who my head of state is, Ive just realised she is the only one I've ever had, so hopefully I wont forget. Did they have any children or grandchildren? Does this have anything to do with P-39s

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## P-39 Expert (Mar 21, 2018)

Peter Gunn said:


> Agreed, which is why I have a hard time with Mr. P-39's assertion of:
> _*"*"Gestation" was very short, production began in December '42 and P-39Ns were serving that same month in New Guinea.*"*_
> 
> I don't see how they could get from Buffalo to New Guinea in like, two weeks?


I'm quoting Edwards Park who was in the AAF and served at Port Moresby, NG. In his book "Angels Twenty" he states that he arrived in NG in December '42 and was issued a brand new P-39N. He's a well known writer and journalist who wrote for Aviation Week and others. Not beyond the realm of possibility, those P-39Ns were just the next version on the production line and their new feature was a newer version of the V-1710. When the last P-39-M rolled out the first N was right behind it. Right after a quick check and test flight they shipped or flew out. At that point in time Bell was rolling out 400 P-39s per month. They had already manufactured 2000+ and pretty much had the process down.
By the way, Park also wrote that his squadron carried 110 gallon drop tanks vs the 75 gallon tanks in all the photos.


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## Stig1207 (Mar 21, 2018)

23rd Fighter Group of the 9th airforce???
The 23rd were the former 'Flying Tigers' and with the 14th AAF, weren't they?

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## P-39 Expert (Mar 21, 2018)

tomo pauk said:


> The increased boost was certainly used on the Fw 190A8, going from previous limit of 1.42 ata to 1.58 or 1.65. Against the previous climbs done at 2400 rpm, the climb at 2700 rpm using as much of the boost as possible reduced time to 8 km by more than 1/4. Shaded areas on the speed & climb graph show performance when over-boost ('Erhoehte Notleistung') was used. Text also notes that overboost via C3 injection was allowed for both S/C speeds, allowed up to 10 minutes. Hopefuly your German is up to the speed, if not the 3rd pic is the translated perf graph:
> 
> 
> View attachment 486624
> ...


Look at your date on the bottom of the third graph: Oct 25 '44. And these graphs typically are prior to the actual production models since they were testing prototypes. You may not agree with me that the Luftwaffe was beaten in March '44, but you should have no doubt that that they were done by October '44. If the production machines actually saw combat it would be a minor miracle.


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## tomo pauk (Mar 21, 2018)

P-39 Expert said:


> Look at your date on the bottom of the third graph: Oct 25 '44. And these graphs typically are prior to the actual production models since they were testing prototypes.



Last sentence is just your opinion - there is plenty of graphs for any given fighter that were a result of series-produced machine flihgt-tested.
This is for the increased emergency power for the Fw 190A8 from here (my bold; I'll post the facsimile of the original doc):
_*Starting from July 1944 all Fw 190 A-8 aircraft will be equipped with "increased emergency".* By overridding the supercharger boost regulator, boost pressures are increased at take-off and emergency power in low supercharger setting from 1,42 ata to 1,58 ata and at the high supercharger setting from 1,42 to 1,65 ata. Thus an increase of speed up to 13.6 mph (22 km/h) is obtained with low supercharger operation and up to 15.5 mph (25 km/h) with high supercharger operation. The maximum operating time for increased emergency is limited to 10 minutes due to thermal reasons.
(*Ab Juli 1944 werden sämtliche Flugzeuge der Baureihe Fw 190 A-8 mit "erhöhter Notleistung" ausgerüstet.* Durch Eingriff in den Ladedruckregler wird der Ladedruck der Start- und Notleistung im Bodenladerbetrieb von 1,42 ata auf 1,58 ata, im Höhenladerbetrieb von 1,42 ata auf 1,65 ata heraufgesetzt. Hierdurch wird ein Geschwindigkeitsgewinn bis 22 km/h bei Bodenladerbetrieb und bis zu 25 km/h im Höhenladerbetrieb erzielt.; (sich Flugleistungen Bl. 15). Die höchstzulässige Betriebsdauer für erhöhte Notleistung ist aus thermischen Gründen 10 Minuten begrenzt.)_



> You may not agree with me that the Luftwaffe was beaten in March '44, but you should have no doubt that that they were done by October '44. If the production machines actually saw combat it would be a minor miracle.



Let's not mix the state of this or that airforce with capabilities and usability of this or that fighter. 
Fw 190A set the bar high in 1941-42 when it is about fighter aircraft, and was still going strong in 1943. P-39N, while a decent fighter, didn't set any bars worth reaching, even if it was faster than Soviet or Japanese fighters.

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## P-39 Expert (Mar 21, 2018)

Peter Gunn said:


> First off, you're welcome, no harm no foul, hope you don't take offense to anything I type, it's not intended to belittle or insult.
> 
> Uh, there are guys here far more able than I to address some of your points above. Actually, I think they already have but YMMV.
> 
> ...


Thanks for your comments. Let me rephrase, I have stated that the air war for fighters was over in March '44. I should have said that the Luftwaffe (and the Japanese) were beaten by March '44. In other words, very little opposition by the Germans and Japanese fighters after that date. No the war wasn't over, but you were very unlikely to encounter enemy fighters after March '44. Plenty of bomber missions, escort, ground attack, flak, ground fire etc. left, but not many enemy fighters. 

Regarding P-39 climb, you must compare airplanes that were in combat service at the same time. Otherwise we are debating "What if Napoleon had B-52 bombers".  The P-39-N in 1943 was the fastest climbing plane we had. Contemporary P-38s were G and F models and it took them 11 minutes to get to 25000'.
Regarding New Guinea in '42, interception was exactly what they were there for. The Japanese had bases all along the north coast of NG and were bombing Port Moresby daily, weather permitting. Those P-39s got there in late April '42 and were immediately in combat with their mission to intercept Jap Navy Betty bombers escorted by Zeros. Tough going. The Bettys came in at between 18000' and 22000' with Zeros above sometimes more than once per day. We were trying desperately to hang onto Port Moresby because that was all that separated the Japanese from Australia. But the big problem was NO RADAR. There was Australian radar but that was hundreds of miles away. No early warning of a Japanese bombing raid other than a few "coastwatchers" (local farmers) who could call in. So the two squadrons of P-39s had to fly 2-4 plane patrols while everyone else just sat in the waiting room waiting to be called. Tough work. The Army finally got radar at Milne Bay in August and conventional interception missions (radar detection, scramble, ground radio vectoring you direction and altitude for contact) followed. Those P-39s (and the Navy at Battle of the Coral Sea) kept the Japanese out of Port Moresby. These P-39s were the earlier D, F and P-400 that had the earlier 1150HP engines and way too much weight. They could get to 23000' to intercept the bombers at 22000' but is was a struggle and they needed that radar, like any other contemporary plane. 
Regarding Guadalcanal, the first P-39s to arrive there were those diverted British P-400s and they had British oxygen systems which were incompatible with ours. No oxygen, they could not be flown over 12000' per regulation. These were truly ground attack planes.


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## Milosh (Mar 21, 2018)

The date on a document is the issuing date, not the testing date.

Since you are so hot on using the WW2 performance site, there are tests for the Spitfire IX from Oct '42 to Oct '44. Using your logic, the Spitfire IX wasn't in service til after Oct '44.

There was 154 Fw190A-8s delivered in March 1944.


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## P-39 Expert (Mar 21, 2018)

Milosh said:


> The date on a document is the issuing date, not the testing date.
> 
> Since you are so hot on using the WW2 performance site, there are tests for the Spitfire IX from Oct '42 to Oct '44. Using your logic, the Spitfire IX wasn't in service til after Oct '44.
> 
> There was 154 Fw190A-8s delivered in March 1944.


Okay, but being wartime and all, wouldn't the issue date come pretty close after the actual test date?

I am hot on wwiiaircraftperformance. An Oct '42 test of the Spitfire IX would indicate that version of the IX would probably be about to start production or have already started production at that time. Unless the test states differently. Wouldn't you agree?


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## buffnut453 (Mar 21, 2018)

P-39 Expert said:


> Okay, but being wartime and all, wouldn't the issue date come pretty close after the actual test date?
> 
> I am hot on wwiiaircraftperformance. An Oct '42 test of the Spitfire IX would indicate that version of the IX would probably be about to start production or have already started production at that time. Unless the test states differently. Wouldn't you agree?



Not necessarily. Depends on the release schedule for the document(s) involved. An initial release may be close to the test date but that same data may be repeated in later versions released many months or years after the test. It all comes down to the source documentation - did it come from the first set of pilot's notes ever written for the aircraft or was it part of a later update or, worse, an overall summary of comparative performances?


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## Glider (Mar 21, 2018)

P-39 Expert said:


> An Oct '42 test of the Spitfire IX would indicate that version of the IX would probably be about to start production or have already started production at that time. Unless the test states differently. Wouldn't you agree?


The first combat report on WW2aircraft.net for a Spit IX is 28th July 1942 approx. 12 months before the P39N entered service.
As an aside I believe that the first USAAF units equipped with the Spit VIII started operations in Aug 1943

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## P-39 Expert (Mar 21, 2018)

buffnut453 said:


> Not necessarily. Depends on the release schedule for the document(s) involved. An initial release may be close to the test date but that same data may be repeated in later versions released many months or years after the test. It all comes down to the source documentation - did it come from the first set of pilot's notes ever written for the aircraft or was it part of a later update or, worse, an overall summary of comparative performances?


Looks to me that most of the tests on wwiiaircraftperformance are by the War Department/Air Corps for new models with a test date on a specific plane identified by individual serial number. In other words, this specific plane was tested on this date and found to have these characteristics. Critical information for Army planners.


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## Hansie Bloeckmann (Mar 21, 2018)

pbehn said:


> Thanks for the information, always nice to know who my head of state is, Ive just realised she is the only one I've ever had, so hopefully I wont forget. Did they have any children or grandchildren? Does this have anything to do with P-39s


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## Hansie Bloeckmann (Mar 21, 2018)

pbehn said:


> Thanks for the information, always nice to know who my head of state is, Ive just realised she is the only one I've ever had, so hopefully I wont forget. Did they have any children or grandchildren? Does this have anything to do with P-39s


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## Hansie Bloeckmann (Mar 21, 2018)

pbehn said:


> Thanks for the information, always nice to know who my head of state is, Ive just realised she is the only one I've ever had, so hopefully I wont forget. Did they have any children or grandchildren? Does this have anything to do with P-39s


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## pbehn (Mar 21, 2018)

Glider said:


> The first combat report on WW2aircraft.net for a Spit IX is 28th July 1942 approx. 12 months before the P39N entered service.
> As an aside I believe that the first USAAF units equipped with the Spit VIII started operations in Aug 1943


Also on 12 September 1942 a MkIX intercepted a Ju 86 at 43,000ft over Southampton.


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## Hansie Bloeckmann (Mar 21, 2018)

pbehn said:


> Thanks for the information, always nice to know who my head of state is, Ive just realised she is the only one I've ever had, so hopefully I wont forget. Did they have any children or grandchildren? Does this have anything to do with P-39s


I meant no offense, just trying to clarify my understanding of the Monarchy in your Great Land. I believe Queen Elizabeth is both a mother and a grandmother, and I wish her a long and happy life. It must be a lonely job at times, but I am sure her children and grandchildren keep her both happy and busy. God Save The Queen.. As far as the P-39 issue is concerned, I didn't realize how much better it might have been to have awaited for another member of this forum to start a thread dealing with the issues that brought America into the War in Europe-from 1941 to its ending in May 1945. 

I very much enjoy reading your learned responses, and I hope you will accept my apology. Hansie


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## P-39 Expert (Mar 21, 2018)

Glider said:


> The first combat report on WW2aircraft.net for a Spit IX is 28th July 1942 approx. 12 months before the P39N entered service.
> As an aside I believe that the first USAAF units equipped with the Spit VIII started operations in Aug 1943


P-39N entered service December '42.

The July '42 Spitfires were just two squadrons that were practically service test planes. A few more test squadrons tricked in before real series production started at the end of '42.


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## wuzak (Mar 21, 2018)

P-39 Expert said:


> I'm quoting Edwards Park who was in the AAF and served at Port Moresby, NG. In his book "Angels Twenty" he states that he arrived in NG in December '42 and was issued a brand new P-39N. He's a well known writer and journalist who wrote for Aviation Week and others. Not beyond the realm of possibility, those P-39Ns were just the next version on the production line and their new feature was a newer version of the V-1710. When the last P-39-M rolled out the first N was right behind it. Right after a quick check and test flight they shipped or flew out. At that point in time Bell was rolling out 400 P-39s per month. They had already manufactured 2000+ and pretty much had the process down.
> By the way, Park also wrote that his squadron carried 110 gallon drop tanks vs the 75 gallon tanks in all the photos.



Edwards Park was given a P-39, squadron letter N.

Pacific Wrecks

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## wuzak (Mar 21, 2018)

P-39 Expert said:


> P-39N entered service December '42.
> 
> The July '42 Spitfires were just two squadrons that were practically service test planes. A few more test squadrons tricked in before real series production started at the end of '42.





> No. 64 Squadron at Hornchurch was the first squadron to go operational with Spitfire IXs (28-July-1942). Deliveries of more powerful Spitfire IXs equipped with Merlin 63, 66, or 70s commenced in early 1943. No 611 Squadron at Biggin Hill was the first to use the Merlin 66 engined Spitfire LF IX on operations (March 1943). Full service approval of +25 lbs boost was granted 10 March 1944, providing considerable improvement in low altitude performance. No. 1 and No. 165 squadrons at Predannack were the first to convert their Spitfires to +25 lbs boost, taking 2 days off from operations in early May 44 to do so.



Spitfire Mk IX Performance Trials

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## buffnut453 (Mar 21, 2018)

P-39 Expert said:


> P-39N entered service December '42.
> 
> The July '42 Spitfires were just two squadrons that were practically service test planes. A few more test squadrons tricked in before real series production started at the end of '42.



Hmmm...four of those "test squadrons" participated in operations over the Dieppe Raid in August 1942. That's still 4 squadrons fully equipped and operational with Spit MkIXs some 4 months before even your earliest date for the P-39N. 

You can't have your cake and eat it by claiming that, somehow, the P-39N could have rapidly entered service by the end of 1942 but then dismiss operational usage of the Spit MkIX in 1942 as just operational testing.

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## Shortround6 (Mar 21, 2018)

P-39 Expert said:


> Regarding P-39 climb, you must compare airplanes that were in combat service at the same time. Otherwise we are debating "What if Napoleon had B-52 bombers".  The P-39-N in 1943 was the fastest climbing plane we had. Contemporary P-38s were G and F models and it took them 11 minutes to get to 25000'.



What month of 1943? P-38Hs were coming out of the Factory in May of 1943.
ANd what happens when you put enough fuel in the P-39 so it doesn't have the endurance of a bottle rocket? 

You might want to check on what a light loaded P-38 could do since you are using the numbers from a light loaded P-39. That 7300lb or under figure is highly suspect. 
That half fuel story is a bit bogus, Fine for figuring out what the plane can do for a few minutes in a fight, horrible for trying to figure out time needed to intercept as you claim the P-39s were doing in New Guinea. I have no doubt the P-39s that were there were trying their damndest to intercept but taking off with 50-60 gal of fuel and flogging the engine beyond recommended time limits just to reach altitude wasn't being done. 

A P-39 at 7300lbs is lucky it has 62.5 gallons on board. Even if you start with around 70 and burn off the extra in warm up and taking off that doesn't leave whole lot. Charts for P-39K at 7400lbs shows 36 gallons needed to reach 25,000ft including warm up and take off using a "combat climb" of take-off power for the first five minutes and emergency maximum for 15 minutes. Now you are at 25,000ft in a combat situation with about 30-36 gallons on board? With an engine burning around 1.5 gallons a minute at full power at that altitude? 
What happens after combat? you _glide _down 10-15,000ft and make a dead stick landing? 


For the Spitfires. There were 4 squadrons of MK IXs at Dieppe. Aug 19th 1942, which rather predates the issue of P-39Ns regardless of Nov/Dec or transit times.

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## parsifal (Mar 21, 2018)

I see yet more mis-information being trolled about, this time this time concerning the availability of radar:

Here are extracts from a definitive article on radar in PNG at the time with selected excerpts (with a few minor changes by me)

From “Echoes Over the Pacific”; Ed Simmonds and Norm Smith

"29RS was the first RAAF radar station established outside mainland Australia. Four radar mechanics and eight radar operators arrived by aircraft at Jackson’s Strip airstrip) on 19 February 1942 under the command of F/O Wadsley Equipment for the Station 29RS arrived 25th February. There were some difficulties in getting the apparatus operational, but the set was working with plotting and reporting procedures in place by the end of March. 

Despite the many problems encountered installation was duly completed and the station was on the air on 18 March 1942 with the array built on a peak rising 690 above its surrounding terrain. Plots were by land line to the Operational Room at Port Moresby.. A Teleradio was kept on stand-by for emergency communication.

Initially the performance of 29RS was poor. The equipment was one of the initial six experimental preproduction models’ about which the mechanics knew very little and had had no operational experience with. The mechanics did not have the necessary matching and phasing instruments to adequately set up the antenna and the aerial coaxial feeders had not been cut to the correct length.

Consequently complaints were received concerning aircraft, both friendly and enemy, arriving at Moresby undetected. Test flights highlighted the unsatisfactory lobe pattern and poor field strength of the system. In an effort to improve the performance the prototype transmitter and receiver were replaced in October 1942 by a factory made model but this was not the solution to the problem. 

It wasn’t until 21 December 1942 that properly qualified staff arrived to match and phase the open wire feeders to the antenna. This work was followed up by test flights on 18, 20 and 22 January 1943. The radar was, at last, operating at full efficiency. Further calibration flights by a Beaufighter, on bearings 180 and 225 degrees at altitude 10,000 ft, gave satisfactory results out to about the 45 mile range at 22000 feet in the direction of the mountains. When not impeded by the terrain, the range of the radar was much better, maximum range of 140 miles. However, detection of aircraft was restricted by the high mountains to the north and west. The blocking effects of the mountains to the east, west and north remained a very difficult issue to overcome. 

Leigh Hoey, a Wireless Operator Mechanic (WOM), who served for more than 17 months on this unit, wrote:.

_The receiver room was a small building constructed of galvanised iron on a small hill and set up so that we could work with lights on during air raids. There we operated AR7 receivers (one had a bullet hole from earlier action) while the transmitters - AT13’s, AT13A’s and AT14’s - were dispersed in huts protected by bunkers. The antennas were mostly quarter wave Marconis. Plots were received by landline from RAAF Radars 29RS near Moresby and 138RS at Waigani. Plots were received by W/T from American Radar RS405 at Yule Island and from the Army Spotters and Coast Watchers. Plain language was used on telephones but normally all radio traffic was in Morse code. An Operations Room clerk sat beside us and passed the plots by telephone to Fighter Sector plotting room as we entered them into the log book. In the Operations Room were Allied Army, Navy and Air Force personnel assessing and disseminating information to fighter aircraft, Ack Ack and searchlight positions, ships and the air raid warning system. Specially trained controllers vectored fighter pilots to their targets during enemy raids. At the ground controlled interception (GCI) unit, 138RS at Waigani Swamp, a controller was able to work directly from the radar thus eliminating the delay, however short, caused when working at the Operations Room via the communication system. 82. In addition the signal section also handled inter-island and mainland traffic and the volume became formidable as the war gained momentum. _

4 Fighter Sector (RAAF) played a vital role in the crucial days of the war and continued as a communication centre until the end. The Americans nearby duplicated much of the RAAF work as well as handling particularised US radio traffic though their equipment was even more challenged by the terrain than the RAAF stuff. 

First American GCI Radar in New Guinea.

In June 1942 the 565th SAW (Signal Air Warning Battalion) arrived in Brisbane (Australia). and gained valuable experience in operating at various sites in Queensland. It was not until 9 September that Lt Roscoe C Sparkes arrived in Port Moresby with the 6th Reporting Platoon of the 2nd Reporting Company of that Battalion. This first American radar Platoon established RS473 on level ground at Waigani Swamp north of Ward’s Strip. The equipment was an SCR516 - a development from the SCR268 gun laying radar modified for air warning - similar to the MAWD used by the RAAF. While the equipment’s maximum range was about 60 miles it gave consistently good results. The station watched for aircraft emerging from the PEs caused by the Owen Stanley Range to the north.

The 4th Platoon transported its radar equipment, an SCR516, aboard a barge to Cape Rodney situated about 125 miles south east of Port Moresby and almost half the distance to Milne Bay. After overcoming landing and transport difficulties they established RS472 on a site previously chosen by air reconnaissance. Results from the station were far from satisfactory the reason for this proved to be the effect of nearby high inland mountains. Not only was detection of targets among the mountains impossible but also back radiation from the same mountains cluttered the screen when scanning over the sea. Several alternative sites were tried without success.

http://radarreturns.net.au/archive/EchoesRRWS.pdf

It would be good if some basic fact checking was undertaken in this discussion before just blathering the first thing that floats into the head.

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## pbehn (Mar 21, 2018)

buffnut453 said:


> Hmmm...four of those "test squadrons" participated in operations over the Dieppe Raid in August 1942. That's still 4 squadrons fully equipped and operational with Spit MkIXs some 4 months before even your earliest date for the P-39N.
> 
> You can't have your cake and eat it by claiming that, somehow, the P-39N could have rapidly entered service by the end of 1942 but then dismiss operational usage of the Spit MkIX in 1942 as just operational testing.


There is another important difference. The RAF squadrons operating MkIX had just switched from MkV, the airfields pilots and ground crew with all equipment was already there working. The P39s from the USA need all the staff transported and all the tools, spares and things they need too. The Battle of the Atlantic was still going on at that time.


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## Shortround6 (Mar 21, 2018)

wuzak said:


> Edwards Park was given a P-39, squadron letter N.
> 
> Pacific Wrecks



I would also note that Park's book says it took them 3 weeks from Hawaii, 4 weeks from San Francisco to get to Townsville by ship.

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## Glider (Mar 21, 2018)

P-39 Expert said:


> P-39N entered service December '42.
> 
> The July '42 Spitfires were just two squadrons that were practically service test planes. A few more test squadrons tricked in before real series production started at the end of '42.


My understanding is that Production of the P39N was in December but entering combat is a different thing. As for your comment about being service test aircraft is more than a little misleading. Some factories were producing Mk IX exclusively from June 42, others converted during the rest of 42 with all converted from Mk V to Mk IX by the end of the year


wuzak said:


> Edwards Park was given a P-39, squadron letter N.
> 
> Pacific Wrecks


Which presumably means it wasn't a P39N as the link says he operated it from mid 1942 until late 43

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## MIflyer (Mar 22, 2018)

The Soviets did not equip the P-39 and P-63 with the same NR-37 cannon as used on the Mig-15.

Go take a look at Chinn's massive work on the history of automatic weapons "The Machine Gun." It is available on line for free. I provided a link to it.

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## P-39 Expert (Mar 22, 2018)

parsifal said:


> I see yet more mis-information being trolled about, this time this time concerning the availability of radar:
> 
> Here are extracts from a definitive article on radar in PNG at the time with selected excerpts (with a few minor changes by me)
> 
> ...


Sorry you didn't make it down the Google list to my source. In "Attack and Conquer, The 8th Fighter group in WWII" by John C. Stanaway and Lawrence J. Hickey. The 8th FG's two squadrons (35th & 36th) in May 1942 was all that was standing between the Japanese on the north side of New Guinea and Australia. The 8th Fighter Control squadron (not pilots, but radar operators) arrived in Milne Bay on August 7, 1942 to set up and operate the new radar station there. Now you are googling Milne Bay on google maps and you can clearly see that Milne Bay is at the far eastern tip of New Guinea and provides an unrestricted view of not only the Lae and Salamalua Jap bases but also New Britain and the Solomon Islands (Guadalcanal et al) and was the ideal location for GCI radar in the area. The problem with trying to put the radar in the Port Moresby area (or Australia) was the 12000' Owen Stanley mountain range between PM and the Japanese on the north side of NG. Most of the problems you site above come from that mountain range blocking radar signals. 

Attack and Conquer is a really good book by the way, a daily diary of the 8th's activities throughout WWII. Big book with lots of pictures.

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## P-39 Expert (Mar 22, 2018)

wuzak said:


> Edwards Park was given a P-39, squadron letter N.
> 
> Pacific Wrecks


Wrong book. Park wrote two books about his tour in New Guinea. "Nanette" was a fictional account based on all the stories he had heard and participated in. His second book, "Angels Twenty" was a nonfiction (factual) account of his tour from December '42. He says he got his P-39N in December in the nonfiction work. Both books are worth your time, very entertaining and provide a day to day look at the perils of WWII in that area.


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## Peter Gunn (Mar 22, 2018)

Still not seeing how the P-39N was in action in the SWPA in 1942. Pacific Wrecks has a list of P-39 losses, the earliest of which seems to be August 1943. While it does not list delivery dates, I find it hard to believe it was in action for 8 - 9 months without a loss.

Also, again, one test of a lightly loaded P-39 does not an operational plane make. You still contend that a_ fully loaded_ P-39 can out climb a _fully loaded_ P-38 or P-51? *We're talking combat ready, fuel and ammo*.

And no, the air war WAS NOT over by March '44.

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## P-39 Expert (Mar 22, 2018)

Shortround6 said:


> What month of 1943? P-38Hs were coming out of the Factory in May of 1943.
> ANd what happens when you put enough fuel in the P-39 so it doesn't have the endurance of a bottle rocket?
> 
> You might want to check on what a light loaded P-38 could do since you are using the numbers from a light loaded P-39. That 7300lb or under figure is highly suspect.
> ...


Let me try and explain this again. In wwiiaircraftperformance, the gross weights listed on the test documents show "mean fuel" or average fuel available during the test. I'm not sure exactly which P-39 variant you are speaking of, but the 7300# weight is for the plane with half fuel. This weight number is for calculations of ratios (power/weight, wing loading etc) since there was a 720# weight difference (120 gal) between an empty P-39 and a full (of fuel) P-39. To get the correct published weight for the P-38, P-39 and P-47 in those tests you need to add back half of the fuel capacity. The planes were tested with full tanks but their weights differed drastically from the time they took off until the time they landed because they were expending their fuel during the test. Any calculation involving weight would need to specify which weight, the weight at takeoff or the weight at landing or the weight in the middle of the flight. So for calculations they used mean or average fuel giving a mean or average weight for the plane. So the figures are for a fully loaded (gross weight) plane at a weight after half the fuel has been burned, or the weight that the plane would likely be in actual combat. The planes tested took off with full tanks, the mean weight figure is for calculations. Nobody in combat took off with 60 gallons of fuel. Hope this helps.

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## P-39 Expert (Mar 22, 2018)

buffnut453 said:


> Hmmm...four of those "test squadrons" participated in operations over the Dieppe Raid in August 1942. That's still 4 squadrons fully equipped and operational with Spit MkIXs some 4 months before even your earliest date for the P-39N.
> 
> You can't have your cake and eat it by claiming that, somehow, the P-39N could have rapidly entered service by the end of 1942 but then dismiss operational usage of the Spit MkIX in 1942 as just operational testing.


Regarding the P-39N entering service in Dec '42, Bell produced 277 planes in November and 302 planes in December. There was no gap in production between the M and the N. They used the same engine power section only differing in the substijtution of the 2.23 reduction gear in the N instead of the 2.00 gear in the M. All Airacobras were the same plane with differences in propellers, different versions of the V-1710, different reduction gears and radios. As the new Ns came off the line they were immediately flown a couple of times (90 minutes total) for service test and shipped or flown off to war. Bell had this procedure down pat since they had already produced 2000+ P-39s and obviously their goal was to get the planes in service asap. Entirely possible to have an N in service in December.


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## buffnut453 (Mar 22, 2018)

P-39 Expert said:


> Regarding the P-39N entering service in Dec '42, Bell produced 277 planes in November and 302 planes in December. There was no gap in production between the M and the N. They used the same engine power section only differing in the substijtution of the 2.23 reduction gear in the N instead of the 2.00 gear in the M. All Airacobras were the same plane with differences in propellers, different versions of the V-1710, different reduction gears and radios. As the new Ns came off the line they were immediately flown a couple of times (90 minutes total) for service test and shipped or flown off to war. Bell had this procedure down pat since they had already produced 2000+ P-39s and obviously their goal was to get the planes in service asap. Entirely possible to have an N in service in December.



As several have stated, there is a world of difference between "in service" and "operational". Your dismissive attitude to the operational use of the Spitfire MkIX is indicative of exactly my point, and yet you seem to ignore the challenges of getting P-39Ns to the front line and in operational use.

Were all the P-39s built in November the N variant and, if not, when did N production commence? How long to get a batch of P-39Ns (aircraft aren't shipped individually but in batches) to the operational theatre? And then how long to uncrate, erect and test the aircraft before they can be provided to the squadron(s)? Add to that Peter Gunn's comment about the earliest P-39N casualty apparently being on 15 August 1943 and it simply beggars belief that the type was operational in December 1942. There's no way the USAAF was able to operate the P-39N for 8+ months without losing a single aircraft.

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## buffnut453 (Mar 22, 2018)

To add some more info about Edwards Park's P-39, see this link about Nanette, again from the Pacific Wrecks website. While the serial number isn't known, the aircraft was in use from mid-1942 onwards. If that's correct, then it can't have been a P-39N.


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## P-39 Expert (Mar 22, 2018)

buffnut453 said:


> To add some more info about Edwards Park's P-39, see this link about Nanette, again from the Pacific Wrecks website. While the serial number isn't known, the aircraft was in use from mid-1942 onwards. If that's correct, then it can't have been a P-39N.


Wrong book. See post #359.


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## buffnut453 (Mar 22, 2018)

P-39 Expert said:


> Wrong book. See post #359.



The info in the Pacific Wrecks website goes beyond what is in the "wrong book". Regarding Park's P-39 it states:

_Assigned to the 5th Air Force, 35th Fighter Group, __41st Fighter Squadron__. Squadron letter N, nose number 74. Assigned to pilot __Edwards Park__. Nickname "Nanette". Operated in New Guinea during middle 1942 until late 1943. A single aircraft silhouette was painted on the left side of the nose.
_
How would Park know to include the mid-1942 arrival of P-39 #74 in his "wrong book" given that he wasn't even in theatre when the aircraft arrived? 

Again, please explain how a P-39N could get to New Guinea by December 1942. We're still awaiting an answer that stacks up with known transportation timeframes.

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## P-39 Expert (Mar 22, 2018)

buffnut453 said:


> As several have stated, there is a world of difference between "in service" and "operational". Your dismissive attitude to the operational use of the Spitfire MkIX is indicative of exactly my point, and yet you seem to ignore the challenges of getting P-39Ns to the front line and in operational use.
> 
> Were all the P-39s built in November the N variant and, if not, when did N production commence? How long to get a batch of P-39Ns (aircraft aren't shipped individually but in batches) to the operational theatre? And then how long to uncrate, erect and test the aircraft before they can be provided to the squadron(s)? Add to that Peter Gunn's comment about the earliest P-39N casualty apparently being on 15 August 1943 and it simply beggars belief that the type was operational in December 1942. There's no way the USAAF was able to operate the P-39N for 8+ months without losing a single aircraft.


Really don't have a dismissive attitude toward the Spitfire IX. One of the finest planes of WWII and the fastest climbing plane. As long as you don't mind the very narrow landing gear and you don't want to actually go any further than Belgium.  Just saying that the Merlin 61 was just being developed and real full Mk IX production didn't get into swing until the end of '42, which is what wwiiaircraftperformance and most historians say. My comparisons have all been with the P-39N vs the enemy planes, not the Spit IX. IX had a two stage engine, hard to compare to a single stage engine for altitude performance.
Regarding the P-39N nothing was really in development, the V-1710-85 had been in production since September and had fully passed it's 150 hour test. The Ns were just the next version on the continuing production line and as they were rolled out they were test flown and shipped or flown off. By that time most were going to the Russians or to AAF training bases anyway.


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## P-39 Expert (Mar 22, 2018)

buffnut453 said:


> The info in the Pacific Wrecks website goes beyond what is in the "wrong book". Regarding Park's P-39 it states:
> 
> _Assigned to the 5th Air Force, 35th Fighter Group, __41st Fighter Squadron__. Squadron letter N, nose number 74. Assigned to pilot __Edwards Park__. Nickname "Nanette". Operated in New Guinea during middle 1942 until late 1943. A single aircraft silhouette was painted on the left side of the nose.
> _
> ...


I can't point to a specific P-39N that was manufactured by Bell and was issued to Lt. Park when he arrived in NG. He says in his book "Angels Twenty" (not the fictional "Nanette") that he got to PM in December and was issued a brand new P-39N. All I know is the N was in production and could have been in NG by that time. Park is long dead or you could take it up with him.  Is it a deal killer if a few Ns snuck out of the factory in late November and were in NG in late December?


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## buffnut453 (Mar 22, 2018)

P-39 Expert said:


> I can't point to a specific P-39N that was manufactured by Bell and was issued to Lt. Park when he arrived in NG. He says in his book "Angels Twenty" (not the fictional "Nanette") that he got to PM in December and was issued a brand new P-39N. All I know is the N was in production and could have been in NG by that time. Park is long dead or you could take it up with him.  Is it a deal killer if a few Ns snuck out of the factory in late November and were in NG in late December?



And there is the whole problem. Aircraft don't "sneak out of the factory" and miraculously end up at a remote operational field just a few weeks later. They are shipped in batches, which means completion of an individual airframe does not mean it started it's journey to the front lines. Again, you cite the lack of break in P-39 production between the M and the N variant which, presumably, means there were established transport mechanisms to take the newly-built airframes to wherever they needed to go. They don't "sneak out" in ones and twos, they are shipped in more sizeable quantities. 

Simply (re)stating "the N was in production and could have been in NG by that time" doesn't answer the fundamental question. In order for a P-39N to be in NG in December 1942, it would have had to be produced right at the start of the month (hence my question about when N production started), and then had virtually no holdups on the way across America and then across the Pacific. 

The nub of the problem here is that one man's personal account mentions that he flew a P-39N in December 1942 when all other evidence suggests he was mistaken. What's more likely, that Mr Park is correct or that he simply got confused writing down things that happened decades previously? Occam's Razor applies, methinks.

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## P-39 Expert (Mar 22, 2018)

buffnut453 said:


> And there is the whole problem. Aircraft don't "sneak out of the factory" and miraculously end up at a remote operational field just a few weeks later. They are shipped in batches, which means completion of an individual airframe does not mean it started it's journey to the front lines. Again, you cite the lack of break in P-39 production between the M and the N variant which, presumably, means there were established transport mechanisms to take the newly-built airframes to wherever they needed to go. They don't "sneak out" in ones and twos, they are shipped in more sizeable quantities.
> 
> Simply (re)stating "the N was in production and could have been in NG by that time" doesn't answer the fundamental question. In order for a P-39N to be in NG in December 1942, it would have had to be produced right at the start of the month (hence my question about when N production started), and then had virtually no holdups on the way across America and then across the Pacific.
> 
> The nub of the problem here is that one man's personal account mentions that he flew a P-39N in December 1942 when all other evidence suggests he was mistaken. What's more likely, that Mr Park is correct or that he simply got confused writing down things that happened decades previously? Occam's Razor applies, methinks.


My sincere apology, obviously I have struck a nerve. P-39Ns were in production in December and Park said he had one in NG. Seems plausible to me. Now please dissect every word of this post, get on the Google machine and prove me wrong again. Like Rodney King once said "Please stop hitting me". I give up.

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## MIflyer (Mar 22, 2018)

You know, both of those books are good but he says something opposite.

In Nanette he says that the P-47's fondest desire was to return to earth and it rumbled happily coming down final. And that the Thunderbolt was just a cold machine, not a living thing like his P-39, Nanette.

In Angels Twenty he says that the P-47 loved playing in the sky and grumbled about the fun being over as they slid down final.

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## buffnut453 (Mar 22, 2018)

P-39 Expert said:


> My sincere apology, obviously I have struck a nerve. P-39Ns were in production in December and Park said he had one in NG. Seems plausible to me. Now please dissect every word of this post, get on the Google machine and prove me wrong again. Like Rodney King once said "Please stop hitting me". I give up.



Not hitting you nor have my nerves been jangled. I'm just asking for some reasoned evidence for your claims. 

I've learned a lot from members on this forum, occasionally because I've been on the receiving end of some detailed critiques of statements I've made. The downside of being such a good learning environment is that the BS detectors are pretty well attuned. 

All I'm asking is that claims are backed up with evidence or at least a reasoned explanation of why something might be true. In the absence of any such data, I guess we'll just have to agree to disagree.

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## pbehn (Mar 22, 2018)

Having worked in shipping for two years nothing gets "immediately shipped off" to anywhere especially from USA. From the USA you need to ship to the port, wait for a vessel, then load, then at the destination unload, that is if any vessel goes directly to your destination and no trans shipment is involved. Flying even if it is physically possible also needs its own infrastructure of pilots transports accommodation etc. In peacetime we didn't have vessels routinely getting sunk as in WW2 but I did experience vessels just being diverted to take more valuable cargo, or more frequently with "tramp" vessels calling at non scheduled ports to load and unload other cargos. When a vessel is sunk not only is the crew, ship and cargo lost but its projected routes are too.


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## P-39 Expert (Mar 22, 2018)

buffnut453 said:


> Not hitting you nor have my nerves been jangled. I'm just asking for some reasoned evidence for your claims.
> 
> I've learned a lot from members on this forum, occasionally because I've been on the receiving end of some detailed critiques of statements I've made. The downside of being such a good learning environment is that the BS detectors are pretty well attuned.
> 
> All I'm asking is that claims are backed up with evidence or at least a reasoned explanation of why something might be true. In the absence of any such data, I guess we'll just have to agree to disagree.


Yes and this is a message board so opinions are the order of the day.

Let me make a few statements of fact: Information about the P-39 has been made available since the fall of the Soviet Union (the main combat user of the type). Also P-39 information was made available in late 2012 on wwiiaircraftperformance.org that I have not been able to locate before then. This new information somewhat contradicts what we have been told for 60 years, like (but not limited to) the Russians used the P-39 for ground attack, the P-39 had terrible performance over 12000', it would spin or even tumble at the drop of a hat, it had a rearward center of gravity, the airwar in Russia was all at low altitude, the 37mm cannon didn't work and on ad nauseum. 

I would much rather debate (all of) you on the merits of the P-39 than arguing with you about how the damn thing was shipped from the factory.

I maintain (as the Russians did) that the P-39 was the equal of the German fighters (FW190 and Me109) at all altitudes, not just down low. They found that the 37mm cannon (properly maintained) was very reliable and even more reliable than the US 20mm cannon. It didn't have any real handling problems. 

And Chuck Yeager in his book said that the P-39 was his favorite plane in WWII and would "gladly fly that little plane off to war". Now he qualifies that statement by saying it was his favorite plane until he got a Merlin P-51B, but again the P-39 was in use from December 1941 and the P-51B didn't get into combat until December 1943.

Now if anyone wants to debate this (in a normal tone of voice) then I'm here for you. I don't really care when (or how) the damn things were shipped.

Bring it.


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## Peter Gunn (Mar 22, 2018)

P-39 Expert said:


> My sincere apology, obviously I have struck a nerve. P-39Ns were in production in December and Park said he had one in NG. Seems plausible to me. Now please dissect every word of this post, get on the Google machine and prove me wrong again. Like Rodney King once said "Please stop hitting me". I give up.


I doubt very much you've "struck a nerve" here, you've just run across the most knowledgeable group of guys on the subject at hand, namely WWII aviation. Sure is sounds _plausible_ a P-39N could have been manufactured in December '42 and been in action the same month. What you'll learn here is not what is plausible, but what actually happened. Logistics dictates ( to me at least ) the P-39N could not have made it to any combat zone in two weeks time, I've learned that from reading many threads on this forum by posters with far more knowledge and source document resources than I can imagine.

SR6 and others have continually tried to explain 2S/2S superchargers v. 1S/1S etc. not to mention crankshaft differences etc. etc. A person can learn a lot from these guys, you just have to be humble enough to realize that sometimes you may have to pony up with valid references to make your point.

Not to single any one poster out, but for example, when drgondog posts, read carefully and take it to the bank that what he says is based in fact. Not coffee table history book "accepted" versions of events, but dyed in the wool, right from the source documentation and education. And that's just the tip of the ice cube, I could name almost a dozen more posters that have knowledge and source material to back up what they say.

So when you start to rewrite history, you best have source documentation ( and a fair amount of it ) to back up what you're trying to say. Everyone here is always open to new interpretations or new discoveries of data, no one is so hidebound in their beliefs that they close their eyes to new information. But the BS meter is finely tuned and will be used immediately when needed.

I cite the example of your statements about the air war being over by March '44, it may sound like I'm nit picking one point, but it's a very important point. You won't find many here that will agree with that for a reason i.e. it's false. When you attach that type of assertion, it calls into question your entire argument, firmly sticking to such an assertion only lowers your credence going forward. One might posit that it would have been better to ask why many here think that statement is false, and ask them to cite sources.

Pardon the long post, as I said, you seem a well read intelligent bloke and you've come to the right place for information and the exchange of same, I just hope you take this to heart and stick around as I think you could contribute to the group here.

Cheers

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## pbehn (Mar 22, 2018)

I would value Chuck Jaegers opinion on all things, however before he flew a P-51B how many other planes did he fly? Wikipedia states he initially flew P-39s at Tenopah and then P-51s at RAF Leiston. So basically he found the P-39 better than his training mounts and not as good as a P-51B, but the Allison powered P51A was comparable in performance at low altitude. Also, he broke the sound barrier in a Bell aircraft and was an employee of Bell post war.

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## parsifal (Mar 22, 2018)

P-39 Expert said:


> Sorry you didn't make it down the Google list to my source. In "Attack and Conquer, The 8th Fighter group in WWII" by John C. Stanaway and Lawrence J. Hickey. The 8th FG's two squadrons (35th & 36th) in May 1942 was all that was standing between the Japanese on the north side of New Guinea and Australia. The 8th Fighter Control squadron (not pilots, but radar operators) arrived in Milne Bay on August 7, 1942 to set up and operate the new radar station there. Now you are googling Milne Bay on google maps and you can clearly see that Milne Bay is at the far eastern tip of New Guinea and provides an unrestricted view of not only the Lae and Salamalua Jap bases but also New Britain and the Solomon Islands (Guadalcanal et al) and was the ideal location for GCI radar in the area. The problem with trying to put the radar in the Port Moresby area (or Australia) was the 12000' Owen Stanley mountain range between PM and the Japanese on the north side of NG. Most of the problems you site above come from that mountain range blocking radar signals.
> 
> Attack and Conquer is a really good book by the way, a daily diary of the 8th's activities throughout WWII. Big book with lots of pictures.




_Sorry you didn't make it down the Google list to my source. In "Attack and Conquer, The 8th Fighter group in WWII" by John C. Stanaway and Lawrence J. Hickey. The 8th FG's two squadrons (35th & 36th) in May 1942 was all that was standing between the Japanese on the north side of New Guinea and Australia_.


8th FG was part of the shuttle style defences that the allies utilised to blunt and finally defeat the hitherto unstoppable Japanese. It was deployed to relieve 75 sqn at the end of April, having undergone some further training in Australia before receiving its deployment orders. Its initial deployment was to 7 mile airfield near Moresby, 37 were despatched, but only 26 arrived.

The remains of 8th FG, the flying element at least, remained in the front line of Moresby’s defences. though to 16 June (according to one source), , when allegedly it was shipped out after having sustained some heavy losses....I have serious doubts about some of the dates from that source, I admit. Some ground elements did remain behind until the end of July, but there were no deployments of either of the fighter formations until a month or so later.

The Group HQ had arrived in Australia in March 1942, the last of three pursuit groups to reach Australia in the first wave of American reinforcements. The group itself operated in detachments in New Guinea, helping fight off the most direct land threat to Australia. Significant detachments moved back to Australia in June 1942 to recover from malaria with both squadrons fully withdrawn by early August (I think)..

The group moved to New Guinea in September 1942, after the battle of milne Bay had been fought and won by the Australians, but it then suffered from a serious outbreak of malaria again and had to withdraw to Australia in February 1943.

The group resumed operations in April 1943 and remained active for the rest of the war. At first it operated over New Guinea, supporting the series of Allied landings along the New Guinea coast, attacked Japanese airfields and provided bomber escorts. It also supported the US Marine landing at Cape Gloucester in February-March 1944.

It was not the sole defence in NG at the time.

_Sorry you didn't make it down the Google list to my source. In "Attack and Conquer, The 8th Fighter group in WWII" by John C. Stanaway and Lawrence J. Hickey. The 8th FG's two squadrons (35th & 36th) in May 1942 was all that was standing between the Japanese on the north side of New Guinea and Australia. _

Its news to me that I used google. I didn’t. In May 1942, in case you’ve forgotten, the main defences of NG were the USN, which fought a hard battle in the Coral Sea. In terms of the land based air assets, there were still a few of 75 sqn remnants present in early may. There were 7 un-airworthy P-40s available. The squadron cannibalised 2, to get the last 5 airborne, 3 were shot down over the next two weeks. The last of 75 sqn was withdrawn by mid-may, leaving the 8th FG as the sole fighter defences until the end of June, at which time both 75 and 76 returned, as well as the first Beaufighter units., 

_The 8th Fighter Control squadron (not pilots, but radar operators) arrived in Milne Bay on August 7, 1942 to set up and operate the new radar station there_.

Work on the first airfield, which became known as No 1 Airstrip, and later gurney, had commenced on 8 June, with Papuan workers under the supervision of ANGAU (No 6 Mobile Works Station RAAF) being the main unit supported by elements of the CMF militia and native labour. These formations commenced construction work from 8th June as stated above. Later elements of the 96th General Service Regiment (GSR) US army and company E of the 46th GSR arrived after 30 June to also to assist. About 500 personnel were involved overall, the vast majority Australians and natives

The first radar unit to be set .up was number 37 RAAF, which did later receive a few radar operators from the US forces which may well have been drawn from 8FG. But was not an American operation, it was an Australian formation, and the radar station had already been set up when the Americans arrive. Number 37 was declared operational at Milne from 8 August, though initially radar performance was disappointing

_Now you are googling Milne Bay on google maps and you can clearly see that Milne Bay is at the far eastern tip of New Guinea and provides an unrestricted view of not only the Lae and Salamalua Jap bases but also New Britain and the Solomon Islands (Guadalcanal et al) and was the ideal location for GCI radar in the area. _

Thanks for the offer to google the whereabouts of Milne Bay, but I don’t need to because ive been there several times whilst serving in the RAN. Dismal place.

With regard to your comments about Milne enjoying “_unrestricted view of not only the Lae and Salamalua Jap bases but also New Britain and the Solomon Islands (Guadalcanal et al) and was the ideal location for GCI radar in the area_”_, _you have got to be sh*tting me. Milne suffers the same problems as Moresby as far as radar shadows except to the south and south east. It has a 12000’ high mountain immediately behind it and is about 582 mi to lae. There are mountainous islands to the north, north east and east of radar. Station.

Maximum radar range for the radars available in 1942 was about 140 miles theoretically, but in practice in the atmospheric and topographic conditions that existed, for many months the range was typically, about 40 miles.


Milne was never seen as a solution to this problem. You are kidding yourself and trying to mislead anyone who might be listening to you (I doubt anyone is though). It was intended solely (or initially) as an early warning base, to prevent seaborne movements by the Japanese via the Louisiade Archipelago channels. Those channels are treacherous and restrictive I can tell you. They needed seaplanes to provide that surveillance, which was mostly provided by 11 sqn PBYs 

_probably the “google maps” you are relying on in turn rely on some of that work still. Milne Bay was important also because it provided a deep water port (well sort of) and a relatively safe channel to that anchorage_

I didn’t need google to find out any of that. Back in the 70’s when I was last there, I was aboard vessels carrying out survey work of those areas, that enabled the area to be finally adequately charted.

_The problem with trying to put the radar in the Port Moresby area (or Australia) was the 12000' Owen Stanley mountain range between PM and the Japanese on the north side of NG. Most of the problems you site above come from that mountain range blocking radar signals. _

Milne Bay had the same problems, but worse than seven mile. Neither base was of any use in detecting the Japanese in their bases anyway, because of range issues. Even under the most ideal conditions, they were both simply too far away to be used as advanced radar stations “chain Home” style.

_Attack and Conquer is a really good book by the way, a daily diary of the 8th's activities throughout WWII. Big book with lots of pictures_

Im sure it is, and its good that its got lots of pictures for you. By the look of it you might try reading it as well.

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## Shortround6 (Mar 22, 2018)

Well, 
We have a fictional book that features a P-39 called Nanette and we have a real P-39 (type unknown) with the call letter N and nicknamed Nanette. Flown by the man who wrote the fictional book.

We also have that _faaasstt _shipment of P-39s from the factory to exactly the right airfield. 
P-39Expert claims Bell built 277 planes in Nov of 1941, AHT says 268 "acceptances" not enough to get to into a tizzy about, there is often a discrepancy between built and "accepted" when you are building and test flying 9-10 planes per day. 
However Another source claims that Bell built 240 P-39Ms starting at some point in November. SO even if the change over from the P-39L to the M was done at midnight of Oct 31st that mean a max of 37 P-39Ns built in Nov. and at the production rate stated that is about 4 days worth. 
By Edwards Park's account it took 4 weeks by ship to get personnel from San Francisco to Australia. so for this scenario to work we need to get "a few planes" to "sneak" out of the factory and somehow get to the west coast in a matter of a few days, make the 4 week sea voyage to Australia, get unloaded, unpacked (reassembled), test flown and issued to the 41st squadron by Dec 31st. Or 35 days from acceptance flight to issue in a combat squadron over 9000 miles away by air. Maybe they used a fast freighter and only took 3 weeks? It is roughly 6150 nautical miles form San Francisco to Townsville. 17 days at 15 kts with absolutely no deviations and no zig zagging. 

For some further information on the 35th fighter group of which the 41st squadron was part of see;
Wayback Machine

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## MIflyer (Mar 22, 2018)

The P-39 was popular with pilots of the caliber of Chuck Yeager not because it was easy to fly but because it was hard. The gearing between the stick and the ailerons was so high you barely had to move the stick. That's fun if you really know what you are doing but a nightmare if you are a green pilot with limited experience and moderate ability. Capt "Winkle" Brown of the Fleet Air Arm flew a P-39 to evaluate tricycle gear for use on carrier decks, and he loved to fly the airplane. 

Probably 20 years ago a friend of mine ferried an airplane to a museum and found they were distraught. They had finished restoration of a P-39 but had no one who knew how to fly it. He said he could fly it and wrung it out for them. He had been a ferry pilot during WWII and had the job of flying the airplanes that had some problems that were beyond the abilities of a typical ferry pilot. One day he went to Nashville to pick up a P-51 that had been parked there by another ferry pilot. The ferry pilot said they were told not to fly the P-51 with any fuel in the rear tank. And with that airplane the rear tank started out empty but kept filling up as it flew. Turned out that for some reason on that airplane they had routed the pressure carb fuel return to the rear tank instead of the right tank.

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## pbehn (Mar 22, 2018)

MIflyer said:


> The P-39 was popular with pilots of the caliber of Chuck Yeager not because it was easy to fly but because it was hard. The gearing between the stick and the ailerons was so high you barely had to move the stick. That's fun if you really know what you are doing but a nightmare if you are a green pilot with limited experience and moderate ability*. Capt "Winkle" Brown of the Fleet Air Arm flew a P-39 to evaluate tricycle gear for use on carrier decks, and he loved to fly the airplane.*
> 
> .


Brown was the first to land a tricycle undercarriage plane, P-39, on a carrier . I don't know how many times but when Bell saw it they recommended it be scrapped.

from Wiki
The Airacobras already in the UK, along with the remainder of the first batch being built in the US, were sent to the Soviet Air force, the sole exception being _AH574_, which was passed to the Royal Navy and used for experimental work, including the first carrier landing by a tricycle undercarriage aircraft on 4 April 1945 on HMS _Pretoria Castle_,[48] until it was scrapped on the recommendation of a visiting Bell test pilot in March 1946.[49]

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## P-39 Expert (Mar 22, 2018)

Peter Gunn said:


> I doubt very much you've "struck a nerve" here, you've just run across the most knowledgeable group of guys on the subject at hand, namely WWII aviation. Sure is sounds _plausible_ a P-39N could have been manufactured in December '42 and been in action the same month. What you'll learn here is not what is plausible, but what actually happened. Logistics dictates ( to me at least ) the P-39N could not have made it to any combat zone in two weeks time, I've learned that from reading many threads on this forum by posters with far more knowledge and source document resources than I can imagine.
> 
> SR6 and others have continually tried to explain 2S/2S superchargers v. 1S/1S etc. not to mention crankshaft differences etc. etc. A person can learn a lot from these guys, you just have to be humble enough to realize that sometimes you may have to pony up with valid references to make your point.
> 
> ...


Really enjoy talking WWII airplanes with you guys, where else can I find anybody who likes this subject.

All I'm saying is I prefer the facts to heresay. Before late 2012 we all had to take all the heresay as fact. After all the data was put online by wwiiaircraftperformance.org we can compare directly every P-39 model against any other plane (except Russian) and see for ourselves. These are the original source documents, the actual government/military tests. Not some numbers in a coffee table book that seldom match the actual tests. Each of us can then answer the original question, could the P-39 handle the Zero or was it training/performance. 

And google N. G. Goludnikov if you want some Russian heresay.

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## Shortround6 (Mar 22, 2018)

P-39 Expert said:


> Let me try and explain this again......................... Hope this helps.



It doesn't because in polite terminology it is so much horse pucky.

Just starting with the US P-36 and P-40 tests we find the P-36 tests described as full fuel and oil, which is a bit disingenuous as on a P-36 "full" fuel did NOT include the tank behind the pilot. That was the overload or ferry tank. Filling it put the aircraft over gross weight and imposed restrictions on flight maneuvers.

Some of the P-40 tests don't describe either fuel state or even the weight of the aircraft. BTW using the date of a test to judge when a plane went into service is dicey at best, one "test" of the XP-40 was dated _July 28, 1941 _which is about the time the P-40D went into production.
later P-40 tests give test weights but often do not give fuel or ammo state which leaves one guessing, especially when on test of a P-40E gives a weigh of 8011lbs and another test says 8033lbs (propeller test) full fuel and oil, six guns fitted but no ammo and no ballast.
Now this gets weird as the manual for the P-40D/E says the gross weight for the E is 8011lbs with 423lbs of ammo and full internal fuel. Fuel load was given as 720lbs in the manual (design load was only 37 gallons in the rear tank. the extra 25.5 gallons, the belly tank and even an extra 460 rounds of ammo (138lbs) and six 20lb bombs all get listed under alternate max loads. Of course the manual was last revised in Sept of 1941 so weights can differ between planned and actual production aircraft.

A 1944 test of the P-40N-5 was done at 8300lbs and included 157 gallons of fuel and ballast in place of ammunition.

There certainly doesn't seem to be any clear or consistent pattern to the condition of US planes tested let alone planes from other countries.

BTW one P-38G test was done with only 50 rounds for the cannon, only two .50 cal machine guns with 200rpg and 180 gallons of fuel.
They got that sucker up to 25,000ft in 7.36 minutes but I have no idea what it actually proves.

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## Glider (Mar 22, 2018)

P-39 Expert said:


> Each of us can then answer the original question, could the P-39 handle the Zero or was it training/performance.
> 
> .


No it couldn't

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## Elmas (Mar 22, 2018)

_View: https://youtu.be/RLT5qbImaJ4_


L’Aeronautica Militare festeggia i cento anni del Comandante Galbusera

Com.te Galbusera was born in 1917 and now is more than 100 years old...

_"It was a very special airplane, let's say, with the engine in the back, then those Italian maniacs always wanted do aerobatics, when they looped they came in this position and then had to continue, but it was too slow and instead of lowering the head, which it did not have _( for the position of the engine)_ they went in a flat spin and so they were screwed so a very good Genoese Pilot, Moresi left his skin, another Sergeant left his skin, even though they were saying, ehhhh, do you know what I say, if you loop, do it fast, but for me it was a fabulous plane because it had a tricycle undercarriage, on the ground it was driven like a car, apart from this tricycle undercarriage it had in the axis of the propeller a cannon of 37 and four machine guns on the wings the engine was a 1200 hp Allison a beautiful engine it was a very pretty airplane…"_


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## P-39 Expert (Mar 22, 2018)

Shortround6 said:


> It doesn't because in polite terminology it is so much horse pucky.
> 
> Just starting with the US P-36 and P-40 tests we find the P-36 tests described as full fuel and oil, which is a bit disingenuous as on a P-36 "full" fuel did NOT include the tank behind the pilot. That was the overload or ferry tank. Filling it put the aircraft over gross weight and imposed restrictions on flight maneuvers.
> 
> ...


I was mostly concerned with the P-39, P-38, P-47 and P-51, but I'll stand by my mean/average fuel.

That manual weight of 8011# was for the D, two more machine guns for the E would get it up to 8400#.

I don't think other countries used the mean/average fuel, they mostly just listed takeoff weight.

Glad you noticed that "ultralight" P-38G. A G grossed 15900# and with average fuel it would be 900# lighter at 15000', but that one was a ton lighter and I have never seen a P-38 photo with only 2 MG in my life. That is the only instance that I have found where a test was conducted on a plane clearly too light for operations. And the site shows this performance curve on some comparative curves. Normal time for a G to 25000' was 11 minutes, 7.36 minutes just goes to show how much weight affects climb.

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## pbehn (Mar 22, 2018)

Shortround6 said:


> They got that sucker up to 25,000ft in 7.36 minutes but I have no idea what it actually proves.



This is what I find difficult to follow and accept. Removing armour, fuel and guns increases climb rate, well even a child would understand that argument, but it is trending towards a Reno racer not a fighter. When a plane can carry a bomb or a tank the tank may increase range by 100 miles but it doesn't increase the bombing range. Calling a plane "in service" especially a new model plane is a nice idea and the defenders of Malta would have loved it, that loading on carriers etc. was tiresome. 

Even the Wiki article on the P 39 discusses stability problems with the P 39 which Bell couldn't replicate, well they couldn't replicate until they removed ballast that simulated ammunition, which seems to show that firing the guns was not recommended by the manufacturer.


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## drgondog (Mar 22, 2018)

P-39 Expert said:


> Really enjoy talking WWII airplanes with you guys, where else can I find anybody who likes this subject.
> 
> All I'm saying is I prefer the facts to heresay. Before late 2012 we all had to take all the heresay as fact. After all the data was put online by wwiiaircraftperformance.org we can compare directly every P-39 model against any other plane (except Russian) and see for ourselves. These are the original source documents, the actual government/military tests. Not some numbers in a coffee table book that seldom match the actual tests. Each of us can then answer the original question, could the P-39 handle the Zero or was it training/performance.
> 
> And google N. G. Goludnikov if you want some Russian heresay.


What you consistently evade with your facts is that AAF replaced P-39s of every type as fast as they could - with P-40, P-38, P-51 and shuffled them off to Training Command, The French and Italian and Russian AF in early 1944.

There was a reason for that. Actually many reasons, but the most compelling is that even the later models had too little external load capability for either CAS or medium range escort of AAF bombers, had terrible performance (and range) for high altitude operations, was a poor second to Spit IX and XIV in 1944 for interceptor/air superiority fighter as point interceptor of battlefield air supremacy.

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## pbehn (Mar 22, 2018)

tomo pauk said:


> Root: NACA 0015, tip: NACA 23009, no washout (2 deg constant incindence).


I always thought that washout was essential and that without it a plane would stall without warning, does 2 deg constant incidence fulfil the same function in some way or did the P39 have another trick in the box?


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## tomo pauk (Mar 22, 2018)

pbehn said:


> I always thought that washout was essential and that without it a plane would stall without warning, does 2 deg constant incidence fulfil the same function in some way or did the P39 have another trick in the box?



The AHT bible at pg. 203-204 notes that stall behavoir of the P-39 was not favorable - there was no warning, no tail buffeting prior the stall. High-speed stall was also tricky business.

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## pbehn (Mar 22, 2018)

tomo pauk said:


> The AHT bible at pg. 203-204 notes that stall behavoir of the P-39 was not favorable - there was no warning, no tail buffeting prior the stall. High-speed stall was also tricky business.


Bejabers, I remembered something that was correct, it's a miracle

Thanks Tomo

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## Shortround6 (Mar 22, 2018)

P-39 Expert said:


> I was mostly concerned with the P-39, P-38, P-47 and P-51, but I'll stand by my mean/average fuel.


Out of the first 3 P-47 tests on WWII Aircraft Performance 2 have 6 guns installed, ammo and fuel state not given, 3rd has a very similar weight (down 5lbs) but 8 guns.
First test of P-47D on the site says:
" all flights at a gross weight at take-off of 13,200 pounds with c.g. at 27.44% m.a.c., gear up. Total useful load included *300 gallons of fuel*, 28 gallons of oil, 525 pounds of ballast in the ammunition boxes, and the pilot. All radio equipment installed; four, 50 cal. M.G. in each wing,"
bolding by me P-47D held 305 gallons in the internal tanks on the early versions. 525 lbs of ammo is just a bit over 1/2 ammo.

another P-47 test
"Airplane ballasted to simulate the following conditions: Six .50 caliber guns; 300 rounds per gun; 305 gallons gasoline; 15 gallons water; 14 pounds pyrotechnics. In this condition the gross weight was 13,234 pounds"

Please link to ANY test on WWII Aircraft Performance
that *says *mean/average fuel or lists a fuel gallon number that is 1/2 the internal fuel? 


> That manual weight of 8011# was for the D, two more machine guns for the E would get it up to 8400#.



Actually the wight in the Manual I have access to for P-40D is 7944#, same 120 gallons of internal fuel, the P-40D was designed to hold 1000 rounds for it's for guns (with the ability to hold 2460 rounds in overload condition), The P-40E cut ammo to 235 rounds per gun but had the ability to hold more.



> I don't think other countries used the mean/average fuel, they mostly just listed takeoff weight.



Bingo, but not what you said earlier 


P-39 Expert said:


> In wwiiaircraftperformance, the gross weights listed on the test documents show "mean fuel" or average fuel available during the test.

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## Shortround6 (Mar 22, 2018)

pbehn said:


> Even the Wiki article on the P 39 discusses stability problems with the P 39 which Bell couldn't replicate, well they couldn't replicate until they removed ballast that simulated ammunition, which seems to show that firing the guns was not recommended by the manufacturer.



details, details.

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## Graeme (Mar 22, 2018)

Australian Airabonita..... Looks a little under-powered....

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## buffnut453 (Mar 22, 2018)

Graeme said:


> Australian Airabonita..... Looks a little under-powered....
> 
> View attachment 486935



Actually, i was thinking it was a little under-undercarriaged!

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## MIflyer (Mar 22, 2018)

Wing washout is for the purpose of enabling the ailerons to remain effective even after the root of the wing stalled. The alternative is differential ailerons, where the ailerons are geared so that as each aileron goes down it hits a limit and then goes back up while the other aileron keeps moving up.

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## P-39 Expert (Mar 23, 2018)

tomo pauk said:


> The AHT bible at pg. 203-204 notes that stall behavoir of the P-39 was not favorable - there was no warning, no tail buffeting prior the stall. High-speed stall was also tricky business.


What is AHT please?


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## b0ned0me (Mar 23, 2018)

Ah, the legendary P-39.
From a performance and handling standpoint the P-39 was a tribute to the capabilities of the Bell sales organisation.
Recognizing the desperate need for competitive aircraft, Bell could always be relied upon to miss every performance requirement while citing delivery needs, and to miss every date requirement citing the need to work on performance.
Given adequate engineering support from NACA, Allison and the AF, Bell could have had an improved P-39 as good as any other late ww2 fighter, in front line service, several months before the F-86.
The US was stuck between Lockheed's small production of expensive, complex, difficult-to-use but high-performance aircraft and Curtiss' high production of simple, robust but obsolescent under-performers. They needed something cheap, reliable with competitive performance and Bell was able to give them an aircraft that was expensive, complex, difficult to operate and an under-performer.

Frankly, when it comes to the P-39 the jokes just write themselves. Within the constraints of the USAAFs then doctrine of 'turbo or bust' it was a creditable attempt at rethinking how to build a better interceptor but turned out to be badly flawed in execution, and unfortunately had to be pressed into service for lack of anything better. Once the first panic was over the western allies had far better aircraft to choose from so it went to the USSR who were delighted to supplement their own tactical low-altitude fighters built in tractor factories by farmers with a zero-cost tactical low-altitude fighter built in aviation factories to aviation specs.

It certainly did a lot of good work but it also got people killed who would have survived in better aircraft, and once aircraft like the P-51 were available it was frankly not worth a cup of warm piss.

Should it have been able to handle the Zero? Depends on what is meant. With better training and tactics might the allied P-39 pilots have died slowly enough and bled the Japanese more, enough to make a difference? Quite possibly.
If two identically skilled pilots squared off in P-39 v A6M with no tactical advantages, should the P-39 driver be expected to win the majority of the time? I doubt it very much.


P-39 Expert said:


> All I'm saying is I prefer the facts to heresay. .


No, you prefer your fanboy obsessions over the experience of the people who actually had dealings with these aircraft in WW2 and everyone who has researched them in the decades since WW2. Just like all the Wehraboos who insist the Germans could have won the war if only they built Napkinwaffe jets in 1941 or got Hugo Boss to make them a sharper-looking uniform.

And there is no such word as heresay. You can have heresy or you can have hearsay, but you cannot combine them into one word. However that is another fact I am sure you will continue to ignore.

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## tomo pauk (Mar 23, 2018)

P-39 Expert said:


> What is AHT please?



"America's hundred thousand", the book dealing with US fighters mostly of ww2. With 606 pages of tables, analysis, graphs, photos and drawings, it is a must for anyone that has interest in the said US A/C. Like all the bibles, it has a glitch or two, but it is a book that I don't consider lending it to anybody 
Link

edit: lending, not borrowing

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## pbehn (Mar 23, 2018)

To me the P-39 had its place in history and was what it was. All aircraft are used until replaced by better performers. In the Late 1930s early 1940s the USA was desperate for aircraft for all roles. The P-39 may not have been a top performer but it did some sort of job until better planes were available. As said earlier, Chuck Jaeger trained on a P39 if there was no P-39 what else was available and better, anything better like a P51 was needed in combat. Just because an aircraft is not the best doesn't mean it is of no use. The Gloster Gladiator was an obsolete bi plane but achieved immortality in Malta when three saved Malta. Well actually that is a legend and the facts are something different, but they were there and did something until replaced by something better.

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## Stig1207 (Mar 23, 2018)

b0ned0me said:


> Curtiss' high production of simple, robust but obsolescent under-performers.



Y'all might wanna duck down behind the lounge now, buddy.

It's one thing to annoy the P-39.......

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## Peter Gunn (Mar 23, 2018)

Shortround6 said:


> Out of the first 3 P-47 tests on WWII Aircraft Performance *2 have 6 guns installed*, ammo and fuel state not given, 3rd has a very similar weight (down 5lbs) but 8 guns.
> 
> *SNIP*


Not to go off topic but wasn't there a bit of experimentation in the 4th FG when they first got Thunderbolts were they removed two of the .50's?

Thanks.

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## Peter Gunn (Mar 23, 2018)

Elmas said:


> _"*SNIP*
> they went in a flat spin and so they were screwed so a very good *Genoese Pilot, Moresi left his skin, another Sergeant left his skin*, even though they were saying, ehhhh, do you know what I say, if you loop, do it fast,
> *SNIP*"_


I'm pretty sure I know what that means but just for clarification ( for my small brain ), I assume they were killed?

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## Elmas (Mar 23, 2018)

Peter Gunn said:


> I'm pretty sure I know what that means but just for clarification ( for my small brain ), I assume they were killed?

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## MIflyer (Mar 23, 2018)

"Given adequate engineering support from NACA, Allison and the AF, Bell could have had an improved P-39 as good as any other late ww2 fighter, in front line service, several months before the F-86."

I wish I could find the reference again, but I recall reading that during WWII an NACA employee was given the job of improving the Allison V-1710 engine and complained "Why should we be bothered with this thing? It's a piece of junk." 

From a mechanical engineering standpoint it would have been child's play to add a 2nd speed to the V-1710's single stage supercharger. Given that the V-1710 was built in an automotive fashion, with engine block, gearcase, and accessory section as separate section it would have far easier than with the one-piece Merlin engine case and need not interrupt production. If required they could have gotten Continental or Maytag Washing Machines or some other company to build the new 2 speed section. Going the next step to a two stage two speed supercharger would have been more challenging, but well within their capabilities. As it was, Packard redesigned the Merlin supercharger for easier production and had Wright redesign the impeller. 

So that taxpayer paid feather merchant decided the Allison was not worth his time and an real opportunity, low hanging fruit, was missed.

A book I read recently on the Bell X-1 program showed that NACA did its level best to sabotage the program. Finally the USAAF said "ta hell with this," put Chuck Yeager in the cockpit and started going somewhere.

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## Shortround6 (Mar 23, 2018)

The P-39 may not have been a bad aircraft but it was not a great one either. It was also a victim of it's size (which contributed to it's performance) and to timing. 
The timing covers a range of things. It covers Allison's slow (but understandable) development of superchargers, The Army's slow (and less understandable) approval of combat power settings. It also covers the rapid improvements to other fighters the US was purchasing at the time. 
The gestation period of aircraft has been brought up already in this thread. By the time you get to the P-39N with 9.60 gears and an approved WEP power rating Bell was already working on what would become the P-63 King Cobra, this had a long and tortured history that dated back to at least April 10th 1941 with the order of two P-39Es which had very little in common with any other P-39, new wing, long fuselage, new engine, etc. 
The Army had also bet heavily on the P-47 with 3 factories either making them or tooling up for them in the fall/winter of 1942. Several thousand are on order with all the extended ordering of parts from subcontractors that entails. 
P-51 production has been extended by the A-36 funding trick and the contract for a large part of the P-51As with Allison's is changed to P-51Bs with Merlins, By Jan of 1943 thousands of Merlin P-51s are on order. 
Lockheed is struggling to solve cooling problems with the P-38 as Allison keeps making higher powered engines. I don't know who was promising what when but the P-38 G had 1325hp engines in June of 1942 and the H had 1425hp engines by March of 1943, the only difference between an H and and early J was the intercooler set up and both planes were produced at the same time for short period until intercooler supplies caught up. granted this was in the fall of 1943. 

The P-39 was simply too small to allow for a significant increase in fuel and too small to fit a larger, more sophisticated supercharger set up. perhaps, if Allison had the engineering staff, a two speed (not two stage) supercharger with larger impeller could have been squeezed in but that was not what was wanted by the customer (the USAAF), not enough performance increase given the time needed to develop and deploy the modifications, and development work went into the two stage Allison for the P-63 which had the larger fuselage to accommodate it. The P-63 still wound up way short of fuel compared to the other planes. 
According to some sources the P-63 was _supposed _to have an intercooler but the company/s involved failed to deliver and the P-63 resorted to water injection.
I would note that all the radial engine fighters wound up with both water injection and intercoolers. 
Any major improvements to the P-39 would probably have meant delays in either the P-63 or P-59 jet programs, and even such improvements as under wing bomb/drop tank points weren't going to really change the capabilities of the US forces in general.

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## b0ned0me (Mar 23, 2018)

MIflyer said:


> I wish I could find the reference again, but I recall reading that during WWII an NACA employee was given the job of improving the Allison V-1710 engine and complained "Why should we be bothered with this thing? It's a piece of junk."


Maybe here? https://history.nasa.gov/SP-4306/ch2.htm


> The Cleveland Laboratory's work on the Allison engine increased its horsepower through the use of water injection and supercharging. However, from Ben Pinkel's point of view, this work was a "tremendous waste of effort" because of the basic flaws in the engine's design. Only after the Army substituted the British Merlin engine, in the P-51 Mustang did the United States finally have a fighter for high-altitude flight.





MIflyer said:


> From a mechanical engineering standpoint it would have been child's play to add a 2nd speed to the V-1710's single stage supercharger.


Maybe, but a child's play BuAer didn't seem interested in. Can't really blame Allison for not pursuing it on their own dime when their main customer was flogging them bloody demanding they achieve 1001 other things by yesterday.

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## P-39 Expert (Mar 23, 2018)

b0ned0me said:


> Ah, the legendary P-39.
> From a performance and handling standpoint the P-39 was a tribute to the capabilities of the Bell sales organisation.
> Recognizing the desperate need for competitive aircraft, Bell could always be relied upon to miss every performance requirement while citing delivery needs, and to miss every date requirement citing the need to work on performance.
> Given adequate engineering support from NACA, Allison and the AF, Bell could have had an improved P-39 as good as any other late ww2 fighter, in front line service, several months before the F-86.
> ...


I did misspell hearsay, wasn't caught by spellcheck. 

Why all the venom? Aren't we just discussing airplanes that are now over 70 years old? Am I not entitled to an opinion?

Please allow me to add an alternative view to all your hearsay.

Regarding your first paragraph, how did we start talking about the F-86? Did I somehow say the P-39 would outfly a Korean War jet? You cite what the US needed. They needed fighter planes in production NOW, not turbocharged superplanes that wouldn't see combat until very late 1942 (P-38) or May 1943 (P-47). So they deleted the turbo to get the P-39 (and P-40) into service asap. The P-39 was available from the beginning of WWI, along with the P-40 and F4F. 

Second paragraph, when was the first panic over? P-38 didn't get into combat until very late 1942. US fought WWII with only the P-39 and P-40 until very late 1942. Most historians agree that the US would have been hard pressed without the P-39 for our first year in the war.

Third paragraph, got people killed? Was one of the safest fighter planes, tricycle landing gear for safer ground handling, almost every fighter pilot flew one in training. TRAINING. Not worth a cup of warm piss? Chuck Yeager's favorite plane, three of the top 4 Russian aces flew it along with scores of 20 victory aces. Warm piss?

Should it have been able to handle the Zero? All models, even the earliest ones were at least 30mph faster than comparable Zeros at all altitudes. Their pilots were navy pilots with experience in China. Our boys were fresh out of flying school with NO experience except for Buzz Wagner who reportedly actually got off the ground at Pearl Harbor. One mission. They had established bases all along the north coast of NG and at Rabaul. US had just arrived at Port Moresby April 30 with 2 squadrons (about 40 planes). Pretty long odds. But these green kids managed a 1:1 kill ratio and kept them out of Port Moresby. Would you have rather flown a plane with no armor or self sealing fuel tanks, or a fully armored and heavily armed plane that was significantly faster?

Thanks for calling me a fanboy. Name calling. I'm 67 years old and enjoy WWII history. Not a fan, and not a boy. I just believe there is more to the P-39 than we have been led to believe. And I think I can prove it with facts and statistics. Not hearsay and name calling.

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## Peter Gunn (Mar 23, 2018)

I'm pretty sure b0ned0me was making a joke that it would take Bell until 1947 to produce a fighter equal to most late WWII fighters. A pretty glib comment I think.

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## yulzari (Mar 23, 2018)

P-39 Expert said:


> I just believe there is more to the P-39 than we have been led to believe.


Whatever the engineering and rivet counters statistics may say mission and machine met in Russia where they were excellent tactical fighter escorts for low flying tactical light and medium bombers. The range was short, the fighting took place within the best power outputs at height of the engine, the firepower was adequate (I still have to be convinced of the 37mm) and the nose wheel reduced ground handling accidents. Elsewhere the OTL machine was a mismatch to it's missions but that might be down to the user's specification rather than Bell's engineering. When there was noting better it was used. When there were better things it was sent to the user who had missions that matched it's performances. A bit like the Valentine tank.


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## Hansie Bloeckmann (Mar 23, 2018)

P-39 Expert said:


> I did misspell hearsay, wasn't caught by spellcheck.
> 
> Why all the venom? Aren't we just discussing airplanes that are now over 70 years old? Am I not entitled to an opinion?
> 
> ...


We are both students of WW2, especially the aircraft and pilots involved. I haven't been a boy for many years, but as a lad, built many model aircraft, both WW1 and WW2 era- American, British, German, Italian- even a few Japanese.
Growing up, the first real scaled models of WW2 and the Korean War that I collected were made by the Topping Co., in Akron, Ohio- true to scale, and made my "attempts" at replicating the real aircraft seem "not quite right"--Hansie


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## pbehn (Mar 23, 2018)

P-39 Expert said:


> Chuck Yeager's favorite plane..


This is not a "fact" and you have posted it twice. Yaeger was a Bell employee in the post war years, he broke the sound barrier in a Bell X1. He could only possibly favour it as a WW2 aircraft considering the performance of other high performance jets he flew. Basically he preferred the P-39 until he flew the P51 but in WW2 he only flew those two as far as I have read. Did he ever attempt any violent manoeuvres with all ammunition spent, for example?

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## Schweik (Mar 23, 2018)

MIflyer said:


> "Given adequate engineering support from NACA, Allison and the AF, Bell could have had an improved P-39 as good as any other late ww2 fighter, in front line service, several months before the F-86."
> 
> I wish I could find the reference again, but I recall reading that during WWII an NACA employee was given the job of improving the Allison V-1710 engine and complained "Why should we be bothered with this thing? It's a piece of junk."
> 
> ...



That is really incredible if true. If they had put a two stage supercharger on the Allison by say, late 1942 it would have saved so many lives, might have even shortened the war.

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## Elmas (Mar 23, 2018)

tomo pauk said:


> Root: NACA 0015, tip: NACA 23009, no washout (2 deg constant incindence).



Geoffrey De Havilland, if I remember well, once said _“a beautiful aeroplane always will fly well”_ but I’m afraid that P-39 probably was the classical exeption that confirms the rule.

In these days, reading the posts of this interesting 3d, I was excavating a little bit more deeply in the Airacobra design, a thing that I never did as after the end of WWII between the American airplane production delivered with MAP two planes were kept as far as possible by Italian Pilots, P-39 and SC2-5 Helldiver (“B” was taken out as, after the Peace treaty, Italy could not have bombers).

Great expectations were placed on the P-39 at his appearance on the stage, not only by the Air Corps but by the whole aeronautical community in the world over: in those times there were still around machines like P-26, not to speak of biplanes, so the appearance of Airacobra was certainly more dazzling than that of, say, F-22 in modern times.

No doubt that many aeronautical designers were looking at this airplane in search of “inspiration”.
So I discovered with my great surprise that Re. 2005 and Airacobra had the same profile in the wing design: a NACA 0015 at the root, symmetrical biconvex 15% thick, needed for structural strenght







And a NACA 5 digit 24009 at the tip, with an high Cl






The designer of Re. 2005, Ing. Roberto Longhi, did work in U.S.A. in the ‘30s at the Republic-Seversky factory before returning to Italy, so the early Reggiane fighters, Re 2000 in particular, have a close resemblance with P-35. He was well aware of the tremendous amount of work made in wind galleries from NACA, while in other countries, Germany excepted, wing profiles were designed “by nose” or, “to be in the safe side” the ubiquitous Clark Y was used.

Ing. Longhi stated in a letter, published by Air Enthusiast Quarterly nr. 2 - 1976: _"...I decided to change the wing section from that of the previous Reggiane fighters to one based on the two profiles utilised by the P-39 Airacobra, as these seemed better suited for the altitudes that were now being demanded. All other Reggiane aicrafts use a modified N38."_

It has recently come out from a Reggiane designer's papers that the airfoil used for the wing profiles prior to Re. 2005 was not the N38 but the NACA CYH, also known as Clark YH, a classic Clark Y with a reflexed trailing edge.











Airfoil at wing root






Airfoil at wing tip

Re 2000, like all contemporary monoplane aircraft, certainly MC 200 and G.50 among Italians ( I have less information about P-35) suffered from bad stall caracteristics, until a German paper at the end of the 30’s explained the importance of a correct wash-out. When a correct wash-out was introduced in the wing of MC 200 the flying caracteristics improved dramatically, and the same wing was retained in Macchi 202 and 205.
Re. 2005 had a wash-out of about -2,2°

So, in Airacobra, the small dimensions, the absence of wash-out in the wings and the inertia coupling, not well understood in those times ( but even it was not well undestood, it had equally his effects...) due to the particular position of the engine and consequent distribution of weights gave to the aeroplane some nasty flying habits, that compelled Pilots to wear "belt and braces" when inside a P-39.
Not the best way to fight with a Zero.

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## P-39 Expert (Mar 23, 2018)

MIflyer said:


> "Given adequate engineering support from NACA, Allison and the AF, Bell could have had an improved P-39 as good as any other late ww2 fighter, in front line service, several months before the F-86."
> 
> I wish I could find the reference again, but I recall reading that during WWII an NACA employee was given the job of improving the Allison V-1710 engine and complained "Why should we be bothered with this thing? It's a piece of junk."
> 
> ...


Just my opinion, but what the Allison needed was not a two speed supercharger but a (mechanical, not turbo) two stage supercharger. 

We've had the two speed argument here before, and I still maintain that low gear's purpose is just to keep the pilot from overboosting the engine at takeoff and low altitude. The P-39 had plenty of performance at low altitude with their single speed unit regulated by the pilot in early models and the automatic boost control after mid '42. The Allison's single speed was in effect "high" gear, and the need for low gear was eliminated by the autoboost control. The whole two speed vs one speed argument is moot in my opinion.

The two STAGE engine was needed to keep up with the two STAGE Merlin 61 and the two stage R-2800s. The two stage engine provided more power at higher altitudes because the first (or auxiliary stage whether it be mechanical or turbo) stage boosted the thin air at high altitude up to sea level thickness and discharged it into the second (internal) stage which boosted it even further to get those fantastic speeds at high altitude. In effect, the first stage fooled the second stage into thinking it had sea level (high density) air at 25000' boosting power tremendously.

Please remember that the two stage engine was pretty much a British/American product. Americans had turbos and mechanical second stages and the British had only mechanical. The Germans, Japanese and Russians didn't have two stage engines in production planes. They had single stage engines, consequentially their critical altitude was around 18000', whereas two stage engines critical altitude was much higher. The two stage engines came into combat in mid 1942 (Spitfire IX), late 1942 (P-38), mid 1943 (P-47). High speeds for these planes was at 25000'-30000'.

Now there WAS a two stage mechanical Allison, the first production model was the V-1710-93 for the P-63. It featured a separate second stage supercharger driven by a jackshaft from the Allison starter dog that drove through a hydraulic clutch that automatically regulated manifold pressure. The -93 developed 1325HP for takeoff and 1180HP at 21500' with 1825HP war emergency. This pushed the P-63 without wing guns to 422mph at 24000'. They bolted a comparable model onto a P-40 and called it the Q and even that old P-40 went 418mph at 24000' and climbed like a rocket. Only 3 of those Q's were built.

More importantly the -93 was in full production in April 1943 and the P-63 didn't fly until October. Why in the world didn't the Army just put one in the P-39? It fit into the experimental P-39E. The contemporary P-39 model was the P-39N at 7650#. Add the 200# auxiliary stage and balance the weight with a larger 4 blade propeller and you have a real hot rod at 8050#. By July 1943 these P-39s would be coming off the production line and would have rivaled the Spitfire IX and P-51B in speed and climb. But the -93 in a P-39 was not to be, probably because the Army didn't want the Russians to have it. They were the main customer for the P-39 at the time.

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## Schweik (Mar 23, 2018)

Schweik said:


> That is really incredible if true. If they had put a two stage supercharger on the Allison by say, late 1942 it would have saved so many lives, might have even shortened the war.



Just to clarify, my comment is referring not just to P-39's, but also to P-40's and early Mustangs, all of which could have been vastly improved if their Allison V-1710 had a two stage supercharger. Even after packard merlins became available, production was limited particularly in the early years. If Allison was able to produce engines of near equivalent capability then we could have built thousands more highly capable front-line fighters (like the 6,000 + later model P-40's they made)

Even early P-38's which were having a lot of trouble with their turbochargers and intercoolers, might have benefited by switching engines to the equivalent of a Merlin 66... they would have done much better I think.


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## MIflyer (Mar 23, 2018)

On the very early P-38's they had to change the supercharger gear in the V-1710 to increase the boost from the mechanical supercharger so they could reduce the boost required from the turbo at high altitudes. Early on they had a problem with the turbos coming apart at high boost. Those "fins" on the side of the booms between the cockpit and the turbos were shields to protect the pilot from disintegrating turbochargers.

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## Ascent (Mar 23, 2018)

The impression I'm getting from all this discussion is that the P39 was a day late and a dollar short. For the western allies there was always something more suited for any role that could be found for it and by the time it had improved something else better was in service. 

It was on the eastern front where it found its niche, it's drawbacks outweighed by it's advantages.

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## Shortround6 (Mar 23, 2018)

It is all very well and good to talk about installing two stage superchargers on P-39s. p-40s and early P-51s...........except...........





*they don't fit.*

In order to work they need intercoolers. Otherwise the intake mixture gets to too hot and the engine goes into detonation. 
This was the trouble the P-38 had from about the 'D' model until the "J". It was the problem the P-63s had. 
Finding another 1 ft or less behind the engine for the larger supercharger housing wasn't the problem (until Allison put the 1st stage in a separate housing and drove it with a seperate drive system). it was finding room for the intercoolers and ducting. 
Please note that a 2 stage Allison in the P-63A could make 1800hp at sea level using 75in and water injection. WIthout water injection it made about 1500hp at 60in but by the time you got to to 21500ft it was down to 1180hp, whether you used water injection or not. 
Please note a Merlin 46 could make 1100hp at 22,000ft with a single stage single speed supercharger and make 1440hp at 14,500ft. No intercooler either.

Everybody wants the performance of the two stage supercharger, nobody wants to *pay the cost*. 
early P-51Bs were slower than Allison power Mustangs at low altitudes because of the higher drag of the larger fuselage, larger radiator/intercooler and heavier weight of the two stage engines. Once you got high enough for the two stage engine to start making significantly more power than the single stage the Merlin Mustangs really went into a world of their own. 

A two stage Allison in a P-63 was around 150lbs heavier than the engine in a P-39N, it was longer and expecting to cool an engine making several hundred hp more needs a slightly bigger radiator (about 20-25lbs more for the P-63) the P-63 used a propeller about 60 lbs heavier. 

You can do it, it takes a lot more changes than some people seem to think. 

The Merlin system worked but it was also a bit on the crude side (at first look) and many engineers were trying to go one better. The Merlin ALWAYS both impellers spinning at the same time and spinning at the same speed. Effective but not very flexible with a two speed drive. P & W's two stage (first flown in 1939 so two stage superchargers aren't unknown in the US) had a single speed supercharger on the engine and a two speed drive with neutral on the auxiliary supercharger drive given three possible combinations. Allison stuck a hydraulic coupling in the drive the auxiliary supercharger giving an infinite number of combinations between a high and low limit. More elegant from an engineering point of view but you had to pay for it somehow. 

The air to air intercooler is more resistant to battle damage. A liquid intercooler suffers just alike a liquid radiator from one or two minor hits. A couple pencil size holes in the airducts of an air to air intercooler isn't going to affect things that much. However keeping all those airducts air tight in day to day operation was more maintenance intensive. You pay your money and take your chances.

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## Shortround6 (Mar 23, 2018)

P-39 Expert said:


> Now there WAS a two stage mechanical Allison, the first production model was the V-1710-93 for the P-63. It featured a separate second stage supercharger driven by a jackshaft from the Allison starter dog that drove through a hydraulic clutch that automatically regulated manifold pressure. The -93 developed 1325HP for takeoff and 1180HP at 21500' with 1825HP war emergency. This pushed the P-63 without wing guns to 422mph at 24000'. They bolted a comparable model onto a P-40 and called it the Q and even that old P-40 went 418mph at 24000' and climbed like a rocket. Only 3 of those Q's were built.
> 
> More importantly the -93 was in full production in April 1943 and the P-63 didn't fly until October. Why in the world didn't the Army just put one in the P-39? It fit into the experimental P-39E. The contemporary P-39 model was the P-39N at 7650#. Add the 200# auxiliary stage and balance the weight with a larger 4 blade propeller and you have a real hot rod at 8050#. By July 1943 these P-39s would be coming off the production line and would have rivaled the Spitfire IX and P-51B in speed and climb. But the -93 in a P-39 was not to be, probably because the Army didn't want the Russians to have it. They were the main customer for the P-39 at the time.



Ah, for a P-39 expert you are making a number of mistakes. 
P-39E was originally designed for the infamous Continental O/IV/V-1410 which was considerably longer than the Allison engine. With no airworth examples of the Continental engine available (or likely to be) in 1942 the design was altered to take the two stage Allison. the fuselage was 1.75 feet longer than the standard P-39s. One of them weighed in at 8918lbs (some sources say they were nicknamed the "lead sled") P-39E also had a bigger wing. Relationship of wing to engine/fuselage may also be different 




Notice where the door is compared to a normal P-39?
Auxiliary supercharger is right about where the oil tank is on a normal P-39.

The P-40Q was hardly a lightweight at 9000lbs when using the V-1710-121 engine, full internal fuel and four guns and ballast to represent 235rpg. 
in an early test it using a V-1710-101 engine weighed 8203 lbs with 160 gallons of fuel which leaves us wondering what was left out.


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## pbehn (Mar 23, 2018)

Elmas said:


> Re 2000, like all contemporary monoplane aircraft, certainly MC 200 and G.50 among Italians ( I have less information about P-35) suffered from bad stall caracteristics, until a German paper at the end of the 30’s explained the importance of a correct wash-out. When a correct wash-out was introduced in the wing of MC 200 the flying caracteristics improved dramatically, and the same wing was retained in Macchi 202 and 205.
> Re. 2005 had a wash-out of about -2,2°
> 
> .


Great post Elmas, but knowledge of washout couldn't just be just held in Germany, the Spitfire flew with it in 1936.

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## Elmas (Mar 23, 2018)

Shortround6 said:


> It is all very well and good to talk about installing two stage superchargers on P-39s. p-40s and early P-51s...........except...........
> 
> 
> 
> ...



_Amateurs talk strategy, professionals talk logistic.

U.S. Army adage._

So in while in Military Aeronautics amateurs talk speed and climb rate, professionals talk about effectiveness to carry out the mission, safety of the handling by an average Pilot, speed of construction, maintenance and repair…

I bet that there are thousandhs of armchair Pilots that strongly believe that this monstruosity







could have been the best fighter of WWII.

If they only had installed a more powerful engine on it…

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## pbehn (Mar 23, 2018)

Elmas said:


> _Amateurs talk strategy, professionals talk logistic.
> 
> U.S. Army adage._
> 
> ...


Not so fast Elmas I have seen the Mx MCLMXXXIV version in "Star Wars" and it turned out to be a world beater

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## MIflyer (Mar 23, 2018)

"could have been the best fighter of WWII.

If they only had installed a more powerful engine on it…"

Yep. The J-33.


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## Elmas (Mar 23, 2018)

pbehn said:


> Great post Elmas, but knowledge of washout couldn't just be just held in Germany, the Spitfire flew with it in 1936.



Quite true, for this very reason Mitchell was such a great aircraft designer. Let's think that all these things were more or less "military secrets" and their circulation was not widespread.
And not only for this, as Mitchell was one of the first aircraft designers to _fully_ understand the structural possibilities of D-boxes and stressed skin structures. This allowed him to design a wing with a profile with a thickness at the root that some of his Colleagues were afraid to use even at the wing tip... Spitfire wing was a piece of art, not just a piece of engineering.

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## pbehn (Mar 23, 2018)

Elmas said:


> Quite true, for this very reason Mitchell was such a great aircraft designer. Let's think that all these things were more or less "military secrets" and their circulation was not widespread.
> And not only for this, as Mitchell was one of the first aircraft designers to _fully_ understand the structural possibilities of D-boxes and stressed skin structures. This allowed him to design a wing with a profile with a thickness at the root that some of his Colleagues were afraid to use even at the wing tip... Spitfire wing was a piece of art, not just a piece of engineering.


Was it a case of many competing theories all of which had some merit but the best choice is only known after much time has passed? Car and motorcycle suspension went round and round in circles for decades finishing up with systems first used in the 1930s for some uses.


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## Shortround6 (Mar 23, 2018)

I would note that the main difference between a _good _mechanical two stage system and a good turbocharger tow stage system is that in the turbo system the auxiliary supercharger is driven by an exhaust gas powered turbine and not a driveshaft from the engine.
You still need the auxiliary impeller and casing and you still need the intercooler and ducting (or intercooler radiator).
Anybody who thinks you can have a significantly smaller mechanically driven two stage _system_ is either settling for less performance or fooling themselves.

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## Shortround6 (Mar 23, 2018)

Elmas said:


> I bet that there are thousandhs of armchair Pilots that strongly believe that this monstruosity
> 
> View attachment 487050
> 
> ...


Well, it was originally planned for that world beating, super sophisticated, paragone among aircraft engines the Continental IV-1410 and was forced to fly with one of those lousy Allisons

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## Elmas (Mar 23, 2018)

Most probably, things like wash-out were, who knows, discovered by chance: if you make a lot of study someting happens, like Penicillin…

Germans, between the Wars, not being allowed to spend money on a numerous army, spent some money making a lot of research both in aerodynamics and structural engineering, in particular of bending and stretching of thin plates, a theoretical research they started well before WWI.

And Mitchell, as is explained in the biografy written by his Son Gordon, a most interesting read, always kept an eye on what was happening in Germany.


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## JJWilson (Mar 23, 2018)

Peter Gunn said:


> Still not seeing how the P-39N was in action in the SWPA in 1942. Pacific Wrecks has a list of P-39 losses, the earliest of which seems to be August 1943. While it does not list delivery dates, I find it hard to believe it was in action for 8 - 9 months without a loss.
> 
> Also, again, one test of a lightly loaded P-39 does not an operational plane make. You still contend that a_ fully loaded_ P-39 can out climb a _fully loaded_ P-38 or P-51? *We're talking combat ready, fuel and ammo*.
> 
> And no, the air war WAS NOT over by March '44.


Hello Peter, I totally agree with your comment on the P-39 and it's climbing ability against two very good climbing aircraft. As for P-39N's being used in the SW Pacific, I also don't recollect hearing about N-Variant P-39's being used there in 42.

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## Shortround6 (Mar 23, 2018)

One source says the K and L didn't get to the SWP until 1943 which makes getting the N there in 1942 even more suspect.


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## MIflyer (Mar 23, 2018)

"You still need the auxiliary impeller and casing and you still need the intercooler and ducting (or intercooler radiator)."

Yes, and the odd thing is nobody but Stanley Hooker seems to have thought of the idea of a liquid cooled aftercooler, even after he did it and it was in production.

When you consider that Hooker was a theoretical aerodynamicist and "not much of an engineer" to use his boss's phrase, you can really see how much genius was involved. Hooker had been fine tuning RR supercharger designs by reducing the ram intake losses and air entry angle for the impeller. For him to instead go to a liquid cooled aftercooler that would enable the package to fit under the hood of a Spitfire or Mustang meant he had to step outside his narrow specialty.

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## Hansie Bloeckmann (Mar 23, 2018)

P-39 Expert said:


> Just my opinion, but what the Allison needed was not a two speed supercharger but a (mechanical, not turbo) two stage supercharger.
> 
> We've had the two speed argument here before, and I still maintain that low gear's purpose is just to keep the pilot from overboosting the engine at takeoff and low altitude. The P-39 had plenty of performance at low altitude with their single speed unit regulated by the pilot in early models and the automatic boost control after mid '42. The Allison's single speed was in effect "high" gear, and the need for low gear was eliminated by the autoboost control. The whole two speed vs one speed argument is moot in my opinion.
> 
> ...


Could you possibly expand on the comment about the Army not wanting the Russians to have that -93 power plant? Thanks, Hansie


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## tomo pauk (Mar 23, 2018)

P-39 Expert said:


> ...
> Now there WAS a two stage mechanical Allison, the first production model was the V-1710-93 for the P-63. It featured a separate second stage supercharger driven by a jackshaft from the Allison starter dog that drove through a hydraulic clutch that automatically regulated manifold pressure. The -93 developed 1325HP for takeoff and 1180HP at 21500' with 1825HP war emergency. This pushed the P-63 without wing guns to 422mph at 24000'. They bolted a comparable model onto a P-40 and called it the Q and even that old P-40 went 418mph at 24000' and climbed like a rocket. Only 3 of those Q's were built.



This is one of better post in this thread. Some nitpicks:
- P-63A, even when using water injection was barely able to beat 400 mph mark; P63C, with a bit better engine might go beyond 420 
- 1800++ HP was available under 5000 ft



> More importantly the -93 was in full production in April 1943 and the P-63 didn't fly until October. Why in the world didn't the Army just put one in the P-39? It fit into the experimental P-39E. The contemporary P-39 model was the P-39N at 7650#. Add the 200# auxiliary stage and balance the weight with a larger 4 blade propeller and you have a real hot rod at 8050#. By July 1943 these P-39s would be coming off the production line and would have rivaled the Spitfire IX and P-51B in speed and climb. But the -93 in a P-39 was not to be, probably because the Army didn't want the Russians to have it. They were the main customer for the P-39 at the time.



Russians did have P-63s, ergo they got the -93s. A 2-stage V-1710 as-is will be very tricky to install on the P-39, if not impossible.
_Ceterum censeo_ - if there is a real surplus of the 2-stage V-1710s, the P-51 is your platform.


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## P-39 Expert (Mar 23, 2018)

Shortround6 said:


> Ah, for a P-39 expert you are making a number of mistakes.
> P-39E was originally designed for the infamous Continental O/IV/V-1410 which was considerably longer than the Allison engine. With no airworth examples of the Continental engine available (or likely to be) in 1942 the design was altered to take the two stage Allison. the fuselage was 1.75 feet longer than the standard P-39s. One of them weighed in at 8918lbs (some sources say they were nicknamed the "lead sled") P-39E also had a bigger wing. Relationship of wing to engine/fuselage may also be different
> View attachment 487046
> 
> ...


The fuselage was indeed lengthened by 1.75' but that was their solution to the extra 200# from the auxiliary stage supercharger. Adding 200# aft of the CG necessitated moving the wing back a little for balance, then the tail had to be moved back to preserve the distance from the CG to the tail for the same leverage. That is why the front cockpit door edge is before the wing leading edge (same as the P-63) while the normal P-39 front door edge is right about even with the wing leading edge. They moved the wing back.

Now is where I differ from what you have read. The engine compartment for the P-39E and the P-63 was still exactly the same size as the P-39. The distance from the front edge of the engine compartment (right before the exhaust stacks at the cockpit turnover structure) and the back bulkhead (almost to the back edge of the carb inlet scoop, you can see the panel edges) is EXACTLY the same. In a normal P-39 that compartment contained (going aft) the engine, coolant tank, then the bulkhead and after that the oil tank. In the P-39E and the P-63 they moved the coolant tank up right behind the cockpit on the right side and put the auxiliary stage behind the engine where the coolant tank was. That area was exactly the same size on the P-39, P-39E and P-63. So the fuselage was lengthened but it was lengthened aft of the engine compartment, not to make room for the auxiliary stage. Now that's not what you read, but that is what happened.

In my opinion it would have been easier to keep the original P-39 dimensions, add the auxiliary stage where the coolant tank had been, and offset the 200# extra weight aft of the CG by installing a larger (heavier) four blade propeller. Notice the E had a three blade propeller because a four blade propeller was not available at the time. That four blade propeller would have helped tremendously at high altitude. Additional balance adjustments could come (if needed) from moving the radios up from the tailcone to right behind the cockpit (you see this in photos all the time) or adding more armor plate right behind the propeller. But the Army had already decided that the P-63 would be balanced by moving the wing back and lengthening the tail cone so that's the way they did it on the P-63's predecessor, the P-39E.

Would have had a two stage P-39 in mid 1943.

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## P-39 Expert (Mar 23, 2018)

tomo pauk said:


> This is one of better post in this thread. Some nitpicks:
> - P-63A, even when using water injection was barely able to beat 400 mph mark; P63C, with a bit better engine might go beyond 420
> - 1800++ HP was available under 5000 ft
> 
> ...


Graphs and tests in wwiiaircraftperformance show a P-63A doing 422mph without wing gun drag. I agree that the -93 would have worked well in a P-51, the -J model was just too late for WWII.

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## pbehn (Mar 23, 2018)

When discussing the success of pilots in P-39s on the eastern front is there any truth at all in the rumours that they were in many cases, late in the war flying P-63s. Since there was an agreement that this wouldn't happen, Soviet records would try to hide it.

Wiki isn't a great resource but says this

By a 1943 agreement, P-63s were disallowed for Soviet use against Germany and were supposed to be concentrated in the Soviet Far East for an eventual attack on Japan.[_citation needed_] However, there are many unconfirmed reports from both the Soviet and German side that P-63s did indeed see service against the _Luftwaffe_. Most notably, one of Pokryshkin's pilots reports in his memoirs published in the 1990s that the entire 4th Guards Fighter Aviation Regiment (4 GvIAP) was secretly converted to P-63s in 1944, while officially still flying P-39s. One account states they were in action at Königsberg, in Poland and in the final assault on Berlin. There are German reports of P-63s shot down by both fighters and flak. Hans Rudel, highest decorated pilot of the Luftwaffe, states in his memoirs, "We often encounter American types of aircraft, especially Airacobras, Kingcobras and Bostons." This was in the Courland front towards the end of the war. [15] Nevertheless, all Soviet records show nothing but P-39s used against Germany.[_citation needed_]

In general, official Soviet histories played down the role of Lend-Lease supplied aircraft in favor of local designs, but it is known that the P-63 was a successful fighter aircraft in Soviet service. A common Western misconception is that the Bell fighters were used as ground attack aircraft.


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## Milosh (Mar 23, 2018)

Deliveries of production P-63As began in October 1943. The USAAF concluded the Kingcobra was *inferior* to the Mustang, and declined to order larger quantities.

And, the P-63 was well behind what would be coming off the NAA production line > the P-51H.


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## drgondog (Mar 23, 2018)

P-39 Expert said:


> Graphs and tests in wwiiaircraftperformance show a P-63A doing 422mph without wing gun drag. I agree that the -93 would have worked well in a P-51, the -J model was just too late for WWII.



To quote an unknown Southern sage, circa 1864 "If a frog had a glass ass, it will only hop once"

If you peruse the AAF Flight Test reports and peel to the summary - Operational Suitability, May 1944. The Eglin Test pilots conclude that the P-63A 'cannot be considered in current form to be an operationally suitable aircraft at this time".

Neither the Allison V-1710-119 for the XP-51J, nor the 1710-143/-145 ever attained reliable HP output to specifications for Boost over 61". NAA quickly lost interest in the XP-51F due to the plague of engine related issues not solved by Allison. After the AAF forced NAA to install the -143/-145 to replace the 1650-11 and -21 after the XP-82/P-82B series, the Allisons effectively castrated the P/F-82 E/F/G.

The Net-Net is that the P-63 with a fully functional Allison 'two-stage', enhanced structural aft section, aileron trim tables, changing hor.stab' incidence to eliminate stick reversals in high speed dives, stiffening the elevator rib distribution to prevent elevator ballooning/rupture in high speed dives plus heavy controls and instability at high speeds - it was deemed 'fun to fly with excellent maneuverability'.

That said, at the Patuxent Fighter Conference in October, 1944, it was one of the lowest ranked fighter in the Conference in the category 'Best above 25K', 'Best below 25K' (both <1%), -------> highest rank 'Best Strafer, #8 at 2%, 'Best stability in a dive #7 at 4%, 

The kindest remark was 'this is what the P-39 should have been'

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## Shortround6 (Mar 23, 2018)

P-39 Expert said:


> Graphs and tests in wwiiaircraftperformance show a P-63A doing 422mph without wing gun drag. I agree that the -93 would have worked well in a P-51, the -J model was just too late for WWII.


 Not only lacking wing gun drag, lacking around 1000lbs of weight compared to a service P-63. 
The graphs give no description of the aircraft involved. 

I also love the part in an earlier post about the V-1793 being in full production in May of 1943. 
May of 1943 saw the engine fully prepared for the model test, which was not actually fully completed until Nov 27th 1943. Yes engines had been built, delivered and were flying in P-63s before Nov 27th but after that date the engines were released for unrestricted use. _Except _the WER rating test was done in Dec of 1943 so any fantasies of P-63s or Super Allison Mustangs flying around with 1800hp at sea level engines need a reality check. Especially considering that the long development time included modified pistons and piston rings to stand up to the water injection and extra power.

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## wuzak (Mar 23, 2018)

P-39 Expert said:


> Wrong book. Park wrote two books about his tour in New Guinea. "Nanette" was a fictional account based on all the stories he had heard and participated in. His second book, "Angels Twenty" was a nonfiction (factual) account of his tour from December '42. He says he got his P-39N in December in the nonfiction work. Both books are worth your time, very entertaining and provide a day to day look at the perils of WWII in that area.



But "Nanette" was the nickname of his P-39 in real service, and it looks like it was squadron code N. And I never mentioned a book.


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## wuzak (Mar 23, 2018)

[QUOTE="MIflyer, post: 1392532, member: 42472]From a mechanical engineering standpoint it would have been child's play to add a 2nd speed to the V-1710's single stage supercharger. Given that the V-1710 was built in an automotive fashion, with engine block, gearcase, and accessory section as separate section it would have far easier than with the one-piece Merlin engine case and need not interrupt production. If required they could have gotten Continental or Maytag Washing Machines or some other company to build the new 2 speed section. Going the next step to a two stage two speed supercharger would have been more challenging, but well within their capabilities. As it was, Packard redesigned the Merlin supercharger for easier production and had Wright redesign the impeller. [/QUOTE]

Wright did not redesign the impeller of the Merlin. They produced the 2 speed dive for Packard Merlins, which was an epicyclic type, rather than the Farman type used by Rolls-Royce. The fact that Rolls-Royce used the Farman gearbox under licence may have had something to do with it.

Don't know that Packard did any significant redesign of the supercharger, to ease production or otherwise.

Packard Merlins retained the same ratings as their British equivalent, the 2 speed drives more or less had the same gear ratios as the Rolls-Royce equivalent.

Packard Merlins were 3 piece designs. There was the crankcase, the cylinder blocks and the cylinder heads. This was developed by Rolls-Royce as their single block head design was difficult to seal. Packard went into production with the separate head design from the outset. Packard developed their own method of sealing between the head and the block, but later changed to be the same as Rolls-Royce.

Merlins weren't designed to be as modular as the V-1710 was, that is true, so changing required some redesign of the crankcase.


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## wuzak (Mar 23, 2018)

Elmas said:


> _"It was a very special airplane, let's say, with the engine in the back, then those Italian maniacs always wanted do aerobatics, when they looped they came in this position and then had to continue, but it was too slow and instead of lowering the head, which it did not have _( for the position of the engine)_ they went in a flat spin and so they were screwed so a very good Genoese Pilot, Moresi left his skin, another Sergeant left his skin, even though they were saying, ehhhh, do you know what I say, if you loop, do it fast, but for me it was a fabulous plane because it had a tricycle undercarriage, on the ground it was driven like a car, apart from this tricycle undercarriage it had in the axis of the propeller a cannon of 37 and four machine guns on the wings the engine was a 1200 hp Allison a beautiful engine it was a very pretty airplane…"_





Peter Gunn said:


> I'm pretty sure I know what that means but just for clarification ( for my small brain ), I assume they were killed?



I'm pretty sure it means they were scared shitless, not that they did.

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## wuzak (Mar 23, 2018)

Shortround6 said:


> The Merlin system worked but it was also a bit on the crude side (at first look) and many engineers were trying to go one better. The Merlin ALWAYS both impellers spinning at the same time and spinning at the same speed. Effective but not very flexible with a two speed drive. P & W's two stage (first flown in 1939 so two stage superchargers aren't unknown in the US) had a single speed supercharger on the engine and a two speed drive with neutral on the auxiliary supercharger drive given three possible combinations. Allison stuck a hydraulic coupling in the drive the auxiliary supercharger giving an infinite number of combinations between a high and low limit. More elegant from an engineering point of view but you had to pay for it somehow.



The advantage of the Merlin's system was that the two stages were always synchronised and matched for flow. With a separate auxiliary stage which could operate at different speeds to the main supercharger there was a risk of the superchargers being mismatched, causing surging.




Shortround6 said:


> The air to air intercooler is more resistant to battle damage. A liquid intercooler suffers just alike a liquid radiator from one or two minor hits. A couple pencil size holes in the airducts of an air to air intercooler isn't going to affect things that much. However keeping all those airducts air tight in day to day operation was more maintenance intensive. You pay your money and take your chances.



The air to air intercooler also had the problem that it needed to be in close proximity of the engine, or that the supercharger discharge goes on a world tour before getting back to the engine.

The liquid to air intercooler gave more options in the location of the radiator section, which could be quite remote from where the engine was.


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## parsifal (Mar 23, 2018)

whats surging? I have an idea, but not certain really.


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## wuzak (Mar 23, 2018)

P-39 Expert said:


> Just my opinion, but what the Allison needed was not a two speed supercharger but a (mechanical, not turbo) two stage supercharger.



Not an unreasonable position.



P-39 Expert said:


> We've had the two speed argument here before, and I still maintain that low gear's purpose is just to keep the pilot from overboosting the engine at takeoff and low altitude. The P-39 had plenty of performance at low altitude with their single speed unit regulated by the pilot in early models and the automatic boost control after mid '42. The Allison's single speed was in effect "high" gear, and the need for low gear was eliminated by the autoboost control. The whole two speed vs one speed argument is moot in my opinion.



You can maintain your opinion, but it is still wrong.

Yes, a 2 speed supercharger in high gear could easily overboost the engine at low altitude. The same could be said for most 2 speed engines' low gear as well. That is what the throttle is for - to control the boost. That is true whether it is high gear or low gear.

Throttling, of course, costs power.

A lower speed 2nd gear would have allowed more power from the V-1710 at low altitude.

But also needed a better supercharger.




P-39 Expert said:


> The two STAGE engine was needed to keep up with the two STAGE Merlin 61 and the two stage R-2800s. The two stage engine provided more power at higher altitudes because the first (or auxiliary stage whether it be mechanical or turbo) stage boosted the thin air at high altitude up to sea level thickness and discharged it into the second (internal) stage which boosted it even further to get those fantastic speeds at high altitude. In effect, the first stage fooled the second stage into thinking it had sea level (high density) air at 25000' boosting power tremendously.



Note that the P&W 2 stage engines, at least early in the war, weren't rated at very high altitudes.

The Merlins came in several varieties, of course. Low altitude versions, like the 66/V-1650-7 sacrificed high altitude performance for more at low and mid altitudes. The 61, 63, and 70 series had higher gear ratios and this higher critical altitudes.

In Merlin 2 stage superchargers there was no fooling the "second stage into thinking it had sea level pressure". The first and second stage both provided boost, as such, having similar pressure ratios (that is, for example, the first stage PR was 2:1, the second stage was 2:1 for an overall of 4:1. I am away at the moment so can't get the proper numbers, maybe SR could fill in the blanks).

The fooling you speak of describes how turbocharged engines worked, for the most part, in WW2.

Note that the 2 stage engines also had multiple speeds. The Merlin and Griffon had 2 speeds, except the Griffon 100 series, which had 3 speeds.

2 stage Jumo 213s had 3 speeds.

V-1710 had variable speed auxiliary supercharger.

P&W had 2 speeds plus natural on their 2 sage engines.

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## wuzak (Mar 23, 2018)

parsifal said:


> whats surging? I have an idea, but not certain really.



I don't have a good explanation.

This might help Centrifugal Compressor Surge - EnggCyclopedia


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## wuzak (Mar 23, 2018)

MIflyer said:


> On the very early P-38's they had to change the supercharger gear in the V-1710 to increase the boost from the mechanical supercharger so they could reduce the boost required from the turbo at high altitudes. Early on they had a problem with the turbos coming apart at high boost. Those "fins" on the side of the booms between the cockpit and the turbos were shields to protect the pilot from disintegrating turbochargers.



The turbos came apart from overspeeding, which was traced back to the wastegate controls, which could freeze at high altitudes.

If P-38s had gears changed it was to give more boost and power.


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## pbehn (Mar 23, 2018)

My head is now hurting. Can someone tell me any area of performance that the latest P-39 was superior to the Spitfire IX or XIV, P-51-B/C, P47 and F4U as of 25 December 1943?


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## wuzak (Mar 23, 2018)

P-39 Expert said:


> The fuselage was indeed lengthened by 1.75' but that was their solution to the extra 200# from the auxiliary stage supercharger. Adding 200# aft of the CG necessitated moving the wing back a little for balance, then the tail had to be moved back to preserve the distance from the CG to the tail for the same leverage. That is why the front cockpit door edge is before the wing leading edge (same as the P-63) while the normal P-39 front door edge is right about even with the wing leading edge. They moved the wing back.
> 
> Now is where I differ from what you have read. The engine compartment for the P-39E and the P-63 was still exactly the same size as the P-39. The distance from the front edge of the engine compartment (right before the exhaust stacks at the cockpit turnover structure) and the back bulkhead (almost to the back edge of the carb inlet scoop, you can see the panel edges) is EXACTLY the same.



Looks like the V-1710 is a tight fit in the P-39

http://www.fiddlersgreen.net/aircraft/Bell-P39-Airacobra/IMAGES/Bell-P-39-Airacobra-Cutaway.jpg


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## MIflyer (Mar 23, 2018)

If you are getting hit in liquid cooled airplane the intercooler/aftercooler is the least of your worries! The aftercooler on the Merlin was right up there behind the engine and the coolant radiator was built into the main radiator. On the Spit IX the added coolant radiator for the aftercooler was located in the same under-wing housing as the oil cooler. Hard to see how you could get hit in either the aftercooler itself or the coolant radiator for it and not lose capabilities that were far more important - like engine cooling and oil. 

Packard had to a lot of work on the Merlin because they could not use the RR approach of experienced craftsmen, who hand-selected each part. Packard wanted to put Merlins together like an American automobile engine, and to do that they had to make the parts to tighter tolerances than did RR.

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## wuzak (Mar 23, 2018)

pbehn said:


> My head is now hurting. Can someone tell me any area of performance that the latest P-39 was superior to the Spitfire IX or XIV, P-51-B/C, P47 and F4U as of 25 December 1943?



It was far superior in the size and uselessness of its main cannon.


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## wuzak (Mar 23, 2018)

MIflyer said:


> Packard had to a lot of work on the Merlin because they could not use the RR approach of experienced craftsmen, who hand-selected each part. Packard wanted to put Merlins together like an American automobile engine, and to do that they had to make the parts to tighter tolerances than did RR.



Bollocks.

This is the biggest myth surrounding the Merlin, probably.

The Merlin had already be productionised in the UK by (or for) Ford, and this was used in most Merlin factories.

Rolls-Royce Derby possibly continued the practice of hand fitting stuff, but then they were doing most of the prototyping and development. And their production numbers were small compared to the shadow factories.

Packard had to change the drawings from 1st angle projection to 3rd angle projection so that their machine operators, inspectors, etc, could read the drawings.

Note that components built in Britain were interchangeable with parts from the US (excepting parts like the supercharger drive, which was of a different design for Packard).

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## pbehn (Mar 23, 2018)

wuzak said:


> It was far superior in the size and uselessness of its main cannon.


I believe the Mosquito had a bigger cannon but size doesn't matter Daaaahling

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## wuzak (Mar 23, 2018)

pbehn said:


> I believe the Mosquito had a bigger cannon but size doesn't matter Daaaahling



The Mosquito wasn't in the list .

Besides, the Mosquito wasn't a fighter, but a fighter bomber, and its cannon was useful!


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## pbehn (Mar 23, 2018)

wuzak said:


> The Mosquito wasn't in the list .
> 
> Besides, the Mosquito wasn't a fighter, but a fighter bomber, and its cannon was useful!


I was of course (in that post) joking, but in principle I cannot see any advantage the P 39 had over any other allied fighter, bearing in mind the Allies as a group had to defend daylight bomber boxes, defend the UK from any attack by any type of aircraft S/E T/E or buzz bomb and achieve air supremacy over Italy, Normandy and the Pas de Calais ...That is just European requirements.


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## Shortround6 (Mar 23, 2018)

MIflyer said:


> Packard had to a lot of work on the Merlin because they could not use the RR approach of experienced craftsmen, who hand-selected each part. Packard wanted to put Merlins together like an American automobile engine, and to do that they had to make the parts to tighter tolerances than did RR.



can we please, _please_, *please *forget this myth. Ford of England had already gone through that before Packard ever got involved. 
I would also note that Packard in the 1930s was America's premier auto maker with more prestige than Cadillac. While not quite the craftsmen RR had Packard was turning out a fraction of the cars the mass auto makers were. 




Such cars were not punched out by untrained labor.

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## Shortround6 (Mar 23, 2018)

pbehn said:


> My head is now hurting. Can someone tell me any area of performance that the latest P-39 was superior to the Spitfire IX or XIV, P-51-B/C, P47 and F4U as of 25 December 1943?



Lawn dart?

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## Elmas (Mar 24, 2018)

wuzak said:


> I'm pretty sure it means they were scared shitless, not that they did.



No, they were killed, and they were just two of many, with P-39.
Even Teresio Martinoli, one of the top Italian scorers, was killed in a P-39, when a worn out Allison failed.
And for an accident in which a Pilot lost his life with a P-39 there were dozens of other scaring situations where a mallet was needed to insert a pin into a particular anatomical formation of a Pilot, which I do not intend to mention now.

_"In june-july 1944, Italians Gruppi 12, 9, 10, 4 moved to Campo Vesuvio
airstrip to re – equip with the P39s.
The site was not suitable and in three months of training 11 accidents
occurred, due to engine failures and poor manteinance of the base.
Three pilots died and two were seriously injured: one of the victims on 25th aug
1944 was the “ace of the aces” Teresio Martinoli."

CURRENTJ.D., American Warplanes of World War Two, Pedia Press, p. 208_

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## P-39 Expert (Mar 24, 2018)

Shortround6 said:


> I would note that the main difference between a _good _mechanical two stage system and a good turbocharger tow stage system is that in the turbo system the auxiliary supercharger is driven by an exhaust gas powered turbine and not a driveshaft from the engine.
> You still need the auxiliary impeller and casing and you still need the intercooler and ducting (or intercooler radiator).
> Anybody who thinks you can have a significantly smaller mechanically driven two stage _system_ is either settling for less performance or fooling themselves.


The big advantage of the Allison mechanical two stage over the turbo is it takes up much less internal volume. In addition to the actual turbo there was the associated internal ducting (14' per engine in the P-38). The exhaust had to be ducted back to the turbo, the compressed turbo air had to be ducted back up to the intercooler (in the wing on F,G and H) then that air had to be ducted to the carburetor. All this ducting had to be properly aligned and sealed for the whole thing to work right. 

The Allison mechanical two stage engine simply ducted the ambient air from the external scoop to the carburetor on the first stage and a short duct to take that compressed air to the internal supercharger. The intercooler was not needed except for WEP and that was cooled by the water injection. All was enclosed in the normal engine bay of the P-63 except for the small water tanks in the leading edge.

The turbo developed a little more power at the expense of all that internal room needed. Turbos worked best on multi engined planes because of their greater internal volume. A single engined turbo plane is the P-47 which was huge for a fighter of that day.


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## P-39 Expert (Mar 24, 2018)

Shortround6 said:


> Not only lacking wing gun drag, lacking around 1000lbs of weight compared to a service P-63.
> The graphs give no description of the aircraft involved.
> 
> I also love the part in an earlier post about the V-1793 being in full production in May of 1943.
> May of 1943 saw the engine fully prepared for the model test, which was not actually fully completed until Nov 27th 1943. Yes engines had been built, delivered and were flying in P-63s before Nov 27th but after that date the engines were released for unrestricted use. _Except _the WER rating test was done in Dec of 1943 so any fantasies of P-63s or Super Allison Mustangs flying around with 1800hp at sea level engines need a reality check. Especially considering that the long development time included modified pistons and piston rings to stand up to the water injection and extra power.


We must be reading the same book. The -93 was in production in May and the model tests were not yet completed but the Army had sufficient confidence in the engine to start putting it in airplanes prior to test completion. After a short rework of the jackshaft these engines were considered very reliable. The development of the piston rings etc. benefited all Allison engines, not just this one. 

The -93 was not really a new "engine". The only thing new about the -93 was the auxiliary stage, the power section was the same as the other contemporary Allison engines. The auxiliary stage was just an impeller inside a diffuser driven by an external shaft from the engine. There were also the step up gears with the hydraulic coupling. Why it took from 1940 until late 1943 to get this auxiliary stage working properly is a mystery to me. This two stage Allison would have really improved the P-39, P-40 and even the P-51.


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## P-39 Expert (Mar 24, 2018)

Hansie Bloeckmann said:


> Could you possibly expand on the comment about the Army not wanting the Russians to have that -93 power plant? Thanks, Hansie


I can't prove this with facts, but I do know that while the Russians were our ally at the time, we still had HUGE political/ideological differences with the communists. We (including Britain) were perfectly happy to let the Nazis and the Communists destroy each other wholesale as long as the Nazis didn't actually knock the Russians out of the war. This leads me to believe that we were parceling out the war products we were giving them under lend-lease so as to give them good, serviceable planes competitive with their Luftwaffe adversaries, but not our very best cutting edge technology. We wanted them to wear down the Nazis prior to our invasion at D-Day. Just my 2 cents worth. Does this help?

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## wuzak (Mar 24, 2018)

It probably took so long because they were sorting out other issues and production.

As a development engine, the -93 would likely have been cleared for flight before it passed the endurance test, which is what was required before production commenced and the engine put in service.

The test for flight clearance was less stringent than the full type test.


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## P-39 Expert (Mar 24, 2018)

pbehn said:


> This is not a "fact" and you have posted it twice. Yaeger was a Bell employee in the post war years, he broke the sound barrier in a Bell X1. He could only possibly favour it as a WW2 aircraft considering the performance of other high performance jets he flew. Basically he preferred the P-39 until he flew the P51 but in WW2 he only flew those two as far as I have read. Did he ever attempt any violent manoeuvres with all ammunition spent, for example?


He most definitely said the P-39 was his favorite plane (until the P-51B arrived) both in his book and on video, both late in his career. And he also stated that he could not make a P-39 tumble. The video is on youtube.

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## P-39 Expert (Mar 24, 2018)

Ascent said:


> The impression I'm getting from all this discussion is that the P39 was a day late and a dollar short. For the western allies there was always something more suited for any role that could be found for it and by the time it had improved something else better was in service.
> 
> It was on the eastern front where it found its niche, it's drawbacks outweighed by it's advantages.


More like in production in time for the beginning of WWII, unlike the P-38, P-47 and P-51. We would have been hard pressed without the P-39 in 1942. Only the P-39, P-40 and F4F were available at the beginning. So, more like a day early, don't know about the dollar short.


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## Hansie Bloeckmann (Mar 24, 2018)

P-39 Expert said:


> I can't prove this with facts, but I do know that while the Russians were our ally at the time, we still had HUGE political/ideological differences with the communists. We (including Britain) were perfectly happy to let the Nazis and the Communists destroy each other wholesale as long as the Nazis didn't actually knock the Russians out of the war. This leads me to believe that we were parceling out the war products we were giving them under lend-lease so as to give them good, serviceable planes competitive with their Luftwaffe adversaries, but not our very best cutting edge technology. We wanted them to wear down the Nazis prior to our invasion at D-Day. Just my 2 cents worth. Does this help?


Yes indeed, very insightful. Having the Nazis faced with a two-front war, with a invasion planned from the Atlantic, was good strategy. And having Stalin apparently willing to sacrifice troops and equipment to keep the Nazis occupied on 2 fronts worked to the advantage of the Allied Powers. Makes me also think that the Russians were looking to copy our higher tech aircraft, so keeping those under Allied control was, "smart poker"!! Many thanks-Hansie


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## pbehn (Mar 24, 2018)

P-39 Expert said:


> He most definitely said the P-39 was his favorite plane (until the P-51B arrived) both in his book and on video, both late in his career. And he also stated that he could not make a P-39 tumble. The video is on youtube.


He may well have, and it is probably true but what other planes did he fly he was at the time just a good trainee pilot. He trained on P39s and then went operational in UK in the P51. To me all he is saying is that he preferred the P39 to his basic trainers, well almost all pilots do.

From Wiki
Soon after entering service, pilots began to report that “during flights of the P-39 in certain maneuvers, it tumbled end over end.” Most of these events happened after the aircraft was stalled in a nose high attitude with considerable power applied. Concerned, Bell initiated a test program. Bell pilots made 86 separate efforts to reproduce the reported tumbling characteristics. In no case were they able to tumble the aircraft. In his autobiography veteran test and airshow pilot R.A. “Bob” Hoover provides an account of tumbling a P-39. He goes on to say that in hindsight, he was actually performing a _Lomcovak_, a now-common airshow maneuver, which he was also able to do in a Curtiss P-40.[36] [N 6] An informal study of the P-39’s spinning characteristics was conducted in the NASA Langley Research Center 20-foot Free-Spinning Tunnel during the 1970s. A study of old reports showed that during earlier spin testing in the facility, the aircraft had never tumbled. However, it was noted that all testing had been done with a simulated full ammunition load, which drew the aircraft’s center of gravity forward. After finding the original spin test model of the P-39 in storage, the new study first replicated the earlier testing, with consistent results. Then, the model was re-ballasted to simulate a condition of no ammunition load, which moved the aircraft’s center of gravity aft. Under these conditions, the model was found to often tumble when thrown into the tunnel.[38]


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## Hansie Bloeckmann (Mar 24, 2018)

Shortround6 said:


> can we please, _please_, *please *forget this myth. Ford of England had already gone through that before Packard ever got involved.
> I would also note that Packard in the 1930s was America's premier auto maker with more prestige than Cadillac. While not quite the craftsmen RR had Packard was turning out a fraction of the cars the mass auto makers were.
> View attachment 487101
> 
> Such cars were not punched out by untrained labor.


Aaaah yes- Packard- "Ask the man who owns one.. One of their several classic hood ornaments, shaped like a nymph with her left extended forward, a ring clasped in the hand- was nicknamed "The Doughnut Pusher". I have a classic Packard ad poster from early 1929, about 8 months before the October Stock Market crash occurred. I'm not sure, but perhaps the 1920's phaeton Gloria Swanson had in the cult movie "Sunset Blvd." might have been a Packard.. A distant family member was a tool maker in the Packard plant in Detroit during the war years, worked 10 hours/day 7 days a week- Make good $..but never owned a Packard-

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## michaelmaltby (Mar 24, 2018)

"... This leads me to believe that we were parceling out the war products we were giving them under lend-lease so as to give them good, serviceable planes competitive with their Luftwaffe adversaries, but not our very best cutting edge technology"
I am afraid this statement doesn't pass the smell test ...  ... the Soviets had a shopping list of things they wanted from the USA and their commissionaires roamed the country ... inspecting factories and mostly getting what they wanted.
What* didn't* they get? 4-engined bombers ... the USA, GB and Commonwealth needed all such bombers for their 2-Front war ... which the Soviets were NOT fighting.
They received P-47s. They received state-of-the-art radar and communications equipment. They received machine tools. They received trucks, tanks, DUCKs. Food. Food. And more Food. _Everything_ they received was what was being used by the Americans themselves.
And what the Soviets didn't received honorably .. they took by subterfuge ... aka Los Alamos project.
http://lend-lease.airforce.ru/english/documents/index.htm


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## pbehn (Mar 24, 2018)

michaelmaltby said:


> "... This leads me to believe that we were parceling out the war products we were giving them under lend-lease so as to give them good, serviceable planes competitive with their Luftwaffe adversaries, but not our very best cutting edge technology"
> I am afraid this statement doesn't pass the smell test ...  ... the Soviets had a shopping list of things they wanted from the USA and their commissionaires roamed the country ... inspecting factories and mostly getting what they wanted.
> What* didn't* they get? 4-engined bombers ... the USA, GB and Commonwealth needed all such bombers for their 2-Front war ... which the Soviets were NOT fighting.
> They received P-47s. They received state-of-the-art radar and communications equipment. They received machine tools. They received trucks, tanks, DUCKs. Food. Food. And more Food. _Everything_ they received was what was being used by the Americans themselves.
> ...


They did receive some four engine bombers, but not part of Lend Lease. They liked them so much they decided to make their own.
Tupolev Tu-4 - Wikipedia

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## P-39 Expert (Mar 24, 2018)

pbehn said:


> He may well have, and it is probably true but what other planes did he fly he was at the time just a good trainee pilot. He trained on P39s and then went operational in UK in the P51. To me all he is saying is that he preferred the P39 to his basic trainers, well almost all pilots do.
> 
> From Wiki
> Soon after entering service, pilots began to report that “during flights of the P-39 in certain maneuvers, it tumbled end over end.” Most of these events happened after the aircraft was stalled in a nose high attitude with considerable power applied. Concerned, Bell initiated a test program. Bell pilots made 86 separate efforts to reproduce the reported tumbling characteristics. In no case were they able to tumble the aircraft. In his autobiography veteran test and airshow pilot R.A. “Bob” Hoover provides an account of tumbling a P-39. He goes on to say that in hindsight, he was actually performing a _Lomcovak_, a now-common airshow maneuver, which he was also able to do in a Curtiss P-40.[36] [N 6] An informal study of the P-39’s spinning characteristics was conducted in the NASA Langley Research Center 20-foot Free-Spinning Tunnel during the 1970s. A study of old reports showed that during earlier spin testing in the facility, the aircraft had never tumbled. However, it was noted that all testing had been done with a simulated full ammunition load, which drew the aircraft’s center of gravity forward. After finding the original spin test model of the P-39 in storage, the new study first replicated the earlier testing, with consistent results. Then, the model was re-ballasted to simulate a condition of no ammunition load, which moved the aircraft’s center of gravity aft. Under these conditions, the model was found to often tumble when thrown into the tunnel.[38]


Some pilots said they could make it tumble, some said they could not.

In any case, for the P-39 to tumble the nose ammo had to be exhausted, you had to be in a near vertical position about to stall and you had to pull the stick back even further to even be in position to try and tumble. The expending of the nose ammo had no effect on any other handling issues, no effect at landing speed or near the ground, or in any other flying attitude. A normal loop entered with sufficient speed to complete the loop posed no problem. Just the isolated instance of climbing near vertical and then pulling the stick back. Not a likely maneuver for anyone who has expended their ammunition. Tumbling was largely a non issue with plenty of disagreement on both sides.

Now if you want to experience a "handling problem", just take a P-38 (any of them before the J-25 that came out in June '44 after the Luftwafe had been defeated) and climb it up to 25000'. Then just nose it over a little into a shallow dive. Not a vertical dive, just a little shallow dive. Almost instantly your controls no longer work and your P-38 starts uncontrollably nosing down trying to perform an inverted loop. You are no longer in control of your P-38 and it is screaming toward earth gaining speed and trying to become inverted. Now THAT'S a handling problem.

Or take your new Merlin P-51 that has been on external fuel and try to make any combat maneuver with a full rear fuselage tank. Your P-51 immediately wants to violently swap ends. Cruise along, sight the enemy, drop your tanks and turn to attack and your P-51 wants to fly backwards. That's a handling problem.

Just turn your P-47. Any type of turn. You slowly mush along while your too small wing tries to get enough air to change your direction. You are outturned by even the German fighters who are the least maneuverable. And you have a very lousy rate of climb before you get to 25000'. Most would consider this a handling problem.

While the P-39 had its problems, the other US fighters had their problems too.

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## P-39 Expert (Mar 24, 2018)

michaelmaltby said:


> "... This leads me to believe that we were parceling out the war products we were giving them under lend-lease so as to give them good, serviceable planes competitive with their Luftwaffe adversaries, but not our very best cutting edge technology"
> I am afraid this statement doesn't pass the smell test ...  ... the Soviets had a shopping list of things they wanted from the USA and their commissionaires roamed the country ... inspecting factories and mostly getting what they wanted.
> What* didn't* they get? 4-engined bombers ... the USA, GB and Commonwealth needed all such bombers for their 2-Front war ... which the Soviets were NOT fighting.
> They received P-47s. They received state-of-the-art radar and communications equipment. They received machine tools. They received trucks, tanks, DUCKs. Food. Food. And more Food. _Everything_ they received was what was being used by the Americans themselves.
> ...


Stalin also constantly complained that the US and Britain were giving him second line equipment. I don't believe he ever got any P-38s or Merlin P-51s. They did get a few P-47s. But the vast majority were P-39s and P-40s with the Brits throwing in Hurricanes and Spitfires.

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## P-39 Expert (Mar 24, 2018)

Hansie Bloeckmann said:


> Yes indeed, very insightful. Having the Nazis faced with a two-front war, with a invasion planned from the Atlantic, was good strategy. And having Stalin apparently willing to sacrifice troops and equipment to keep the Nazis occupied on 2 fronts worked to the advantage of the Allied Powers. Makes me also think that the Russians were looking to copy our higher tech aircraft, so keeping those under Allied control was, "smart poker"!! Many thanks-Hansie


Be careful, I don't think anyone on this site is permitted to agree with me.

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## Milosh (Mar 24, 2018)

I am sure I read of a P-47 chasing a 109 around the slag heaps during Bodenplatte.



P-39 Expert said:


> While the P-39 had its problems, the other US fighters had their problems too.



Other US fighters had work arounds or fixes while the P-39 never did.

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## Milosh (Mar 24, 2018)

Stalin did get some P-51s and 4 engine bomber tho not via L-L.

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## Shortround6 (Mar 24, 2018)

P-39 Expert said:


> The big advantage of the Allison mechanical two stage over the turbo is it takes up much less internal volume. In addition to the actual turbo there was the associated internal ducting (14' per engine in the P-38). The exhaust had to be ducted back to the turbo, the compressed turbo air had to be ducted back up to the intercooler (in the wing on F,G and H) then that air had to be ducted to the carburetor. All this ducting had to be properly aligned and sealed for the whole thing to work right.
> 
> The Allison mechanical two stage engine simply ducted the ambient air from the external scoop to the carburetor on the first stage and a short duct to take that compressed air to the internal supercharger. The intercooler was not needed except for WEP and that was cooled by the water injection. All was enclosed in the normal engine bay of the P-63 except for the small water tanks in the leading edge.
> 
> The turbo developed a little more power at the expense of all that internal room needed. Turbos worked best on multi engined planes because of their greater internal volume. A single engined turbo plane is the P-47 which was huge for a fighter of that day.



The Allison two stage was simpler but then you got less performance.
The -93 was rated at 1325hp for take-off at 54in, and made 1150hp at 22,400ft at 51.5in. Please note that the last is probably as much as the supercharger set will allow.
The -89/91 engines for the P-38 gave 1425hp for take-off at 54in, and were rated at 1425hp at 24,900ft at.......54in. 275hp 2500ft higher. in large part due to the turbos however without the intercoolers the power would have been restricted due to detonation.

ANd compared to the Merlin 61 the V-1710-93 was a bodge. The Merlin 61 was rated at 1390hp at 23,500ft at 60in and the V-1650-3 used in the P-51B was rated at 1330hp at 23,300ft using 66-67in. Lack of intercooler was costing several hundred HP at altitude. Stuffing the -93 Allison into P-51s was NOT going to get you a plane equal to the Merlin Mustang. 

Comparing the P-47 is bogus. You are trying to compare a 1150hp engine to a 2000hp engine. The 2000hp engine is obviously larger, heavier, and requires a bigger turbo and a bigger intercooler and larger air ducts than an 1150 hp engine. 

Compare P-47 to Hawker Typhoon or Corsair, the only other 2000hp single engine fighters of it's time frame. Engines got much better in just a few years and 2000hp engines got a lot smaller real quick. 

Allison was playing catch-up to the Merlin with two stage superchargers. The lack of intercooler hurt high altitude performance. Early P-63s carried 100 gallons of gas and 25 gallons (186.5lbs) of water/alcohol which does nothing for cruise or range. Later P-63s got 126 gallons of fuel. 
late P-47s got a 30 gallon water tank to go with their 370 gallons of fuel but then that pushed their WEP to 2560-2600hp at 27,000ft or above. 
They weren't using the water to compensate for a lack of intercooling (they were using because air cooled engines don't cool as well as liquid cooled engines)


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## P-39 Expert (Mar 24, 2018)

pbehn said:


> My head is now hurting. Can someone tell me any area of performance that the latest P-39 was superior to the Spitfire IX or XIV, P-51-B/C, P47 and F4U as of 25 December 1943?


P-39 was not superior to the Spitfire IX or Merlin P-51, I have never stated this. Those had two STAGE engines for high altitude performance. 

The F4U and Hellcat had two stage mechanical R-2800s. The P-39N substantially outclimbed both the Corsair and Hellcat. Those planes and the P-47 (those operational in 1943) climbed about the same as the FW190, a little under 3000fpm initially and around 1800fpm at 20000' with a service ceiling of 37000'. The N climbed at near 4000fpm initially and 2650fpm at 20000' with a service ceiling of 38500'. The N was faster under 15000' and a little slower at 25000', 375mph vs about 390mph for the Corsair which was faster than the Hellcat. Hard to believe the N had a higher ceiling than Corsairs and Hellcats.

Since the Hellcat was considered the unquestioned master of the Japanese planes, the P-39N should have been able to handle Zeros like the Hellcat. Zeros were 330-340mph planes, Hellcats and P-39Ns were 40-50mph faster at all altitudes.

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## Shortround6 (Mar 24, 2018)

P-39 Expert said:


> Or take your new Merlin P-51 that has been on external fuel and try to make any combat maneuver with a full rear fuselage tank. Your P-51 immediately wants to violently swap ends. Cruise along, sight the enemy, drop your tanks and turn to attack and your P-51 wants to fly backwards. That's a handling problem.
> 
> Just turn your P-47. Any type of turn. You slowly mush along while your too small wing tries to get enough air to change your direction. You are outturned by even the German fighters who are the least maneuverable. And you have a very lousy rate of climb before you get to 25000'. Most would consider this a handling problem.
> 
> While the P-39 had its problems, the other US fighters had their problems too.



While the tumbling problem with the P-39 is a gross exaggeration (although it may have been spin prone) both of your examples ar gross exaggertaions which get us nowhere in figuring out what was going on back then. 

To get into trouble like you describe for the P-51 you had to disobey the pilots manual instructions. It was done on occasion, however _standard procedure _was to take-off on one of the wing tanks ( I forget which, it was the vapor return tank) and switch to the rear tank as soon as possible, burn it down to about 25 gallons, switch to the drop tanks and use them. when you punched off the drop tanks no handling problem. In fact you were supposed to land using the fuel from the rear tank with the main wing tanks empty. On long escort missions they may have compromised on how much fuel they left in the rear tank before switching to the drop tanks. 

as the P-47, lets see, 300 sq ft wing for a 13,000lb airplane. FW 190A-6, 197 sq ft for a 9100lb airplane, yep P-47s wing was too small?
P-47s were evolving the early ones sure had a poor rate of climb But in less than 6 months over the winter of 1943/44 they got better propellers and two different water injection set ups, the first moved the max manifold pressure from 52in to 56in, the 2nd moved it to 64-65 in. CLimb rate at the lower altitudes increased by as much as 33% at certain altitudes. Not a threat to a Spitfire but some of those poor climbing 190s you talk about were in for some rude shocks. 

All aircraft had at least a few problems. The P-39 simply didn't bring enough to the table to warrant continued production or extensive improvement. Too much had to be changed and the layout of the plane made large upgrades problematic. At what point do you simply start over? Like the P-63 and that one missed the boat. Better than the P-39 but the boat had already left the dock.

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## P-39 Expert (Mar 24, 2018)

Shortround6 said:


> While the tumbling problem with the P-39 is a gross exaggeration (although it may have been spin prone) both of your examples ar gross exaggertaions which get us nowhere in figuring out what was going on back then.
> 
> To get into trouble like you describe for the P-51 you had to disobey the pilots manual instructions. It was done on occasion, however _standard procedure _was to take-off on one of the wing tanks ( I forget which, it was the vapor return tank) and switch to the rear tank as soon as possible, burn it down to about 25 gallons, switch to the drop tanks and use them. when you punched off the drop tanks no handling problem. In fact you were supposed to land using the fuel from the rear tank with the main wing tanks empty. On long escort missions they may have compromised on how much fuel they left in the rear tank before switching to the drop tanks.
> 
> ...


In order to spin a plane must first stall. According to the training films and other sources the P-39 had excellent stall characteristics with plenty of warning and no wing drop. I wouldn't recommend spinning one, but you had to get into substantial trouble before that happened.

Regarding the fuselage tank, I read a pilot's comments that it was a court martial offense to use the fuselage tank before exhausting the drop tanks. Any usage of the fuselage tank prior to exhausting the drop tanks meant a loss of range if the drop tanks had to be dropped before they were empty. Use your fuselage tank before your drop tanks and you have one third less internal fuel after they are dropped.

Both the FW190 and the P-47 wings were too small. Both were known as sleds and the FW190 had real stall problems and the resulting spin was quite an experience with control reversal. 

There were a lot of propeller comparisons in wwiiaircraftperformance for the P-47, but again did any of these props actually get used before 1944? The P-47D-10 test on Oct 11 1943 said it used the STANDARD Curtiss 12'2" propeller that had been used on all the production P-47s to date. One thing that I don't like about wwiiaircraft is all the experimental testing with different propellers and exotic fuels that never got into use before the Luftwaffe was defeated in March 1944. So a lot of information is on that site about planes that never saw the light of day, or if they did it was too late to have a meaningful impact on the war. Oh well.

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## BiffF15 (Mar 24, 2018)

P-39 Expert said:


> Some pilots said they could make it tumble, some said they could not.
> 
> In any case, for the P-39 to tumble the nose ammo had to be exhausted, you had to be in a near vertical position about to stall and you had to pull the stick back even further to even be in position to try and tumble. The expending of the nose ammo had no effect on any other handling issues, no effect at landing speed or near the ground, or in any other flying attitude. A normal loop entered with sufficient speed to complete the loop posed no problem. Just the isolated instance of climbing near vertical and then pulling the stick back. Not a likely maneuver for anyone who has expended their ammunition. Tumbling was largely a non issue with plenty of disagreement on both sides.
> 
> ...



P-39,

You are correct that pretty much every aircraft had its vices, which remains true to this day (on this I agree). However place yourself in one of the above planes, deep in enemy territory on a long’ish mission. Every one of those examples you gave with the exception of the 38 & 39 things got better as fuel / ammo went down (and with less fuel things got better for those two). However, from my perspective the lower the fuel in my plane the harder I can push it, the more options I have maneuver wise, which oh by the way is the same for my adversary. The P39 vice is particularly critical as turning fights work down in altitude and should the Airacobra “bite” with a tumble you are fighting your plane and the enemy simultaneously for your life. The regular Joe fighter pilot is not going to bury his nose at low altitudes (P38), or mission plan with the odds of engaging soon after takeoff (P51) which will put you in a losing place from the get go. 

I have always been a fan of the early war fighters (38, 39 & 40). However, should I be the one flying in combat and the choice was mine I would probably go with what the AAF chose, the Mustang, Thunderbolt in ETO, and or those plus the Lightning in the SWP. Previously pointed is what the AAF chose, and the difficult part for you to perhaps get your arms around seems to be the why. Those guys making those choices were there in the thick of it. 

Cheers,
Biff

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## pbehn (Mar 24, 2018)

P-39 Expert said:


> In order to spin a plane must first stall. According to the training films and other sources the P-39 had excellent stall characteristics with plenty of warning and no wing drop. I wouldn't recommend spinning one, but you had to get into substantial trouble before that happened.
> 
> Regarding the fuselage tank, I read a pilot's comments that it was a court martial offense to use the fuselage tank before exhausting the drop tanks. Any usage of the fuselage tank prior to exhausting the drop tanks meant a loss of range if the drop tanks had to be dropped before they were empty. Use your fuselage tank before your drop tanks and you have one third less internal fuel after they are dropped.
> 
> ...


The rear fuselage tank and 100 gal external tanks were to perform specific missions. The instructions given to the pilot were quite clear and I have read them here many times. I believe what I read because some of the people doing the writing work on these planes and know or knew people who flew the missions. 
The effect on the CoG of the rear tank and the necessity to drain, not empty it was researched. To my knowledge it was a wartime special measure, no P51 today is allowed to fly with those fuel loads, the plane was borderline unstable. However with the P39 the reports of tumbling and flat spins were actually not believed by Bell, only when they did tests with no ammunition were they believed. Now this means that the plane had not been fully tested before entering service, having no ammunition is a normal condition on a combat plane.

If the LW was defeated in March 1944 who put the Me262 into service and what use was the P51D?

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## BiffF15 (Mar 24, 2018)

P-39 Expert said:


> Since the Hellcat was considered the unquestioned master of the Japanese planes, the P-39N should have been able to handle Zeros like the Hellcat. Zeros were 330-340mph planes, Hellcats and P-39Ns were 40-50mph faster at all altitudes.



The simple problem with this is airfields. The USN planes had movable ones and the AAF did not. Next problem is range. The 51, 47, and 38 all had the legs so they could cover the distances required and still have station time to fight before bingo (RTB fuel state). 

Cheers,
Biff

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## Shortround6 (Mar 24, 2018)

P-39 Expert said:


> P-39 was not superior to the Spitfire IX or Merlin P-51, I have never stated this. Those had two STAGE engines for high altitude performance.
> 
> The F4U and Hellcat had two stage mechanical R-2800s. The P-39N substantially outclimbed both the Corsair and Hellcat. Those planes and the P-47 (those operational in 1943) climbed about the same as the FW190, a little under 3000fpm initially and around 1800fpm at 20000' with a service ceiling of 37000'. The N climbed at near 4000fpm initially and 2650fpm at 20000' with a service ceiling of 38500'. The N was faster under 15000' and a little slower at 25000', 375mph vs about 390mph for the Corsair which was faster than the Hellcat. Hard to believe the N had a higher ceiling than Corsairs and Hellcats.
> 
> Since the Hellcat was considered the unquestioned master of the Japanese planes, the P-39N should have been able to handle Zeros like the Hellcat. Zeros were 330-340mph planes, Hellcats and P-39Ns were 40-50mph faster at all altitudes.



You are relying on that stripper N (or at the least low fuel) using WEP power for your performance figures. OK I will concede that this N, which shows up sometime in the middle of 1943 in combat theaters, could handle a Zero,_* IF *_the Zeros were delivered to the close vicinity of the P-39s airbase.
SEE:http://zenoswarbirdvideos.com/Images/P-39/P39FOIC.pdf
P-39Q FLight operation chart for P-39Q with 87 gallons of fuel and weight between 7200-7600lbs using the same engine as the N (?)
The Small tank P-39s couldn't go anywhere and get back. Even with a drop tank you are restricted to around 100 miles or less over Europe. 
In the Pacific you can go a bit further (lower cruising speeds work) but base protection interceptor is a rather limited role for plane thousands of miles from home.
More general purpose planes were wanted for the investment in logistics and ground crew.

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## drgondog (Mar 24, 2018)

P-39 Expert said:


> In order to spin a plane must first stall. According to the training films and other sources the P-39 had excellent stall characteristics with plenty of warning and no wing drop. I wouldn't recommend spinning one, but you had to get into substantial trouble before that happened.
> 
> Regarding the fuselage tank, I read a pilot's comments that it was a court martial offense to use the fuselage tank before exhausting the drop tanks. Any usage of the fuselage tank prior to exhausting the drop tanks meant a loss of range if the drop tanks had to be dropped before they were empty. Use your fuselage tank before your drop tanks and you have one third less internal fuel after they are dropped.
> 
> ...


You bring so much criticism from others because you wander astray with value judgments about other aircraft that simply aren't based on facts.

The FW 190 was regarded by most that flew it, including post war luminaries like Wing Captain Winkle Brown to be one of the most responsive and good handling fighters of the war. Second point about 190 stall - yes it had a vicious stall response - due largely to no washout for outer 20% of semi span. That said, many LW pilots PUT the 190 into a spin because it was easy to recover from. A favorite trick was full throttle showing exhaust smoke and a spin to fool a pursuing pilot into thinking he had shot the 190 down.

Second, The P-47 (highest) , Bf 109G, P-51B, FW 190A (about the same) had a wing loading within ~ 5% of each other at full internal combat load. There were no 'lead sleds' in comparison until the escort altitudes were reached and the HP available for the P-51B and P-47D compared to HP required began to heavily favor both US fighters. The P-47D easily out turned the FW 190 above 25,000 feet - and conversely was out turned by the Bf 109 and FW 190A under 20,000 feet (Ditto climb and acceleration). Nothing out rolled an FW 190, including a P-39/63 on its very best day.

March 1944 marked the point in time when the P-51B eliminated safe sanctuary for the LW T/E day and night fighter as bomber destroyers, as well as introduced the heavy attrition of LF Reich over central and deep Germany/Poland/CZ. The operative word is 'Introduced'. It was the beginning of the end of the LW ability to resist the Invasion on June 6, but a lot of aircrews (day and night) were lost between March 1 and June 5, 1944. The bleeding continued throughout the summer and finally ended with Bodenplatte in the West.

As to 'stability'? Yes the P-51B/D was limited in high G maneuvers until approximately 20-25 gallons of fuel had been burned down in the 85 gallon fuselage tank. Easily solved. SOP for mid Germany escort was to fill the fuse tank to 65 gallons. For long range (Stettin/Posnan), burn 25 gallons climbing to 25,000 feet from UK, then switch to externals. There were no other factors affecting aft CG for the Mustang, but shooting most ammo from nose was a factor for the P-39. According to pilot notes, the pitch controls were extremely sensitive (AHT pg 200) resulting in comments like "If you moved the stick 1" the resulting change in level flight CL of 0.20 to 'new stall CL' of 1.4 with normal CG location - resulting into stall/spin". With aft CG/Ammo expended, the flight stability deteriorated - "After the CG moved back, the airplane would do strange things' including snap rolls, spins, pure tumbles' as the stick forces per G of maneuver were below all other operational US fighters and below AAF standards.

At normal landing speeds per flight test report (AHT, pg 203) "Stalls always developed with no warning of approach, no buffeting of the aircraft or controls". One G and accelerated stalls were similar - "The P-39 would do the most wicked stall of any airplane I flew. That is why there were so many stall-spin accidents."

I suspect from an aero standpoint that the lack of wash-out for the P-39 was the major contributor to lack of aileron warning or authority in near stall conditions. It is clear that stick force per G and particularly for both roll and elevator response were primary factors for entering accelerated stall conditions leading to departures.

Most of the comments presented by Dean were extracted from both AAF Flight tests at Eglin as well as the many pilots that flew it as anecdotal summaries. The P-63 allegedly solved some of the stick force issues but Stab/Control remained the gating factor preventing AAF acceptance as operationally suitable..

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## MIflyer (Mar 24, 2018)

For those who have not read it, this is an interesting account of the 67th Ftr Squadron and its P-400's on Guadalcanal:

https://ia902205.us.archive.org/17/items/PacificCounterblow/PacificCounterblow.pdf

It says they looked into reducing the weight of the P-39 and by the end of September 1942 were able to strip a P-39K of 650 lb of its original equipment. It also says that Gen Harmon asked DC for the P-38, P-47, or the P-40 with the Merlin engine. I guess that explains why those P-40F's got to Guadalcanal.

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## Shortround6 (Mar 24, 2018)

P-39 Expert said:


> In order to spin a plane must first stall. According to the training films and other sources the P-39 had excellent stall characteristics with plenty of warning and no wing drop. I wouldn't recommend spinning one, but you had to get into substantial trouble before that happened.
> 
> Regarding the fuselage tank, I read a pilot's comments that it was a court martial offense to use the fuselage tank before exhausting the drop tanks. Any usage of the fuselage tank prior to exhausting the drop tanks meant a loss of range if the drop tanks had to be dropped before they were empty. Use your fuselage tank before your drop tanks and you have one third less internal fuel after they are dropped.
> 
> ...


 Many evaluations of the P-39 contradict that statement about stalls. and speaking about control reversal. On the P-39 with wing guns and full ammo loads the proper spin recovery use of ailerons was opposite the proper use of ailerons without or with light load of ammo. 

You keep claiming one thing and then back tracking. It is true the P-47 couldn't turn with a 109 but the against the 190 it was not so clear cut. And an Aircobra trying to turn against a 109 may not be happy with the result so why pick on the P-47 to begin with? 

A Mustang was _supposed _to be able to get home from the point where it dropped it's tanks and fought for 20 minutes over a distance of 460 miles. The rear tank extended the _planning _radius to 700 miles. Obviously there were a bunch of missions where the rear tank didn't need to be used or would work perfectly well if some fuel was burned off. A P-51D could do about 5 miles per gallon at 370mph true at 25,000ft. even 25 gallons was good for 125 miles. 

You keep getting called on the March 1944 date. That may be the date at which point somebody/s decided the outcome was no longer in doubt, the timing of the outcome was not anywhere near certain and thousands of airmen (on both sides) died in the next year. The air war was hardly over.

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## pbehn (Mar 24, 2018)

www.taphilo.com/history/WWII/Loss-Figures-Aircraft-USA-Training.shtml
The accident rate per 100,000 hrs training/no of fatalities
P38 = 139/379
P39 = 245/395
P40 = 188/350
P47 = 127/455
P51 = 105/137

Looking at the table which is difficult to copy here, the P 39 was not only more likely to have an accident than the other types, if it had an accident it was more likely to be fatal.

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## DarrenW (Mar 24, 2018)

P-39 Expert said:


> The P-39N substantially outclimbed both the Corsair and Hellcat. Those planes and the P-47 (those operational in 1943) climbed about the same as the FW190, a little under 3000fpm initially and around 1800fpm at 20000' with a service ceiling of 37000'.



Hi P-39 Expert,
While I agree that the P-39N had an excellent rate of climb, I would add that the P-47 didn't climb nearly as well as the Corsair or Hellcat until the advent of 100/150 fuels and the paddle blade propeller. The F4U-1 and F6F-3/5 easily had initial climb rates ranging between 3,000 - 3,600fpm (depending on power settings and use of water injection), while a P-47 wouldn't normally touch 3,000fpm unless it was running at the highest combat boost levels and sporting a paddle prop.


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## Dimlee (Mar 24, 2018)

michaelmaltby said:


> I am afraid this statement doesn't pass the smell test ...  ... the Soviets had a shopping list of things they wanted from the USA and their commissionaires roamed the country ... inspecting factories and mostly getting what they wanted.
> What* didn't* they get? 4-engined bombers ... the USA, GB and Commonwealth needed all such bombers for their 2-Front war ... which the Soviets were NOT fighting.
> They received P-47s. They received state-of-the-art radar and communications equipment. They received machine tools. They received trucks, tanks, DUCKs. Food. Food. And more Food. _Everything_ they received was what was being used by the Americans themselves.
> And what the Soviets didn't received honorably .. they took by subterfuge ... aka Los Alamos project.
> http://lend-lease.airforce.ru/english/documents/index.htm



Well, the Soviets just did not get ALL what they wanted. Request lists included B-17, B-24, B-29, Mosquitto, late Spitfire, P-61, etc. They wanted to have H2S radars, Nordon sights and much more. Hence the keynote of Soviet (and much of Russian language post-Soviet) historical literature: "they gave us left-overs, they kept the best for themselves, it was not fair!".

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## P-39 Expert (Mar 24, 2018)

Shortround6 said:


> You are relying on that stripper N (or at the least low fuel) using WEP power for your performance figures. OK I will concede that this N, which shows up sometime in the middle of 1943 in combat theaters, could handle a Zero,_* IF *_the Zeros were delivered to the close vicinity of the P-39s airbase.
> SEE:http://zenoswarbirdvideos.com/Images/P-39/P39FOIC.pdf
> P-39Q FLight operation chart for P-39Q with 87 gallons of fuel and weight between 7200-7600lbs using the same engine as the N (?)
> The Small tank P-39s couldn't go anywhere and get back. Even with a drop tank you are restricted to around 100 miles or less over Europe.
> ...


Wasn't a "stripper" N. Test was at combat weight with AVERAGE fuel. Add 360# back (60 gals, half fuel) and you get 7634# Gross weight of P-39N was 7650#. This was done to get the average weight for this flight. WEP only used below 16000', above the critical altitude WEP not available, by definition. The climb figures on the Oct 17, '42 test were at military power, no WEP. These were faster climb rates up to 25000' than any P-38F/G, P-40, P-47, P-51, Corsair, Hellcat, Wildcat, FW190, Me109, Zero, Oscar in combat in 1943. Not faster than the Spitfire IX or P-51B (December).

Your P-39Q operations chart clearly shows internal capacity of 86 gallons. The Russians requested the reduction since that's apparently all they needed since they seldom flew with drop tanks. N (and all older P-39s) originally had the full 120 gallon internal capacity. Normal combat P-39N carried a 110gallon drop tank. That's 120 internal plus 110 drop=230gals and drop tanks of 156 gallons and 175 gallons were also available.


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## pbehn (Mar 24, 2018)

Dimlee said:


> Well, the Soviets just did not get ALL what they wanted. Request lists included B-17, B-24, B-29, Mosquitto, late Spitfire, P-61, etc. They wanted to have H2S radars, Nordon sights and much more. Hence the keynote of Soviet (and much of Russian language post-Soviet) historical literature: "they gave us left-overs, they kept the best for themselves, it was not fair!".


You can put a spin on anything, the B 29 was the most expensive military project ever done at the time, who gives such things away, by the hundred? The USA wanted more mosquitos themselves but the fact is everyone wanted mosquitos at one stage. When you look at all that Russia actually was given completely free of charge their complaints are a bit OTT.


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## P-39 Expert (Mar 24, 2018)

DarrenW said:


> Hi P-39 Expert,
> While I agree that the P-39N had an excellent rate of climb, I would add that the P-47 didn't climb nearly as well as the Corsair or Hellcat until the advent of 100/150 fuels and the paddle blade propeller. The F4U-1 and F6F-3/5 easily had initial climb rates ranging between 3,000 - 3,600fpm (depending on power settings and use of water injection), while a P-47 wouldn't normally touch 3,000fpm unless it was running at the highest combat boost levels and sporting a paddle prop.


I'm trying to limit the planes to those that were fighting in 1943.


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## Dimlee (Mar 24, 2018)

pbehn said:


> You can put a spin on anything, the B 29 was the most expensive military project ever done at the time, who gives such things away, by the hundred? The USA wanted more mosquitos themselves but the fact is everyone wanted mosquitos at one stage. When you look at all that Russia actually was given completely free of charge their complaints are a bit OTT.



I was ironic. Let me put one more smiley to emphasize that..

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## pbehn (Mar 24, 2018)

Dimlee said:


> I was ironic. Let me put one more smiley to emphasize that..


I worked briefly in Russia and got the complaints first hand.

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## Shortround6 (Mar 24, 2018)

P-39 Expert said:


> Wasn't a "stripper" N. Test was at combat weight with AVERAGE fuel. Add 360# back (60 gals, half fuel) and you get 7634# Gross weight of P-39N was 7650#. This was done to get the average weight for this flight. WEP only used below 16000', above the critical altitude WEP not available, by definition. The climb figures on the Oct 17, '42 test were at military power, no WEP. These were faster climb rates up to 25000' than any P-38F/G, P-40, P-47, P-51, Corsair, Hellcat, Wildcat, FW190, Me109, Zero, Oscar in combat in 1943. Not faster than the Spitfire IX or P-51B (December).
> 
> Your P-39Q operations chart clearly shows internal capacity of 86 gallons. The Russians requested the reduction since that's apparently all they needed since they seldom flew with drop tanks. N (and all older P-39s) originally had the full 120 gallon internal capacity. Normal combat P-39N carried a 110gallon drop tank. That's 120 internal plus 110 drop=230gals and drop tanks of 156 gallons and 175 gallons were also available.



DO you have ANY evidence that combat weight was at half fuel? You keep repeating but give no proof. 

IN fact we may both be wrong.
http://www.wwiiaircraftperformance.org/P-39/P-39_Aircraft_Performance_Characteristics.jpg
Gross weights of Ns at 7393.7 and 7395.? I am not going to argue over a few pounds but both Ns are shown with 87 gallons of fuel. 
Many books say that the "N"s were produced with 87 gallon capacity. Kits were supplied to bring them back to 120 gallons that could be installed in the field. 
Military power was 44.5in of MAP, full WEP was 57in. this test was done at 50.5in (take-off power) until the supercharger could no longer supply that pressure. 
Not WEP but not military power either. and then we have.
http://zenoswarbirdvideos.com/Images/P-39/P39TOCLC.pdf

P-39 Q at 7200lbs needs 9.3 minutes to get to 25,000ft using take off power for the first 5 minutes, and uses 33 gallons of it's 87 gallons just to get there.
P-39Q at 7600lbs needs 10.1 minutes to get to 25,000ft using take off power for the first 5 minutes and uses 34 gallons to get there. 
the under wing pods created that much drag?????
Elapsed time to altitude was at 0 degrees C or 32 degrees F. 

we also have the penciled in chart saying 4.1 minutes to 14,600ft? 

and 





about 300lbs heavier (120 gals fuel?) but even using MIlitary power for the first few minutes ( and NO drag from wing guns) needs over 9 minutes to get to 25,000ft. 

We also have the basic Bf 109G climbing to 7000 meters ( 22,966ft) in 8 minutes so your p-39 had better be on watch. which climbed faster where I don't know. 
I would also note that a plain Spitfire MK V using 16lbs boost (below 8,800ft) can make it to 24,000ft in 8.15 mins using a single speed single stage supercharger. 

Now just for balancing things out a bit, the super P-39N is climbing at 1940fp at 25,000ft, the Spitfire V is climbing at 1740fps at 24,000ft and the 109G (basic?) is climbing at at least 2066 at 22,966.
A P-39Q at 7871lbs was climbing at 1570fpm at 25,000.

The P-39 has to be very careful about weights and altitude or it can get into big trouble. 
Falling into the ocean because you don't have enough fuel can also ruin a pilots day


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## tomo pauk (Mar 24, 2018)

P-39 Expert said:


> I'm trying to limit the planes to those that were fighting in 1943.



In the Allied camp, the Spitfire IX, VIII, XII and Typhoon offer overall better performance and payload, that includes bigger drop tank volume. A P-39N/Q qith 87 US gals (72.5 imp glas) of fuel + 75 US gals (that is maximum, not 110 US gals) in drop tanks is next to useless for ETO, MTO and Asia/Pacific. Even the Spitfire V is better in some categories.
The P-40F and N are a bit slower, the N with less fuel and less guns can compete vs. Axis stuff, but it is again useless in ETO, MTO and Asia/Pacific. It can carry more fuel, though, and with 'normal' internal fuel it is can be useful. P-51A offers greater speed and far better range, the P-51 not so much.
P-47 (1943 - toothpick prop, 130 grade fuel, no ADI) can hold it's own vs. Axis best above 20000 ft, and dominates most of them above 25000 ft, with proper drop tanks ot was escorting bombers 375 miles away from East Anglia in Autumn of 1943. P-38 has it's own host of porblems, buat also it's crucial abilities - US commanders asked for more of those, they dont clamor for more P-39s.

I'll happily conceede that P-39N was either better or equal to the best Soviet, Japanese or Italian fighters, apart the range vs. Japanese gear. Unfortunately, it's advantage vs. Fw 190A-3/A-4 and Bf 109G-2/G-6 are limited to low to mid altitude, and climb performance depends on how much fuel tankage is installed and somehow getting the pilot on Fw 190 not to use 2700 rpm for climb. Ironically, both German A/C are longer ranged than P-39N with reduced fuel. 

All of the mentioned Western A/C (bar Bf 109, maybe) have far better capability to carry external ordnance than the P-39. I'll repeat once again - the P-39N was not solving any real problem the Anglo-American (including Commonwealth) air forces had in 1943.

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## XBe02Drvr (Mar 24, 2018)

pbehn said:


> However with the P39 the reports of tumbling and flat spins were actually not believed by Bell, only when they did tests with no ammunition were they believed. Now this means that the plane had not been fully tested before entering service, having no ammunition is a normal condition on a combat plane.


Whoa! Bell had to have been playing "Disingenuous" here. The idea that the possibility of aft CG stability issues never entered their minds, considering the unconventional layout of their bird begs credibility. And then to build a wing with no washout, thus guaranteeing a buffetless, violent stall? And whoever thought of not including the entire range of CG scenarios in flight testing?
IIUC, the purpose of the midships engine was to minimize polar moment of inertia and enhance agility. Any kindergartner can forsee that this will likely result in very light stick force gradients and a "twitchy" machine prone to over controlling and PIOs unless compensated for in the flight control linkages. Add that to the wobbly aft CG and the sharp stall characteristics, and you've got a tailor made "lieutenant loser". (The unintended Lomcevak is a free of charge fringe benefit! People pay good money at amusement parks across the land to experience thrills like that.)
It's hard to believe Bell would not have been aware of this, or that they would knowingly foist such a deathtrap on the government.
I've read here and there in dark ages of prehistory that USAAC Wright Pat forced a number of changes on Bell Aircraft to comply with some high ranking infantry officer in Procurement's concept of "improvements". IIRC, this included reducing the wing area to "go faster, like a GeeBee", adding a heavy radio behind the cockpit to talk to ground troops, and removing some bobweights from the elevator linkage and some other (don't remember) weight from the nose section.
Since we seem to have a P-39 expert in our midst, maybe he can enlighten us on this. Fact or fiction? And if fiction, any idea where that story came from?
Cheers,
Wes

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## Shortround6 (Mar 24, 2018)

I don't know about any of that but a _reasonable _explanation of the "tumbling" (at least reasonable to me, a non pilot) is on Page 256 of "Cobra" by Birch Mathews. 

" The attitude from which a maneuver most resembling tumbling occured was that resulting from a stall with the airplane in a vertical position, following which the stick was pushed violently forward and held there for a prolonged period with high power still applied. From it's vertical attitude the nose of the airplane was pushed over as a result of the forward stick motion. The airplane performed a portion of an inverted snap roll, faltered momentarily and then did one or two turns of an oscillatory inverted spin. It then moved suddenly into a normal left hand spin of high rotational velocity. After one to three turns the spin became normal when the the engine was throttled. 
In no case did the airplane do one complete tumble although its spen and snap roll were done so rapidly that at first glance, the manuever could be misinterpreted as an end-over-end motion. IN all cases, recovery form the the left spin was entirely normal when proper spin recovery technique was employed" 

Later on the page is says 
" With an extreme aft center of gravity, the airplane could be made to enter a snap roll and inverted oscillatory spin where the nose passed through the horizon two times during each 360 degree rotation." 

I can agree that the P-39 never tumbled (or did so only under the rarest of circumstances) but that does not mean the plane was vice less or couldn't catch out an unwary pilot. 
Stalls at low speed in landing configuration are often not the same as stalls in clean condition in high speed turns.

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## DarrenW (Mar 24, 2018)

P-39 Expert said:


> I'm trying to limit the planes to those that were fighting in 1943.


I understand that is what you were doing, but to lump all R-2800 engined fighters flying in 1943 as having similar initial climb rates is simply incorrect. Both Navy fighters could comfortably reach 3,000 fpm, but this was not the case with Thunderbolt as it struggled in the climb before the paddle prop was introduced and even then it still couldn't match the Corsair or Hellcat.


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## pbehn (Mar 24, 2018)

XBe02Drvr said:


> Whoa! Bell had to have been playing "Disingenuous" here. The idea that the possibility of aft CG stability issues never entered their minds, considering the unconventional layout of their bird begs credibility. And then to build a wing with no washout, thus guaranteeing a buffetless, violent stall? And whoever thought of not including the entire range of CG scenarios in flight testing?
> IIUC, the purpose of the midships engine was to minimize polar moment of inertia and enhance agility. Any kindergartner can forsee that this will likely result in very light stick force gradients and a "twitchy" machine prone to over controlling and PIOs unless compensated for in the flight control linkages. Add that to the wobbly aft CG and the sharp stall characteristics, and you've got a tailor made "lieutenant loser". (The unintended Lomcevak is a free of charge fringe benefit! People pay good money at amusement parks across the land to experience thrills like that.)
> It's hard to believe Bell would not have been aware of this, or that they would knowingly foist such a deathtrap on the government.
> I've read here and there in dark ages of prehistory that USAAC Wright Pat forced a number of changes on Bell Aircraft to comply with some high ranking infantry officer in Procurement's concept of "improvements". IIRC, this included reducing the wing area to "go faster, like a GeeBee", adding a heavy radio behind the cockpit to talk to ground troops, and removing some bobweights from the elevator linkage and some other (don't remember) weight from the nose section.
> ...


I agree, I am by no means well read on the subject, but I am much better read than I was a week ago. There are documented statements of poor stall performance. Handling or stability problems with ammunition expended are also documented which had to be brought to Bells attention. The one mission flown by the RAF was straffing barges near Dunkerque, the pilots I would suspect returned with no ammunition in a completely different plane to the one they took off in. I have no access to any flight reports but I strongly suspect the British tested the P 39 without ammunition/ballast and said "you must be joking" Additionally, wing washout causes drag, and is a price worth paying in the compromises made. All the P39s rivals would have gone faster with no washout. 

Much is made of the P39 having a tricycle undercarriage landing gear, I would suggest it would be a very dangerous beast as a tail dragger.

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## XBe02Drvr (Mar 24, 2018)

pbehn said:


> I would suggest it would be a very dangerous beast as a tail dragger.


AMEN!!


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## XBe02Drvr (Mar 24, 2018)

Shortround6 said:


> The airplane performed a portion of an inverted snap roll, faltered momentarily and then did one or two turns of an oscillatory inverted spin. It then moved suddenly into a normal left hand spin


Ever see an airshow acro plane do a Lomcevak? You just described it to a tee. I'm told the word is Czech and is (mis)translated as "crazy mixed-up headache". Having ridden through a couple in a Pitts, I can vouch for the accuracy of the term. The ultimate sensation of hostageness. You ever notice that nobody does them at low altitude at airshows (or anywhere else)? Takes a few seconds to uncage your eyeballs afterward.
Days of future passed! That sort of behaviour, an inverted oscillatory spin with the nose whipsawing up and down and the rotation rate and bank angle fluctuating randomly and not synchronously, became pretty common in the jet age. IIRC, spin in the F4J was described as: "random oscillations around all three axis with buffeting, a high rate of descent, and probable dual flameout". IIRC, recovery was: "average fluctuations of AOA needle to determine if positive or negative stall, average turn needle to determine direction of rotation, apply appropriate stick and rudder for type of spin. Deploy RAT if flameout occurs. If control not regained passing 10,000 AGL, EJECT."
I knew a crew who missed that last directive by a thousand feet, stopping rotation by 9,000 and still augered in. They managed to achieve a level pitch attitude passing through 1,000, but at some phenomenal G load and an impossible sink rate, and the plane snapped inverted in the midst of the ejection sequence.
Cheers,
Wes

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## Greg Boeser (Mar 24, 2018)

P-39expert cites _Attack and Conquer._
So will I. The 8th FG entered combat 30 April 1942 with P-39Ds and P-400s, within 5 days they had lost 9 pilots and 14 aircraft. Clearly, the pilots were no match for the Tainan AG. The P-39 lacked range to effectively bring battle to the enemy, and were hard pressed to defend their own air base. slow climb performance meant that with the short warning afforded the Port Moresby defenders, they often had no choice but to scramble out to sea to avoid being swatted down while in the climb. Trying to engage the Japanese while still in a climb was suicide as demonstrated by the 75 Sqn. RAAF.
The 8th and 35th FGs held the line in New Guinea during 1942, but suffered considerable losses.
The 80th FS was reequipped with P-38s and entered combat 30 March 1943. The P-38 was a game changer. As the book states, the 35th and 36th Fighter Squadrons continued to fly combat missions in spite of the fact that the P-38 was pushing the fight out of the radius of other fighter types. Both squadrons eventually re-equipped, The 35th got P-40Ns in late 43, and the 36th got some P-39Qs before converting to P-47s in early 44. Both eventually got P-38s

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## Elmas (Mar 25, 2018)

_View: https://youtu.be/og7fCw85Qns_


Performed by Maggiore Andrea Rossi, then (2005) "Solista" of the Pattuglia Acrobatica Nazionale.

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## Elmas (Mar 25, 2018)

_View: https://youtu.be/hLeYWkx2Jlg_


If you watch at this video the Instructor do insist that landing in P-39 must be done on the main undercarriage, keeping the nose well up to the end ( from 33'.00 circa). As all airplanes with tricycle landing gear must do, of course.

But probably the tricicle undercarriage, that required this markedly nose-up attitude was one of the reasons responsible for the bad handling of P-39 at low speeds.

The combination of nose-up, CG aft, ammunition expended, no wash-out in the wings, inertia coupling due to the position of the engine and possibly other incidental factors like a little bit to slow landing speed _("..be careful not coming too fast_" says the Instructor at 32.00...), some unfavourable wind conditions, a jerky handling of the stick from a inexperienced Pilot, could have led very easily to a nasty situation.


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## P-39 Expert (Mar 25, 2018)

Greg Boeser said:


> P-39expert cites _Attack and Conquer._
> So will I. The 8th FG entered combat 30 April 1942 with P-39Ds and P-400s, within 5 days they had lost 9 pilots and 14 aircraft. Clearly, the pilots were no match for the Tainan AG. The P-39 lacked range to effectively bring battle to the enemy, and were hard pressed to defend their own air base. slow climb performance meant that with the short warning afforded the Port Moresby defenders, they often had no choice but to scramble out to sea to avoid being swatted down while in the climb. Trying to engage the Japanese while still in a climb was suicide as demonstrated by the 75 Sqn. RAAF.
> The 8th and 35th FGs held the line in New Guinea during 1942, but suffered considerable losses.
> The 80th FS was reequipped with P-38s and entered combat 30 March 1943. The P-38 was a game changer. As the book states, the 35th and 36th Fighter Squadrons continued to fly combat missions in spite of the fact that the P-38 was pushing the fight out of the radius of other fighter types. Both squadrons eventually re-equipped, The 35th got P-40Ns in late 43, and the 36th got some P-39Qs before converting to P-47s in early 44. Both eventually got P-38s


Keep in mind a few salient points, first these were older P-39s with the lower rated engine and way too much weight. With the ever present drop tank their combat ceiling (altitude above which any plane will climb at only 1000fpm or less) was about 18000'. The Bettys came in at between 18000' and 22000' with their Zero escort at about 24000'. These older P-39s (D,F,K,L) could have easily been modified in the field by simply removing the 4 x .30 wing guns along with their mounts, chargers heaters and ammunition boxes (and of course the ammo itself which was the heaviest component) and these planes would climb with the P-38s that, by the way, were not even available until very late in the year. And those Jap raids were frequently intercepted by those P-39s, no radar and extra weight included. 

Second, the Japanese pilots were among the best in the world being Navy carrier pilots with experience in China. Our kids at PM were all fresh out of flying school with no experience except for Buzz Wagner who supposedly got off the ground at Pearl Harbor. Most experts consider pilot quality to be more important than plane quality all other factors being equal. Theirs were much much better at this point in the war. 

Third,we didn't have effective radar until after August 1942 so the raids were largely unopposed. These raids could come at any time from Lae only 200 miles away and their Zero escort didn't even need drop tanks. Later at Guadalcanal the Jap raids came from much farther away so they almost always came at noon making them very predictable. 

Fourth, we were tremendously outnumbered. Japanese had functioning bases all along the NG coast backed up by their huge base at Rabaul. Their maintenance facilities were functional. Our maintenance/supply early on at Moresby consisted mainly of pulling a functional part off of one of the many wrecks at the end of the runway. By the time the P-38 appeared in the theater attrition at Moresby, Coral Sea, Midway and the first three months of Guadalcanal had seriously reduced the Japanese Navy pilot quality and our pilots were much better trained than in April '42.

The fact that the green outnumbered American kids kept the Japanese out of Moresby was a real tribute to their courage and tenacity. Lighter equipped P-39s and functioning radar would have made the job a lot easier. The later arriving Lightnings benefited from better pilots, declining Jap pilots, functioning radar and much more efficient maintenance.

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## P-39 Expert (Mar 25, 2018)

Elmas said:


> _View: https://youtu.be/hLeYWkx2Jlg_
> 
> 
> If you watch at this video the Instructor do insist that landing in P-39 must be done on the main undercarriage, keeping the nose well up to the end ( from 33'.00 circa). As all airplanes with tricycle landing gear must do, of course.
> ...



All planes were encouraged to land on their main landing gear first. The slight nose up attitude on the ground did not transfer to flight, the P-39 flew level like a normal plane. P-39 was much easier to handle on the ground than a tail dragger, you could see straight ahead and taxied like driving a car.

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## Elmas (Mar 25, 2018)

P-39 Expert said:


> All planes were encouraged to land on their main landing gear first. The slight nose up attitude on the ground did not transfer to flight, the P-39 flew level like a normal plane. P-39 was much easier to handle on the ground than a tail dragger, you could see straight ahead and taxied like driving a car.



I cannot more unconditionally agree with you about that, and so does Com.te Galbusera in his interview and also Jeffrey Quill, the well known Spitfire test Pilot, was amazed about the handling of P-39 on the ground, and he did insist to have Supermarine Attacker with a tricycle landing gear.
_"Very strange that Vickers, who was a main producer of equipment for landing gears, did not accept my proposal"_ he remembers in his memories.
Probably the British were so scared from landing P-39s after the one and only mission they flew wit it to exclude completely tricycle landing gear from their aeroplanes once and for all.  Joking, of course. I know that Meteor and Vampire had tricycle landing gear.
While I do easily accept the fact that P-39 flew level ( but up to a point...) our opinions differ about the handling of P-39 i_n flight_, and in particular _at landing_...


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## P-39 Expert (Mar 25, 2018)

MIflyer said:


> For those who have not read it, this is an interesting account of the 67th Ftr Squadron and its P-400's on Guadalcanal:
> 
> https://ia902205.us.archive.org/17/items/PacificCounterblow/PacificCounterblow.pdf
> 
> It says they looked into reducing the weight of the P-39 and by the end of September 1942 were able to strip a P-39K of 650 lb of its original equipment. It also says that Gen Harmon asked DC for the P-38, P-47, or the P-40 with the Merlin engine. I guess that explains why those P-40F's got to Guadalcanal.


The P-39 comes off better in this Guadalcanal summary than others that I have read.

The P-400s had no oxygen (wrong equipment) so any flying above 12000' was forbidden. Those that got to 14000' had to be feeling the effects. 

After regular P-39s arrived they seem to have handled themselves admirably. Interesting how on some missions they were tasked with bombing and then climbing up to become their own escort. More efficient than having SBDs for bombing and Wildcats for escort.

No Wildcat in WWII could match the speed of any P-39 at any altitude and were 30-40mph slower at all altitudes. Standard P-39 could match the Wildcat in climb and outclimb with later models (M, N, Q) substantially outclimbing it. Wildcats were effective against the Japanese because of superior pilot quality of the Navy/Marine aviators.


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## MIflyer (Mar 25, 2018)

The F4F-4 had a two stage supercharger and its success as an interceptor owes much to that fact. Right about the altitude where a P-39 hit the wall the F4F literally kicked into high gear. Its maneverabilty was quite good as well.

Now why did the Wildcat have a two stage supercharger? I was going to write my next article on that and was doing research at the Smithsonian Air and Space Museum before Wings/Airpower folded. The answer comes from four events:

1. Billy Mitchell, 1921.
2. YB-17 interception of the liner Roma
3. Y1B-17
4. USN Panics

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## MIflyer (Mar 25, 2018)

Just read a couple of accounts of the P-39 in a book I bought recently, “Flying American Combat Aircraft of WWII.”

One account was from the Med, the 35th Fighter Squadron; I found this especially interesting for I have read very little of any P-39 use in Europe. The other is from Guadalcanal and that’s always interesting. Here is a summary:

Med and the ‘Canal: Never had it tumble but it stalled almost without warning and many crashes resulted from pilots getting too slow on final, especially in training. Some pilots did say they tumbled and it took them 15,000 ft to recover. A stall in the traffic pattern probably meant it was all over. It was very easy to land if you were careful about airspeed.

Med and the ‘Canal: Very sensitive on the controls, and better than the P-40 and P-47 in that respect but it also offered a danger to novice pilots

The ‘Canal: Fastest climbing US fighter from sea level to 12,000 ft but you hit a brick wall at 12,000 ft and was virtually worthless above 15,000 ft.

Med and the ‘Canal: Range was too much short. At the ‘Canal they were often escorting troopships and had to remain in that vicinity, so hit and run tactics were not an option. On returning to base on the “Canal they usually had fuel enough to land, period, not enough to go around. On one case the P-39’s were returning from a patrol and had just enough fuel to land, while overhead P-40’s were dogfighting with Zeros. One P-40 had a Zero on his tail he could not shake, at about 2000 ft and was yelling for help. While the P-39’s were coming into land the P-40 with the Zero about 40 ft behind were at about a 90 degree angle to them. One of the P-39’s made a sharp bank and used a 70 degree deflection shot to blow away the Zero, then rolled back onto final and landed.

Med and the ‘Canal: Very easy to taxi but there were serious overheating problems on the ground. P-39’s had to take off either first or last when mixed in with other aircraft, usually last to conserve their limited fuel.

Med and the ‘Canal: The 37MM was great for strafing and a single well placed shot could clean the troop out of a barge or destroy an enemy automobile.

The Canal: The 37MM was worthless in air combat due to the different trajectory from the machine guns. He never even fired the 37MM in air combat.

Med and the ‘Canal: Great airplane for bellying in, ditching, or bailing out of.

The ‘Canal: Maneuverability was nil at 12,000 to 15,000 ft and poor below that.

Med: Had relatively poor turning characteristics.

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## P-39 Expert (Mar 25, 2018)

MIflyer said:


> The F4F-4 had a two stage supercharger and its success as an interceptor owes much to that fact. Right about the altitude where a P-39 hit the wall the F4F literally kicked into high gear. Its maneverabilty was quite good as well.
> 
> Now why did the Wildcat have a two stage supercharger? I was going to write my next article on that and was doing research at the Smithsonian Air and Space Museum before Wings/Airpower folded. The answer comes from four events:
> 
> ...


It did have a two stage supercharger, the first in any production combat plane. Didn't seem to be as efficient as others. Look at the performance graphs, I stand by my statement about the P-39 being faster at all altitudes.

Regarding the P-40, it had the same engine as the P-39 and weighed 750# more (8400-7650). There is no physical way possible for the P-40 to have the same performance in climb or level speed. Physically impossible. Merlin P-40 was faster than the Allison P-40, but no faster then the P-39.


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## P-39 Expert (Mar 25, 2018)

MIflyer said:


> Just read a couple of accounts of the P-39 in a book I bought recently, “Flying American Combat Aircraft of WWII.”
> 
> One account was from the Med, the 35th Fighter Squadron; I found this especially interesting for I have read very little of any P-39 use in Europe. The other is from Guadalcanal and that’s always interesting. Here is a summary:
> 
> ...


P-39 would overheat if kept on the ground. Not as big a problem as you think, since the P-39 taxi was with full forward vision and you just drove it like a car. After starting the engine you just did your preflight checks on the way to the end of the runway. Once you got there, mag and prop check and then just take off. The tail draggers couldn't see straight ahead over the engine so they had to serpentine everywhere or have a guy sit on the wing. 

The 37mm cannon was better than most give it credit for. Yeager said the 37mm "had some trajectory" and was like "throwing a grapefruit". But the trajectory was not that bad inside the effective air to air gunnery range. Inside of about 400 yards the difference in the drop of the .50 caliber MGs and the 37mm cannon was negligible so you could fire all three at once. One strike from the 37mm cannon was usually deadly for anything it hit. Outside of 400 yards you were not likely to hit anything anyway. The jamming problem was largely solved from the L model on with the little exhaust vents just ahead of the gun bay doors. The gun was an "open breach" that would freeze at higher altitudes. Those little vents exhausted heated air ducted up from the coolant radiator through the cockpit effectively heating the gun bay to near cockpit temperature. Russians considered the 37mm more reliable than the 20mm in the P-400 and D-1. For all the P-39 faults it did have excellent cockpit climate control.


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## pbehn (Mar 25, 2018)

P-39 Expert said:


> Regarding the P-40, it had the same engine as the P-39 and weighed 750# more (8400-7650). There is no physical way possible for the P-40 to have the same performance in climb or level speed. Physically impossible. Merlin P-40 was faster than the Allison P-40, but no faster then the P-39.


This may be true, that the P39 was faster than the P40 but it is an aerodynamic issue not weight, the P51B was faster by about 30MPH than a Spitfire with the same engine and heavier too. How did the P51 and P39 compare with identical engines?


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## pbehn (Mar 25, 2018)

P-39 Expert said:


> No Wildcat in WWII could match the speed of any P-39 at any altitude and were 30-40mph slower at all altitudes. Standard P-39 could match the Wildcat in climb and outclimb with later models (M, N, Q) substantially outclimbing it. Wildcats were effective against the Japanese because of superior pilot quality of the Navy/Marine aviators.


The Wildcat was a carrier capable fighter which made its first "kill" on Christmas day 1940 over Scapa Flow, it was very robust, easy to fly and had excellent range, it remained in service with the USA and UK navies until the end of the war because although the Hellcat was better in most respects it wasn't better at all of them, the Hellcat being introduced in 1943.


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## michaelmaltby (Mar 25, 2018)

".... How did the P51 and P39 compare with identical engines?"
The Alison-powered P-51 was more successful ... cheap to build. easy to maintain, no bad habits except high (laminar flow) landing speed and the short comings associated with tail draggers AC's, IMO.


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## pbehn (Mar 25, 2018)

michaelmaltby said:


> ".... How did the P51 and P39 compare with identical engines?"
> The Alison-powered P-51 was more successful ... cheap to build. easy to maintain, no bad habits except high (laminar flow) landing speed and the short comings associated with tail draggers AC's, IMO.


Chuck Yaeger preferred the P-51.


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## Peter Gunn (Mar 25, 2018)

P-39 Expert said:


> *SNIP*
> 
> Regarding the fuselage tank, _*I read a pilot's comments that it was a court martial offense to use the fuselage tank before exhausting the drop tanks.*_ Any usage of the fuselage tank prior to exhausting the drop tanks meant a loss of range if the drop tanks had to be dropped before they were empty. Use your fuselage tank before your drop tanks and you have one third less internal fuel after they are dropped.
> 
> *SNIP*


Say what now? I believe you read wrong.

Also the Luftwaffe was beaten by June '44? Interesting. They were certainly in no position to challenge Overlord, but beaten? Hardly likely.


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## pbehn (Mar 25, 2018)

Shortround6 said:


> Many evaluations of the P-39 contradict that statement about stalls. and speaking about control reversal. On the P-39 with wing guns and full ammo loads the proper spin recovery use of ailerons was opposite the proper use of ailerons without or with light load of ammo.
> .


I find this intriguing, my "in" is 100% "trigued"

If a full ammunition load requires action "A" in a stall, AND no ammunition requires action "B" in a stall, AND action "A" and action "B" are completely opposite. There must be a point of ammunition weight where the conditions cross over. My question is, at this point do both actions "A" and "B" both work equally well or is the pilot completely screwed with no chance?


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## tomo pauk (Mar 25, 2018)

P-39 Expert said:


> Regarding the P-40, it had the same engine as the P-39 and weighed 750# more (8400-7650). There is no physical way possible for the P-40 to have the same performance in climb or level speed. Physically impossible. Merlin P-40 was faster than the Allison P-40, but no faster then the P-39.



P-40F (1st delivered in January 1942) was sligtly faster than the P-39D, K or L on most of altitudes, it provided better range/radius, armament suite was better, range was longer, service ceiling was higher.

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## Elmas (Mar 25, 2018)

Pierre Clostermann's memories are certainly controversial, but he states that, in May 1945, a few hours before Doenitz called to surrender, his unit lost six of the twelve Tempests that strafed a German airport. From memory, I'm not at home now.

The Nazi Titanic

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## MIflyer (Mar 25, 2018)

"But probably the tricicle undercarriage, that required this markedly nose-up attitude was one of the reasons responsible for the bad handling of P-39 at low speeds."

You don't go to a nose high attitude until you flare, and that is a few feet above the runway. You are trying to stall it at that point.


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## Elmas (Mar 25, 2018)

MIflyer said:


> "But probably the tricicle undercarriage, that required this markedly nose-up attitude was one of the reasons responsible for the bad handling of P-39 at low speeds."
> 
> You don't go to a nose high attitude until you flare, and that is a few feet above the runway. You are trying to stall it at that point.



Of course. The problem is if how many are "a few". That measure could be different between and experienced and unexperienced pilot.


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## varsity07840 (Mar 25, 2018)

P-39 Expert said:


> Keep in mind a few salient points, first these were older P-39s with the lower rated engine and way too much weight. With the ever present drop tank their combat ceiling (altitude above which any plane will climb at only 1000fpm or less) was about 18000'. The Bettys came in at between 18000' and 22000' with their Zero escort at about 24000'. These older P-39s (D,F,K,L) could have easily been modified in the field by simply removing the 4 x .30 wing guns along with their mounts, chargers heaters and ammunition boxes (and of course the ammo itself which was the heaviest component) and these planes would climb with the P-38s that, by the way, were not even available until very late in the year. And those Jap raids were frequently intercepted by those P-39s, no radar and extra weight included.
> 
> Second, the Japanese pilots were among the best in the world being Navy carrier pilots with experience in China. Our kids at PM were all fresh out of flying school with no experience except for Buzz Wagner who supposedly got off the ground at Pearl Harbor. Most experts consider pilot quality to be more important than plane quality all other factors being equal. Theirs were much much better at this point in the war.
> 
> ...



Wagner was not at Pearl Harbor. He was the commanding officer of the 17th Pursuit Squadron in the Philippines before being evacuated to Australia.


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## pbehn (Mar 25, 2018)

MIflyer said:


> "But probably the tricicle undercarriage, that required this markedly nose-up attitude was one of the reasons responsible for the bad handling of P-39 at low speeds."
> 
> You don't go to a nose high attitude until you flare, and that is a few feet above the runway. You are trying to stall it at that point.


From what I have read on this thread you are desperately trying to remember how many rounds of ammunition are still in the nose at that point.


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## wuzak (Mar 25, 2018)

To, summarise, the P-39N introduced in 1943 gave performance similar to the Spitfire V of 1941, in some areas better and others worse, and inferior to the Spitfire IX in 1942?

Many P-39Ns were delivered with less fuel capacity than the Spitfire V, though some had more and others could be fitted with extra tankage in the field, but how many were?

Oh, the P-39 drove like a limousine on the ground, which must have been comforting to the pilots struggling to reach an altitude where they could engage the enemy aircraft sent to bomb the shit out of the airfield.

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## Elmas (Mar 25, 2018)

U-2, the trickiest plane to land, has a "chase-car" with a another U-2 Pilot inside, telling his Colleague when to stall the plane.

Up close with the U-2 Dragon Lady

And inside a U-2 cockpit just _la crème de la crème_ of the Pilots are admitted...

At his first flight with a Typhoon, Clostermann nearly destroyed the plane as he tought that the big wings of the Tiffy had a lot of lift...


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## varsity07840 (Mar 25, 2018)

Besides the quality of their pilots, the F4Fs were effective because their 2 stage 2 speed engines allowed them to get to the altitudes necessary to engage Japanese bombers.

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## pbehn (Mar 25, 2018)

Elmas said:


> At the first flight with a Typhoon, Clostermann nearly destroyed the plane as he tought that the big wings of the Tiffy had a lot of lift...



You cannot see lift, you must be told in some way that you are close to being out of it, Clostermann spent a long time on Spitfires.


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## swampyankee (Mar 25, 2018)

XBe02Drvr said:


> Ever see an airshow acro plane do a Lomcevak? You just described it to a tee. I'm told the word is Czech and is (mis)translated as "crazy mixed-up headache". Having ridden through a couple in a Pitts, I can vouch for the accuracy of the term. The ultimate sensation of hostageness. You ever notice that nobody does them at low altitude at airshows (or anywhere else)? Takes a few seconds to uncage your eyeballs afterward.
> Days of future passed! That sort of behaviour, an inverted oscillatory spin with the nose whipsawing up and down and the rotation rate and bank angle fluctuating randomly and not synchronously, became pretty common in the jet age. IIRC, spin in the F4J was described as: "random oscillations around all three axis with buffeting, a high rate of descent, and probable dual flameout". IIRC, recovery was: "average fluctuations of AOA needle to determine if positive or negative stall, average turn needle to determine direction of rotation, apply appropriate stick and rudder for type of spin. Deploy RAT if flameout occurs. If control not regained passing 10,000 AGL, EJECT."
> I knew a crew who missed that last directive by a thousand feet, stopping rotation by 9,000 and still augered in. They managed to achieve a level pitch attitude passing through 1,000, but at some phenomenal G load and an impossible sink rate, and the plane snapped inverted in the midst of the ejection sequence.
> Cheers,
> Wes


A friend got to fly an F-106 simulator, and got the plane to stall at 35,000 AGL. The instructor said he did well; it only took 50,000 ft to recover. 

Many aircraft had horrifyingly bad stall-spin characteristics, even by the standards of combat aircraft. With the reduced training frequently inherent in rapid military expansions, predictable behavior near stall is crucial, unless one wants to lose more pilots to accidents than combat.

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## swampyankee (Mar 25, 2018)

Elmas said:


> _View: https://youtu.be/hLeYWkx2Jlg_
> 
> 
> If you watch at this video the Instructor do insist that landing in P-39 must be done on the main undercarriage, keeping the nose well up to the end ( from 33'.00 circa). As all airplanes with tricycle landing gear must do, of course.
> ...





In general, pilots report that tricycle gear aircraft are much easier to land. I would be very surprised were the P-39 was an exception.


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## P-39 Expert (Mar 25, 2018)

varsity07840 said:


> Wagner was not at Pearl Harbor. He was the commanding officer of the 17th Pursuit Squadron in the Philippines before being evacuated to Australia.


Thank you. But he was at Moresby with the first two squadrons.


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## MIflyer (Mar 25, 2018)

"The problem is if how many are "a few"."

Yes, that's among the key things to learn. Making a perfect landing 15 ft off the runway is unpleasant. Making a landing which was meant to be 15 ft below the runway is even less pleasant. With over 700 hours in my personal airplane I can't say all of them are either perfect or even exactly the same. 

"In general, pilots report that tricycle gear aircraft are much easier to land."

Yes, I have flown both and trikes are easier to land. Where they are really easier, though, is if you land and then give it the power to do a touch and go.

As for the comparison to a Spitfire V, I believe a Clipped and Cropped Spit V would blow away a P-39 at low altitude.


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## P-39 Expert (Mar 25, 2018)

wuzak said:


> To, summarise, the P-39N introduced in 1943 gave performance similar to the Spitfire V of 1941, in some areas better and others worse, and inferior to the Spitfire IX in 1942?
> 
> Many P-39Ns were delivered with less fuel capacity than the Spitfire V, though some had more and others could be fitted with extra tankage in the field, but how many were?
> 
> Oh, the P-39 drove like a limousine on the ground, which must have been comforting to the pilots struggling to reach an altitude where they could engage the enemy aircraft sent to bomb the shit out of the airfield.


P-39N in production between December '42 and April '44 was faster and climbed faster at all altitudes than the Spitfire V. The Spitfire IX was superior in speed and climb to the P-39N and entered full series production about the same time. The comparison I'm making is between the P-39N and the German fighters. Everyone else seems to have me in an argument over the Spitfire.

Regarding fuel, the P-39N carried 120 internal and the Spitfire carried 100 US gallons. During N production the Russians requested that we start deleting the wing guns from the factory and reducing internal fuel capacity. The N and Q gradually reduced capacity to as little as 86 gallons. The wing guns stayed until the late Q models. Apparently less fuel and no wing armament worked for them.


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## buffnut453 (Mar 25, 2018)

P-39 Expert said:


> P-39N in production between December '42 and April '44 was faster and climbed faster at all altitudes than the Spitfire V. The Spitfire IX was superior in speed and climb to the P-39N and entered full series production about the same time. The comparison I'm making is between the P-39N and the German fighters. Everyone else seems to have me in an argument over the Spitfire.



While you're focusing on direct comparisons with German fighters, I think others are extending the discussion to the next logical step. Even if the P-39N is better than German fighters in early 1943, is it sufficiently better to warrant the Allies changing from the fighters that were actually operated to the P-39N? The consensus answer seems to be that, no, the P-39N didn't offer enough of an advantage over contemporary German fighters to merit the change, whereas other types like the P-51 and Spitfire had more "grow room" to allow them to keep up with German aeronautical advantages. 




P-39 Expert said:


> Regarding fuel, the P-39N carried 120 internal and the Spitfire carried 100 US gallons. During N production the Russians requested that we start deleting the wing guns from the factory and reducing internal fuel capacity. The N and Q gradually reduced capacity to as little as 86 gallons. The wing guns stayed until the late Q models. Apparently less fuel and no wing armament worked for them.



Reducing fuel works when you're in a land war where you can establish airfields near the front line. It won't work so well for western Europe in 1943 where airfields were stuck in the UK and hence the only way to extend reach into the enemy's back yard was via longer-range airframes.

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## pbehn (Mar 25, 2018)

P-39 Expert said:


> P-39N in production between December '42 and April '44 was faster and climbed faster at all altitudes than the Spitfire V. The Spitfire IX was superior in speed and climb to the P-39N and entered full series production about the same time. The comparison I'm making is between the P-39N and the German fighters. Everyone else seems to have me in an argument over the Spitfire.
> 
> QUOTE] .


This is the crux of the whole discussion and what is slowly driving me nutz. The P 39N was in Production in December 1942 and the Spitfire mk IX was in squadron service during the previous summer. Would you replace Spitfire Mk Vs with P39-Ns or Mk IXs? and it isn't just a question of speed and rate of climb, it is also a question of serviceability, safety and loss rates. The P-39 was dangerous, relative to all other US fighters to its own pilots, even in training, I posted the stats and you made no comment. Using semantic tricks like "full series production" is not impressive, the fact is that the Mk IX was in production in mid 1942, there is a limit to how quickly any new type can be introduced and in terms of logistics switching all factories over when you don't have all the parts just means losing months of production. The Mk V may have been outclassed in 1942 but it was better than nothing.

Before the war started Hawkers were allowed to export Hurricanes because they could produce them faster than the RAF could train all their staff to use them. By 1940 production had doubled and each hurricane just got sent where it was needed because by that time everyone knew what it was, only pilots to fly them was an issue.

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## XBe02Drvr (Mar 25, 2018)

Elmas said:


> U-2, the trickiest plane to land, has a "chase-car" with a another U-2 Pilot inside, telling his Colleague when to stall the plane.


NOT telling him when to stall the plane!! Telling him how high his forward "bicycle" main gear wheel is off the ground. The object here is to "roll it on" so the plane touches with zero sink rate and is flying level in ground effect with its forward main wheel lightly touching the runway as the wheel spins up. Then as the plane gradually slows the pilot can ease the nose upward until the rear main lightly rolls on. THERE IS NO STALL INVOLVED. It's like a taildragger pilot making a wheel landing, or a floatplane touching down.
If either of the U2s mains touches with any appreciable sink rate, the shock strut rebound and resulting AOA change of that monster wing WILL set up a porpoising/PIO sequence all the way to the smoking crater at the end of the runway.
Cheers,
Wes


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## XBe02Drvr (Mar 25, 2018)

swampyankee said:


> In general, pilots report that tricycle gear aircraft are much easier to land. I would be very surprised were the P-39 was an exception.


The P-39 quite likely was that exception. Ever try to transition a Cessna 180 pilot into a Mooney 231? Probably quite similar to AT-6 into P-39. Here's why. (drgondog, jump in if I'm wrong). The C-180 (and the AT-6) is a fairly powerful, but somewhat draggy tail dragger with predictable balanced control response and typical taildragger landing behaviour. The Mooney (and the P-39) is sleek and slippery with a nose-high tricycle gear, controls that are much lighter and more sensitive in pitch than in the other axis, a higher approach speed than other similar aircraft, and a low wing with flaps set deep in ground effect in touchdown configuration.
Can you spell FLOATER? That poor Cessna pilot sure learned how to spell that day. Fortunately we had 8700 feet of asphalt to play with. The average WWII fighter strip didn't.
The poor Mooney salesman was convinced we were going to wreck his demonstrator. Instead the Cessna guy bought it from him, and everybody lived happily ever after.
Cheers,
Wes

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## parsifal (Mar 25, 2018)

_Third,we didn't have effective radar until after August 1942 so the raids were largely unopposed. These raids could come at any time from Lae only 200 miles away and their Zero escort didn't even need drop tanks. Later at Guadalcanal the Jap raids came from much farther away so they almost always came at noon making them very predictable. 
_
Wrong. There was radar from March 1942, but it was not very effective radar until much much later, probably mid 1943 at the earliest.


_ Fourth, we were tremendously outnumbered. Japanese had functioning bases all along the NG coast backed up by their huge base at Rabaul. Their maintenance facilities were functional. Our maintenance/supply early on at Moresby consisted mainly of pulling a functional part off of one of the many wrecks at the end of the runway. By the time the P-38 appeared in the theater attrition at Moresby, Coral Sea, Midway and the first three months of Guadalcanal had seriously reduced the Japanese Navy pilot quality and our pilots were much better trained than in April '42._

Wrong. According to the translated "Japanese army Operations In the South Pacific 1942-3" there 43 land based planes under 17 Area Army based at rabaul and 14 flying boats. 20 of the land based a/c were fighters, of which 9 were detached to Lae. . By 1 August, on the eve of Watchtower these deployments had increased tp 63 land based and 13 flying boats. There was one bomber base, at Rabaul, and an auxiliary fighter strip at Lae. Airfileds were being constructed (by 1 august) at Gona, buin and Guadacanal. These strtength reports included IJN attachments to the 17Army.

_ The fact that the green outnumbered American kids kept the Japanese out of Moresby was a real tribute to their courage and tenacity. Lighter equipped P-39s and functioning radar would have made the job a lot easier. The later arriving Lightnings benefited from better pilots, declining Jap pilots, functioning radar and much more efficient maintenance._

Baloney......

They were not green, and they weren't solely American. in fact the majority of defenders, including air assets were Australian

Stop referring to the Japanese as "Japs', its rude and uncalled for. stop trying to claim credit for the defence of PNG. it isn't yours to claim.

and stop telling gigantic porkies, that would be a great start.

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## XBe02Drvr (Mar 26, 2018)

parsifal said:


> They were not green, and they weren't solely American. in fact the majority of defenders, including air assets were Australian


It wasn't the "green young American" P-39 pilots that kept the IJA out of Port Moresby, it was the not-so-green, but even younger Aussie Marines fighting an outnumbered and unsupported desperate defensive action against the Japanese in the stinking jungles of the Owen Stanley Mountains. If the Japanese had broken through that, all the skimpy assets available in Oz at the time could not have kept them out of Port Moresby. Let's not be patting ourselves too much on the back, here. Grunts on the ground carried the day.
Cheers,
Wes

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## parsifal (Mar 26, 2018)

The US marines fighting on Guadacanal is their own story known reasonably well to most Americans. The story of the fight across the Owen Stanley ranges is not a fight known well to the US.

The story of this fight is invariably an account of the 39th Battalion. A militia formation, it was known as a 'choco" outfit......chocolate soldiers that would melt at the first sign of any heat being applied to them. they were to prove this label utterly without foundation . 809 went into action, 25 came out at the end, with the formation still in the front line leading the ferocious assaults on the Japanese in the buna-gona battles.

Its story can be found at the AWM research site:

"Following Japan's sudden entry into the Second World War, a new 39th was raised as part of the 30th Brigade to garrison Port Moresby. The 39th joined the 49th Infantry Battalion, already in Moresby, and the 53rd Infantry Battalion, which had been quickly formed in Sydney. The 39th arrived in Moresby at the start of January 1942, with little military training.

The 39th was initially used for garrison duties and working parties. In June it was ordered to proceed up the Kokoda Trail to block any possible Japanese overland advance. The 39th B Company and troops from the Papuan Infantry Battalion (PIB) reached Kokoda on 15 July. Japanese forces landed at Gona, on the north coast of Papua, a week later and quickly moved inland.

The first clash occurred at Awala on 23 July and the Australians fell back to Kokoda. On 29 July the Japanese attacked Kokoda and the Australians were forced to withdrawal to Deniki early the next morning. On 8 August the 39th launched a counter-attack at Kokoda but, outnumbered and short of ammunition, fell back to Deniki after two days of fighting. The Australians eventually managed to repeal the ongoing Japanese attack and on 14 August the 39th and PIB fell back to Isurava.

Fighting ceased for almost two weeks. During this time the 39th was joined by the 53rd and the headquarters of the 30th Brigade. On 23 August the 2/14th and 2/16th Battalions from the 7th Division 21st Brigade also reached the area. The Japanese resumed their advance on 26 August. Despite hard fighting the Australians were forced back to Eora Creek on 30 August, Templeton's Crossing on 2 September, and Efogi three days later.

Exhausted, the 39th was relieved and sent down the track to Koitaki to rest. The 7th Division 25th Brigade (comprising the 3rd Infantry Battalion and the 2/1st Pioneer Battalion) came in to reinforce the Australian effort. Bitter fighting ensued and the Australians withdrew to Imita Ridge on 17 September. However, the Japanese had reached their limit and on 24 September began to withdrawal. The Australians reoccupied Kokoda on 2 November.

Meanwhile, after a month at Koitaki, the 39th returned to Port Moresby in mid-October, where it prepared defensive positions at Pyramid Point. The interlude from fighting was brief.

Having pushed the Japanese back across the Kokoda Trail, the 16th and 25th Brigades and two inexperienced American regiments were engaged in the "battle of the beachheads" at Buna, Gona, and Sanananda. The Japanese positions were well-prepared and heavily defended. At the end of November the 30th Brigade was flown across the Owen Stanley's to reinforce the attack. The 39th became attached to the 21st Brigade.

The 21st Brigade captured Gona village on 1 December and the Japanese withdrew to Gona Mission. The Australians advanced on the Mission on 6 December but were stopped by the Japanese. The 39th D Company was "literally shot to pieces". The combined fighting strength of the 21st Brigade was now down to 755 men, of whom 403 were from the 39th. Nonetheless, on 8 December the 39th attacked again and captured half of the Japanese defences by nightfall. Gona Mission was captured the next day and on 18 December the 39th took the last Japanese position at the creek west of Gona.

Fierce fighting continued further along the coast and on 21 December the 21st Brigade and 39th moved to the Sanananda Track. The next morning the 39th moved into a forward position called Huggins' Road Block. The 39th defended the area and attacked nearby Japanese positions. In the New Year it withdrew to Soputa and returned to the 30th Brigade.

The 39th had suffered heavily. When the battalion was flown to Moresby on 25 January it mustered a mere handful of soldiers - 7 officers and 25 men. It rested at Morseby and gradually gained strength as men returned from hospital".

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## DarrenW (Mar 26, 2018)

P-39 Expert said:


> Hard to believe the N had a higher ceiling than Corsairs and Hellcats.



That's because it really didn't. In most reference books and other well respected sources the F6F-3 will show a reported service ceiling anywhere between 37,300 - 38,400 feet, and I've seen Navy reports showing as high as 38,600 feet in military power with an overload weight of 12,680lbs. The report you are referencing shows a particular P-39N (s/n 42-4400) at 7,274lbs with a ceiling of 38,500 feet. How is that any kind of real advantage? Plus, besides the occasional airplane doing reconnaissance work, who the heck was fighting at 38,000 feet anyway during WWII????



P-39 Expert said:


> Since the Hellcat was considered the unquestioned master of the Japanese planes, the P-39N should have been able to handle Zeros like the Hellcat. Zeros were 330-340mph planes, Hellcats and P-39Ns were 40-50mph faster at all altitudes.



The Airacobra couldn't "handle the Zeros like the Hellcat" because speed isn't the only ingredient that makes an airplane a good fighting machine.The Hellcat had excellent handling and dogfighting capabilities, the Airacobra didn't. The Hellcat was immensely strong and could take a beating and still get the job done and bring the pilot home alive. The Airacobra wasn't. The Hellcat had long-range capability which allowed it to seek out and destroy the enemy wherever it may be. The Airacobra didn't. Lastly, the Hellcat never had to be stripped of guns, armor, or gasoline just to make it faster, climb better, maneuver quicker, or fly higher. The Airacobra DID!!!!!

Look, the Airacobra was a sleek little ship and did well on the post-war race circuit but it wasn't a truly war winning aircraft like you are trying to make it out to be, in any variant or any guise. I respect the men who flew her and that they were able to achieve some success because the odds were definitely stacked against them. And I really didn't want to pile on even more negative comments about your pet airplane but you left me no choice. 

You are definitely a well-educated and learned man who knows a sh--t ton about aviation history. And I happen to like the Airacobra, all it's shortcomings notwithstanding. I have learned great deal about it from this thread and I thank you for it. Problem is, I'm left feeling that the Airacobra was even more of an abysmal failure than I believed it to be in the first place! Just please refrain from the wild-ass comments regarding it's supposed virtues and try concentrating on the proven characteristics of the machine, both the good and the bad. I think that approach might help sway people to your way of thinking, rather than saying the same unsubstantiated fact over and over hoping that it will eventually stick.

But that's just my opinion and one of many here on this forum....

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## parsifal (Mar 26, 2018)

The 8 PG performed an important function for a 1.5 month period, but it is more than a stretch to claim it as responsible for the successful defence of Moresby, much less the defeat of the Japanese at Milne. in the case of the battle across the Owen stanleys, the battle did not begin until 23 July, at which time there were no flying elements of the 8FG left in NG at the time. They did return in September , and may have provided some CAS at that time, but were certainly not that successful at it. Hudon and Wirraway formations backed up by some US B-26 and A-20 formations were the main ground support components. Without a doubt however, the mainstay of airpower supporting in a decisive way the ground fighting were the efforts of 33 sqn (transport). An otherwise disheartening menagerie of various a/c types, this units, more than all the other airborne assets combined provided the necessary logistic support needed to keep the fight going.

In Milne bay, US support was unimportant. 75 and 76 sqns RAAF along with a Hudson sqn (also RAAF unit ID I forget right now) provided the air defence and air support needed to defeat this rather poorly thought out Japanese attack.

but I object to the misrepresentation of the 8FG as the saviours of the pauan campaign. they were a part of it, and in some degree successful, but they were in no way more critical than at least half a dozen other heroic efforts, some Australian, some American.

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## XBe02Drvr (Mar 26, 2018)

parsifal said:


> The story of the fight across the Owen Stanley ranges is not a fight known well to the US.


Nope, it was your ballgame, in your front yard, with all the players from your teams, and all the heroes were yours. RIP. The rest of the free world thanks you.
Cheers,
Wes

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## Ascent (Mar 26, 2018)

Not this forum obviously, most people here have studied their history, but I get the impression that a lot of American people don't realise they weren't the only ones fighting the Japanese.

Would that be right?

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## DarrenW (Mar 26, 2018)

Ascent said:


> Not this forum obviously, most people here have studied their history, but I get the impression that a lot of American people don't realise they weren't the only ones fighting the Japanese.
> 
> Would that be right?



Yes, and I would go as far as to say that they know very little if any of the roll America played there as well. To them, Imperial Japan was basically a "victim" of American foreign policy and that they were forced to attack the western powers as they had no other recourse but to do so. Utter nonsense.

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## pbehn (Mar 26, 2018)

DarrenW said:


> That's because it really didn't. In most reference books and other well respected sources the F6F-3 will show a reported service ceiling anywhere between 37,300 - 38,400 feet, and I've seen Navy reports showing as high as 38,600 feet in military power (52" Hg) with an overload weight of 12,680lbs. The report you are referencing shows a particular P-39N (s/n 42-4400) at 7,300lbs with a ceiling of 38,500 feet. How is that any kind of real advantage? Plus, besides the occasional airplane doing reconnaissance work, who the heck was fighting at 38,000 feet anyway during WWII????



From what I have read elsewhere on this forum the service ceiling isn't the maximum height a plane can reach, it must still be able to do something apart from fly in a straight line. A climb rate of 100ft/min for example, having some fuel and guns on board is also looked at favourably.

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## wuzak (Mar 26, 2018)

P-39 Expert said:


> P-39N in production between December '42 and April '44 was faster and climbed faster at all altitudes than the Spitfire V. The Spitfire IX was superior in speed and climb to the P-39N and entered full series production about the same time. The comparison I'm making is between the P-39N and the German fighters. Everyone else seems to have me in an argument over the Spitfire.



Not by much.

Considering the Spitfire V was in production in early 1941, and in service very shortly after.





P-39 Expert said:


> Regarding fuel, the P-39N carried 120 internal and the Spitfire carried 100 US gallons. During N production the Russians requested that we start deleting the wing guns from the factory and reducing internal fuel capacity. The N and Q gradually reduced capacity to as little as 86 gallons. The wing guns stayed until the late Q models. Apparently less fuel and no wing armament worked for them.



It would seem that not all had 120USG fuel fitted from the factory. In fact, most didn't.



> After completion of the first 166 P-39Ns, the USAAF requested that four fuel cells be removed in order to reduce the internal fuel capacity from 120 to 87 US gallons, and so to reduce the maximum permissible gross weight from 9100 lbs to 8750 lbs. This kept weight down, but unfortunately it also restricted range. Therefore, kits were provided that allowed the four fuel cells to be refitted in the field.


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## XBe02Drvr (Mar 26, 2018)

DarrenW said:


> Yes, and I would go as far as to say that they know very little if any of the roll America played there as well. To them, Imperial Japan was basically a "victim" of American foreign policy and that they were forced to attack the western powers as they had no other recourse but to do so. Utter nonsense.


Japan was a "victim" of its own compulsion to be a first rate world power despite its lack of domestic natural resources to do so. This put it on an inevitable collision course with those empires who had beaten them to it and were already exploiting pretty much all of the available resources.
I find it ironic that the US, arguably the least "imperial" of the major powers, would be the first to step on the tripwire and set off the explosion. If Hitler hadn't had Europe tied up in knots it might have been someone else that set it off. Britain, France, and the Netherlands all had empires in the area.
Cheers,
Wes

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## pbehn (Mar 26, 2018)

XBe02Drvr said:


> Japan was a "victim" of its own compulsion to be a first rate world power despite its lack of domestic natural resources to do so. This put it on an inevitable collision course with those empires who had beaten them to it and were already exploiting pretty much all of the available resources.
> I find it ironic that the US, arguably the least "imperial" of the major powers, would be the first to step on the tripwire and set off the explosion. If Hitler hadn't had Europe tied up in knots it might have been someone else that set it off. Britain, France, and the Netherlands all had empires in the area.
> Cheers,
> Wes


The UK and USA declared war on Japan within hours of each other because both had been attacked, in addition to Pearl Harbour the Japanese attacked Malaya, Singapore and Hong Kong.

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## swampyankee (Mar 26, 2018)

Ascent said:


> Not this forum obviously, most people here have studied their history, but I get the impression that a lot of American people don't realise they weren't the only ones fighting the Japanese.
> 
> Would that be right?




Quite possibly, even though most textbooks used in secondary schools are consistent in covering the existence of Commonwealth and Chinese forces, they may understate the importance, by concentrating on US areas of interest.


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## P-39 Expert (Mar 26, 2018)

Shortround6 said:


> DO you have ANY evidence that combat weight was at half fuel? You keep repeating but give no proof.
> 
> IN fact we may both be wrong.
> http://www.wwiiaircraftperformance.org/P-39/P-39_Aircraft_Performance_Characteristics.jpg
> ...


Notice that the P-39 is doing 400mph at 16000'? Ever see that in any reference book?

Just asking, how do you get the whole graph to appear in your post? Everytime I try to upload a graph it attaches as a pdf that must be opened. Yours shows up already open. Thanks in advance for your help.


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## wuzak (Mar 26, 2018)

P-39 Expert said:


> Just asking, how do you get the whole graph to appear in your post? Everytime I try to upload a graph it attaches as a pdf that must be opened. Yours shows up already open. Thanks in advance for your help.




Attach a picture, not a pdf file


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## Just Schmidt (Mar 26, 2018)

[QUOTE="

Oh, the P-39 drove like a limousine on the ground, which must have been comforting to the pilots struggling to reach an altitude where they could engage the enemy aircraft sent to bomb the shit out of the airfield.[/QUOTE]

We might be missing something here. The P 39 beats all other contemporary aircraft in its ability to double as a light tank while still on the ground. The trajectory of the 37' even means the nose up attitude is no problem, in fact allowing it to lob in the grenades from above.

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## Shortround6 (Mar 26, 2018)

P-39 Expert said:


> Keep in mind a few salient points, first these were older P-39s with the lower rated engine and way too much weight. With the ever present drop tank their combat ceiling (altitude above which any plane will climb at only 1000fpm or less) was about 18000'. The Bettys came in at between 18000' and 22000' with their Zero escort at about 24000'. These older P-39s (D,F,K,L) could have easily been modified in the field by simply removing the 4 x .30 wing guns along with their mounts, chargers heaters and ammunition boxes (and of course the ammo itself which was the heaviest component) and these planes would climb with the P-38s that, by the way, were not even available until very late in the year.



ANd why were they flying with drop tanks?
These older, low powered planes had the full 120 gallon internal capacity. 

The K and L had 1325hp engines for take-off and a near 1600hp in WEP once authorized, it was only good for a few thousand feet (in cool weather) but calling them low powered is a bit of a stretch. However they probably didn't get to the combat theaters in 1942 as they didn't have Star Trek transporter to get them there that you think the P-39N had. 

I would also note that many of the performance tests are done with 262lbs of ammo. This is also the weight of ammo listed in the some of pilots manual. This TOTAL weight of ammo for the 37mm, the .50 cal guns and .30 cal guns. For the the .30s it is 300rpg, not the often listed 1000rpg max. So book and test performance figures are already using 168lbs (aprox.) less ammo than max. The guns are worth 99lbs and the remaining ammo is 72lbs. 
Nobody held guns to the heads of the pilots in the combat areas and forced them to fly with full ammo boxes, especially when the the 300rpg load was considered "normal" and the 1000rpg load was considered overload or "alternative loading".

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## MIflyer (Mar 26, 2018)

I got interested in the Battle of the Coral Sea and read a few books on it; there is not that much around. Then I read the Osprey book on P-39's and something popped out at me.

When the IJN headed into battle, the objective being the invasion of Port Moresby, they requested that seaplane units in the area provide recon support. The response from those units was that they could not help.

A few days before the battle Buzz Wagner led a force of P-39's to attack Japanese seaplane bases along the coast of NG. This resulted in a huge furball that led to the loss of some P-39's as well as a like number of Zeros. I doubt it was even a coordinated attack in terms of overall strategy, but the P-39's contributed to the Battle of the Coral Sea.

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## Elmas (Mar 26, 2018)

Just Schmidt said:


> [QUOTE="
> 
> Oh, the P-39 drove like a limousine on the ground, which must have been comforting to the pilots struggling to reach an altitude where they could engage the enemy aircraft sent to bomb the shit out of the airfield.



We might be missing something here. The P 39 beats all other contemporary aircraft in its ability to double as a light tank while still on the ground. The trajectory of the 37' even means the nose up attitude is no problem, in fact allowing it to lob in the grenades from above.[/QUOTE]

Yes, the only problem is that the main armor ( more than 1400 pounds) is behind, and not in front, of the Pilot...


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## pbehn (Mar 26, 2018)

Attached is a document from a lecture given by A.C. Lovesey in 1945 on the development of the Merlin, there are many graphs and charts, a good read.
http://wwiiaircraftperformance.org/merlin-lovesey.pdf

One shows the increase in power from 1000BHP on 85 Octane fuel to 2600BHP for 15 mins max on 150 oct fuel and water injection.

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## XBe02Drvr (Mar 26, 2018)

No!
Damnit! How do you delete a post you've screwed up??


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## XBe02Drvr (Mar 26, 2018)

Elmas said:


> Yes, the only problem is that the main armor ( more than 1400 pounds) is behind, and not in front, of the Pilot...


No, he's there to shield poor Allison!


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## pbehn (Mar 26, 2018)

XBe02Drvr said:


> No, he's there to shield poor Allison!


I thought he was there to resolve a CoG issue, in lieu of ammunition?


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## XBe02Drvr (Mar 26, 2018)

Good point!
Send all your overweight pilots to the P-39s!


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## Shortround6 (Mar 26, 2018)

P-39 Expert said:


> It did have a two stage supercharger, the first in any production combat plane. Didn't seem to be as efficient as others. Look at the performance graphs, I stand by my statement about the P-39 being faster at all altitudes.
> 
> Regarding the P-40, it had the same engine as the P-39 and weighed 750# more (8400-7650). There is no physical way possible for the P-40 to have the same performance in climb or level speed. Physically impossible. Merlin P-40 was faster than the Allison P-40, but no faster then the P-39.


The F4F was a fat porker of an airplane. It would need a boat load more power to equal the P-39 in speed. However when turning at altitude (over 20,000ft?) it had a lower wing loading due to it's 20% bigger wing, it also had a lower power loading due the engine making 150-200more hp at these higher altitudes. 
P-40F was as fast as a P-39 (pre K) at these altitudes and climbed better, generally 150-200fpm better which doesn't sound like much but when you are at 1500fpm and dropping to 530-300fpm of climb it is actually quite substantial. 
The P-40F was good for several thousand more feet of altitude than than the Aircobras with 8.80 supercharger gears. 
Early P-51s could run away and hide from a P-39 but their climb rate was pathetic at high altitudes using the same basic engine. 

Part of the problem with comparing the two stage R-1830 and a single stage Allison (or Merlin) is that the R-1830 had a cooling problem. 
The Supercharger may well have been inefficient but the R-1830 was restricted to 2550rpm in high gear compared to the 2700rpm it used in neutral or low gear. What combat pilots did in combat I don't know but test figures have to be looked at with that in mind. Air cooled engines, with very few exceptions, do not take kindly to over boosting. 
The P & W supercharger was also designed when the US was using or planning on 100/100 fuel, not 100/125 or 100/130. 
I don't know if the intercooler wasn't big enough or if the cooling fins on the cylinders weren't big enough. 
Please note the early R-1830s, the early Wright 1820s and the Wright R-2600s _NEVER _got WEP ratings.
Later higher powered versions all got extensive modifications.

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## Shortround6 (Mar 26, 2018)

P-39 Expert said:


> The 37mm cannon was better than most give it credit for. Yeager said the 37mm "had some trajectory" and was like "throwing a grapefruit". But the trajectory was not that bad inside the effective air to air gunnery range. Inside of about 400 yards the difference in the drop of the .50 caliber MGs and the 37mm cannon was negligible so you could fire all three at once. One strike from the 37mm cannon was usually deadly for anything it hit. Outside of 400 yards you were not likely to hit anything anyway. .



It is not so much the trajectory as the time of flight requires different amounts of lead, in deflection shooting. Not a big problem if you are shooting almost stationary targets on the ground/water. Or slow moving bombers but against maneuvering fighters? 300mph airplane moves 44ft in 1/10 of a second. 
That and the slow rate of fire made getting hits on fleeting targets very difficult.

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## Shortround6 (Mar 26, 2018)

P-39 Expert said:


> P-39N in production between December '42 and April '44 was faster and climbed faster at all altitudes than the Spitfire V. The Spitfire IX was superior in speed and climb to the P-39N and entered full series production about the same time. The comparison I'm making is between the P-39N and the German fighters. Everyone else seems to have me in an argument over the Spitfire.
> 
> Regarding fuel, the P-39N carried 120 internal and the Spitfire carried 100 US gallons. During N production the Russians requested that we start deleting the wing guns from the factory and reducing internal fuel capacity. The N and Q gradually reduced capacity to as little as 86 gallons. The wing guns stayed until the late Q models. Apparently less fuel and no wing armament worked for them.



excusing the typo of the production date (N production ended in APril '43) 

we are back to repeating ourselves over the P-39s fuel capacity and performance. You don't get both the 120 gal fuel capacity *and* the the high rate of climb. Pick one. 

The argument with the Spitfire is your claim that the P-40N could out climb everything but a Spitfire MK IX and your rather absurd claim that the Spitfire IX wasn't in full production until very late 1942 ( I guess the 4 squadrons at Dieppe in Augs were just using dozens of the prototype MK IXs?).

Against the much older MK V your one test P-39N may be technically ahead, but not by much, if any, at certain altitudes and not enough to make a real difference even at 20-25,000ft. 

There was no _gradually reduced capacity to as little as 86 gallons. _you either had the full suite of 12 fuel cells with 120 gallons or you had the 8 tank suite of 87 gallons. The one gallon difference can be written off as a difference in translations or counting full fuel vs usable fuel. 
Some loadings of the P-39 count 104 gallons of fuel but that is simply not filling the 120 gallon tanks all the way. Early P-51 loadings show 105 gallons of fuel "normal" and 180 gallons as overload. There were never 105 gallon tanks. Same with some P-40 loadings and _many_ navy weight charts. 

Please note that a full set of self-sealing fuel tanks for the P-39 weighed close to 290lbs so taking out the 4 smallest tanks/cells with the worst capacity to weight ratio is going to save a lot more weight than just the 33 gallons of fuel. The self sealing material was heavy. The production of the 87 gallon P-39s coincided with several light weight P-40 projects, culminating in the P-40N. Some of the P-40Ls had done the simple strip routine, yank a pair guns, yank some armor, yank a fuel tank and restrict ammo to the remaining guns. The P-40N was a much more thorough job, although yanking the electric starter and reducing the size of the battery went a little far, blaming the Russians for the reduction in fuel capacity for the P-39s seems a bit unfair unless you have actual documentation? 

Please remember when judging use on the Russian front that most Russian aircraft had pretty poor armament by western standards. The LAGG-3 and Yaks having for the vast majority, a single 20mm and two 12.7mmm guns _at best. _Some deleted the 2nd 12.7mm gun due to weight/performance or supply issues? Some flew with a single 20mm, a single 12.7 and a single 7.62. LA-5s had two 20mm guns firing through the prop, lower cycle rate and ammo capacity was ??? Russian 20mm ammo used a light shell, about 75% the weight of the 20mm Hispano shell and with even less HE per shell. I would note that the Yak-9T with 37mm gun is usually credited with a single 12.7mm machine gun as additional armament.

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## Peter Gunn (Mar 26, 2018)

Well, in the long run, this has been a very entertaining and informative thread. I'm not surprised it's still going on. For my perspective, I've said all I want to say, basically the P-39 wasn't too late, just too useless, especially in the ETO.

Past that, Peace out.

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## FLYBOYJ (Mar 26, 2018)

Gentlemen, some general comments about the P-39's tricycle landing gear and flying characteristics.

First - if the P-39 is operated within the guidelines of the POH, there will be no adverse ground handling characterizes. I'll go on to say (sticking my neck out) that the P-39 was probably easier to handle on landing, roll out and taxi than any other US tail wheel fighter of the war, again when operated properly. 

Although tricycle aircraft, in general handle better on the ground than tail draggers, they can bite you if you do not land on speed and immediately put too much weight on the nose at high speed, in may cases this will cause a NLG shimmy - the B-24 was notorious for this.

As far as the P-39 flying straight and level, all these comments made but no one mentions that in most if not all flight regimes you can trim out any inherent pitch up or down condition, so I take these comments with a grain of salt.


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## pbehn (Mar 26, 2018)

Shortround6 said:


> excusing the typo of the production date (N production ended in APril '43)
> 
> we are back to repeating ourselves over the P-39s fuel capacity and performance. You don't get both the 120 gal fuel capacity *and* the the high rate of climb. Pick one.
> 
> ...


From my point of view and what "P39" seems to miss about the Spitfire MkV being used in the discussion is that for long periods of 1942 the RAF didn't operate the Mk V over France because it was completely outclassed. A slight improvement on it was not what was needed. The Pas de Calais was where the Germans thought the Allies would land, indeed they did at Dieppe, it would always be contested by Germany with their best fighters for as long as they could. The Mk IX was better in many respects to the FW190 but the main point was it could get away.


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## Shortround6 (Mar 26, 2018)

FLYBOYJ said:


> Gentlemen, some general comments about the P-39's tricycle landing gear and flying characteristics.................. so I take these comments with a grain of salt.



The P-39 may very well have been easier to handle on the ground, very surprising if it wasn't, and some tail dragger US fighters had a few unique problems of their own, F4Fs for one. 

However the transition from approach to actual wheels down may have been a problem?
The P-39 having a higher landing speed than most other (P-38 excepted) US 1942 fighters. While not bad compared to P-47s and late P-51s the P-39 may be 10-20mph faster than P-40s or the navy planes. 

Flying any plane on the brink of stall may not be easy and even if a plane is not vicious (rolling on it's back in the blink of eye ) a lack of stall warning can catch the unwary in a difficult position. 
Now for many of these planes add 10% or more to approach speed in Pacific Island ( or North African) locations and add 10-20% to the landing run and the potential for landing accidents goes up. 
Later planes (like P-47s) almost needed bomber airfields but by then the training was better and the landing fields were getting better on average.


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## P-39 Expert (Mar 26, 2018)

Shortround6 said:


> Many evaluations of the P-39 contradict that statement about stalls. and speaking about control reversal. On the P-39 with wing guns and full ammo loads the proper spin recovery use of ailerons was opposite the proper use of ailerons without or with light load of ammo.
> 
> You keep claiming one thing and then back tracking. It is true the P-47 couldn't turn with a 109 but the against the 190 it was not so clear cut. And an Aircobra trying to turn against a 109 may not be happy with the result so why pick on the P-47 to begin with?
> 
> ...


Regarding the March '44 date, most historians say that the Luftwaffe was beaten by that date. Otherwise how did we manage the D-Day invasion the first week of June? I did say the airwar was over by March '44, bad choice of words. The Luftwaffe was beaten by March. To the point that they had to hoard fighters to save them for any big battle they might foresee. They had not been wiped from the face of the earth, but they no longer could put up the most feeble fight without hoarding. They didn't have the fuel to fly them anyway.

I HAVE NEVER BACKTRACKED ON ANYTHING I HAVE POSTED HERE. Yes, acknowledged a few small errors, the airwar was not over in March, I meant to say the Luftwaffe was beaten in March. And the British themselves said the P-400 (one of the heaviest P-39 versions) would easily outturn an Me109E getting on it's tail in three turns.

The P-51 would try to swap ends with a full fuselage tank. Are you going to dispute everything I say? You have so far.


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## FLYBOYJ (Mar 26, 2018)

Shortround6 said:


> *Flying any plane on the brink of stall may not be easy and even if a plane is not vicious (rolling on it's back in the blink of eye ) a lack of stall warning can catch the unwary in a difficult position. *
> Now for many of these planes add 10% or more to approach speed in Pacific Island ( or North African) locations and add 10-20% to the landing run and the potential for landing accidents goes up.
> Later planes (like P-47s) almost needed bomber airfields but by then the training was better and the landing fields were getting better on average.


And much of this is alleviated with proper training. If you "follow the numbers" there should never be an issue. Also be advised that these vicious tendencies may not happen as quickly as you think.


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## P-39 Expert (Mar 26, 2018)

pbehn said:


> www.taphilo.com/history/WWII/Loss-Figures-Aircraft-USA-Training.shtml
> The accident rate per 100,000 hrs training/no of fatalities
> P38 = 139/379
> P39 = 245/395
> ...


Great chart. In 1942 the P-39 had a lower loss rate than the P-40 (351 vs 507). In 1943 the P-39 had a lower loss rate than the P-40 (228 vs 297). In 1944 the P-39 losses were greater than the P-40 (228 vs 127) but remember that by '44 the P-39 was the main advanced combat trainer and almost every fighter pilot flew a P39 in training. Would think that training accident rate would be higher than normal operating accident rate.


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## P-39 Expert (Mar 26, 2018)

XBe02Drvr said:


> Whoa! Bell had to have been playing "Disingenuous" here. The idea that the possibility of aft CG stability issues never entered their minds, considering the unconventional layout of their bird begs credibility. And then to build a wing with no washout, thus guaranteeing a buffetless, violent stall? And whoever thought of not including the entire range of CG scenarios in flight testing?
> IIUC, the purpose of the midships engine was to minimize polar moment of inertia and enhance agility. Any kindergartner can forsee that this will likely result in very light stick force gradients and a "twitchy" machine prone to over controlling and PIOs unless compensated for in the flight control linkages. Add that to the wobbly aft CG and the sharp stall characteristics, and you've got a tailor made "lieutenant loser". (The unintended Lomcevak is a free of charge fringe benefit! People pay good money at amusement parks across the land to experience thrills like that.)
> It's hard to believe Bell would not have been aware of this, or that they would knowingly foist such a deathtrap on the government.
> I've read here and there in dark ages of prehistory that USAAC Wright Pat forced a number of changes on Bell Aircraft to comply with some high ranking infantry officer in Procurement's concept of "improvements". IIRC, this included reducing the wing area to "go faster, like a GeeBee", adding a heavy radio behind the cockpit to talk to ground troops, and removing some bobweights from the elevator linkage and some other (don't remember) weight from the nose section.
> ...


All hearsay. Everything except the actual government/military tests are hearsay. Somebody said this or that and it may have been taken out of context.

I don't know much about washout, but the symmetrical airfoil was in use prior to and throughout the war. If it was a pilot killer it would have been discontinued.

There was more than one purpose for the midships engine. It allowed the very heavy armament of the 37mm cannon, allowed the use of the tricycle undercarriage, and allowed a very streamlined nose contour as well as the enhanced agility. Properly equipped it did not have a rearward CG. Planes can't fly with a rearward CG.

I'm unaware of the Wright Patterson incident. Hap Arnold ordered a complete wind tunnel test of the P-39 by the NACA) shortly after the turbo was discarded which recommended the small reduction of wingspan and lowering the canopy profile along with eliminating the turbo and intercooler and moving the coolant radiator and oil radiators to the wing center section. This was the final configuration that lasted throughout production.

Whether Bell was aware or not, they certainly never "foisted a deathtrap" on the government. The government (military) dictated exactly how any military plane was built and tolerated no deviation from that. The contractors gave the military exactly what they contracted. Any blame lies with the military.


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## pbehn (Mar 26, 2018)

P-39 Expert said:


> Regarding the March '44 date, most historians say that the Luftwaffe was beaten by that date. Otherwise how did we manage the D-Day invasion the first week of June? I did say the airwar was over by March '44, bad choice of words. The Luftwaffe was beaten by March. To the point that they had to hoard fighters to save them for any big battle they might foresee. They had not been wiped from the face of the earth, but they no longer could put up the most feeble fight without hoarding. They didn't have the fuel to fly them anyway.
> .



Any historian who says that the Luftwaffe was defeated in March 1944 does not know the meaning of the word defeat.

Operation Steinbock was a German bombing campaign that ran from January to 29 May 1944
Operation Steinbock - Wikipedia

The last German aircraft to crash in the UK was a Ju 88 on the night of 3/4 March 1945, it was one of approximately 100 to infiltrate the RAF bomber stream 24 RAF planes were destroyed 9 damaged with 78 RAF personnel plus 17 civilians killed. The LW lost 22 aircraft with 12 damaged and 48 crew killed. You can say the LW was weakened and in a hopeless position but it wasn't completely defeated until the last days of the war.


Operation Gisela - Wikipedia
aircrashsites.co.uk/air-crash-sites-5/the-last-of-the-luftwaffe/


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## MIflyer (Mar 26, 2018)

Actually I read of a case of a P-38 pilot who was not satisfied with merely strafing Japanese airbases but landed and taxied around shooting the place up. He did it a couple of times before the Japanese finally got him on about the third try. Back in the early 70's, I think it was, someone found the remains of a P-38 on a former Japanese airbase. They asked the natives there, who explained the pilot's tactics.

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## P-39 Expert (Mar 26, 2018)

Greg Boeser said:


> P-39expert cites _Attack and Conquer._
> So will I. The 8th FG entered combat 30 April 1942 with P-39Ds and P-400s, within 5 days they had lost 9 pilots and 14 aircraft. Clearly, the pilots were no match for the Tainan AG. The P-39 lacked range to effectively bring battle to the enemy, and were hard pressed to defend their own air base. slow climb performance meant that with the short warning afforded the Port Moresby defenders, they often had no choice but to scramble out to sea to avoid being swatted down while in the climb. Trying to engage the Japanese while still in a climb was suicide as demonstrated by the 75 Sqn. RAAF.
> The 8th and 35th FGs held the line in New Guinea during 1942, but suffered considerable losses.
> The 80th FS was reequipped with P-38s and entered combat 30 March 1943. The P-38 was a game changer. As the book states, the 35th and 36th Fighter Squadrons continued to fly combat missions in spite of the fact that the P-38 was pushing the fight out of the radius of other fighter types. Both squadrons eventually re-equipped, The 35th got P-40Ns in late 43, and the 36th got some P-39Qs before converting to P-47s in early 44. Both eventually got P-38s


As I said before the pilots were no match for the Japanese navy pilots. Our kids were green and the Japanese navy pilots were experienced. The P-39 (early heavy D,F,K and L) were all at least 30mph faster than the Zero at all altitudes. They were hard pressed to defend their base yet with all these disadvantages they managed a 1:1 kill ratio.


pbehn said:


> This may be true, that the P39 was faster than the P40 but it is an aerodynamic issue not weight, the P51B was faster by about 30MPH than a Spitfire with the same engine and heavier too. How did the P51 and P39 compare with identical engines?


Best I can tell from the charts the P-51A and the P-39N (same engine in both) had about a 10mph difference at all altitudes. The P-39N being lighter than the P-51A climbed a lot faster..


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## Elmas (Mar 26, 2018)

Shortround6 said:


> The P-39 may very well have been easier to handle on the ground, very surprising if it wasn't, and some tail dragger US fighters had a few unique problems of their own, F4Fs for one.
> 
> However the transition from approach to actual wheels down may have been a problem?
> The P-39 having a higher landing speed than most other (P-38 excepted) US 1942 fighters. While not bad compared to P-47s and late P-51s the P-39 may be 10-20mph faster than P-40s or the navy planes.
> ...



There was a war goin' on... you have to fly in situations where even the gulls stay on the ground.
To fly a war mission, where actually you have to kill someone, and you know that someone will do his best to try to kill you, is not exactly as to fly a training mission in Southern California or from Decimomannu AB to spend some ammunition in Capo Frasca.
Even Decimomannu AB can be dangerous of course, it is not rare to have 60 kts mistral over there. And a flying accident is a kill the enemy got at no expense.
So to return from a mission in the middle of a tropical storm, landing, at the best, on Marston mats, with an oveheated engine, some holes here and there, fuel to zero, knowing that your plane will not forgive an error at landing, by my personal point of view could only be described as scaring.
Personaly I would have been in this situation inside a Macchi 202 or in a Spitfire or in a Hellcat, but I see that some other gentlemen would prefer to be inside a P-39.
_De gustibus non est disputandum_, ancient Romans used to say.

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## P-39 Expert (Mar 26, 2018)

pbehn said:


> Any historian who says that the Luftwaffe was defeated in March 1944 does not know the meaning of the word defeat.
> 
> Operation Steinbock was a German bombing campaign that ran from January to 29 May 1944
> Operation Steinbock - Wikipedia
> ...


Okay, they were weakened to the point of curtailing operations to hoard their remaining planes for last ditch efforts. Definitely in a weakened and hopeless position, especially with Allied airpower reaching its maximum production. Plus no fuel to fly or even train. Call it what you want, they were done.


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## pbehn (Mar 26, 2018)

P-39 Expert said:


> Okay, they were weakened to the point of curtailing operations to hoard their remaining planes for last ditch efforts. Definitely in a weakened and hopeless position, especially with Allied airpower reaching its maximum production. Plus no fuel to fly or even train. Call it what you want, they were done.


Certainly not in March 1944 not by a long way, fuel was a major issue especially after Bagration but in March 1944 they were not defeated and not "done".

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## Shortround6 (Mar 26, 2018)

P-39 Expert said:


> .
> 
> I HAVE NEVER BACKTRACKED ON ANYTHING I HAVE POSTED HERE. Yes, acknowledged a few small errors, the airwar was not over in March, I meant to say the Luftwaffe was beaten in March. And the British themselves said the P-400 (one of the heaviest P-39 versions) would easily outturn an Me109E getting on it's tail in three turns.
> 
> The P-51 would try to swap ends with a full fuselage tank. Are you going to dispute everything I say? You have so far.



Last first, yes I am going to dispute the things I think are wrong, of which there is a lot. Like 
_And the British themselves said the P-400 (one of the heaviest P-39 versions) would easily outturn an Me109E getting on it's tail in three turns._

The P-400 was not one of the heaviest if you compare like to like ( like comparing P-39s with 120 gallon fuel tanks and nearly full fuel) 
The 20mm cannon was over 100lbs lighter than the 37mm. The 60 round drum was lighter than the 30 rounds of 37mm ammo. 
The basic weight (no fuel, oil, ammo or pilot) for a P-400 was 6328lbs
for a P-39D it was 6290, for a P-39D-2 it was 6421lbs and for a P-39K it was 6392lbs , for a P-39L it was 6467lbs (different prop) and for an early P-39Q it was 6416lbs with the small 87 gallon fuel cells. 
Please be careful comparing weights as some accounts/charts, move the pilots weight ( which varied from 160 to 200lbs) and oil from one catagory to another. 
Hard to how the P-400 is one of the heaviest if you put the same amount of gas and machine gun ammo in the planes.
But hey, lets not let facts get in the way of a good theory. 

As for out turning an 109E, who cares, the 109 went out of production in the winter of 1940/41 and the 109F could easily out turn the 109E using the same engine let alone the improved engines introduced during the summer of 1941. More powerful engine allowed less altitude loss in a given turn. 

Others have covered the March 1944 nonsense.

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## pbehn (Mar 26, 2018)

Elmas said:


> _De gustibus non est disputandum_, ancient Romans used to say.


Not only Romans I knew an Italian bar maid who spoke like that too.


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## Elmas (Mar 26, 2018)

This one?

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## pbehn (Mar 26, 2018)

Elmas said:


> View attachment 487371
> 
> 
> This one?


Close, but she was blonde. Most Italian bars are run by families, or they are where I worked. The "staff" do the job as part of family life, not so much for the money, they frequently have other jobs. I knew one who was a linguist fluent in Latin, another was an art collector/trader, an expert in impressionist art and another was one of only three qualified female football referees in Italy. I cant say they were all beautiful but they were all stylish and interesting.

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## P-39 Expert (Mar 26, 2018)

pbehn said:


> This is the crux of the whole discussion and what is slowly driving me nutz. The P 39N was in Production in December 1942 and the Spitfire mk IX was in squadron service during the previous summer. Would you replace Spitfire Mk Vs with P39-Ns or Mk IXs? and it isn't just a question of speed and rate of climb, it is also a question of serviceability, safety and loss rates. The P-39 was dangerous, relative to all other US fighters to its own pilots, even in training, I posted the stats and you made no comment. Using semantic tricks like "full series production" is not impressive, the fact is that the Mk IX was in production in mid 1942, there is a limit to how quickly any new type can be introduced and in terms of logistics switching all factories over when you don't have all the parts just means losing months of production. The Mk V may have been outclassed in 1942 but it was better than nothing.
> 
> Before the war started Hawkers were allowed to export Hurricanes because they could produce them faster than the RAF could train all their staff to use them. By 1940 production had doubled and each hurricane just got sent where it was needed because by that time everyone knew what it was, only pilots to fly them was an issue.


Not trying any semantic tricks. Squadron #64, #11, and #401 operational July '42 and #402 the next month with the Merlin 61, then from early 1943 with the Merlin 63, 66 and 70. So four squadrons in the last half of 1943. I would call that a good service test batch. They apparently did get into combat with victories in 1942 and having escorted some 8th AF short range missions.


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## Milosh (Mar 26, 2018)

P-39 Expert said:


> As I said before the pilots were no match for the Japanese navy pilots. Our kids were green and the Japanese navy pilots were experienced. The P-39 (early heavy D,F,K and L) were all at least 30mph faster than the Zero at all altitudes. They were hard pressed to defend their base yet with all these disadvantages they managed a 1:1 kill ratio.



What do you mean by 'green'? The first US pilots to fly combat were career USAAC pilots. 

1:1? Was that vs all Japanese a/c?


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## XBe02Drvr (Mar 26, 2018)

Milosh said:


> What do you mean by 'green'? The first US pilots to fly combat were career USAAC pilots.


Every pilot is "green" when they first fly combat, whether they're lifers or first tour nuggets.
Cheers,
Wes


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## Glider (Mar 26, 2018)

It would be wrong to assume that all the Japanese pilots had experience in China. It's a bit like assuming that all the Luftwaffe pilots had experience in Spain

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## P-39 Expert (Mar 26, 2018)

DarrenW said:


> That's because it really didn't. In most reference books and other well respected sources the F6F-3 will show a reported service ceiling anywhere between 37,300 - 38,400 feet, and I've seen Navy reports showing as high as 38,600 feet in military power with an overload weight of 12,680lbs. The report you are referencing shows a particular P-39N (s/n 42-4400) at 7,274lbs with a ceiling of 38,500 feet. How is that any kind of real advantage? Plus, besides the occasional airplane doing reconnaissance work, who the heck was fighting at 38,000 feet anyway during WWII????
> 
> 
> 
> ...


My sincere apology. The official government/military tests on the P-39N (10/17/42) show a service ceiling of 38500' and the Hellcat (3/16/44) with 37000'. Top speed at 23000' (Hellcat critical altitude) of 379.5mph for the Hellcat and 375mph for the P-39N. At the Hellcat critical altitude of 23000' climb was 1500fpm while the P-39N climbed at 2285fpm. Thats 150% faster than the Hellcat. Same speed, faster climb. Not hearsay, official government tests. Tell me again how great a dogfighter the Hellcas was.

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## Glider (Mar 26, 2018)

P-39 Expert said:


> My sincere apology. The official government/military tests on the P-39N (10/17/42) show a service ceiling of 38500' and the Hellcat (3/16/44) with 37000'. Top speed at 23000' (Hellcat critical altitude) of 379.5mph for the Hellcat and 375mph for the P-39N. At the Hellcat critical altitude of 23000' climb was 1500fpm while the P-39N climbed at 2285fpm. Thats 150% faster than the Hellcat. Same speed, faster climb. Not hearsay, official government tests. Tell me again how great a dogfighter the Hellcas was.


Both were not as good as the 109G
Service ceiling - P39 38,500 109G 39,000+
Speed 23,000 ft - P39 375 mph 109G 403 mph
Climb at 23,000 ft - P39N 2,28 ft/min 109G 2,605 ft/min

plus of course the 109 was less likely to bite you


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## pbehn (Mar 26, 2018)

P-39 Expert said:


> Not trying any semantic tricks. Squadron #64, #11, and #401 operational July '42 and #402 the next month with the Merlin 61, then from early 1943 with the Merlin 63, 66 and 70. So four squadrons in the last half of 1943. I would call that a good service test batch. They apparently did get into combat with victories in 1942 and having escorted some 8th AF short range missions.


What are you talking about? There were 5,656 Spitfire MkIXs built between June 1942 and December 1944. Are you saying there were 4 squadrons in service half way through the total production run? I am tired of this whac-a-mole  discussion. Regardless of anything anyone posts you go back to the same issues every few days. I strongly suspect that you continue to insist the Luftwaffe was defeated in March 1944 to explain production of P-39s halting in May 1944.

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## P-39 Expert (Mar 26, 2018)

Shortround6 said:


> excusing the typo of the production date (N production ended in APril '43)
> 
> we are back to repeating ourselves over the P-39s fuel capacity and performance. You don't get both the 120 gal fuel capacity *and* the the high rate of climb. Pick one.
> 
> ...


Yes I DO get the 120 gallons with the high rate of climb. I'll stand by the P-39N test on 10-17-42 as being at the average weight of that particular flight. The weights listed on the official performance tests (not manifjold comparisons or propeller comparisons on the exact same plane ie weight is the same) all show the test article to be light by about half the weight of the internal fuel with full loads of ammo, oil etc. This was the AVERAGE weight of the plane on that particular flight.

P-39C 6689 test 7075 published weight difference 386# or 64 gallons
P-39D 7525 test 7850 " 325# 54
P-39M 7430 test 7650 " 220# 37 
P-39N 7274 test 7650  376# 63 

Every plane tested in an official performance test was lighter than published gross weight by roughly half the fuel. I can do this for the P-38 also but I'm not, look it up yourself. They are using an average weight for that particular flight on that day for calculations and ratios.

There certainly WAS a gradually reduced capacity. The N started with 120 gallons and was gradually reduced in subsequent production blocks until the Q had as little as 86 with the full 120 gradually restored in subsequent production blocks. The 104 gallon figure refers to the fuel left after deducting the 16 gallons in the reserve tank, actually a part of the inside left wing tank. Self sealing rubber fuel tanks weighed 260# total for the 12 tanks.

Most Russian fighters WERE underarmed by western standards. They referred to the 37mm cannon and the twin .50 caliber MGs (they deleted wing guns) as devastating armament with one hit from the cannon normally bringing down almost any plane. I agree with you on the Russian 20mm "light" shell and I believe the Germans 20mm was also light. I have seen comparisons where they say the American/British Hispano was the equivalent of three Browning .50 cal. MGs and the German 20mm was equivalent to 66% of a 20mm Hispano.


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## P-39 Expert (Mar 26, 2018)

pbehn said:


> What are you talking about? There were 5,656 Spitfire MkIXs built between June 1942 and December 1944. Are you saying there were 4 squadrons in service half way through the total production run? I am tired of this whac-a-mole discussion. Regardless of anything anyone posts you go back to the same issues every few days. I strongly suspect that you continue to insist the Luftwaffe was defeated in March 1944 to explain production of P-39s halting in May 1944.


Look, I just went back and re-read the SpitIX vs Me109G comparison and that is what it states exactly. They had four squadrons of Spitfire IXs with Merlin 61s and they went to the Merlin 63, 66 and 70 in early 1943. Read it yourself. Like you said, they only made 5656 MK IXs, not a big run.


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## KiwiBiggles (Mar 26, 2018)

P-39 Expert said:


> they only made 5656 MK IXs, not a big run


That over a quarter of the entire Spitfire production.


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## pbehn (Mar 26, 2018)

KiwiBiggles said:


> That over a quarter of the entire Spitfire production.


And over half of total P39 production.


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## tomo pauk (Mar 26, 2018)

P-39 Expert said:


> My sincere apology. The official government/military tests on the P-39N (10/17/42) show a service ceiling of 38500' and the Hellcat (3/16/44) with 37000'. Top speed at 23000' (Hellcat critical altitude) of 379.5mph for the Hellcat and 375mph for the P-39N. At the Hellcat critical altitude of 23000' climb was 1500fpm while the P-39N climbed at 2285fpm. Thats 150% faster than the Hellcat. Same speed, faster climb. Not hearsay, official government tests. Tell me again how great a dogfighter the Hellcas was.



Hellcat's rated altitude for climb was 20000-20500 ft for military power, not 23000 ft. 
At 25000 ft, Hellcat climbed at 1280 - 1600 fpm (~12500 lbs, 'overload fighter' condition), P-39M at 1400 fpm (on 7430 lbs, ie. all 120 gals of fuel), P-39N at 1900 fpm (7274 lbs - reduced fuel), P-39Q at 1570 fpm (7871 lbs - ballasted to represent 120 gals of fuel and ammo for all 5 guns, gun pods present), but also just 1365. One does not need to be rocket scientist to see that reduction of weight improves rate of climb, while also reducing range and thence usability. We also have a thing where the Hellcat represents a good manered aircraft (just what was needed for naval fighters), unlike the P-39. Add the double the radius/range and Hellcat is a much more useful fighter.
About the RoF figure of 2285 fpm @ 23000 ft for the P-39N - what is the source?

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## Shortround6 (Mar 26, 2018)

P-39 Expert said:


> Yes I DO get the 120 gallons with the high rate of climb. I'll stand by the P-39N test on 10-17-42 as being at the average weight of that particular flight. The weights listed on the official performance tests (not manifjold comparisons or propeller comparisons on the exact same plane ie weight is the same) all show the test article to be light by about half the weight of the internal fuel with full loads of ammo, oil etc. This was the AVERAGE weight of the plane on that particular flight.
> 
> P-39C 6689 test 7075 published weight difference 386# or 64 gallons
> P-39D 7525 test 7850 " 325# 54
> ...



Unless ALL planes are tested this way the comparisons get hard to make and it doesn't matter how many times you repeat it, it doesn't make it true.
Some of the P-38 tests were done at absurdly low weights. I have already give you the fuel capacities or weights for the P-36 and P-40 tests and the reasons why, they were tested at the _design weight_ but obviously they got lighter the longer the test lasted. Starting the test hundreds of pounds light is certainly shading things. 



> Every plane tested in an official performance test was lighter than published gross weight by roughly half the fuel. I can do this for the P-38 also but I'm not, look it up yourself. They are using an average weight for that particular flight on that day for calculations and ratios.



Please post link to ANY test were they SAY that is what they are doing. Your refusal to post sources is getting more than annoying. 



> There certainly WAS a gradually reduced capacity. The N started with 120 gallons and was gradually reduced in subsequent production blocks until the Q had as little as 86 with the full 120 gradually restored in subsequent production blocks. The 104 gallon figure refers to the fuel left after deducting the 16 gallons in the reserve tank, actually a part of the inside left wing tank. Self sealing rubber fuel tanks weighed 260# total for the 12 tanks.



You certainly have a different definition of _gradually. _Everything I have read says it was either/or. Either you had the 120 gallon tank set up once they had self sealing tanks or you had the 86/87 gallon setup. There was NOTHING in between. 
Please give a reference for anything that says otherwise.

Refit kits were supplied to bring the fuel capacity back up to 120 gallons on the planes with the 86/87 gallon ( I am not going to argue about 1 gallon) tanks and NO the 86/87 tanks didn't start with the "Q" they started with the "N"s
Sources include AHT, "Cobra" By Birch Mathews (who says some of the Ms had 86 gallons) 
Joe Baugher says that the Fuel reduction came after the first 166 "N"s with 2095 Ns being built.

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## pbehn (Mar 26, 2018)

P-39 Expert said:


> Look, I just went back and re-read the SpitIX vs Me109G comparison and that is what it states exactly. They had four squadrons of Spitfire IXs with Merlin 61s and they went to the Merlin 63, 66 and 70 in early 1943. Read it yourself. Like you said, they only made 5656 MK IXs, not a big run.


You repeatedly take a factoid and extrapolate it. The 4 squadrons were issued with the MK IX then received an uprated version about 8 months later, but that is about how long a plane was used or superseded in service. The three American "Eagle Squadrons were issued with Mk IXs in September 1942. The Mk V was not being produced anymore, the RAF rarely had more than 1000 front line fighters in service but used over 2000 per year, that is how quickly a front line fighter becomes obsolete, lost, damaged or just worn out.

From Wiki
Operating within the RAF were three "Eagle" squadrons: units manned by American pilots who had joined the RAF. First formed in 1940 and initially equipped with Hurricanes, these units converted to Spitfire Vbs in 1941. They were re-equipped with Spitfire IXs in early September 1942 and were disbanded in late-September 1942 as their aircrew and aircraft were transferred to the fledgling USAAF's Eighth Air Force to become the nucleus of the 4th Fighter Group.[70]


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## Glider (Mar 26, 2018)

Does the 5656 Spitfire IX number include the MXVI which was basically the same aircraft with a different engine and the Mk VIII with a similar performance?

Put the and if I remember the total came to about 8,250 give or take


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## pbehn (Mar 26, 2018)

Glider said:


> Does the 5656 Spitfire IX number include the MXVI which was basically the same aircraft with a different engine and the Mk VIII with a similar performance?
> 
> Put the and if I remember the total came to about 8,250 give or take


No, I was using data from here.
Supermarine Spitfire (late Merlin-powered variants) - Wikipedia
*Mark* *Built by* *Numbers Built* *Notes*
F VII, H.F VII Supermarine 140 First Mk VII September 1942
F VIII, L.F VIII Supermarine 1,658 First Mk VIII 11 November 1942
F IX, H.F IX, L.F IX Supermarine, Castle Bromwich 5,656 First Mk IX _BR581_ June 1942
PR X Supermarine 16 First Mk X May 1944
PR XI Supermarine 471 First Mk XI November 1942
XVI Castle Bromwich 1,054 First Mk XVI October 1944

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## DarrenW (Mar 26, 2018)

P-39 Expert said:


> My sincere apology. The official government/military tests on the P-39N (10/17/42) show a service ceiling of 38500' and the Hellcat (3/16/44) with 37000'. Top speed at 23000' (Hellcat critical altitude) of 379.5mph for the Hellcat and 375mph for the P-39N. At the Hellcat critical altitude of 23000' climb was 1500fpm while the P-39N climbed at 2285fpm. Thats 150% faster than the Hellcat. Same speed, faster climb. Not hearsay, official government tests. Tell me again how great a dogfighter the Hellcas was.



You are quite the persistent fellow, I'll give you that much. So you want "official government/military tests" huh? Well besides the one I told you about in my last posting (s/n 42874/38,600 feet/report date 25 Apr 1945), there were these "official tests" as well....

Service ceiling results:
1) F6F-3 (s/n 42633) 38,000 feet. (report date 1 Sep 1944)

2) F6F-3 (s/n 02982) 38,900 feet. (report date 27 Nov 1944)

Maximum speed results (military power only):
1) F6F-3 (s/n 25820) 385 mph @ 23,500 feet. (report date 26 Aug 1943)

2) F6F-3 (s/n 41588) 382 mph @ 22,400 feet (report date 9 Jul 1945)

Do you happen to have more than one "official government/military test" showing the those particular numbers for speed and altitude of the most awesomeous P-39N that you tout so heavily? I'd love to see it, and I'm not being sarcastic. And surely you aren't suggesting that on any given day the average Airacobra could "handle" an average Hellcat in a one-on-one dogfight (pilot skill being equal of course)??? It had serious trouble with an airplane that basically had a 50 mph speed deficit so how could it ever deal with one that equaled and at times even surpassed it's own top-end speed????

I never disputed the superior climb rate of the P-39N, so why are you harping on it now? I've also never said that the speeds of the two types weren't for all intents and purposes roughly equal at altitudes exceeding 22,000 feet, as a few miles per hour here or there of difference wouldn't amount to a hill of beans in a real world situation anyway. But you can easily see from the testing I presented that the F6F-3 has obviously flown faster and climbed higher during some tests than others (and we haven't even discussed WEP yet). That's how it is because testing isn't performed in a vacuum. There's a lot of variables that come into play and these variables effect the outcome of tests (like temperature, wind velocity, pilot experience, aircraft weight, fit and finish of the particular aircraft, ect.)

I sincerely hope that you're not using the test results from 17 Oct 1942 as something *ALL* P-39Ns were capable of because that's a huge leap of faith my friend. I also hope that I didn't strike a nerve earlier regarding your beloved fighter, and if I did I truly apologize and wish no hard feelings between us going forward....

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## Glider (Mar 26, 2018)

pbehn said:


> No, I was using data from here.
> Supermarine Spitfire (late Merlin-powered variants) - Wikipedia
> *Mark* *Built by* *Numbers Built* *Notes*
> F VII, H.F VII Supermarine 140 First Mk VII September 1942
> ...


Makes a decent number doesn't it

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## pbehn (Mar 26, 2018)

Glider said:


> Makes a decent number doesn't it


By my reckoning almost as many late Merlin variants as the whole of P-39 production.

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## Shortround6 (Mar 26, 2018)

By the end of 1942 the Spitfire MK IX was in service with the following squadrons according to "The British Fighter" by Francis Mason.
No 64
No 72
No 81
No 122
No 133 (Eagle)
No 306 (Polish)
No 315 (Polish)
No 331 (Norwegian)
No 332 (Norwegian)
No 340 (French)
No 401 (Canadian)
No 402 (Canadian)
No 611 (Aux Af) 

13 squadrons total?
I have no idea how many planes in each squadron or if they were fully operational. 
Unless someone has proof to the contrary I would say that the notion that the Spitfire IX was _only_ in use by 4 squadrons or production was being done at a low rate while operational testing was done seems to be in error.

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## Milosh (Mar 26, 2018)

Spitfire production numbers can be found here, Spitfire - Main


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## Milosh (Mar 26, 2018)

Shortround6 said:


> I have no idea how many planes in each squadron or if they were fully operational.
> Unless someone has proof to the contrary I would say that the notion that the Spitfire IX was _only_ in use by 4 squadrons or production was being done at a low rate while operational testing was done seems to be in error.



16 + 2 with 46 squadrons (all MKs) operational as of 1.1.43

oops forgot the link, 
_View: https://www.scribd.com/document/85616206/RAF-Strength-1939-45-Fighter-Bomber-Coastal-Commands-AIR-22_

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## pbehn (Mar 26, 2018)

Shortround6 said:


> By the end of 1942 the Spitfire MK IX was in service with the following squadrons according to "The British Fighter" by Francis Mason.
> No 64
> No 72
> No 81
> ...


Good post S/R, by that time two Eagle squadrons 71, and 121 had transferred to the USAAF with their aircraft.


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## pbehn (Mar 26, 2018)

Shortround6 said:


> Unless someone has proof to the contrary I would say that the notion that the Spitfire IX was _only_ in use by 4 squadrons or production was being done at a low rate while operational testing was done seems to be in error.


Initial production was low at Supermarine with production starting at Castle Bromwich later.


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## Shortround6 (Mar 26, 2018)

Most new models start slow or at only one factory, but very few aircraft stall for a number of months with only a few squadrons using them.
Like having 4 squadrons in service in Aug and still having only 4-5 in service in Dec. A few planes did but they are rarities and well noted.


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## Greg Boeser (Mar 26, 2018)

pbehn said:


> You repeatedly take a factoid and extrapolate it. The 4 squadrons were issued with the MK IX then received an uprated version about 8 months later, but that is about how long a plane was used or superseded in service. The three American "Eagle Squadrons were issued with Mk IXs in September 1942. The Mk V was not being produced anymore, the RAF rarely had more than 1000 front line fighters in service but used over 2000 per year, that is how quickly a front line fighter becomes obsolete, lost, damaged or just worn out.
> 
> From Wiki
> Operating within the RAF were three "Eagle" squadrons: units manned by American pilots who had joined the RAF. First formed in 1940 and initially equipped with Hurricanes, these units converted to Spitfire Vbs in 1941. They were re-equipped with Spitfire IXs in early September 1942 and were disbanded in late-September 1942 as their aircrew and aircraft were transferred to the fledgling USAAF's Eighth Air Force to become the nucleus of the 4th Fighter Group.[70]


Hey, you missed the part where they were issued Brewster Buffalos!

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## pbehn (Mar 26, 2018)

Shortround6 said:


> Most new models start slow or at only one factory, but very few aircraft stall for a number of months with only a few squadrons using them.
> Like having 4 squadrons in service in Aug and still having only 4-5 in service in Dec. A few planes did but they are rarities and well noted.


Total production at Supermarine was only 557 A/C up to June 1943 when it stopped at Supermarine. Note with the MkIX, the Mk XVI was in principle identical but was with a Packard Merlin 1053 were made.. From something I posted earlier but can no longer find, the IX were used at Dieppe escorting B 17s which I would imagine would need some time training on the aircraft and training with the bombers.


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## buffnut453 (Mar 26, 2018)

Shortround6 said:


> By the end of 1942 the Spitfire MK IX was in service with the following squadrons according to "The British Fighter" by Francis Mason.
> No 64
> No 72
> No 81
> ...



Standard equipment would be 12 Initial Equipment and 6 Immediate Reserve airframes. There was some variation due to losses or, occasionally, an excess of airframes on a particular squadron. However, a total of 18 machines is a good working average for an operationally-declared fighter squadron.


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## Shortround6 (Mar 26, 2018)

Thank you, I have only that account in that book and I don't want to read more into it than is there. Many squadrons got a least a few aircraft for training before being declared operational but the difference between 4 squadrons and 13 is substantial and should make up for any partially equipped squadrons.


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## buffnut453 (Mar 26, 2018)

In order to be declared operational, a squadron would need to have a full complement of the new aircraft. To do otherwise would greatly limit operational flexibility. The squadron would typically be withdrawn from the front line to be re-equipped and ensure the full complement of new airframes was fully trained and functioning. Naturally, there were exceptions due to operational contingencies but, by and large, you wouldn't have a mixed squadron of both MkVs and MkIXs for very long, if at all.


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## wuzak (Mar 26, 2018)

P-39 Expert said:


> There certainly WAS a gradually reduced capacity. The N started with 120 gallons and was gradually reduced in subsequent production blocks until the Q had as little as 86 with the full 120 gradually restored in subsequent production blocks. The 104 gallon figure refers to the fuel left after deducting the 16 gallons in the reserve tank, actually a part of the inside left wing tank. Self sealing rubber fuel tanks weighed 260# total for the 12 tanks.



Joe Baugher's site says only the first 166 P-30Ns had 120USG, the remainder having 87USG (plus some had a field kit to bring them back up to 120USG, but how many were?).


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## wuzak (Mar 26, 2018)

P-39 Expert said:


> Yes I DO get the 120 gallons with the high rate of climb. I'll stand by the P-39N test on 10-17-42 as being at the average weight of that particular flight. The weights listed on the official performance tests (not manifjold comparisons or propeller comparisons on the exact same plane ie weight is the same) all show the test article to be light by about half the weight of the internal fuel with full loads of ammo, oil etc. This was the AVERAGE weight of the plane on that particular flight.



Which is interesting for when you compare to Spitfire V tests.

The British method seems to have been to correct the measure performance back to 95% of take-off weight. So at higher loading than the P-39N figures you quote.

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## pbehn (Mar 26, 2018)

Am I missing something with these tests? If a plane like a P39 uses 30% of its fuel to get to 25,000 ft what is the use of a test with half load? It will only have a sixth of a tank left when it gets there, just enough to get back safely.

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## wuzak (Mar 26, 2018)

pbehn said:


> No, I was using data from here.
> Supermarine Spitfire (late Merlin-powered variants) - Wikipedia
> *Mark* *Built by* *Numbers Built* *Notes*
> F VII, H.F VII Supermarine 140 First Mk VII September 1942
> ...



The IX was supposed to be the "interim" 2 stage Merlin model, the definitive ones were to be the VII (high altitude with extended wing tips) and VIII. 

Some early production VIIIs were converted to take the Griffon 61 in early 1943, becoming VIIIGs, essentially prototypes for the XIV.

The XIV was also regarded as interim, Supermarine at the time working on the new wing for the Spitfire 21.

The war situation often dictated the production of interim types over the developed versions, as they could quickly be put into production. That was definitely the case with the Spitfire IX, the early models being, basically, up-engined Vs.

The Mk.V was also a product of convenience. The Spitfire III was being developed around the Merlin XX in 1940. The III had superior performance to the V, which was essentially a Mk.I with a Merlin 45 fitted, but required more changes to the airframe and would have delayed production significantly.

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## DarrenW (Mar 26, 2018)

From P-39N test report dated 17 October 1942:
_Gross Weight at take-off was 7274 pounds....
_
How does "gross weight at take-off" EVER equate to "average weight"? I can see if it just simply said "weight" as that leaves some ambiguity, but this? Are you sure you don't want to change your mind about this???

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## parsifal (Mar 26, 2018)

RAF (and CW) fighter squadrons through to the end of 1942 had 18-22 a/c on hand including their reserves. There were normally normally 12 operational. In periods of sustained operations squadrons listed as ready could possess an average _operational _strength of between 6 and 9 aircraft and still be listed as “ready”.

In 1943 through to the end of the war the “establishment” strength was increased to 24 aircraft. I reasonably certain this included reserve aircraft, though I have read in some sources that this was the frontline strength, with up to 6 additional in reserve.

An RAF squadron 1943and on was a fairly meaty formation.

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## BiffF15 (Mar 27, 2018)

P39,

I’m a little confused here so help me out. Your driving point here is that the Airacobra should have been used quite differently than it was. It, according to you had quite an impressive climb rate to about 20k, was nimble (as long as CG was forward), was short legged, and had good ground handling characteristics. 

Sounds good except in SWP it couldn’t get to the fight except in extreme circumstances on the offensive due to short legs, and in the defense role when scrambled could not get above the Zeros for an offensive bounce. 

In the ETO / MTO it didn’t have the legs or altitude capability required to escort the bomber stream which would regulate it to a CAS role. In that role you have a choice between it or a P47. The latter could be reconfigured for escort tomorrow (multi-role or multi-use) which oh by the way could drop down and go hunting for targets of opportunity on the long ride home increasing damage inflicted on the enemy.

Even today kids going to fly fighters get topped off in the AT-38C prior to showing up at their respective FTUs (Fighter Replacement Units or AKA school houses). In WW2 they put them in P39s and P40s to get them more experienced prior to arriving in theater. The reason those aircraft were chosen was availablity. The reason those aircraft were available was for some reason they were not as combat effective as other assets that were on hand.

Please show me where I’m wrong. When doing so please follow the general forum rules of no one person accounts or claims.

Cheers,
Biff

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## P-39 Expert (Mar 27, 2018)

Shortround6 said:


> By the end of 1942 the Spitfire MK IX was in service with the following squadrons according to "The British Fighter" by Francis Mason.
> No 64
> No 72
> No 81
> ...


Yes I guess I read that wrong in wwiiaircraftperformance. Still, 13 squadrons with 18 planes per squadron (12 plus 8 reserve) is still only 234 planes. Certainly more than my "service test" estimate but still not a lot of production for 6 months (July-Dec "42).


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## P-39 Expert (Mar 27, 2018)

tomo pauk said:


> Hellcat's rated altitude for climb was 20000-20500 ft for military power, not 23000 ft.
> At 25000 ft, Hellcat climbed at 1280 - 1600 fpm (~12500 lbs, 'overload fighter' condition), P-39M at 1400 fpm (on 7430 lbs, ie. all 120 gals of fuel), P-39N at 1900 fpm (7274 lbs - reduced fuel), P-39Q at 1570 fpm (7871 lbs - ballasted to represent 120 gals of fuel and ammo for all 5 guns, gun pods present), but also just 1365. One does not need to be rocket scientist to see that reduction of weight improves rate of climb, while also reducing range and thence usability. We also have a thing where the Hellcat represents a good manered aircraft (just what was needed for naval fighters), unlike the P-39. Add the double the radius/range and Hellcat is a much more useful fighter.
> About the RoF figure of 2285 fpm @ 23000 ft for the P-39N - what is the source?


The source is wwiiaircraftperformance.org. Go there and look it up. I am comparing the P-39N (not the M or Q) to the Hellcat, both official government performance tests. Facts. Hellcat and the N had about the same speed at about the same altitude but the N vastly outclimbed the Hellcat at all altitudes.


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## P-39 Expert (Mar 27, 2018)

BiffF15 said:


> P39,
> 
> I’m a little confused here so help me out. Your driving point here is that the Airacobra should have been used quite differently than it was. It, according to you had quite an impressive climb rate to about 20k, was nimble (as long as CG was forward), was short legged, and had good ground handling characteristics.
> 
> ...


Certainly not trying to confuse anyone, just trying to promote facts. My point is that we have all read all the negative statements on the P-39 for decades. Everyone here is parroting the same information "slow, no climb, couldn't climb over 12000', tumbled etc). My point is that I've been reading about WWII history for decades as you have but new information has become available (late 2012) with official government/military performance tests for the P-39, virtually all models. These are facts instead of hearsay. These facts present the P-39 in a much better light. If you have not seen these official tests, please go and look for yourself. It will change your outlook.

The reference books that I have read (virtually everyone I could get my hands on) seldom agreed on performance numbers for all the US fighters. I constantly wondered why all the discrepancies. This new information allows us to compare the official government/military data plane by plane at every altitude. 

The old information you read about the P-39 not being able to get above a Zero is patently false with the N model (produced Dec '42 through April '43). The N outclimbed any model of the Zero at all altitudes by a substantial margin. At all altitudes. Look at the numbers for both planes and directly compare them. This old bromide started when writers said the P-39 couldn't intercept the Japanese Bettys escorted by Zeros. Well, NO plane can intercept another plane without early warning radar (which was ineffective until August '42) or flying patrols. But the writers didn't mention that. Now forever "the P-39 couldn't climb above the Zero". Newer information contradicts that with facts.

The P-39 was no more short legged than the P-47 which was in combat from May '43 (8th AF) and didn't even have drop tank capability until that August. P-39N was already out of production before the P-47 even entered combat.


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## P-39 Expert (Mar 27, 2018)

wuzak said:


> Which is interesting for when you compare to Spitfire V tests.
> 
> The British method seems to have been to correct the measure performance back to 95% of take-off weight. So at higher loading than the P-39N figures you quote.


Okay, so now the British have a method of computing the "average weight per specific flight" like the US Army then, right? A Spitfire IX weighing 7500# corrected to 95% would be reduced by 7500x5%=375#. The average weight correction for the P-39N was 376# (7650-7274=376). 

Is somebody actually saying that the British also used a form of "average weight". Impossible, right?


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## P-39 Expert (Mar 27, 2018)

DarrenW said:


> From P-39N test report dated 17 October 1942:
> _Gross Weight at take-off was 7274 pounds....
> _
> How does "gross weight at take-off" EVER equate to "average weight"? I can see if it just simply said "weight" as that leaves some ambiguity, but this? Are you sure you don't want to change your mind about this???


One more time, just for you.  All airplanes weigh more at takeoff than at landing because they burn their fuel. In the P-39 this difference was 900# (120 gal). For ratios or performance calculations involving aircraft weight, the problem is what weight to use? And the difference was a substantial 900#. The plane could not fight on the runway at takeoff nor could it fight in the landing pattern. So they used a calculation (that I'm sure is a lot more complex than my "half fuel" generalization) to come to an average weight during that one flight to base their weight ratios on.

I read this somewhere and can't locate the source again, but there you go.


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## pbehn (Mar 27, 2018)

P-39 Expert said:


> Yes I guess I read that wrong in wwiiaircraftperformance. Still, 13 squadrons with 18 planes per squadron (12 plus 8 reserve) is still only 234 planes. Certainly more than my "service test" estimate but still not a lot of production for 6 months (July-Dec "42).


It wasn't 13 it was 15 squadrons, as per my previous post, 2 Eagle squadrons transferred to the USAAF with their Mk IX aircraft, you may have heard of the Eagle squadrons, they were formed with pilots from the USA, bless 'em. 

It takes a long time to put an aircraft into service, the more squadrons you have in service the more planes need replacing due to combat loss and accidents. At the start of the battle of Britain (June) the UK had 565 S/E fighters, during the battle June to October the UK was producing circa 1000 S/E fighters.at the end we had 721 fighters. So despite producing circa 5,000 fighters the number available in squadron service increased by 156.
Document-42: Aircraft production during the Battle of Britain

It is exactly the same with any aircraft, if you take the number of P-51s in service in UK 1943/45 as a measure of production in USA you miss thousands of aircraft.

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## Shortround6 (Mar 27, 2018)

P-39 Expert said:


> Yes I guess I read that wrong in wwiiaircraftperformance. Still, 13 squadrons with 18 planes per squadron (12 plus 8 reserve) is still only 234 planes. Certainly more than my "service test" estimate but still not a lot of production for 6 months (July-Dec "42).


And here you are confusing two things. Aircraft produced at the factories and and aircraft issued to squadrons. Not the same thing.
Each Air Force differed a bit but for the British aircraft seldom went from the factory straight to a service squadron. There were usually some sort of depot where reserve aircraft were kept and final work done on them, like live firing guns or sorting out radios. How many Spitfires were in depot at the end of the year I don't know.
Counting aircraft at the end of the year as the years production also has a few flaws as it doesn't count losses. 
Like 133 squadron losing 11/12 aircraft in one day due to weather/navigation while on an escort mission for B-17s. 

Still it shows that the RAF and more importantly, The USAAF had no need for the P-39 in Europe in winter/spring of 1943. The RAF was equipping 2-3 squadrons per month in the fall of 1942 with Spitfire IXs, the Spitfire VIII with wing tanks was already on order. The US had the P-47s showing up and had several thousand Merlin Mustangs on order. The American big push over the winter/spring of 1943 was North Africa. 
In Jan 1943 for example, the 78th fighter group starts to re-equip with P-47Cs. It had come to the UK with P-38s but all of it's aircraft and many of it's pilots were sent to North Africa to replace losses there. By the end of January the 56th fighter group is also receiving P-47Cs (in crates).
You not only need planes, you need pilots and ground crew to form squadrons and just about _everything _has to be imported. Britain cannot feed itself so the rations for ground crew have to be shipped in. Equipping units with P-39s would have been an expensive luxury for very little return.

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## pbehn (Mar 27, 2018)

Shortround6 said:


> The RAF was equipping 2-3 squadrons per month in the fall of 1942 with Spitfire IXs, the Spitfire VIII with wing tanks was already on order. The US had the P-47s showing up and had several thousand Merlin Mustangs on order. The American big push over the winter/spring of 1943 was North Africa. .


Great post S/R, as you probably noticed pinning down production of the Spitfire is like nailing a blancmange to a wall because the pressing needs of the conflict forced changes that weren't planned. The Mk VII and VIII were actually more advanced airframe designs than the Mk IX which started out using MkV airframes. The Mk VIII being a different airframe was designated for use abroad and was used in Malta Italy and the far east where it played its part in defeating the Arakan offensive. The first production Mk VIII rolled out in Nov 1942.

Since it is the Merlin engine fitted that was the important factor in performance the Mk VII VIII IX and XVI were essentially the same basic plane.

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## Shortround6 (Mar 27, 2018)

P-39 Expert said:


> One more time, just for you.  All airplanes weigh more at takeoff than at landing because they burn their fuel. In the P-39 this difference was 900# (120 gal). For ratios or performance calculations involving aircraft weight, the problem is what weight to use? And the difference was a substantial 900#. The plane could not fight on the runway at takeoff nor could it fight in the landing pattern. So they used a calculation (that I'm sure is a lot more complex than my "half fuel" generalization) to come to an average weight during that one flight to base their weight ratios on.
> 
> I read this somewhere and can't locate the source again, but there you go.



Some tests will show the weight or estimated weight of the aircraft as it climbs. 
Everybody knew the planes got lighter as the fuel burned off, doing performance figures at gross weight or close to it was sort of a worst case. 
As in if taking off with full tanks (or full minus the fuel needed to warm up and clear the runway) the performance will _not be any worse. 
It may (should) be better as fuel burns off. _
Taking off with a half tank gives better numbers and may reflect what _could _happen in combat but also is near useless for planning intercepts. 
It also gives a false impression of high altitude capability. 
For example a Hurricane I at 6316lbs needs about two minutes less time to climb to 25,000ft than a Hurricane I at 6750lbs, no surprise but which number do you use when planning intercepts?
Also note that at 26,000ft the lighter plane could still climb at 990fpm while the heavier one was climbing at 810fpm roughly 80% and that service ceiling changed by about 1500ft. 
The difference in the Hurricanes was not caused by fuel but I just used them to illustrate the point. Using half fuel numbers _may _give you numbers that are more accurate for an encounter 1/2 way through a mission. They give you crap numbers if you are caught near your own airfield. 
Having worst case numbers means you may be pleasantly surprised, having best case numbers means the surprises are much less likely to be pleasant.

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## drgondog (Mar 27, 2018)

P-39 Expert said:


> One more time, just for you.  All airplanes weigh more at takeoff than at landing because they burn their fuel. In the P-39 this difference was 900# (120 gal). For ratios or performance calculations involving aircraft weight, the problem is what weight to use? And the difference was a substantial 900#. The plane could not fight on the runway at takeoff nor could it fight in the landing pattern. So they used a calculation (that I'm sure is a lot more complex than my "half fuel" generalization) to come to an average weight during that one flight to base their weight ratios on.
> 
> I read this somewhere and can't locate the source again, but there you go.



Do not bring fists to a gunfight in a fact oriented group. Please.

First a better rule of thumb for high octane aviation fuel is 6#/gallon ----------> 120 gallons -----------> 720 pounds.

Professional flight testing for Range/Speed/Climb for USAAF during WWII ALWAYS stated the condition and load out of the airframe. The guidelines you should use for Performance comparisons should begin with full internal combat load out of fuel, guns, ammo and oil.

You keep referring to 1:1 ratio of P-39 vs IJN in SWP. What are your sources?

You constantly reference the P-39N performance as superior to IJN fighters as well as, Army fighters - yet IIRC there was only One P-39 Ace in the SWP (none in North Africa) for US pilots that flew them in combat before wholesaling them to the Italians and French. By contrast there were many F-4F, P-40 aces in SWP and by Commonwealth pilots in North Africa - all in a target rich environment.

The extreme climb to altitude capability relative to other top 'in service' fighters such as F6F, Spit IX, FW 190 and Bf 109 somehow failed to materialize in the key US battles in desperate times, namely Guadalcanal and the Solomons campaigns - to the extent that even when the vaunted P-39N arrived, it was never a choice for air superiority over P-40K through L or P-38 - and remained in service in 1943 simply because the much needed P-38 and P-47 and even P-51A were not available in sufficient numbers to entirely replace them.

The VVS used them in low to mid altitude - AKAIK, never as high altitude interceptors. What do you cite as the reasons that USAAF theatre commanders used to plead for replacements? And given influx of newer P-40 and P-38 and P-47, shuttled the P-39 fleet to CAS role and short range role at that?

Perhaps, take a cut at the reasons you think that AAF pulled them from Theatre combat planning and TO&E in mid 1943 as US production of the P-51B and P-47D ramped up? Well before first deployment of the P-51A and P-51B?

If more than 'a feeling', please cite sources?

If not, I have a suggestion ---------> dive into research of the Med Air Force and Air Marshall Coningham, then into noted AWPD planners Generals Lawrence Kuter (developer of FM-100 7/43) and Muir Fairchild as the AAF doctrine for Tactical Air requirement included aircraft capable of air superiority over the battlefield in addition to CAS. These two gentlemen were Essential to the acquisition and increased Prioritization of the P-51A and Merlin P-51B over Oliver Echols objections - and for a brief time, responsible for the dedication of the first year of P-51B to TAC for Recon and CAS - before clearer heads pulled them into subordination to 8th AF in November 1943.

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## Shortround6 (Mar 27, 2018)

I would note that there was sometimes a variation.



drgondog said:


> The guidelines you should use for Performance comparisons should begin with full internal combat load out of fuel, guns, ammo and oil.



A lot of times there was a difference between "design" weight and even max clean gross weight (no external stores). The "G" load ratings were often done at "design" weight which was sometimes with less than full internal fuel and ammo for example. 
For the P-39 it _seems_ that the ammo load was 300rpg for the .30 cal wing guns for example. The ammo boxes could hold 1000rpg but the extra weight, while counted for max gross was not in "normal/design" gross weight. 
This is why the conditions of the test need to be spelled out. 
The Navy played an awful lot of games with weight both pre-war and early war with intercept weight loadings counting partial fuel and partial ammo loads, with full internal fuel and full ammo being called overload. Once they were in combat in the Pacific I doubt very highly if F4Fs flew off carrier decks with just 200rpg and less than full internal fuel tanks. Navy even had weight charts showing F4Fs with only two guns if carrying bombs. Another load-out that never saw the light of day in combat. 

However I would agree that if not stated otherwise then full fuel, oil, guns and ammo (subject to what was considered "normal") should be assumed to be the condition of the plane. Or suitable ballast for anything not in the plane for test.

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## pbehn (Mar 27, 2018)

P-39 Expert said:


> *The old information you read about the P-39 not being able to get above a Zero is patently false with the N model (produced Dec '42 through April '43). The N outclimbed any model of the Zero at all altitudes by a substantial margin.* At all altitudes. Look at the numbers for both planes and directly compare them. This old bromide started when writers said the P-39 couldn't intercept the Japanese Bettys escorted by Zeros. Well, NO plane can intercept another plane without early warning radar (which was ineffective until August '42) or flying patrols. But the writers didn't mention that. Now forever "the P-39 couldn't climb above the Zero". Newer information contradicts that with facts.
> .


This is a bit of a non sequitur. The important information is not the relative climb rates it is how high you have to get and how long you have to do it. This is more a function of RADAR range, efficiency in detecting then getting airborne and cruise speed of the attacking force. If a force is detected at 20,000 ft doing 200MPH 100 miles away you have 30 minutes to get to the interception point at that altitude, getting above when climbing at less than 1000ft min is much more difficult.

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## DarrenW (Mar 27, 2018)

P-39 Expert said:


> The source is wwiiaircraftperformance.org. Go there and look it up. I am comparing the P-39N (not the M or Q) to the Hellcat, both official government performance tests. Facts. Hellcat and the N had about the same speed at about the same altitude but the N vastly outclimbed the Hellcat at all altitudes.



Your N model Airacobra couldn't meet Army cooling requirements on a chilly day in October (in Dayton, Ohio of all places!) and you expect it to somehow run efficiently in the steamy-hot jungles of the Southwest Pacific???? I am quite positive that this little nugget was added to the already growing list of reasons why it was felt that this airplane was unsuited for USAAF combat operations and off-loaded to the Russians in hoards, as they were desperate and would fly anything that had two wings.

Also, that P-39N flight was at war emergency settings but I was only quoting the F6F-3 at military power settings. If we factor in the use of ADI you can add 10-15 mph to the Hellcat's top speed. I say this because 60 percent of all Hellcats had WEP by January 1944 (source: AHT) so it's not a stretch to believe that a portion of them were so equipped during the time frame you are concerned about (year 1943). I also have a test document from January 1944 which clocked an F6F-3 at 391 mph @ 25,000 feet. On top of that, the document states that the actual maximum speed of this particular Hellcat was most likely never fully realized. And with the 200+ extra horsepower it most assuredly had a far improved climb rate as well. Are you getting all of this?

And you are dead wrong about the actual weight of that particular P-39N on the 17th of October.......


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## DarrenW (Mar 27, 2018)

P-39 Expert said:


> Okay, so now the British have a method of computing the "average weight per specific flight" like the US Army then, right? A Spitfire IX weighing 7500# corrected to 95% would be reduced by 7500x5%=375#. The average weight correction for the P-39N was 376# (7650-7274=376).
> 
> Is somebody actually saying that the British also used a form of "average weight". Impossible, right?



Most British flight test document that I have come across will give a take-off weight AND a "mean weight", which was 95% of take-off. This took into account the fuel burned during the tests. Why is it so hard to believe that take-off weight isn't the same as average weight????


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## Milosh (Mar 27, 2018)

P-39 Expert said:


> Yes I guess I read that wrong in wwiiaircraftperformance. Still, 13 squadrons with 18 planes per squadron (12 plus 8 reserve) is still only 234 planes. Certainly more than my "service test" estimate but still not a lot of production for 6 months (July-Dec "42).


Till the end of Dec '42 ~390 Spitfire IXs had been produced. You can double check with the link in Post 603. 

How many P-39Ns had been produced in that time period?

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## Shortround6 (Mar 27, 2018)

Bell built 299 P-39s in Dec alone, but Fighters in Britain (even in Depot) beat the heck out of fighters in Buffalo New York. 
And depending on shipping space, do you send P-39s or P-47s ?????


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## P-39 Expert (Mar 27, 2018)

drgondog said:


> Do not bring fists to a gunfight in a fact oriented group. Please.
> 
> First a better rule of thumb for high octane aviation fuel is 6#/gallon ----------> 120 gallons -----------> 720 pounds.
> 
> ...


Yes a gallon of gas weighs 6 pounds. It was early this morning when I was doing this math. Sorry for the error. 

Please read the official performance tests for the P-39 at wwiiaircraftperformance that were made available in late 2012. If you haven't analyzed this yet it could change your views on the P-39. These official military performance tests state the loads of each plane. The P-39N test states armament of one 37mm cannon with 30 rounds, two .50 caliber MGs with 250 rpg and four .30 caliber MGs with 300 rpg. The N was fully equipped when tested. Again, the weight reflects the average fuel weight during the flight.

Only one P-39 ace, Bill Fiedler was unfortunately killed shortly after his 5th victory in an accident, a P-38 careened off the runway during takeoff and killed Fiedler sitting in his plane. Many Pacific aces got their first few kills in the P-39 before going on to P-38s. Had they kept their P-39s many more would have undoubtedly become aces. The Russians had 3 of their top 4 aces flying the P-39 and scores of aces with 20 victories or more flying the P-39 against the Luftwaffe. There were plenty of P-39 aces.

The VVS used them at low-mid altitude. This is one of my favorite myths. All the Russian combat was below 15000', right? Not really. Was there some treaty or rule that kept the Luftwaffe 109s at low altitude? Certainly not. The standard combat formation for the VVS in 1943 was the "Flying Bookshelves" or "Kuban Stairs" consisting of a squadron (12 planes) flying at three levels, 5km (16500') for the lowest four, 7km (23000') for the highest four and the remaining four in between. Not much combat over 8km (26000'). About like western Europe where the B-17 and B-24 flew at 25000' with their escort at the same altitude or a little above at 26000/26500'. The Russians' mission was intercepting German tactical bombers and escorting their own tactical bombers and both flew under 15000', but that German escort was certainly not flying that low. Plenty of combat up just about as high as either side wanted to go.

Why did the AAF pull them so quickly to be replaced by the P-38, P-47 and P-51? Please remember I'm comparing the P-39N which was produced between Dec '42 and April '43. During that period the P-38F/G had just begun combat in Dec '42 and the P-47 would not see combat until May '43 after the N was out of production. These were the AAFs turbocharged super planes that were in production but not yet in combat. They had a vested interest in playing down the P-39 accomplishments and overstating their new planes. How would it play to have the AAF saying "We're giving the Russians a great little plane here, but our Lightnings and Thunderbolts are not quite ready yet". The AAF's motto was "Better planes coming", but the better planes were not that much better if at all in their earlier models. The Lightning couldn't dive and the Thunderbolt couldn't climb, and neither were very maneuverable at all. The Thunderbolt had a very short Spitfire-like range before they got drop tanks in August '43, and then still couldn't get much into Germany proper. But the biggest problem was cost. Now there are various cost figures for these planes that all got lower as production ramped up, but the Lightning was about 2.5 times the cost of a P-39 ($50k) and the Thunderbolt was about 1.7 times. American won WWII because we could pay the cost, but if a LIghtning cost 2.5 times as much then it should have been 2.5 times as capable. Put another way, you got almost a group of P-39s for every squadron of LIghtnings, or instead of the 9500 lightnings produced you could have had almost 24000 P-39s. Nobody really looks at it this way, but that's the way it was.


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## Milosh (Mar 27, 2018)

A good rule of thumb is combat range is ~ 1/3 range.

Using that rule, a P-39Q had a combat range of 175mi.

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## pbehn (Mar 27, 2018)

Shortround6 said:


> Bell built 299 P-39s in Dec alone, but Fighters in Britain (even in Depot) beat the heck out of fighters in Buffalo New York.
> And depending on shipping space, do you send P-39s or P-47s ?????


Castle Bromwich produced a maximum of 320 planes in a month, and produced 12, 129 Spitfires in total. It may have been able to produce more MkIX s but it is a question of logistics and marrying up engine and air frame production. In addition to producing new airframes, the ramping up of production of the latest Merlin also took time, in the absence of enough Merlin 60/70 series engines then Mk Vs were produced, in the absence of Mk VII and VIII airframes then MkIX were produced. Whereas a Mk IX was better than a MKV a Mk was better than nothing, it stayed in service until 1944.


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## P-39 Expert (Mar 27, 2018)

Milosh said:


> Till the end of Dec '42 ~390 Spitfire IXs had been produced. You can double check with the link in Post 603.
> 
> How many P-39Ns had been produced in that time period?


9500 or so P-39s produced between January 1941 and August '44. About half went to Russia. Most of those were the superior N and Q models produced from Dec '42 which comprised about 7000 of the total 9500. N and Q differed only in wing armament (4 .30s vs 2 .50s) and since the Russians removed the wing guns the Russian N and Q were pretty much the same plane. Earlier D, F, K and L had the 12000' engines, the M, N and Q had the 15000' engines that were about 100hp better at all altitudes.


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## pbehn (Mar 27, 2018)

P-39 Expert said:


> 9500 or so P-39s produced between January 1941 and August '44. About half went to Russia. Most of those were the superior N and Q models produced from Dec '42 which comprised about 7000 of the total 9500. N and Q differed only in wing armament (4 .30s vs 2 .50s) and since the Russians removed the wing guns the Russian N and Q were pretty much the same plane. Earlier D, F, K and L had the 12000' engines, the M, N and Q had the 15000' engines that were about 100hp better at all altitudes.


You continually use words like "superior" well 1,300 is superior to 1,200HP but in late 1942 early 43 the USA was introducing the P--47 and the UK the Typhoon and Griffon Spitfire, the game had moved up to 1600-2000BHP for top line fighters.

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## P-39 Expert (Mar 27, 2018)

Milosh said:


> View attachment 487461
> 
> 
> A good rule of thumb is combat range is ~ 1/3 range.
> ...


Okay, lets see what a P-39N would do. 120 gals internal plus a drop tank of 110 gals = 230 gals. Takeoff and climb to 5000' reserve is 20 gals so now we're down to 210 gals available. A P-39N burned 62gph at 25000' at 2600rpm max continuous power so we have a theoretical 3.4 hours to escort those bombers. Reduce that by 15 minutes combat and a 20 minute landing reserve so now we have 2.8 hours of actual escort time. We're flying faster than the bombers (230mph) so we're weaving to keep from getting ahead of them. So really we're covering the same ground as the bombers but flying faster. The bombers will cover 640 miles in that 2.8 hours and we're going out AND back so our roughly estimated combat radius is about 320 miles. About 50 miles less than a Thunderbolt with drop tanks. If we can cruise at less than 2600rpm maximum cruise (not recommended over Europe) then we can go farther. All hail the mighty Thunderbolt.

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## drgondog (Mar 27, 2018)

Milosh said:


> View attachment 487461
> 
> 
> A good rule of thumb is combat range is ~ 1/3 range.
> ...


Milosh - where did you find that particular Chart? Is has several errors but the format is one I will put in my new book about the P-51B


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## P-39 Expert (Mar 27, 2018)

pbehn said:


> You continually use words like "superior" well 1,300 is superior to 1,200HP but in late 1942 early 43 the USA was introducing the P--47 and the UK the Typhoon and Griffon Spitfire, the game had moved up to 1600-2000BHP for top line fighters.


I'm saying the N and Q were "superior" to the earlier P-39 models. Compare the N to the Typhoon. About the same speed but N climbs a lot faster.


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## Milosh (Mar 27, 2018)

Bill, ww2 fighter range - Bing images


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## pbehn (Mar 27, 2018)

P-39 Expert said:


> I'm saying the N and Q were "superior" to the earlier P-39 models. Compare the N to the Typhoon. About the same speed but N climbs a lot faster.


The Typhoon dropped 1000kg bombs on Normandy, carrying 4 x 20mm cannon there and back with extensive armour.

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## pbehn (Mar 27, 2018)

Milosh said:


> Bill, ww2 fighter range - Bing images


Can you put a Spitfire Mk IX on the ground protecting all the allied equipment pls

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## Peter Gunn (Mar 27, 2018)

P-39 Expert said:


> Okay, lets see what a P-39N would do. 120 gals internal plus a drop tank of 110 gals = 230 gals. Takeoff and climb to 5000' reserve is 20 gals so now we're down to 210 gals available. A P-39N burned 62gph at 25000' at 2600rpm max continuous power so we have a theoretical 3.4 hours to escort those bombers. Reduce that by 15 minutes combat and a 20 minute landing reserve so now we have 2.8 hours of actual escort time. We're flying faster than the bombers (230mph) so we're weaving to keep from getting ahead of them. So really we're covering the same ground as the bombers but flying faster. The bombers will cover 640 miles in that 2.8 hours and we're going out AND back so our roughly estimated combat radius is about 320 miles. About 50 miles less than a Thunderbolt with drop tanks. If we can cruise at less than 2600rpm maximum cruise (not recommended over Europe) then we can go farther. All hail the mighty Thunderbolt.


Are you seriously contending that the P-39 could do the job of the Thunderbolt in the ETO?



Well all hail the mighty Airacobra...

In one of the older threads, I believe drgondog has a post or two on escort range ( for the Mustang, but you can extrapolate ) and planning of same, none of it theoretical.

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## pbehn (Mar 27, 2018)

P-39 Expert said:


> Okay, lets see what a P-39N would do. 120 gals internal plus a drop tank of 110 gals = 230 gals. Takeoff and climb to 5000' reserve is 20 gals so now we're down to 210 gals available. A P-39N burned 62gph at 25000' at 2600rpm max continuous power so we have a theoretical 3.4 hours to escort those bombers. Reduce that by 15 minutes combat and a 20 minute landing reserve so now we have 2.8 hours of actual escort time. We're flying faster than the bombers (230mph) so we're weaving to keep from getting ahead of them. So really we're covering the same ground as the bombers but flying faster. The bombers will cover 640 miles in that 2.8 hours and we're going out AND back so our roughly estimated combat radius is about 320 miles. About 50 miles less than a Thunderbolt with drop tanks. If we can cruise at less than 2600rpm maximum cruise (not recommended over Europe) then we can go farther. All hail the mighty Thunderbolt.


How much fuel is used by a P39 carrying a 110 gal external tank for warm up take off and climb to 25,000ft? What is the cruise speed of a P39 on max continuous at 25,000ft with external tank?


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## DarrenW (Mar 27, 2018)

P-39 Expert said:


> They had a vested interest in playing down the P-39 accomplishments and overstating their new planes. How would it play to have the AAF saying "We're giving the Russians a great little plane here, but our Lightnings and Thunderbolts are not quite ready yet".





DarrenW said:


> You are definitely a well-educated and learned man who knows a sh--t ton about aviation history.



After hearing your rant about some sort of secret conspiracy against the Airacobra, I'm seriously considering retracting this statement LOL!!!!

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## Peter Gunn (Mar 27, 2018)

P-39 Expert said:


> *SNIP*
> Put another way, you got almost a group of P-39s for every squadron of LIghtnings, or instead of the 9500 lightnings produced you could have had almost 24000 P-39s. Nobody really looks at it this way, but that's the way it was.


But why would you want 24,000 P-39s? I get your passion for the airplane, but the AAF was hardly stupid when they dumped it in favor of _capable_ designs. Also, one squadron of P-38's was worth more than a group of P-39's on operations. George Welch sure didn't think too much of it, but maybe he was wrong as well.

Also, do you think no one here has looked at data since before 2012? Dude, you have authors and historians in here.

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## Milosh (Mar 27, 2018)

P-39 no need for guesstimate calculations for the Flight Operation Instruction Chart can be found here, P-39 manuals, P-39 Airacobra Pilots Flight Operating Instructions

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## drgondog (Mar 27, 2018)

P-39 Expert said:


> Okay, lets see what a P-39N would do. 120 gals internal plus a drop tank of 110 gals = 230 gals. Takeoff and climb to 5000' reserve is 20 gals so now we're down to 210 gals available. A P-39N burned 62gph at 25000' at 2600rpm max continuous power so we have a theoretical 3.4 hours to escort those bombers. Reduce that by 15 minutes combat and a 20 minute landing reserve so now we have 2.8 hours of actual escort time. We're flying faster than the bombers (230mph) so we're weaving to keep from getting ahead of them. So really we're covering the same ground as the bombers but flying faster. The bombers will cover 640 miles in that 2.8 hours and we're going out AND back so our roughly estimated combat radius is about 320 miles. About 50 miles less than a Thunderbolt with drop tanks. If we can cruise at less than 2600rpm maximum cruise (not recommended over Europe) then we can go farther. All hail the mighty Thunderbolt.



If you want to develop a Kentucky windage scale model please consider the following:
Start and warm up engines, taxi to transient, take off in pairs and orbit as elements build into flights and into squadrons and finally assemble on group leader for climb. All of the preliminary fuel consumption will be near Max continuous power (Normal @ 39-40"Hg) with approximately 1-2 minutes of Take Off Power ~MP. Tanks would be switched to external tank (75 gallon CL) and climb at Max continuous until 25000 feet. The drag on the P-39 is at maximum while the tank is full. Time for warm up, Take Off, assembly and climb to 25000 feet ~ 25 minutes with total fuel consumption of approximately 30-35 gallons (including 10-15 internal, 20 external) leaving 105-110 internal and 55 external. Remove the fuel required for loiter/reserve for let down and landing - another ~ 10 gallons. So, at start of Cruise for R/V point you start with 120-25=95 gallons of internal fuel plus 55 external.

For mission planning the Combat Radius must account for a.) drop tanks for combat leaving only internal fuel, b.) 5 minutes of Combat Power, c.) 15 minutes of Military Power at an average of ~2.5 to 3X Cruise Power consumption. That translates to burning 20+ gallons of your remaining (120-15-25) for takeoff/formation assy) - leaving you with 60 gallons to get home and land with reserve.

Before going back to your escort cruise scenario, let's pause:

AT optimal cruise power setting with low RPM/MP the Allison at 10K was ~ 60+ gallons per hour and the cruise speed with external tank was 20-30mph less than in clean mode. If the optimal cruise speed of the P-39 was the same as the turbo/supercharged P-38 at 25000 feet (doubtful) then 250mph TAS less 30mph=220 mph TAS for external 75 gallon tank (with 55 remaining internally) --------> less than 1 hour and approximately 220 miles from start of escort cruise at 25000 feet (optimistic) before dropping empty tanks.

If combat occurs under above scenario, then the 60 gallons at 250 mph (now clean) gets you back over the channel in the 1 hour of optimal fuel consumption. 

The Brequet equations will yield a more optimistic range based on ratio of L/D and the fact that Induced Drag will decline as the weight fraction of fuel decreases over time.

Two points - I have never seen equivalent Range tests performed at Eglin for P-39 (as exist for P-51 and P-47) but I know that the Power/Thrust available per pound of fuel consumed for the P-39 Allison at 25K is much less than the P-51. The Mustang Packard consumed about the same fuel per hour but the cruise speed for max mileage at both 10,000 and 25,000 feet were so much higher because of the superior L/D of the Mustang. The cruise speed of the P-51B/D was about 290-305 mph TAS at 25000 feet for optimal range - a FAR better combat state than either P-39 or P-38.

Second point - I am Not positive about the aggregate estimates of internal fuel consumption for the narrative for P-39 and substituted a P-51B narrative. Would be delighted of you can point me to a source that clarifies operational data for the P-39 for warm up, take off, climb and cruise (clean and w/external 75 gallon tank) at 25K

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## pbehn (Mar 27, 2018)

Peter Gunn said:


> Are you seriously contending that the P-39 could do the job of the Thunderbolt in the ETO?


This is what "whataboutery" results in. Whatever the strengths and weaknesses of the P-47 were it wasn't up to the job at the time. Neither was the P-38 though both together provided numbers for missions to be made, things to be learned and progress made. The answer was the P51 which was not only more powerful and aerodynamic than the P 39 it carried more fuel with a total of 489 US gal for the P-51D, it is purely academic whether the P39 was better than the P47, the Spitfires range was also increased and it was used on long range missions, they required huge numbers acting in waves escorting the bomber group AND additional planes to escort individual bombers who couldn't keep with the group.

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## drgondog (Mar 27, 2018)

Milosh said:


> Bill, ww2 fighter range - Bing images


Thank you !

I haven't seen one yet that accurately depicts Combat Radius for the P-38H to P-38 J w/o LE tanks to P-38J with either LE 55 gallon tanks installed as kits or production. Ditto on differentiating the P-51B w/o 85 gallon tank to P-51B/C with 85 gallon tank to Radius with 75 gallon vs 110 gallon external tanks.

The Lockheed P-38 55 Gallon LE kits started arriving in UK in late November (Ditto P-51B 85 gallon Fuselage tank kits) but neither were capable of Berlin missions until Big Week and March 1944 when enough per FG were finally installed. .


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## DarrenW (Mar 27, 2018)

P-39 Expert said:


> Please read the official performance tests for the P-39 at wwiiaircraftperformance that were made available in late 2012



The actual documents may have been mostly unavailable to the general public, but the data from them could most certainly be found in period books of the time. For instance, here is the performance figures for the P-39N that I gleaned from _Combat Aircraft of the World (_W.R. Taylor_)_ which was published way back in 1969. See any similarities with your oft-quoted document?

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## P-39 Expert (Mar 27, 2018)

pbehn said:


> How much fuel is used by a P39 carrying a 110 gal external tank for warm up take off and climb to 25,000ft? What is the cruise speed of a P39 on max continuous at 25,000ft with external tank?


Like I said in my post, reserve for warm up, take off and climb to 5000' is 20 gal. Climbing the remaining 20000' to 25000' took about 10 minutes but remember while you are climbing you should be headed toward your target so you are not losing this 10 minutes. P-39Q Pilot's Manual shows 267mph at 25000' with drop tank. Q had the wing guns so you can probably add about 15mph to that for the N since it didn't have the drag of those guns, so around 283mph.


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## P-39 Expert (Mar 27, 2018)

drgondog said:


> If you want to develop a Kentucky windage scale model please consider the following:
> Start and warm up engines, taxi to transient, take off in pairs and orbit as elements build into flights and into squadrons and finally assemble on group leader for climb. All of the preliminary fuel consumption will be near Max continuous power (Normal @ 39-40"Hg) with approximately 1-2 minutes of Take Off Power ~MP. Tanks would be switched to external tank (75 gallon CL) and climb at Max continuous until 25000 feet. The drag on the P-39 is at maximum while the tank is full. Time for warm up, Take Off, assembly and climb to 25000 feet ~ 25 minutes with total fuel consumption of approximately 30-35 gallons (including 10-15 internal, 20 external) leaving 105-110 internal and 55 external. Remove the fuel required for loiter/reserve for let down and landing - another ~ 10 gallons. So, at start of Cruise for R/V point you start with 120-25=95 gallons of internal fuel plus 55 external.
> 
> For mission planning the Combat Radius must account for a.) drop tanks for combat leaving only internal fuel, b.) 5 minutes of Combat Power, c.) 15 minutes of Military Power at an average of ~2.5 to 3X Cruise Power consumption. That translates to burning 20+ gallons of your remaining (120-15-25) for takeoff/formation assy) - leaving you with 60 gallons to get home and land with reserve.
> ...


My source is the P-39Q Pilots Manual, google it. At 25000' the P-39Q burned 62 gallons per hour at 2600rpm (maximum cruise power aka maximum continuous power), the highest cruising power available at that altitude. Full power at 25000' would cost you about 71gph. My estimate was prepared just like the manual says to plan a mission. I stand by those figures.


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## pbehn (Mar 27, 2018)

P-39 Expert said:


> Like I said in my post, reserve for warm up, take off and climb to 5000' is 20 gal. Climbing the remaining 20000' to 25000' took about 10 minutes but remember while you are climbing you should be headed toward your target so you are not losing this 10 minutes. P-39Q Pilot's Manual shows 267mph at 25000' with drop tank. Q had the wing guns so you can probably add about 15mph to that for the N since it didn't have the drag of those guns, so around 283mph.


Please refer to and answer Drgondog's post on a similar subject. Prior to logging on to this forum I couldn't have asked the question I did, it is from reading posts like his that I have learned something.

There is much more to it than just taking off. One escort plane was part of squadron and a group of circa 600 that need to form up and rendezvous first with each other and then with the bomb group.

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## Shortround6 (Mar 27, 2018)

P-39 Expert said:


> 9500 or so P-39s produced between January 1941 and August '44. About half went to Russia. Most of those were the superior N and Q models produced from Dec '42 which comprised about 7000 of the total 9500. N and Q differed only in wing armament (4 .30s vs 2 .50s) and since the Russians removed the wing guns the Russian N and Q were pretty much the same plane. Earlier D, F, K and L had the 12000' engines, the M, N and Q had the 15000' engines that were about 100hp better at all altitudes.



The K and L had engines rated at 1325hp for take-off NOT WEP although they were down to 1150hp at 12,000ft. 
The 1200hp engines in the M, N and Q did NOT have 100hp more at all altitudes. They didn't have at the lower altitudes. 

They had around 50hp more than the old engines in the Ds and Fs. below 12,000ft. 

They had 125hp less than the K and L below a few thousand feet an NO, use of WEP does not make up for that. 
The old engines were allowed to use 1490hp up to 4300ft
The K & L engines could make 1580hp up to 2500ft.
Both engines then tapered off to 1150hp at 12,000ft.
The "super" engine was allowed 1410hp up to 9600ft.

I have no idea how you get 100hp _ better at all altitudes _out of that. 

yes they were better at higher altitudes.

I did a little number crunching and taking a P-39Q with 87 gallon tanks and taking out the wing .50s and replacing them the four .30 cal armament gives you a take-off weight of 7411lbs with full fuel, oil, ammo and pilot. Getting down under 7300lbs is going to take some effort. 

AS far as the P-39 vs early P-47 as an escort fighter, ROFLMAO.

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## P-39 Expert (Mar 27, 2018)

Peter Gunn said:


> But why would you want 24,000 P-39s? I get your passion for the airplane, but the AAF was hardly stupid when they dumped it in favor of _capable_ designs. Also, one squadron of P-38's was worth more than a group of P-39's on operations. George Welch sure didn't think too much of it, but maybe he was wrong as well.
> 
> Also, do you think no one here has looked at data since before 2012? Dude, you have authors and historians in here.


I'm just making a point about the dollar cost of the two planes. Those Lightnings were expensive. Not saying Welch was wrong, wasn't he the guy who was crashing his P-39s so he could get P-38s? Also the first man to break the sound barrier (F-86 diving). Sorry Chuck Yeager.  And I believe he actually got airborne at Pearl Harbor (had him mixed up with Buzz Wagner). Depends on the model of the P-39. Older ones (D,F,K,L) not as capable as later models (M, N and Q). N actually the better of the three. If he had an old one he was probably crashing them on purpose. 

I'm neither an author nor historian. But if you haven't looked at the P-39 in wwiiaircraftperformance.org then you don't have the latest information. And I can tell that a whole lot of you authors and historians haven't.

And by the way, am I a moron? I have a masters degree and I read pretty good. Am I not capable of reading a page of information and commenting on it?

Look, I have read everything I could find on WWII and before late 2012 I thought exactly the same as you. The P-39 was a turd based on all the hearsay and stat books that don't agree with each other. But now you can compare all the planes (except Russian) straight up and compare them accurately. PLEASE GO TO THE SITE. I'm no shill for them, it's free. Or just keep on repeating what William Green and the rest say about the P-39. 

BTW, you guys are dead meat, I have finally figured out how to post a photo that is already open. So you'll soon be seeing the graphs already open.


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## Milosh (Mar 27, 2018)

P-39 Expert said:


> Okay, lets see what a P-39N would do. 120 gals internal plus a drop tank of 110 gals = 230 gals. Takeoff and climb to 5000' reserve is 20 gals so now we're down to 210 gals available. A P-39N burned 62gph at 25000' at 2600rpm max continuous power so we have a theoretical 3.4 hours to escort those bombers. Reduce that by 15 minutes combat and a 20 minute landing reserve so now we have 2.8 hours of actual escort time. We're flying faster than the bombers (230mph) so we're weaving to keep from getting ahead of them. So really we're covering the same ground as the bombers but flying faster. The bombers will cover 640 miles in that 2.8 hours and we're going out AND back so our roughly estimated combat radius is about 320 miles. About 50 miles less than a Thunderbolt with drop tanks. If we can cruise at less than 2600rpm maximum cruise (not recommended over Europe) then we can go farther. All hail the mighty Thunderbolt.



Bombers speed was closer to 180mph. Actually, you are flying further than the bombers if you are weaving.

Post the FOIC for the P-39N.


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## Peter Gunn (Mar 27, 2018)

Just FYI, I've been visiting wwiiaircraftperformance.org for 10 years.

See pbehn's post #658. I felt well read on the subject when I got here, but had to check the ego at the door and totally concur with what he says in his post.

See drgondog's post #652, there isn't much he doesn't know about this subject and has been extremely helpful ( and continues to be so ) and extremely patient ( I can attest to that ). When he lays out a scenario like he did in that post you can take it to the bank as they say.

No, I do not consider you a moron.

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## Glider (Mar 27, 2018)

pbehn said:


> Please refer to and answer Drgondog's post on a similar subject. Prior to logging on to this forum I couldn't have asked the question I did, it is from reading posts like his that I have learned something.
> 
> There is much more to it than just taking off. One escort plane was part of squadron and a group of circa 600 that need to form up and rendezvous first with each other and then with the bomb group.


I Was Waiting for someone to mention this, nicely done

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## pbehn (Mar 27, 2018)

Peter Gunn said:


> See drgondog's post #652, there isn't much he doesn't know about this subject and has been extremely helpful ( and continues to be so ) and extremely patient ( I can attest to that ). When he lays out a scenario like he did in that post you can take it to the bank as they say.
> .


It is not only Drgondog's posts but others too. For example, Bill Runnels longest mission he said was 11 1/2 hours. The P 51 was considered a miracle because it could complete 6 hr missions. That huge difference in time plus the huge difference in speed of a fighter and bomber meant wave after wave of escorts handing over to each other, all of which needs fuel and all of which needs a contingency to avoid the FUBAR of a bomb group over Germany with no escort. Oh and did I mention the Bombers didn't have a "target" (sometimes listed by Stona), they had a list in case the priority target was obscured. No escort ever set course for the target, on many missions only about 20% even went there.

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## DarrenW (Mar 27, 2018)

P-39 Expert said:


> Or just keep on repeating what William Green and the rest say about the P-39.



I presented an excerpt from a book, published almost half a century ago, with the very same performance figures for the vaunted P-39N that you are now raving about in 2018. How is this ground breaking information?

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## Elmas (Mar 27, 2018)

I can admit that, like all botched interceptors, P-39 could have been relegated to ground attack: to think of it as an escort fighter








I always tought that an escort fighter had to sheperd his buddies from well above, and not far below.


Shooting to a Me-109 or a FW 190 with a 37 mm? Game with feathers is usually hunted with pellets, of various sizes...

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## DarrenW (Mar 27, 2018)

P-39 Expert said:


> Tell me again how great a dogfighter the Hellcas was.





P-39 Expert said:


> If we can cruise at less than 2600rpm maximum cruise (not recommended over Europe) then we can go farther. All hail the mighty Thunderbolt.





P-39 Expert said:


> Compare the N to the Typhoon. About the same speed but N climbs a lot faster.



So let me see if I have this straight. You believe the N model of the Airacobra to be better dogfighter than the Hellcat, a better escort fighter than the Thunderbolt, and a better ground attack machine than the Typhoon. And even though the authorities knew this to be true you want us to believe that they still decided to keep the crappy planes and give the great P-39N to the French, Italians and Russians. Maybe it's you who thinks that we're the morons here....

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## DarrenW (Mar 27, 2018)

drgondog said:


> Milosh - where did you find that particular Chart? Is has several errors but the format is one I will put in my new book about the P-51B



How far along are you with it? I would love to buy a copy when it finally is in print.


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## P-39 Expert (Mar 27, 2018)

Shortround6 said:


> The K and L had engines rated at 1325hp for take-off NOT WEP although they were down to 1150hp at 12,000ft.
> The 1200hp engines in the M, N and Q did NOT have 100hp more at all altitudes. They didn't have at the lower altitudes.
> 
> They had around 50hp more than the old engines in the Ds and Fs. below 12,000ft.
> ...



The chart below may help. Looks like just about 100hp difference at every altitude.


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## drgondog (Mar 27, 2018)

DarrenW said:


> How far along are you with it? I would love to buy a copy when it finally is in print.


 In the writing stage - Timeline complete for all the details and sources. Most data collected for Performance Comparisons, most photos gathered by still looking for FW 190 A-2 through A-7 with various armament mods, Ditto for Bf 109G-1 through G-6. Tables complete, sourcing side view elevations - a year away

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## DarrenW (Mar 27, 2018)

_Bell P-39 Airacobra - Wikipedia

A total of 149 P-39s would be used: the P-39N for training, while newer Qs were used in the front line....
_
You see, even the Italians realized how inadequate the P-39N was and relegated it to non-combat units!

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## DarrenW (Mar 27, 2018)

Sounds like a winner to me! Good luck and please let us know when it's available for purchase.


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## P-39 Expert (Mar 27, 2018)

DarrenW said:


> So let me see if I have this straight. You believe the N model of the Airacobra to be better dogfighter than the Hellcat, a better escort fighter than the Thunderbolt, and a better ground attack machine than the Typhoon. And even though the authorities knew this to be true you want us to believe that they still decided to keep the crappy planes and give the great P-39N to the French, Italians and Russians. Maybe it's you who thinks that we're the morons here....


You're exaggerating a little, all I'm saying is that the P-39 wasn't as bad as you thought. Was competitive with most planes (especially in 1943) except for the Spitfire IX and the Merlin P-51 (Dec '43) and they had two stage engines. Got it's bad reputation in '42 because it was overloaded by the AAF (British with the P-400 contract actually) and didn't have oxygen at Guadalcanal. AAF gave up on it just as the P-38 was about to enter combat (late '42). Problem was the P-39N was starting production and with the 9.6 geared engine was a MUCH better plane. They shuttled them off to training command and the Russians who loved them and demanded more. And the early Lightnings (F/G) and Thunderbolts (B/C) were not as great as advertised until vastly improved models came basically after the Luftwaffe was done. That's what I think anyway.

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## Shortround6 (Mar 27, 2018)

P-39 Expert said:


> My source is the P-39Q Pilots Manual, google it. At 25000' the P-39Q burned 62 gallons per hour at 2600rpm (maximum cruise power aka maximum continuous power), the highest cruising power available at that altitude. Full power at 25000' would cost you about 71gph. My estimate was prepared just like the manual says to plan a mission. I stand by those figures.




May I say balderdash!

As to any extra performance due to deleting wing guns from the P-39Q and going back to the four .30 cal guns.

P-39Q at sea level with drop tank.....259mph...2600rpm.......39in map.......96 gallons an hour
P-39K at sea level with drop tank.....256mph....2600rpm......37.5in map.....96 gallons an hour

Not seeing any big reduction in drag here. certainly not 10-15mph worth. 

You want the performance of the 87 gallon plane but you want the endurance of the 120 gallon tank plane. Sorry, reality doesn't work that way. 
you also are planning on using a 110 gallon drop tank which seems to be only slightly more common than unicorns. No mention of them in P-39 manuals. I am sure they existed somewhere but then adding another 210lbs of fuel just makes the initial climb out worse. 
There is no need to guess at the fuel needed to get to 25,000ft, it is in the tables in the manuals.
for a P-39Q with a take off weight of about 8100lbs Which is close enough to our P-39X with four wing guns, 87 gallons of internal fuel and a 76 gallon drop tank (within 50lbs?) it needs 39 gallons using a combat climb and 42 gallons using a ferry climb. 
ALl of these planes took of using one of the main tanks and switched to the drop tanks (subject to restrictions of CG) as soon as possible. However most of the planes arranged for any venting, overflow form the carb to go back to the main tank used for take-off so they partially filled in flight. 

True test/criteria of combat radius is not how far you can get in but how far you can get back from, extra large drop tanks are no help. 
after you drop the tanks you need 20 minutes at max power for the P-39, other planes were rated at 5 minutes WEP and 15 minutes at military power at altitude. P-39 can't make military power at these altitudes so take what you can get. It will suck up 82 gallons an hour at 20,000ft at nax continuous so perhaps the 71 gallons hour is an underestimate for full power at 25,000ft?
If we use the pounds of fuel per hour for military power at 15,500ft (1125hp for 138 gallons=0.736) and use it for 772hp at 25,000ft we get a consumption of 94.7 gallons an hour. Round it down to 90 or 1.5 gallons per minute.
Combat allowance is 30 gallons, leaves 57 gallons in our 87 gallon plane assuming that the return fuel fully filled the wing tank. Now you have to get the heck out of Dodge. You can fly at 224IAS (313 true) at 20,000ft using 77 gallons an hour. You do want 16 gallons or so (the reserve?) to find your own airfield and land so you have about 40-41 gallons for the withdrawal. chart says 40 gallons is good for 150 miles but you can slow down some over the Channel. 
Basically you can escort a bit past Amsterdam and Antwerp. Paris might be out of reach.

cutting things too close leads to incidents Like No 133 Squadron in their Spitfires being blown off course by high winds and 11 planes out of twelve being lost.

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## Shortround6 (Mar 27, 2018)

P-39 Expert said:


> The chart below may help. Looks like just about 100hp difference at every altitude.


Changing the goal posts?

Original statement. 

"Earlier D, F, K and L had the 12000' engines, the M, N and Q had the 15000' engines that were about 100hp *better* at all altitudes."

Now we have " just about 100hp *difference* at every altitude."

I don't know what college or degree you have but in most of the world being 100hp _below, _while being a *difference*, is in no way, shape or form 
*better*. 

the chart is also for WEP power.

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## pbehn (Mar 27, 2018)

P-39 Expert said:


> The chart below may help. Looks like just about 100hp difference at every altitude.



P-39... you are debating about small details, but missing the big picture. When a nation goes to war things change very quickly. From 1936 to 1940 the Spitfire was the MkI version, by 1942 it was on to the Mk IX and that doesn't involve various PR and early Seafires. The Dieppe raid took place in August 1942. This had
B-17 Bombers escorted by Spitfire 4 squadrons of MkIXs
Typhoons in Service, one month later the first Tempest prototype flew
First Kill and loss of the P-51A therefore in squadron service. The Merlin engine P-51B/C were on order and first flew in May 1943.
The P 47 was arriving and became operational in Jan 1943
The P 38 started being used from Iceland in August 1942

At the time things were changing faster than most could keep track of. Any use of the P39 in 1943 would have seen it suffer the same fate as the Spitfire Mk V and whatever the cost of an aircraft is the pilot is worth more. The British lost whole flights of aircraft over France and generally had a loss rate of 5-1 against with the Spitfire V in 1941/42, the P39 even in the N version only promised more of the same.


Also, when discussing December 1942 as the start of production of the P-39N please note this is 20 months before the first operational use in squadron service of both the Me262 and Gloster Meteor

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## DarrenW (Mar 27, 2018)

P-39 Expert said:


> You're exaggerating a little, all I'm saying is that the P-39 wasn't as bad as you thought. Was competitive with most planes (especially in 1943) except for the Spitfire IX and the Merlin P-51 (Dec '43) and they had two stage engines. Got it's bad reputation in '42 because it was overloaded by the AAF (British with the P-400 contract actually) and didn't have oxygen at Guadalcanal. AAF gave up on it just as the P-38 was about to enter combat (late '42). Problem was the P-39N was starting production and with the 9.6 geared engine was a MUCH better plane. They shuttled them off to training command and the Russians who loved them and demanded more. And the early Lightnings (F/G) and Thunderbolts (B/C) were not as great as advertised until vastly improved models came basically after the Luftwaffe was done. That's what I think anyway.



Ok, NOW you're being a little more reasonable with your assertions. Maybe from here on out we can actually learn a little from each other.


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## DarrenW (Mar 27, 2018)

So tell me P-39 Expert, which time frame are we to limit ourselves to when discussing the various merits of the P-39N? Would it have survived past the summer/fall of 1944 as a viable fighter plane if only given a chance? And I'm talking in both the ETO and PTO. And what kind of growth do you see it needing, if any, in order to handle the latest German and Japanese aircraft that entered the picture during this same time period?


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## Shortround6 (Mar 27, 2018)

P-39 Expert said:


> You're exaggerating a little, all I'm saying is that the P-39 wasn't as bad as you thought. Was competitive with most planes (especially in 1943) except for the Spitfire IX and the Merlin P-51 (Dec '43) and they had two stage engines. Got it's bad reputation in '42 because it was *overloaded by the AAF (British with the P-400 contract actually)* and didn't have oxygen at Guadalcanal. AAF gave up on it just as the P-38 was about to enter combat (late '42). Problem was the P-39N was starting production and with the 9.6 geared engine was a MUCH better plane. They shuttled them off to training command and the Russians who loved them and demanded more. And the early Lightnings (F/G) and Thunderbolts (B/C) were not as great as advertised until vastly improved models came basically after the Luftwaffe was done. That's what I think anyway.



Still looking for the *PROOF* of the bolded part. Please post either links or books/page numbers.

The N was a _marginally_ better plane. Changing the critical altitude by 3500ft didn't amount to a hill of beans when other planes were changing critical altitude by much larger amounts.
DB605A in the Bf 109G ws good for 1355ps at 18700ft. 200 more HP 3000ft feet higher in a smaller, lighter plane.
P-39N vs 109G............P-39 is toast.


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## Glider (Mar 27, 2018)

P-39 Expert said:


> You're exaggerating a little, all I'm saying is that the P-39 wasn't as bad as you thought.


Not really. The P39N was clearly a better aircraft than the P39D. But so what, the Typhoon was a lot better than the Hurricane, the Spit IX better than the Spit V, the P47 better than the P40 and P43 Lancer, the 109F better than the 109E


> Was competitive with most planes except for the Spitfire IX and the Merlin P-51 (Dec '43) and they had two stage engines.


 Wrong again, as a GA aircraft the P39 was almost useless, it didn't carry much of a payload, couldn't carry it very far and had a number of worrying defects in it's weight. As a fighter in 1943, the Typhoon gave it a run for its money and the Typhoon's biggest fans wouldn't claim it was a great fighter


> Got it's bad reputation in '42 because it was overloaded by the AAF (British with the P-400 contract actually) and didn't have oxygen at Guadalcanal.


 Total bull unless you want to fight in a plane that was a match for the Zero and KI43 in fragility with no armour, self sealing fuel tank and no radio (if you had your way). Pilots flying for you would have Voodoo dolls with your effigy on them.


> AAF gave up on it just as the P-38 was about to enter combat (late '42). Problem was the P-39N was starting production and with the 9.6 geared engine was a MUCH better plane. They shuttled them off to training command and the Russians who loved them and demanded more.


 The AAF gave up on them because they had little range, no payload, were fragile and much better aircraft such as the P47D were close to production, or in production as the P51 or available e.g. Spit IX/VIII plus of course the 109 was all over the P39
Why did the Russians love them, because the vast majority of their combat was at low level where the P39 was best and even they didn't use them for ground attack.


> And the early Lightnings (F/G) and Thunderbolts (B/C) were not as great as advertised until vastly improved models came basically after the Luftwaffe was done. That's what I think anyway.


I would take a P47 over the P39 any day, and so did the USAAF

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## P-39 Expert (Mar 27, 2018)

Shortround6 said:


> May I say balderdash!
> 
> As to any extra performance due to deleting wing guns from the P-39Q and going back to the four .30 cal guns.
> 
> ...



Your 96 gph figure is at sea level. P-39Q burned 62gph at 25000' at max continuous 2600rpm from the pilots manual. Developed less power at 25000' so burned less gas.

The gondola wing guns on the Q cause the speed reduction and you are comparing two planes with different (versions of the same) engines that developed different power.

110 gal tank was nearly ubiquitous in the 8th AF in England for Thunderbolts, they also had a paper version of the tank. 110 gal tank was also used extensively in New Guinea.

The fuel to climb to 25000' IS in the manual, but that is assuming that you climb to 25000' over your own base and then start your cruise. Deduct the 20 gallon reserve to get to 5000' then climb the rest of the way to 25000' on your target heading as part of cruise.

Regarding weight, I'm figuring closer to 8400# at takeoff (7650# with 120gal internal plus 750# for the 110 gal including tank). There is no way that the N/Q could burn MORE than 62gph at 25000' That was max continuous at 2600rpm. Only higher power setting was 3000rpm combat military where it burned about 71gph. No WEP at this height. The higher the altitude the less power hence less fuel burned above critical altitude. Go a little higher than 25000' and burn even less fuel.

So back to my original formula per the pilot's manual. 120gal + 110gal drop = 230gal less 20 gallon reserve for T/O and climb to 5000'. Turn to your heading and climb the remaining 20000' flying toward your target. I don't care how you figure it, the remaining 210 gals after deducting reserve for T/O is burned at 62gph which will take you 3.4 hours. Deduct 15 minutes for combat at 3000rpm and 20 minutes landing reserve and you have 2.8 hours of actual escort time. You fly faster than the B-17/24 but you weave to stay with them so you are going their speed which is about 230mph x 2.8 hrs = 644mi. Half of that is your combat radius 322 miles at max continuous 2600rpm after all reserves. That's not even factoring in that you may come home at a lower power setting and lighter weight. That's how the pilot's manual says to do it. Of course this is theoretical and the pilot had to monitor both his fuel gauge and the clock. Pretty simple really, when your 110gal drop tank ran dry it was time to head home with your internal fuel and reserves.


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## varsity07840 (Mar 27, 2018)

P-39 Expert said:


> You're exaggerating a little, all I'm saying is that the P-39 wasn't as bad as you thought. Was competitive with most planes (especially in 1943) except for the Spitfire IX and the Merlin P-51 (Dec '43) and they had two stage engines. Got it's bad reputation in '42 because it was overloaded by the AAF (British with the P-400 contract actually) and didn't have oxygen at Guadalcanal. AAF gave up on it just as the P-38 was about to enter combat (late '42). Problem was the P-39N was starting production and with the 9.6 geared engine was a MUCH better plane. They shuttled them off to training command and the Russians who loved them and demanded more. And the early Lightnings (F/G) and Thunderbolts (B/C) were not as great as advertised until vastly improved models came basically after the Luftwaffe was done. That's what I think anyway.


So, you have a VERY short range aircraft with armament that includes useless .30 cal and 37mm gun(s), an altitude performance that in no way comes close to the P-47 and P-38, not to mention the P-51. It can't land on or take off from aircraft carriers. What's the upside of the P-39N?

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## Shortround6 (Mar 27, 2018)

I would note that short ranged as the P-47C was it had roughly double the range of an 87 gallon Aircobra at similar low speeds. 
In fact an 87 gallon Aircobra was roughly equal in range to the P-47C when using a *75 gallon drop tank.*
Trouble is the drop tank knocked about 30mph indicated off the airspeed.


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## pbehn (Mar 27, 2018)

P-39 Expert said:


> You're exaggerating a little, all I'm saying is that the P-39 wasn't as bad as you thought.



Although this post was directed at DarrenW it could be directed at almost everyone on this forum, you assume what our opinion is and evangelise to change that opinion. This is an international forum and we all have our point of view and even our favourites. Mine is the Hurricane, not on any metric of performance, but just for being there, when nothing else was and being of a design that was simple enough to build and fly that it turned the issue over to number of pilots available not aircraft. Despite all the fabulous aircraft produced in WW2 my opinion doesn't and won't change, even though I enjoy such discussion.​

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## pbehn (Mar 27, 2018)

Shortround6 said:


> I would note that short ranged as the P-47C was it had roughly double the range of an 87 gallon Aircobra at similar low speeds.
> In fact an 87 gallon Aircobra was roughly equal in range to the P-47C when using a *75 gallon drop tank.*
> Trouble is the drop tank knocked about 30mph indicated off the airspeed.


As I understand it, the P47s range was as long as it was asked to be. When asked for a long range P47 Republic came up with the "N" version, which was about equal/on par with the P 51.


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## DarrenW (Mar 27, 2018)

I was trying to help out your cause Mr. P-39 but it would seem that I have been over-ruled!

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## Milosh (Mar 27, 2018)

Still waiting for the FOIC for the P-39N to be posted.


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## Shortround6 (Mar 27, 2018)

pbehn said:


> As I understand it, the P47s range was as long as it was asked to be. When asked for a long range P47 Republic came up with the "N" version, which was about equal/on par with the P 51.



The P-47 edit>N<end edit also required a new engine, new propeller knowledge, a new turbo and water injection. It couldn't have been built in 1942, at least not successfully.

I would note that the short ranged P-47 could fly at 200IAS (300mph true?) at 25,000ft without drop tank using 95 US gallons an hour. So even if it reached 25,000ft with only 200 gallons left in the tanks it could fly 215 miles further than a P-39Q carrying a 75 gallon drop tank and while going 30mph faster.

Now figure how good an escort the P-39 would have been.

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## pbehn (Mar 27, 2018)

Shortround6 said:


> The P-47 also required a new engine, new propeller knowledge, a new turbo and water injection. It couldn't have been built in 1942, at least not successfully.
> 
> I would note that the short ranged P-47 could fly at 200IAS (300mph true?) at 25,000ft without drop tank using 95 US gallons an hour. So even if it reached 25,000ft with only 200 gallons left in the tanks it could fly 215 miles further than a P-39Q carrying a 75 gallon drop tank and being going 30mph faster.
> 
> Now figure how good an escort the P-39 would have been.


Are you telling me that between the late 1930s and early 1940s people in the aviation industry learned a lot very quickly? Excuse me, I must take a seat and take time to absorb this.


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## DarrenW (Mar 27, 2018)

Glider said:


> Pilots flying for you would have Voodoo dolls with your effigy on them.


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## Shortround6 (Mar 27, 2018)

pbehn said:


> Are you telling me that between the late 1930s and early 1940s people in the aviation industry learned a lot very quickly? Excuse me, I must take a seat and take time to absorb this.


 Sorry, I type too fast and leave things out, I meant the P-47*N *couldn't have been built in 1942. The early P-47s obviously were. 

But yes, knowledge was being gained very quickly. Maybe even faster than cell phones advance now


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## pbehn (Mar 27, 2018)

Shortround6 said:


> Sorry, I type too fast and leave things out, I meant the P-47*N *couldn't have been built in 1942. The early P-47s obviously were.
> 
> But yes, knowledge was being gained very quickly. Maybe even faster than cell phones advance now


Of course it was there was a war on, everything goes quicker in war time. Now tell me a time between 1939 and 45 when the Spitfire didn't need a better engine, a better field of view, better wings, better armament and better cooling. Of the thousands produced I doubt the maximum of any type that was completely identical apart from paintwork (squadron markings) was only a few hundred.


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## Milosh (Mar 27, 2018)

I think someone forgot to look at the other charts in the P-39Q manual.

So,
warm up, take-off, climb to 25k - 40gal
cruise to target - 62gal (minimum for 1 hour, 2 hour 124gal)
combat - 40gal (max)

Gee, that leaves 88gal left out of the 230gal the a/c started with for 1 hour of cruise time. That is not factoring in lost fuel if the drop tank had to be dropped before empty.

AAF heavy bombers cruised at 180mph or less.

edit: As been pointed and made a correction.

Still, 180-200mi barely gets the bombers over Holland.

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## DarrenW (Mar 27, 2018)

pbehn said:


> This is an international forum and we all have our point of view and even our favourites. Mine is the Hurricane, not on any metric of performance, but just for being there, when nothing else was and being of a design that was simple enough to build and fly that it turned the issue over to number of pilots available not aircraft. Despite all the fabulous aircraft produced in WW2 my opinion doesn't and won't change, even though I enjoy such discussion.



I'm in complete agreement with pbehn. For whatever reason we all gravitate toward one aircraft or another, mine happens to be the Grumman Hellcat (big surprise, right?), yours the Airacobra. But I learned early on that the people on this forum know *A LOT* more than you might initially give them credit for. There are some seriously well-read aviation enthusiasts here, along with bonafide pilots, engineers, designers, artists, and practically everything else that has something to do with the passion of flight. Just being a fan of a particular airplane and spewing your opinion everywhere just isn't enough if you want to persuade people to your way of thinking.

It was extremely humbling to realize that my opinion about a particular WWII aircraft wasn't the only one in the universe, and I'm a better person for it. People like Tomo and pbehn in particular set me straight early on and I'm glad I decided to ease off a little and not let my ego get in the way of learning something new or having an open mind to vewing things a little bit differently going forward.

I for one am not saying that the points you've made thus far have zero merit. My main problem was your approach. I was hoping that you could make a powerful argument for the Airacobra, and in particular the P-39N, because it is often neglected by historians. It was when you began to denigrate the abilities of truly remarkable aircraft to somehow lift the Airacobra up a notch or two that you lost some credibility with me.

I just hope we can put this discussion back where it was about 4,000 posts ago and start over with a fresh look at the facts. Do you think that's even possible?

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## Shortround6 (Mar 27, 2018)

Milosh said:


> I think someone forgot to look at the other charts in the P-39Q manual.
> 
> Climb to 25,00ft took 39 > 42 gal.
> 
> ...



you have to read the fine print, lower right of middle chart, "Fuel includes warm up and take-off allowance."

I will note that on some other planes the warm up and take-off allowance on the engine chart doesn't seem to match up with the fuel needed to climb to altitude  

The P-39 cannot fight with the tank attached.

I would also note that climb to altitude chart is for a plane weighing 8100lbs. MR P-39 Expert wants to put another 68 gallons in/under the plane (408lbs) a bigger drop tank (10-15lbs?) _and_ replace the 4 outer fuel cells, 70-80lbs? over 500lbs more?


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## DarrenW (Mar 27, 2018)

Well it looks like the climb rate of the P-39Q loaded to 7,200lbs can be equaled or even bested by the F6F-3 under similar WEP conditions. But seeing that it's not the N model, does this even count?

F6F-3:






P-39Q:


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## wuzak (Mar 27, 2018)

P-39 Expert said:


> Regarding weight, I'm figuring closer to 8400# at takeoff (7650# with 120gal internal plus 750# for the 110 gal including tank). There is no way that the N/Q could burn MORE than 62gph at 25000' That was max continuous at 2600rpm. Only higher power setting was 3000rpm combat military where it burned about 71gph. No WEP at this height. The higher the altitude the less power hence less fuel burned above critical altitude. Go a little higher than 25000' and burn even less fuel.



No WEP at the altitude at which you want to fight?

Wouldn't that mean you are pretty muck fucked?


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## wuzak (Mar 27, 2018)

DarrenW said:


> The actual documents may have been mostly unavailable to the general public, but the data from them could most certainly be found in period books of the time. For instance, here is the performance figures for the P-39N that I gleaned from _Combat Aircraft of the World (_W.R. Taylor_)_ which was published way back in 1969. See any similarities with your oft-quoted document?



The documents have, probably, been publicly available for decades. I'm sure that authors of books have researched them, as did Mike Williams at wwiiperformance.org, publishing his results in 2012.

Getting the documents in question likely required a trip down to the national archives of the US (or whatever they are called).


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## wuzak (Mar 27, 2018)

P-39 Expert said:


> Why did the AAF pull them so quickly to be replaced by the P-38, P-47 and P-51? Please remember I'm comparing the P-39N which was produced between Dec '42 and April '43. During that period the P-38F/G had just begun combat in Dec '42 and the P-47 would not see combat until May '43 after the N was out of production. These were the AAFs turbocharged super planes that were in production but not yet in combat. They had a vested interest in playing down the P-39 accomplishments and overstating their new planes. How would it play to have the AAF saying "We're giving the Russians a great little plane here, but our Lightnings and Thunderbolts are not quite ready yet". The AAF's motto was "Better planes coming", but the better planes were not that much better if at all in their earlier models. The Lightning couldn't dive and the Thunderbolt couldn't climb, and neither were very maneuverable at all. The Thunderbolt had a very short Spitfire-like range before they got drop tanks in August '43, and then still couldn't get much into Germany proper. But the biggest problem was cost. Now there are various cost figures for these planes that all got lower as production ramped up, but the Lightning was about 2.5 times the cost of a P-39 ($50k) and the Thunderbolt was about 1.7 times. American won WWII because we could pay the cost, but if a LIghtning cost 2.5 times as much then it should have been 2.5 times as capable. Put another way, you got almost a group of P-39s for every squadron of LIghtnings, or instead of the 9500 lightnings produced you could have had almost 24000 P-39s. Nobody really looks at it this way, but that's the way it was.



Did they have a vested interest in paying down the achievements of the P-39 in order to acquire more P-40s? From an earlier post of drgondog's, it seems that is what happened prior to P-38s, P-47s and P-51s being available in quantity.


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## Shortround6 (Mar 27, 2018)

wuzak said:


> No WEP at the altitude at which you want to fight?
> 
> Wouldn't that mean you are pretty muck fucked?



Not really, plenty of planes fought at altitudes well above WEP or it's equivalent. Think Spitfire Is and 12lbs boost in the BoB,
However the later P-39s were over 7000lb airplanes with around 770-780hp at 25,000ft (including RAM). And in 1943 that puts you behind the curve.


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## Elmas (Mar 28, 2018)

DarrenW said:


> _Bell P-39 Airacobra - Wikipedia
> 
> A total of 149 P-39s would be used: the P-39N for training, while newer Qs were used in the front line....
> _
> You see, even the Italians realized how inadequate the P-39N was and relegated it to non-combat units!



Not only, but in the strafing missions in the Balkans, knowing that P-39s, of any Mk, were easy meat for G-6s and G-10s, Regia Aeronautica had to escort them with the few worn-out Macchi 205 remaining. Strange, for a fighter escort...

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## wuzak (Mar 28, 2018)

Shortround6 said:


> Not really, plenty of planes fought at altitudes well above WEP or it's equivalent. Think Spitfire Is and 12lbs boost in the BoB,
> However the later P-39s were over 7000lb airplanes with around 770-780hp at 25,000ft (including RAM). And in 1943 that puts you behind the curve.



Surely using maximum rpm and wide open throttle counts as WEP, even when above FTH?

Before the Spitfire Is were allowed +12psi boost, WEP was at +9psi boost and FTH was higher. So, surely that is still WEP?


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## Shortround6 (Mar 28, 2018)

Terms may differ between nations. 
But basically, for the US, critical altitude is the altitude at which the throttle is fully open and the supercharger is supplying the rated amount of pressure (mass of air). In the case of the Allison it is making 1150-1125hp, that was the rated military power. Above that altitude, as the air gets thinner, the power falls off as the supercharger is maxed out, it can't supply any more air. 
Below critical altitude you have the choice/ability to open the throttle and allow the supercharger to work closer to it's maximum ability in the denser air. This subject to detonation limits of the fuel and to the strength of the engine. 
Here is a chart for the Merlin XX






At a given point in time the Air Ministry could decide that 9lbs boost was all the engine could stand on a regular basis. And the max height at which the engine/supercharger could supply 9lbs of boost is the critical altitude.
But they might decide that 12bs was Allowable for short periods *and * with increased maintenance (pulling and inspecting spark plugs, checking oil for metal particles)
That would be WEP or whatever a particular country chose to call it. But it doesn't work above the original critical height. 
They may decide to say that the altitude at which they can get 12lbs is the _new_ critical height and you do get a bit of boost between where you get 12lbs and the old 9lb critical height.
AS they improved fuel, strengthened parts and gained experience in how long the engines would last they would sometimes bump the max pressure up again to 15 and then 18lbs and the altitudes at which those pressure were available dropped the critical altitude. 
Please note that had they opened the throttle on the original engine they could have had that power at those altitudes at any time (subject to fuel and breaking the engine). 
For the Merlin 2850rpm was, except for the very early years, the max continuous power rpm and the allowable pressure varied a bit. 3000rpm might be considered military power or emergency power or some other term, But 3000rpm and 4lbs of boost at 24,000ft from a Merlin XX would not be considered as WEP. It would NOT require notations in log books or notification of the engineering officer that such a power setting was used. 

I hope I have explained that properly?

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## Peter Gunn (Mar 28, 2018)

pbehn said:


> _*It is not only Drgondog's posts but others too.*_ For example, Bill Runnels longest mission he said was 11 1/2 hours. The P 51 was considered a miracle because it could complete 6 hr missions. That huge difference in time plus the huge difference in speed of a fighter and bomber meant wave after wave of escorts handing over to each other, all of which needs fuel and all of which needs a contingency to avoid the FUBAR of a bomb group over Germany with no escort. Oh and did I mention the Bombers didn't have a "target" (sometimes listed by Stona), they had a list in case the priority target was obscured. No escort ever set course for the target, on many missions only about 20% even went there.


Agreed, I did not mean to leave out/insult the many contributors that make far more informative posts than I, I merely used that as a prime example of the caliber of knowledge on this board. I've read and studied aviation history since the 1960's ( basically all my life ) but do not feel I have much to contribute here, I check my ego at the door and have *learned a lot*, which is daunting considering what I _thought_ I knew when I first got here. Many of you have been extremely patient with my many dumb questions and for that you have my thanks.

OK, I'm off the soapbox now.

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## Shortround6 (Mar 28, 2018)

I too have learned a lot. Much from other contributors and some just from doing extra research. The scope of WW II aviation is such that one person (or even a small group) can not know everything and many here have areas in which they are quite knowledgeable and other areas where they are less so. But by sharing we all become more knowledgeable and the group as a whole is quite a large resource.

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## P-39 Expert (Mar 28, 2018)

varsity07840 said:


> So, you have a VERY short range aircraft with armament that includes useless .30 cal and 37mm gun(s), an altitude performance that in no way comes close to the P-47 and P-38, not to mention the P-51. It can't land on or take off from aircraft carriers. What's the upside of the P-39N?


The upside of the P-39 in general is that it was available from the start of WWII along with the P-40 and F4F Wildcat. That was all we had for combat until the P-38 Lightning got into combat very late that year. As the P-38 was entering combat in the Pacific and Mediterranean the much improved P-39N was beginning production and around 2000 were completed before the line switched to the Q model in April '43. N and Q were almost exactly alike differing only in wing armament. Since the Russians removed the wing armament on the P-39s the N and Q were basically the same plane. 7000+ planes built to this standard between 12/42 and 8/44. Seems to me that a little weight reduction by the AAF would have improved these models like the Russians did. I'm comparing the P-39N to other planes in combat in 1943, like the P-38, P-40, P-47 (May '43), Hellcat (Aug '43), Corsair (Feb '43), FW190, Me109G, Zero and Oscar. The two stage Merlin P-51 only saw combat from Dec '43. The Spitfire IX had the same Merlin engine as the P-51B but weighed 2500# less than a P-51D so its climb rate was absolutely amazing and significantly higher than any of these planes. Great plane if you wanted to go to Belgium and back.

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## P-39 Expert (Mar 28, 2018)

wuzak said:


> Surely using maximum rpm and wide open throttle counts as WEP, even when above FTH?
> 
> Before the Spitfire Is were allowed +12psi boost, WEP was at +9psi boost and FTH was higher. So, surely that is still WEP?


Talking about the Allison, no sir, WEP (in the US) was combat emergency power and extremely hard on the engine requiring the crew chief to do extensive maintenance prior to the next flight. There was a little wire or seal across the throttle and if you went past that into WEP your friend the crew chief had a lot of extra work to do and usually some candid comments for the pilot. Engines were recommended to be CHANGED after only 10 hours at WEP (only good for 5 minutes at a time). Takeoff and Military power were limited to 5 minutes (15 minutes after mid '42) and extra maintenance was not required. 

WEP was not available above the critical altitude (FTH) of the engine since at that altitude the engine was already at max RPM and max boost. The only way to get more power would be to increase RPM but 3000RPM was the absolute maximum for the Allison. So no WEP above the critical altitude. WEP began in late '42.


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## pbehn (Mar 28, 2018)

P-39 Expert said:


> The upside of the P-39 in general is that it was available from the start of WWII along with the P-40 and F4F Wildcat. .


Some concepts are complex and difficult to absorb at first. It is essential to proceed step-by-step.

Step 1.

WWII started on 3rd Sept. 1939. as far as Western nations were concerned, July 7 1937 as far as Japan and China are concerned although Japan had been expanding throughout the 1930s.

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## P-39 Expert (Mar 28, 2018)

Shortround6 said:


> I would note that short ranged as the P-47C was it had roughly double the range of an 87 gallon Aircobra at similar low speeds.
> In fact an 87 gallon Aircobra was roughly equal in range to the P-47C when using a *75 gallon drop tank.*
> Trouble is the drop tank knocked about 30mph indicated off the airspeed.


Can we please use the normal 120 gallon internal capacity? PLEASE. The 87 gallon capacity was at the request of the Russians and only used on some N and Qs. A SPITFIRE had more range than a P-39 with 87 gallons.

The 110 gallon drop tank was in extensive use with the 8th AF in England and in the Pacific.

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## P-39 Expert (Mar 28, 2018)

wuzak said:


> No WEP at the altitude at which you want to fight?
> 
> Wouldn't that mean you are pretty muck fucked?


See post #707. WEP was almost dangerously hard on the engine, military power was available at the fighting altitudes.

Just asking, but you can say fucked, but I can't say J*p? Is cursing permitted here? If so........

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## pbehn (Mar 28, 2018)

P-39 Expert said:


> Can we please use the normal 120 gallon internal capacity? PLEASE. The 87 gallon capacity was at the request of the Russians and only used on some N and Qs. A SPITFIRE had more range than a P-39 with 87 gallons.
> 
> The 110 gallon drop tank was in extensive use with the 8th AF in England and in the Pacific.


By all means and compare it to the Normal internal capacity of the P 51A of 180 gals, and the P51B of 268 galls. Did I mention that the Mustang Mk1 was the first allied single engine fighter to enter German airspace, in 1942.

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## DarrenW (Mar 28, 2018)

Shortround6 said:


> But basically, for the US, critical altitude is the altitude at which the throttle is fully open and the supercharger is supplying the rated amount of pressure (mass of air).



Great explanation Shortround6, it helps me to further understand engine ratings. I've noticed that critical altitude with the application of WEP can be significantly lower than it would be without it's use. For example, let's say you are able to safely develop 60" Hg of manifold pressure at 18,500 feet, which is the critical altitude in high blower. But without WEP you are limited to 52" Hg and with this setting you reach critical altitude in high blower at 22,500 feet. Now would I be correct to say that, although the critical altitude while in WEP is 4,000 feet lower, the engine _could_ still produce more horsepower at 22,500 feet than if I just kept manifold pressure at the 52" Hg setting at that altitude? Or in this case does the use of WEP serve no useful purpose above the 18,500 foot altitude?

I hope my question isn't too wordy or hard to understand.....


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## Shortround6 (Mar 28, 2018)

P-39 Expert said:


> Can we please use the normal 120 gallon internal capacity? PLEASE. The 87 gallon capacity was at the request of the Russians and only used on some N and Qs. A SPITFIRE had more range than a P-39 with 87 gallons.
> 
> The 110 gallon drop tank was in extensive use with the 8th AF in England and in the Pacific.


 But you keep wanting to use the performance of the 87 gal versions. 
And according to some sources quite a few of the Ns and Qs had the smaller capacity. Like out of the first 500 P-40Ns after no 166.
The 900 N-1s had the smaller tanks but kits to bring them back up, likewise the 695 N-5s had the small tanks plus kits. P-39Q-1 had the small tanks, P-39Q-5s had small tanks. P-39Q-10s went back to the 120 gallon tanks from the factory. 
How they were used in the field may be different. 

You keep saying the weight of the P-39N in the test was because of averaging fuel capacity and then you want to use those numbers as justification for using it as an escort fighter.
Guess what, when you drop the external tank you are near full fuel, minus only the amount used for take-off _that was not replaced _by the fuel return from the carb while flying on the drop tank. 

*A *110 gallon tank was used in both Europe and in the Pacific, now the question is was it used by P-39s of which the 8th Air Force had few, if any. 
Does the use of a 110 gallon tank push the plane into a restricted weight catagory? P-39Q with the wing .50s went 8106lbs, you want an extra 68 gallons of fuel. Basically about 500lbs more with the weight of the tanks less the weight difference for the .50 cal guns (about 160lbs for the guns and ammo over the .30 cal installation)
And a few more pounds for the extra oil. P-39Q needed an extra 41lbs of oil when carrying a 75 gal drop tank.

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## Shortround6 (Mar 28, 2018)

DarrenW said:


> Great explanation Shortround6, it helps me to further understand engine ratings. I've noticed that critical altitude with the application of WEP can be significantly lower than it would be without it's use. For example, let's say you are able to safely develop 60" Hg of manifold pressure at 18,500 feet, which is the critical altitude in high blower. But without WEP you are limited to 52" Hg and with this setting you reach critical altitude in high blower at 22,500 feet. Now would I be correct to say that, although the critical altitude while in WEP is 4,000 feet lower, the engine _could_ still produce more horsepower at 22,500 feet than if I just kept manifold pressure at the 52" Hg setting at that altitude? Or in this case does the use of WEP serve no useful purpose above the 18,500 foot altitude?
> 
> I hope my question isn't too wordy or hard to understand.....


It would be my understanding that there would be a decreasing level of power from 18,500ft to 22,500ft as the MAP fell from 60" to 52" in this case.
No extra power at 22,500ft but perhaps 56" of pressure at 20,500ft giving about 1/2 the power difference of the WEP at 18.5 and the military power at 22.5.

Hope that helps.

In the case of water injection it sometimes helps above the critical altitude of the blower as it does make the charge denser by helping cool it.

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## DarrenW (Mar 28, 2018)

P-39 Expert said:


> I'm comparing the P-39N to other planes in combat in 1943, like the P-38, P-40, P-47 (May '43), *Hellcat (Aug '43), Corsair (Feb '43)*, FW190, Me109G, Zero and Oscar.



Why do you continue to compare a lightweight army fighter to a shipboard naval aircraft? You do realize that if one decided to navalise the Airacobra the additional weight it would gain in such a venture would be problematic. I thought you wanted to remove equipment not add more? Or are you claiming that the P-39N could perform carrier duty as good as or better than these two Navy types without any modifications whatsoever?

And if you were unsure about what this would entail, here's some things to think about:

Navalised aircraft - Wikipedia

A navalised aircraft typically differs from its land-based equivalent by:

The airframe, engine and avionics are marinised against salt water corrosion.
It is designed to be used on a flight deck. For a fixed wing aircraft this typically means catapult attachment points, a tailhook and strengthened undercarriage. 
It is designed to occupy minimum hangar space – for example the wings may fold.
There is enhanced protection against water ingress (including that from hosing down with fresh water to get rid of salt water).
Equipment such as sensors and weapons are optimised for naval roles.
The avionics is compatible with the complex electronic equipment of a warship, and that there is no electromagnetic interference between the two.
There is provision for ditching at sea.
So in your expert opinion, how much would the total weight of the scrawny P-39N increase with these added features? 

Also, yesterday I asked a question regarding the viability of the Airacobra as a front-line fighter in 1944 and beyond but you haven't commented on it yet. I sure hope that you're not avoiding the topic just because it may put your pet aircraft in a bad light.....


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## DarrenW (Mar 28, 2018)

Shortround6 said:


> It would be my understanding that there would be a decreasing level of power from 18,500ft to 22,500ft as the MAP fell from 60" to 52" in this case.
> No extra power at 22,500ft but perhaps 56" of pressure at 20,500ft giving about 1/2 the power difference of the WEP at 18.5 and the military power at 22.5.
> 
> Hope that helps.
> ...



Thank you for the explanation it was most helpful.


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## P-39 Expert (Mar 28, 2018)

DarrenW said:


> Well it looks like the climb rate of the P-39Q loaded to 7,200lbs can be equaled or even bested by the F6F-3 under similar WEP conditions. But seeing that it's not the N model, does this even count?
> 
> F6F-3:
> View attachment 487513
> ...


Back at you dude.  And no WEP. And your chart is from a test exploring larger water metering jets for WEP between Feb '44 and Feb '45 so highly doubtful if these measures could have been implemented in combat planes before the Japanese flyers were beaten in mid '44. The second climb chart is from a normal production F6F3.

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## P-39 Expert (Mar 28, 2018)

Shortround6 said:


> Changing the goal posts?
> 
> Original statement.
> 
> ...


Shortstop, I really appreciate you challenging EVERY SINGLE STATEMENT that I make. Thanks.

Did you read this chart that I sent you? It shows the 9.6 engines developing over 100 more HP at every altitude above 8000' and WEP is available only below 4500' for the 8.8 engines and 9500' for the 9.6 engines. I stand by my statement.

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## Glider (Mar 28, 2018)

pbehn said:


> Of course it was there was a war on, everything goes quicker in war time. Now tell me a time between 1939 and 45 when the Spitfire didn't need a better engine, a better field of view, better wings, better armament and better cooling. Of the thousands produced I doubt the maximum of any type that was completely identical apart from paintwork (squadron markings) was only a few hundred.


A digression I know but of all the 747's that were built only


pbehn said:


> By all means and compare it to the Normal internal capacity of the P 51A of 180 gals, and the P51B of 268 galls. Did I mention that the Mustang Mk1 was the first allied single engine fighter to enter German airspace, in 1942.


A little picky I know but PR Spits flew over germany more or less from the start


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## DarrenW (Mar 28, 2018)

P-39 Expert said:


> Back at you dude.



LOL OK surfer boy! 

So was the penciled in climb rate of the P-39N available like that from the website?  Also, those climb rates given in the _un-doctored_ chart that I provided were possible at normal safe power levels when using ADI so I'm am quite certain that an F6F-3 in service was capable of those numbers at those specific ratings. So again I ask you, do you have more than one official government document showing the remarkable performance of the P-39N that you are so proud of?

And there are many climb charts on the website for the F6F-3. Why only post this particular one? Oh I know, because it's the one displaying the poorest climb performance for the machine...


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## Shortround6 (Mar 28, 2018)

Well, P-39 not-so-expert. 
Make factual statements and I won't challenge them.

I read the chart, as you should have realized when I said it was for WEP ratings. Presenting it a 2nd time doesn't change that. 

You can stand by your statement, the statement that the 9.60 engines made 100 more hp at ALL altitudes is still wrong. 

The statement that the difference is about 100hp is correct. But it is a different statement and does not validate the first one.

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## P-39 Expert (Mar 28, 2018)

DarrenW said:


> The actual documents may have been mostly unavailable to the general public, but the data from them could most certainly be found in period books of the time. For instance, here is the performance figures for the P-39N that I gleaned from _Combat Aircraft of the World (_W.R. Taylor_)_ which was published way back in 1969. See any similarities with your oft-quoted document?
> 
> View attachment 487468


Excellent question. All I'm saying is wwiiaircraftperformance puts all the information in one place where direct comparisons can easily be made. Your example shows the P-39N with a top speed of 399mph at 9700'. That one line description, while completely accurate, covers only the speed at one altitude, ceiling and no climb figures whatsoever. This would lead the normal observer to think that the P-39N was only a low altitude plane. With wwiiaircraft you can directly compare speed/climb at all altitudes for all the planes. See some of the charts I have supplied. Plus it lists the test criteria and dates. Beats hunting all over for the information. Hope this helps.

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## Shortround6 (Mar 28, 2018)

I would note that the change of engine in the P-39 was not really a great improvement, 
It basically moved the critical altitude of the Allison engine from 12,000ft to 15,500 and gave it around 100hp more at the _higher _altitudes. 

I would note that the Merlin XII engine used in the Spitfire MK II raised the point at which the Merlin made 1000-1030hp by several thousand feet and nobody really claims the SPitfire II was a big improvement over the Spitfire I. 
The Spitfire V with the Merlin 45 moved the 6lb boost point up another several thousand feet. 
The Hurricane II with the Merlin XX moved the 6lb boost point from 18,000ft on a MK I to over 23,000ft. 

Moving the critical altitude of the engine by 3,500ft and still being in the mid teens in late 1942/early 43 is hardly world class.

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## P-39 Expert (Mar 28, 2018)

DarrenW said:


> LOL OK surfer boy!
> 
> So was the penciled in climb rate of the P-39N available like that from the website?  Also, those climb rates given in the _un-doctored_ chart that I provided were possible at normal safe power levels when using ADI so I'm am quite certain that an F6F-3 in service was capable of those numbers at those specific ratings. So again I ask you, do you have more than one official government document showing the remarkable performance of the P-39N that you are so proud of?
> 
> And there are many climb charts on the website for the F6F-3. Why only post this particular one? Oh I know, because it's the one displaying the poorest climb performance for the machine...


The site gives the official govt/military performance tests in print format with graphs on most of the planes. No climb graph for the P-39N but there is a speed graph. The tests in print format offer climb figures for all altitudes up to the absolute ceiling in 5000' increments. No trouble to transfer those numbers on top of the Hellcat climb graphs so they can be compared directly. Also the test in your un-doctored chart are testing non-standard parts (those water injection nozzles) late in the war. The additional Hellcat chart that I provided is from a normal production F6F3 and agrees with the other normal Hellcat charts there. You shouldn't compare a late war test of specialized equipment to a normal production plane.

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## pbehn (Mar 28, 2018)

P-39 Expert said:


> The two stage Merlin P-51 only saw combat from Dec '43. The Spitfire IX had the same Merlin engine as the P-51B but weighed 2500# less than a P-51D so its climb rate was absolutely amazing and significantly higher than any of these planes. Great plane if you wanted to go to Belgium and back.


The problem with being a single type fan boy is that when discussing other types you descend into clichés. The Spitfire was always short ranged compared to the Mustang and others but not in absolute terms. The Spitfire Mk IX eventually had a max internal fuel load of 114 imp gal (136 US)and a total maximum internal plus external of 284 imp. gal (341 US). Its day job was to stop people in Belgium and France going to UK and back, at any altitude from sea level to 43,000ft.

The still air range of the Mk XVI (mk IX with Packard Merlin) was 1200miles with a total fuel load of 255 gals.

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## Peter Gunn (Mar 28, 2018)

Lots of dead electrons in here. Having gone through this thread again, I still don't think you understand how a supercharger works, I don't think you understand how range works for mission planning. You have steadfastly refused to understand how shit works when explained by some very knowledgeable folks. You realize that virtually everyone here knows who Buzz Wagner, George Welch et. al. were, what WEP and the little wire is, where to find info on wwiiaircraftperformance, none of this is groundbreaking stuff here.

You are and entitled to your opinion and you have tried to back up arguments with some facts but they have been constantly refuted and still the circle argument goes on. I'm beginning to find it laughable that apparently the AAF, RAF and virtually everyone else except the VVS ( for very good reasons stated by others ) were all stupid to pass on this amazing war winning plane.

If it was so hot, why wasn't it used for escort in the ETO by 8th FC? Why couldn't it intercept Japanese bombers over Guadalcanal ( when the F4F could )? Why did virtually EVERYONE dump it in favor of at least the P-40 ( if not something even better ) the first chance they had?

Eh, good luck, and as I said earlier, Peace Out.

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## P-39 Expert (Mar 28, 2018)

Shortround6 said:


> I would note that the change of engine in the P-39 was not really a great improvement,
> It basically moved the critical altitude of the Allison engine from 12,000ft to 15,500 and gave it around 100hp more at the _higher _altitudes.
> 
> I would note that the Merlin XII engine used in the Spitfire MK II raised the point at which the Merlin made 1000-1030hp by several thousand feet and nobody really claims the SPitfire II was a big improvement over the Spitfire I.
> ...


Couple of things, first we seem to get bogged down with engine to engine comparisons. We should be comparing the PLANES to each other. A Hellcat had a 2000HP engine and a P-39N had a 1200HP engine, yet their performance is very similar. Engine to engine comparisons are fun, but the plane performance is more important IMO.

The small critical altitude improvement of 3500' from the 8.8 engines to the 9.6 engines doesn't sound like much but it did result in an additional 100 horsepower (I think we agree on this now) and even that doesn't sound like much. But, that 100HP improved the speed of a P-39 by 20mph and improved climb by some 1000fpm. A worthy improvement if you ask me.

One last thing on the endurance and the 20 gallon Reserve for T/O & Climb to 5000'. That reserve was the simple method for the pilot to plan his mission. He could take the available fuel, deduct the reserve and then use the available GPH figures from the charts to compute endurance. It did take 35 gallons or so to climb to 25000' but one did not climb to that altitude over his base and then turn to head to the target. You deducted the reserve which got you to 5000' then continued climbing in the direction of the target at best climb speed of 170mph INDICATED. True airspeed at 170 indicated was 238mph TRUE airspeed at 20000'. So as you are climbing you are also moving toward the target at 238mph average. Say it takes about 10 minutes to climb from 5000' to 25000'. You are now at 25000' but you are also 40 miles closer to your target. If you are not climbing but are in level flight for 10 minutes you cover 47 miles (282mph for 10 min). The difference is only 7 miles. This method is what the pilot's manual told the pilot to use to compute endurance and it proved to be pretty accurate.

By the way, I'm not mad at anybody and really enjoying our discussions on old airplanes. I have started using smiley faces and doing my best not to sound like an a-hole when I post. If I have offended anybody then please accept my sincere apology. Thanks to everyone for their replies and comments.

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## DarrenW (Mar 28, 2018)

P-39 Expert said:


> Also the test in your un-doctored chart are testing non-standard parts (those water injection nozzles) late in the war.



The Hellcat achieved those rates nevertheless. And the report was finalized in 1945 but actual testing occurred from February 1944 onwards. Are you saying that the U.S. Navy wouldn't take full advantage of the findings in this test? You do know that there was still plenty of fighting left, or were the Japanese fully beaten by March 1944 too? 



And part of my reason for presenting it was to show that there's all kind of data out there and you haven't seen or read it all. Your ONE document regarding the P-39N will never be enough, because as a researcher one must have multiple examples for which to draw accurate conclusions from. And besides this, you continually ignore the basic fact that the P-39N, in the ONE test report you have presented, wasn't meeting US Army operating requirements.

So for a third time, what are your thoughts on the usefulness of the P-39N in 1944? Could it really deliver the same usefulness as say a P-47D or P-38J/L? As you can see I'm leading up to something here....


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## P-39 Expert (Mar 28, 2018)

Peter Gunn said:


> Lots of dead electrons in here. Having gone through this thread again, I still don't think you understand how a supercharger works, I don't think you understand how range works for mission planning. You have steadfastly refused to understand how shit works when explained by some very knowledgeable folks. You realize that virtually everyone here knows who Buzz Wagner, George Welch et. al. were, what WEP and the little wire is, where to find info on wwiiaircraftperformance, none of this is groundbreaking stuff here.
> 
> You are and entitled to your opinion and you have tried to back up arguments with some facts but they have been constantly refuted and still the circle argument goes on. I'm beginning to find it laughable that apparently the AAF, RAF and virtually everyone else except the VVS ( for very good reasons stated by others ) were all stupid to pass on this amazing war winning plane.
> 
> ...


Sorry I'm so stupid especially after all you guys have tried your best to help me. Sorry again for my posts quoting facts direct from government/military tests or the pilot manuals. 

Why couldn't it intercept Japanese bombers over Guadalcanal when the F4F could? Gee, I don't know. Maybe the attached graph will help. The P-39K is the dotted line. 7650# with the older less powerful engine tested in May '42.


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## DarrenW (Mar 28, 2018)

P-39 Expert said:


> A Hellcat had a 2000HP engine and a P-39N had a 1200HP engine, yet their performance is very similar. Engine to engine comparisons are fun, but the plane performance is more important IMO.



Yes, we all get it that the P-39 was fast for the amount of power available. But it came at a huge price. It had many deficiencies that were basically non-existent in other US fighter aircraft of it's time. Lack of useful range and payload, light construction (compared to other US warplanes) which made it far more vulnerable to enemy fire, and substandard armor protection for both pilot and engine, just to name a few.


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## Shortround6 (Mar 28, 2018)

I get a bit suspicious when small changes in an aircraft make huge changes in performance.
I will even grant that the P-39N had 150-160hp more at the higher altitudes but the climb figures don't track well.

I will try to post the relevant figures later.


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## Shortround6 (Mar 28, 2018)

DarrenW said:


> Yes, we all get it that the P-39 was fast for the amount of power available. But it came at a huge price. It had many deficiencies that were basically non-existent in other US fighter aircraft of it's time. Lack of useful range and payload, light construction (compared to other US warplanes) which made it far more vulnerable to enemy fire, and substandard armor protection for both pilot and engine, just to name a few.



Many accounts speak well of it's construction or protection or I am reading the wrong ones?
It did have a number of deficiencies which may have been hard to design out. 
I would note that some of these were _supposed _to be fixed by the P-39E which changed to the P-76 and up to 4000 were order at one point before the whole thing was canceled in favor of the P-63. 
The Bell engineers went through two almost total redesigns of the P-39 trying for something better which leaves one wondering how much improvement you can get from a relatively small change in the supercharger gear ratio?? 
No test results but something to think about.


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## DarrenW (Mar 28, 2018)

P-39 Expert said:


> Sorry I'm so stupid especially after all you guys have tried your best to help me.



You said it, we didn't.

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## DarrenW (Mar 28, 2018)

Shortround6 said:


> Many accounts speak well of it's construction or protection or I am reading the wrong ones?



I'm referring to what I have read in America's Hundred Thousand and a few other places. I can take a look and post a few examples later. One that comes to mind is that the placement of the engine behind the pilot made it very vulnerable to enemy fire from the rear (which apparently the P-39 received a lot of ) but there are others. Let me take a look....


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## CORSNING (Mar 28, 2018)

1943, sea level to 15000 ft: the best fighter?
POST #29
I posted this back in 1 October 2012. In the five and one half years (almost) I have
continued my research with the help of several others. I would like to point out that
range was not a big consideration in this post.
To answer the original question asked by P-39 expert...NO, in the Pacific theater
of Operation, the P-39 at no time could be considered to have 'handled' the Zero.
One of the A6M's greatest assets was its range, it could strike anywhere and at
any time. The P-39N with its internal fuel capacity allowing it a 360 ml. range just
was not enough to get the job completely done in the PTO.

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## drgondog (Mar 28, 2018)

P-39 Expert said:


> Can we please use the normal 120 gallon internal capacity? PLEASE. The 87 gallon capacity was at the request of the Russians and only used on some N and Qs. A SPITFIRE had more range than a P-39 with 87 gallons.
> 
> The 110 gallon drop tank was in extensive use with the 8th AF in England and in the Pacific.


The 110 gallon tank was used initially in late 1943 on P-47C/D C/L but AFAIK never on the P-39. First used on P-51B in May 1944.

I'm unaware that Bell added a tank pressurization capability such as slaving off exhaust or instrument vacuum pump. Did Bell modify the P-39 so that they could carry ANY tank above 20K? Do you have any source documentation of either a mission flown with 110 gallon tank or any mission flown above 20K w/75 gallon combat tank?

Please point to your sources.


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## DarrenW (Mar 28, 2018)

P-39 Expert said:


> Thanks to everyone for their replies and comments.



And I thank you. It's been entertaining to say the least. So are you ready to capitulate and admit that your hypothesis regarding the P-39N's worth was overstated or will you continue to drag this on and on with no end in sight?


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## wuzak (Mar 28, 2018)

Shortround6 said:


> I get a bit suspicious when small changes in an aircraft make huge changes in performance.
> I will even grant that the P-39N had 150-160hp more at the higher altitudes but the climb figures don't track well.
> 
> I will try to post the relevant figures later.



I too am suspicious when a 10% power increase gives nearly 50% increase in climb rate....

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## pbehn (Mar 28, 2018)

I like the conclusions to the test on the P39, a bit odd for a single engine combat plane. combat

1. The P-39 should not be spun intentionally under any circumstances.

2. The P-39 should not be snap rolled as the roll usually ends in a spin.

3. The best spin recovery is to simultaneously apply opposite rudder and neutralize the stick.

4. Power should be cut immediately if a power on spin is entered.

5. Care must be excercised during the recovery to prevent an accelerated stall and re-enty into the spin.

6. The wing tip spin chute does not aid recovery of the P-39Q from a flat spin.



Reading the report, the pilot bailed out as a result of 6
www.wwiiaircraftperformance.org/P-39/P-39Q_Spin.pdf

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## DarrenW (Mar 28, 2018)

There has been some discussion whether the P-39N tested on 17/Oct/1942 had the reduced fuel capacity or not. I apologize if this has been brought up already, but I found this information on Joe Baugher's website:

_Bell P-39N Airacobra

After completion of the first 166 P-39Ns, the USAAF requested that four fuel cells be removed in order to reduce the internal fuel capacity from 120 to 87 US gallons, and so to reduce the maximum permissible gross weight from 9100 lbs to 8750 lbs. This kept weight down, but unfortunately it also restricted range. Therefore, kits were provided that allowed the four fuel cells to be refitted in the field. _

_The first 166 P-39Ns were fitted with an Aeroproducts propeller having a diameter of 10 feet 4 inches. Beginning with the 167th P-39N, the Aeroproducts propeller was enlarged to 11 feet 7 inches in diameter, an increase of six inches. _

_*The 500 P-39Ns were followed by 900 P-39N-1s* (Model 26C). These differed only in some minor internal changes which altered the location of the center of gravity._

From where I stand the tested aircraft would have had the reduced fuel load of 87 gallons, as it was a P-39N-1 and not an earlier P-39N (of which only the first 166 manufactured had 120 gallons of internal fuel). But I lost track if this factoid is actually relevant anymore....

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## MIflyer (Mar 28, 2018)

Here's the best P-39 box art I have ever seen.

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## wuzak (Mar 28, 2018)

You can see the pilot looking into the sky, seeing a Spitfire V and wistfully thinking "I wish I had one of them".

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## DarrenW (Mar 28, 2018)

It is very nice artwork indeed but having the Airacobra pilots caught on the ground during an attack isn't the best way to convey a fighter plane's supposed prowess IMHO....


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## buffnut453 (Mar 28, 2018)

DarrenW said:


> It is very nice artwork indeed but having the Airacobra pilots caught on the ground during an attack isn't the best way to convey a fighter plane's supposed prowess IMHO....



Perhaps not...but, then again, an aircraft getting caught on the ground has nothing to do with the performance of the aircraft and everything to do with the intelligence, early warning and C3 capabilities.

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## DarrenW (Mar 28, 2018)

I agree. But to promote your favorite plane I'm pretty sure that you wouldn't pick an avatar with the Oscar shooting down the Buffalo, now would you?  Even though it happened on occasion, through no fault of the pilot or aircraft involved....


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## buffnut453 (Mar 28, 2018)

The original of my avatar actually has one Ki-43 being downed but at least 3 Buffalos being shot down...so it's pretty balanced. 

I also accept that joe public in general wouldn't comprehend the niceties of air raid warning.


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## DarrenW (Mar 28, 2018)

buffnut453 said:


> The original of my avatar actually has one Ki-43 being downed but at least 3 Buffalos being shot down...so it's pretty balanced.
> 
> I also accept that joe public in general wouldn't comprehend the niceties of air raid warning.



Oh sorry to hear that, wish it went better for the Buffalos!

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## DarrenW (Mar 28, 2018)

This is one of my all time favorites from Revell.

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## parsifal (Mar 29, 2018)

This is a link to another forum on box art images

Model Box Art

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## DarrenW (Mar 29, 2018)

parsifal said:


> This is a link to another forum on box art images
> 
> Model Box Art



Thanks Parsifal for the link, it's awesome! Brings back some really nice memories for me.....


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## CORSNING (Mar 29, 2018)

For those who haven't found it yet:
The Box Art Den


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## P-39 Expert (Mar 29, 2018)

Shortround6 said:


> I get a bit suspicious when small changes in an aircraft make huge changes in performance.
> I will even grant that the P-39N had 150-160hp more at the higher altitudes but the climb figures don't track well.
> 
> I will try to post the relevant figures later.


A big reason why the climb for the N is a lot better than older P-39s is the increase from 5 minutes to 15 minutes for military power rating. This happened mid '42 along with finally discarding the port backfire screens. This increase to 15 minutes apparently was for other engines too since this is reflected in the P-47 (R2800) tests.

With the 5 minute limit the engine power had to be reduced from 3000rpm (take off/military) to 2600rpm (max. continuous) after 5 minutes. Climb was a lot slower since HP was reduced. This is on all the charts of the P-38, P-39, P-40, P-47 and P-51 (Allison models). Once the limit was increased to 15 minutes the climb for all those planes was greatly improved above the 5 minute mark. If this was retroactive to the older engines (like WEP) then those P-39D, F, K, and L would have been greatly improved also. 

Oddly the climb test was a straight climb from takeoff up to the service ceiling. Good for tests, but in actual practice if the pilot was at combat power (3000rpm) and during that 5 minutes had to climb he didn't reduce power to 2600rpm for the climb. So the tests actually understated climb after the first 5 minutes.

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## P-39 Expert (Mar 29, 2018)

CORSNING said:


> 1943, sea level to 15000 ft: the best fighter?
> POST #29
> I posted this back in 1 October 2012. In the five and one half years (almost) I have
> continued my research with the help of several others. I would like to point out that
> ...


All P-39s were faster than all Zeros by about 40mph at all altitudes. Climb on the older models was not as fast above 12000' on the test graphs, but at 3000rpm it climbed as fast at all altitudes. Due to circumstances the P-39 was used mostly in the defensive role in '42 at Moresby and Guadalcanal so range wasn't as big a consideration. 

The P-38 is considered to have excellent range. It held 150gal/engine internal. The P-39 held 120. After deducting the Reserve (for T/O and climb to 5000') of 25gal for the P-38 and 16 gal for the P-39 the useable fuel for both planes was 125 for the P-38 and 104 for the P-39. 21 whole gallons. The P-38 had a 165 gallon drop tank/engine and the P-39 had drop tanks of 75gal, 110, 158 and 175gal available. Range could have been increased to P-38 levels if needed.

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## P-39 Expert (Mar 29, 2018)

drgondog said:


> The 110 gallon tank was used initially in late 1943 on P-47C/D C/L but AFAIK never on the P-39. First used on P-51B in May 1944.
> 
> I'm unaware that Bell added a tank pressurization capability such as slaving off exhaust or instrument vacuum pump. Did Bell modify the P-39 so that they could carry ANY tank above 20K? Do you have any source documentation of either a mission flown with 110 gallon tank or any mission flown above 20K w/75 gallon combat tank?
> 
> Please point to your sources.


Edwards Park in his factual book "Angels Twenty" indicates use of the 110gal drop tank as standard. On a couple of interception missions at Moresby he talks of climbing to 24000' to intercept the Bettys and Zeros with his 110gal drop tank attached. Upon contact with the enemy they dropped their tanks and he says his P-39 felt "light as a feather, wonderfully agile and responsive. I would have loved to have flown it for a little while to enjoy it, but (his flight leader) was dropping his nose toward that (enemy) formation...". Why intercept incoming bombers with a drop tank? Seems odd, but virtually every mission was with drop tanks and the P-39s were loaded that way for those missions.

Park was actually there as a 2nd Leutenant pilot, so his experiences were actual fact. He wrote a second book, "Nanette" which covered the same material but was fiction and contained all of the outrageous stories he had heard about other pilots in NG. Quite funny and entertaining. Both books were a capsule of everyday life for those guys serving in NG and a fun read.

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## P-39 Expert (Mar 29, 2018)

DarrenW said:


> And I thank you. It's been entertaining to say the least. So are you ready to capitulate and admit that your hypothesis regarding the P-39N's worth was overstated or will you continue to drag this on and on with no end in sight?


Sorry, but I'm not going away. I'll keep giving you the facts as long as you want to listen.

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## pbehn (Mar 29, 2018)

So what was the climb performance and air speed while climbing with 110 external tank?


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## Shortround6 (Mar 29, 2018)

P-39 Expert said:


> Sorry, but I'm not going away. I'll keep giving you the facts as long as you want to listen.




Then give us facts, not stories like the British deliberately overloaded their P-39s with armor and guns to get out of a contract, (and Bell was dumb enough to agree to such a change in contract talks).


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## drgondog (Mar 29, 2018)

P-39 Expert said:


> Oddly the climb test was a straight climb from takeoff up to the service ceiling. Good for tests, but in actual practice if the pilot was at combat power (3000rpm) and during that 5 minutes had to climb he didn't reduce power to 2600rpm for the climb. So the tests actually understated climb after the first 5 minutes.



In actual Practice, the time to climb test was at maximum power available by the 'book' - and does not understate anything. That specific test was performed to get an idea what the airplane could be expected to do for the weight and balance conditions cited in the test.

The primary reason was to gauge interception capability and often flown in AAF 'Fighter Condition' of reduced fuel and ammo and no external stores.

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## MIflyer (Mar 29, 2018)

Actually I read an article by a pilot who flew Spit V's in the Med. On his first flight just after takeoff he got intercepted by a P-39 and got "shot down" multiple times while he was trying to build up some airspeed.

Of course, if he had been flying a Clipped and Cropped Spitfire V it might have been a different story.

I love that P-39 artwork partially because it reminds me so much of a cover from a "Men's" magazine I saw in the 60's Very similar kind of a painting, a P-39 pilot opening the door and entering his airplane as enemy aircraft approach in the sky. Except that also scrambling into their Airacobras in the background were a bunch of beautiful scantily clad women.


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## wuzak (Mar 29, 2018)

P-39 Expert said:


> A big reason why the climb for the N is a lot better than older P-39s is the increase from 5 minutes to 15 minutes for military power rating. This happened mid '42 along with finally discarding the port backfire screens. This increase to 15 minutes apparently was for other engines too since this is reflected in the P-47 (R2800) tests.



I can see how the time to altitude would be reduced by this, but peak rate of climb should be unchanged.


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## wuzak (Mar 29, 2018)

drgondog said:


> In actual Practice, the time to climb test was at maximum power available by the 'book' - and does not understate anything. That specific test was performed to get an idea what the airplane could be expected to do for the weight and balance conditions cited in the test.
> 
> The primary reason was to gauge interception capability and often flown in AAF 'Fighter Condition' of reduced fuel and ammo and no external stores.



Would several climb tests at military power be undertaken starting at different altitudes, to see the climb response when already in the air?


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## Shortround6 (Mar 29, 2018)

Ok, I am going to try to list P-39 climb rates. 

model..........weight............altitude............power...............FPM
P-39D...........7525...............15,000............865.................1880
P-39D...........7525...............20,000............710.................1300
P-39D...........7525...............25,000............585...................800
P-39M...........7430...............15,000..........1040.................2640
P-39M...........7430...............20,000............880.................2000
P-39M...........7430...............25,000............725.................1400
P-39N...........7274...............15,000...........1060.................3340
P-39N...........7274...............20,000............885..................2630
P-39N...........7274...............25,000............745..................1940
P-39Q...........7821...............15,000...........1050.................2840
P-39Q...........7821...............20,000............882..................2200
P-39Q...........7821...............25,000............740..................1570
P-63A...........8286...............15,000............UNK..................3210
P-63A...........8286...............20,000............UNK..................2800
P-63A...........8286...............25,000..........<1150?................2200

The P-39D was using 2600rpm and not 3000rpm like the other planes.
_The P-39 M, N and Q all used_ _essentially the same engine_, the 9.60 supercharger gear model although the P-39M used a 2.0 reduction gear to the prop and the N & Q used a 2.33, so we have different props and perhaps different propeller efficiency. 
P-63 is actually the XP-63A. power figures not given in climb chart but engine rated at 1150hp at 22,400ft with no RAM Power at 15,000 and 20,000 should be greater. XP-63A figures may not be from test instruments? 

all figures from the tests at WWII Aircraft Performance

I chose these altitudes because they pertain to the high altitude intercept and/or escort scenarios and because, for the P-39s at least, WEP would not be a factor. As for the weight difference between the D and M, there is roughly a 75lb weight difference between the Aeroproducts hydraulic propeller and the Curtiss electric propeller. 

Make of them what you will.

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## Shortround6 (Mar 29, 2018)

P-39 Expert said:


> The P-38 is considered to have excellent range. It held 150gal/engine internal. The P-39 held 120. After deducting the Reserve (for T/O and climb to 5000') of 25gal for the P-38 and 16 gal for the P-39 the useable fuel for both planes was 125 for the P-38 and 104 for the P-39. 21 whole gallons. The P-38 had a 165 gallon drop tank/engine and the P-39 had drop tanks of 75gal, 110, 158 and 175gal available. Range could have been increased to P-38 levels if needed.



More FUN FACTS?

How about reading the manuals instead of wild guesses based on such a flawed premise?

P39Q at 200mph IAS at 20,000ft burned 41 gallons an hour. or 4.9miles per gallon.
A P-38F at 190mph IAS at 20,000ft burned 67 gallons an hour or 2.8 miles per gallon.

But wait it gets better 

P-39Q at 222mph IAS at 20,000ft is turning 2600rpm and burning 60 gallons an hour 3.07mpg
A P-38F at 225mph IAS at 20,00ft has engines turning at 2150rpm and is burning 83 gph(? chart is fuzzy) for 2.7MPG

These figures are for clean aircraft.
So, assuming the P-38F needs 80 gallons for take-off climb and finding it's own airfield and the magic P-39 only needs 16 we have, at 222-225IAS at 20,000ft the P-38F flying 594 miles while the P-39Q flies 319 miles.

The only way you are going to get a P-39 to fly as far as a P-38 is to tow it.

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## Shortround6 (Mar 29, 2018)

For any new members who haven't explored this site fully yet (and it is Huge)

scores if not hundreds of manuals can be found here.

Other Mechanical Systems Tech.

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## DarrenW (Mar 29, 2018)

P-39 Expert said:


> Sorry, but I'm not going away. I'll keep giving you the facts as long as you want to listen.



We like facts a lot around here. And now that it's quite apparent the P-39N-1 tested on 17 October 1942 had the reduced fuel capacity, how will your "facts" change to suit your flimsy arguments? And listening is a two way street, are you willing to listen to the facts as well?

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## Peter Gunn (Mar 29, 2018)

DarrenW said:


> I agree. But to promote your favorite plane I'm pretty sure that you wouldn't pick an avatar with the Oscar shooting down the Buffalo, now would you?  Even though it happened on occasion, through no fault of the pilot or aircraft involved....


Hey now, let's not go casting aspersions on the Buff... them's fightin' words.

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## DarrenW (Mar 29, 2018)

Shortround6 said:


> P-39Q at 222mph IAS at 20,000ft is turning 2600rpm and burning 60 gallons an hour 3.07mpg
> .



So in a nutshell the P-39Q (or N, take your pick), wouldn't have more than about an hour or so of flight time available at that altitude in a clean condition, and maybe about two hours with the 75 gallon drop tank. And in order to get that sort of endurance you better hope you don't get in a fight along the way. A 200 mile radius is nothing to write home about, especially for an aircraft doing supposed escort work.


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## DarrenW (Mar 29, 2018)

Peter Gunn said:


> Hey now, let's not go casting aspersions on the Buff... them's fightin' words.



No way Peter, I happen to be a big fan of the Buff!

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## Ascent (Mar 29, 2018)

MIflyer said:


> Actually I read an article by a pilot who flew Spit V's in the Med. On his first flight just after takeoff he got intercepted by a P-39 and got "shot down" multiple times while he was trying to build up some airspeed.
> 
> Of course, if he had been flying a Clipped and Cropped Spitfire V it might have been a different story.
> 
> I love that P-39 artwork partially because it reminds me so much of a cover from a "Men's" magazine I saw in the 60's Very similar kind of a painting, a P-39 pilot opening the door and entering his airplane as enemy aircraft approach in the sky. Except that also scrambling into their Airacobras in the background were a bunch of beautiful scantily clad women.


Any aircraft that's just taken off and struggling for speed and altitude is a sitting duck for anything already airborne.

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## pbehn (Mar 29, 2018)

DarrenW said:


> We like facts a lot around here. And now that it's quite apparent the P-39N-1 tested on 17 October 1942 had the reduced fuel capacity, how will your "facts" change to suit your flimsy arguments? And listening is a two way street, are you willing to listen to the facts as well?


Every "fact" presented is a masterpiece of omission. Range always the one with the most fuel, power always at the highest rating regardless of time. Rate of climb for the lightest etc etc. There is a flat out denial of any stall spin characteristics even though "aircraftperformance" has a report saying it should never be spun or snap rolled. The plane gave no warning of stall (in the manual) and had a landing speed of 100-110 MPH, how do you do a wheels up landing? The performance quoted by S/R of the D model is abysmal. The P39 was not an equal of the Spitfire MkV in most respects indeed hardly better than a Hurricane in most. It wasn't an equal of the F4F let alone later US fighters. It was a pup, not as good as any front line allied fighter in 1942 but better than some Soviet fighters which is why it was given to the Russians.

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## Elmas (Mar 29, 2018)

pbehn said:


> I like the conclusions to the test on the P39, a bit odd for a single engine combat plane. combat
> 
> 1. The P-39 should not be spun intentionally under any circumstances.
> 
> ...



An Italian pilot recalls: _"... I owe my life to the fact that I never let myself try to do acrobatics with the P-39 ."_
I can't find the link anymore, unfortunately.

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## pbehn (Mar 29, 2018)

Elmas said:


> An Italian pilot recalls: _"... I owe my life to the fact that I never let myself try to do acrobatics with the P-39 ."_
> I can't find the link anymore, unfortunately.


Incredibly it was used as a training aircraft, I don't know what sort of training though.

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## P-39 Expert (Mar 29, 2018)

pbehn said:


> So what was the climb performance and air speed while climbing with 110 external tank?


Climb with tank is not shown on P-39N test, so I don't know for sure.

The graph below is for the P-39K and is representative of the earlier P-39s (D,F,K and L) with the 8.8 supercharger gears and weighing approximately 7650#. As you can see, the dotted line is with belly tank, the solid line is without. This indicates a 300-350fpm lower climb rate with the tank.

Also please notice the curved line between 12500' and 15000'. That represents the point at which the pilot decreased rpm from 3000 (max) to 2600 (max continuous or max cruise) after the 5 minute mark complying with the time limit for those earlier engines. This reflects a substantial decrease in climb rate due to the lower HP for 2600rpm. The heavy dashed line at each 5000' interval is my estimate of climb after the five minute limit was increased to 15 minutes in mid '42. Just for fun.

Also notice the "SECRET" stamped in the upper right corner.

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## P-39 Expert (Mar 29, 2018)

buffnut453 said:


> Perhaps not...but, then again, an aircraft getting caught on the ground has nothing to do with the performance of the aircraft and everything to do with the intelligence, early warning and C3 capabilities.


I just now noticed that your avatar photo is a Brewster Buffalo. Supposedly the Finns soundly whipped the Russians with that plane until they had to finally capitulate.


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## pbehn (Mar 29, 2018)

P-39 Expert said:


> Climb with tank is not shown on P-39N test, so I don't know for sure.


This shows 18 minutes to 25,000 ft
If your enemy is doing 180MPH they can go 54 miles in any direction in that time and you are hardly going any faster in terms of ground speed.

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## Elmas (Mar 29, 2018)

pbehn said:


> Incredibly it was used as a training aircraft, I don't know what sort of training though.



Pilots who survived were certainly outstanding Pilots.


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## drgondog (Mar 29, 2018)

wuzak said:


> Would several climb tests at military power be undertaken starting at different altitudes, to see the climb response when already in the air?



Yes - but normally initiated at incremental altitudes to determine initial ROC from level flight when WEP or MP applied.

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## buffnut453 (Mar 29, 2018)

Elmas said:


> Pilots who survived were certainly outstanding Pilots.



Or just plain lucky.


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## pbehn (Mar 29, 2018)

Elmas said:


> Pilots who survived were certainly outstanding Pilots.


I was thinking of the many aspects of training, some like navigation and take off landing procedures are quite undemanding on the aircraft but I just don't see how you can train for combat with no risk of stall or spin.


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## P-39 Expert (Mar 29, 2018)

wuzak said:


> Would several climb tests at military power be undertaken starting at different altitudes, to see the climb response when already in the air?


The test program for these planes was exhausting. Many flights at the different altitudes meticulously recorded by the pilots and the array of test equipment installed in the test plane. They didn't depend on the plane's instruments but used additional test equipment. Undoubtedly they did test climb at all altitudes and both at max power and max continuous power, but the graph shows a continuous climb from sea level up to the ceiling. Hope this helps.

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## drgondog (Mar 29, 2018)

pbehn said:


> Incredibly it was used as a training aircraft, I don't know what sort of training though.


In late 1943 forward, both P-39s and P-40s were the steed of choice for Advanced Fighter Training prior to deployment offshore. There was a very narrow window in which the destination FG (US) were flying P39 or P-40/

My father's transition was P-40K at Sarasota, then 2.5 hours in P-51B at Goxhill in late May, 1944, then first combat mission (and victory credit) in P-51B on D-Day. He never flew the P-39.

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## pbehn (Mar 29, 2018)

P-39 Expert said:


> The test program for these planes was exhausting. Many flights at the different altitudes meticulously recorded by the pilots and the array of test equipment installed in the test plane. They didn't depend on the plane's instruments but used additional test equipment. Undoubtedly they did test climb at all altitudes and both at max power and max continuous power, but the graph shows a continuous climb from sea level up to the ceiling. Hope this helps.


Good heavens man! What do you think other testing organisations did, either companies or nations? Read the runes or studied tea leaves? The technology was very advanced all over the world, they just didn't produce lovely print outs from a bubble jet printer. As a former inspector who spent a life time looking at such things in a different field I can see where some "results" are written in when outside of the main area of interest. Here an example. From 0 to 12,400 ft rate of climb is exactly 2,720ft/min. I could possibly believe they would be similar, but not the same down to <1ft/min

Altitude
Ft. Speed MPH R.P.M. B.H.P. Rate ofclimb Ft/Min Time of climb Min.

-0000 -157 3000 1150 2720 0000 
- 5,000 169 3000 1150 2720 1.84
-10,000 183 3000 1150 2720 3.68
*12,400 190 3000 1150 2720 4.56


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## pbehn (Mar 29, 2018)

drgondog said:


> In late 1943 forward, both P-39s and P-40s were the steed of choice for Advanced Fighter Training prior to deployment offshore. There was a very narrow window in which the destination FG (US) were flying P39 or P-40/
> 
> My father's transition was P-40K at Sarasota, then 2.5 hours in P-51B at Goxhill in late May, 1944, then first combat mission (and victory credit) in P-51B on D-Day. He never flew the P-39.


Both my father and my uncle were bobbing about in boats on D-Day, I wonder if they saw him.


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## P-39 Expert (Mar 29, 2018)

DarrenW said:


> We like facts a lot around here. And now that it's quite apparent the P-39N-1 tested on 17 October 1942 had the reduced fuel capacity, how will your "facts" change to suit your flimsy arguments? And listening is a two way street, are you willing to listen to the facts as well?


No reduced fuel. If that P-39N had only 87 gallons then it would be only 33 gallons light x 6 pounds/gallon or 198# lighter. The N weighed 7650# loaded with 120 gallons internal, the cannon plus 2 .50 caliber machine guns and 4 .30 caliber wing guns and ammunition, and a 200# pilot with parachute. 7650# less half fuel (60 gal or 360#) resulting in an average weight for that flight of 7290# vs the listed weight of 7274#. Off by 16#. Same for the official performance tests (not different propeller tests etc) of the P-38, and P-47. Look it up.

Regarding facts, I am quoting the facts from the official government tests.

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## P-39 Expert (Mar 29, 2018)

Shortround6 said:


> Ok, I am going to try to list P-39 climb rates.
> 
> model..........weight............altitude............power...............FPM
> P-39D...........7525...............15,000............865.................1880
> ...



At first glance those numbers look good to me. Note how your P-39D figures are EXACTLY the same as the P-39K graph in my post #773. The P-39K had about the same weight and the 8.8 geared engine as the D. And your P-39N numbers are EXACTLY the same as those I drew on the Hellcat climb chart in my post #717. That N could climb, eh?

The D did use 2600rpm after it reached 5 minutes, but was 3000rpm prior to that. You start your chart with 15000' and the shift occurred at 12500'. 

The change in reduction gears, originally 1.8 in the D/F, then 2.0 in the K/L and 2.23 in the M/N/Q was to accommodate larger propellers. The larger propellers had to turn slower to keep the tips from going supersonic. Like you said, the newer hydraulic props were lighter than the Curtiss electric props. The only real difference in the M and the N was the different reduction gear but it sure made a big difference in climb, wouldn't you agree? So glad you posted this, facts are fun, no?


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## DarrenW (Mar 29, 2018)

P-39 Expert said:


> No reduced fuel. If that P-39N had only 87 gallons then it would be only 33 gallons light x 6 pounds/gallon or 198# lighter. The N weighed 7650# loaded with 120 gallons internal, the cannon plus 2 .50 caliber machine guns and 4 .30 caliber wing guns and ammunition, and a 200# pilot with parachute. 7650# less half fuel (60 gal or 360#) resulting in an average weight for that flight of 7290# vs the listed weight of 7274#. Off by 16#. Same for the official performance tests (not different propeller tests etc) of the P-38, and P-47. Look it up.
> 
> Regarding facts, I am quoting the facts from the official government tests.



Could you show us the "official government test" document which stipulated a normally loaded weight of 7,452lbs for a P-39N-1? And one not drawn in No. 2 pencil this time please....


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## P-39 Expert (Mar 29, 2018)

pbehn said:


> I like the conclusions to the test on the P39, a bit odd for a single engine combat plane. combat
> 
> 1. The P-39 should not be spun intentionally under any circumstances.
> 
> ...


Every pilots manual for an American WWII fighter had a warning not to snap roll or spin that airplane. The recovery methods are normal.

I don't think the spin chute was standard equipment, but was used on planes undergoing spin tests.


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## DarrenW (Mar 29, 2018)

P-39 Expert said:


> Every pilots manual for an American WWII fighter had a warning not to snap roll or spin that airplane.



That is patently false!

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## pbehn (Mar 29, 2018)

P-39 Expert said:


> Every pilots manual for an American WWII fighter had a warning not to snap roll or spin that airplane. The recovery methods are normal.
> 
> I don't think the spin chute was standard equipment, but was used on planes undergoing spin tests.


You have obviously made that up. The report recommends the pilots manual be modified as per their recommendations, so not normal. Are you saying that all US fighter pilots were forbidden from spinning and rolling a combat aircraft?


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## Dimlee (Mar 29, 2018)

Great thread, I learned a lot about P-39. Many thanks to all contributors. 
One can disagree with P-39 Expert's argumentation but he did bring a lot of interesting information to think over. And he is standing well so far - under the barrage.

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## pbehn (Mar 29, 2018)

Dimlee said:


> Great thread, I learned a lot about P-39. Many thanks to all contributors.
> One can disagree with P-39 Expert's argumentation but he did bring a lot of interesting information to think over. And he is standing well so far - under the barrage.


I don't know if we have clearly established when the war started and ended yet.

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## Shortround6 (Mar 29, 2018)

Simple, the war started Dec 7th 1941 and the air war ended March of 1944

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## P-39 Expert (Mar 29, 2018)

DarrenW said:


> Could you show us the "official government test" document which stipulated a normally loaded weight of 7,452lbs for a P-39N-1? And one not drawn in No. 2 pencil this time please....


The P-39N pilots manual is not online, or at least I can't find it. I can find manuals for the K/L and the Q.






This chart is from the P-39K which was equipped the same. Empty weight 5658# including radios, oxygen equipment and fluids. The third column shows normal gross of 7648# including 120 gallons of fuel, oil, guns, ammo, armor plate and glass, and a 200# pilot with chute. First column is with a 75 gal drop tank, second column is with a bomb. Most all P-39s weight chart looked like this.

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## P-39 Expert (Mar 29, 2018)

Dimlee said:


> Great thread, I learned a lot about P-39. Many thanks to all contributors.
> One can disagree with P-39 Expert's argumentation but he did bring a lot of interesting information to think over. And he is standing well so far - under the barrage.


Thank you sir. The fight continues. We will never surrender.

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## Shortround6 (Mar 29, 2018)

P-39 Expert said:


> The only real difference in the M and the N was the different reduction gear but it sure made a big difference in climb, wouldn't you agree? So glad you posted this, facts are fun, no?



What troubles me about those figures is the P-39s apparent extreme sensitivity to power and and weight. 
The P-39Q used the same engine and prop as the P-39N and yet the addition of 557lbs knocked 500fpm off the climb at 15,000ft, 430 fpm off at 20,000 and 370fpm off at 25,000. 
Also note that the P-63, although it had about 1000lbs more weight, may have had around 1300hp at 15,000ft and 1200hp at 20,000ft.

Those P-39N figures are in an official document but I suspect you would be very hard pressed to get them in the field.

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## pbehn (Mar 29, 2018)

P-39 Expert said:


> The P-39N pilots manual is not online, or at least I can't find it. I can find manuals for the K/L and the Q.
> View attachment 487696
> 
> 
> This chart is from the P-39K which was equipped the same. Empty weight 5658# including radios, oxygen equipment and fluids. The third column shows normal gross of 7648# including 120 gallons of fuel, oil, guns, ammo, armor plate and glass, and a 200# pilot with chute. First column is with a 75 gal drop tank, second column is with a bomb. Most all P-39s weight chart looked like this.


P-39 Flight Manual

on this very forum.

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## P-39 Expert (Mar 29, 2018)

pbehn said:


> You have obviously made that up. The report recommends the pilots manual be modified as per their recommendations, so not normal. Are you saying that all US fighter pilots were forbidden from spinning and rolling a combat aircraft?[/QUO
> 
> Forbidden from INTENTIONALLY spinning per the manual. And a "snap roll" is different from a regular roll, look it up.


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## DarrenW (Mar 29, 2018)

P-39 Expert said:


> Thank you sir. The fight continues. We will never surrender.



What's this "we" stuff???  But I do agree it's been a real hoot discounting your facts one by one. Can you at least try to stick to one set of facts from now on, please???


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## DarrenW (Mar 29, 2018)

Having limits on spins is not the same as being FORBIDDEN to perform one!


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## drgondog (Mar 29, 2018)

pbehn said:


> Both my father and my uncle were bobbing about in boats on D-Day, I wonder if they saw him.


An interesting question - the shoot down occurred near Janville as 15 Stukas were caught sneaking in at dusk 100' off the deck.

The Area Patrol was between 10 and 15K and following RTB, dropped to the deck for strafing when the 357FS called the Ju-87s rallied the two squadrons in for the shoot. Went out in a direct line from Janville so nowhere near Normandy.

His first combat mission was at 0251 to 0851 on an Area Patrol just east of the Beachhead - dropping down to shoot stuff up behind German lines near Caen... so this one possible

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## Greyman (Mar 29, 2018)

In the interest of comparing like with like - range figures from British data sheets:

Though one difference is the P-39's figures all seem to be for 15,000 feet and the others for 20,000 feet.

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## pbehn (Mar 29, 2018)

drgondog said:


> An interesting question - the shoot down occurred near Janville as 15 Stukas were caught sneaking in at dusk 100' off the deck.
> 
> The Area Patrol was between 10 and 15K and following RTB, dropped to the deck for strafing when the 357FS called the Ju-87s rallied the two squadrons in for the shoot. Went out in a direct line from Janville so nowhere near Normandy.
> 
> His first combat mission was at 0251 to 0851 on an Area Patrol just east of the Beachhead - dropping down to shoot stuff up behind German lines near Caen... so this one possible



Well my father certainly wouldn't have, you have a limited field of view in a destroyers boiler room, searching for U Boats on the edge of the fleet., my uncles job was actually to identify "friend or foe" to the ships gunners on a converted US "Liberty" flak ship. The gunners were straight from the USA with obviously no experience in identification. My uncle called out friend or foe and the US commander of gunners issued the order to fire. They only saw 10 minutes of "action" in the two weeks he was there, but that was very "hairy", he got a nice commendation from the captain.


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## P-39 Expert (Mar 29, 2018)

Shortround6 said:


> What troubles me about those figures is the P-39s apparent extreme sensitivity to power and and weight.
> The P-39Q used the same engine and prop as the P-39N and yet the addition of 557lbs knocked 500fpm off the climb at 15,000ft, 430 fpm off at 20,000 and 370fpm off at 25,000.
> Also note that the P-63, although it had about 1000lbs more weight, may have had around 1300hp at 15,000ft and 1200hp at 20,000ft.
> 
> Those P-39N figures are in an official document but I suspect you would be very hard pressed to get them in the field.


The P-39Q was burdened with the gondola underwing guns which cost about 15mph top speed and affected climb/ceiling also. Basically the same plane as the N except for the wing guns. Hard to compare the two planes, but the Russians removed the wing guns in both making them both the same plane.


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## XBe02Drvr (Mar 29, 2018)

DarrenW said:


> Having limits on spins is not the same as being FORBIDDEN to perform one!


Our Navy Flying Club T-34 was placarded against spins, although at Pensacola they were spun every day. It's just that the civilian type certificate for the T-34B was test flown by the California Forest Department for use as a firefighting air tanker leader, and they didn't see any need to do all the spin testing for their purposes. So the FAA (CAA) issued the certificate with that restriction. There was no aerodynamic or structural reason why it couldn't do them, as I discovered when I pushed it a little too hard in a steep turn and found myself in a spin. It spun nicely and recovered instantly when asked.
Cheers,
Wes

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## P-39 Expert (Mar 29, 2018)

DarrenW said:


> What's this "we" stuff???  But I do agree it's been a real hoot discounting your facts one by one. Can you at least try to stick to one set of facts from now on, please???


Can you point to one single P-39 performance fact from these official tests that you have "discounted". And there were 10 different P-39 models so there are a lot of facts. My story about the British and the P-400 differs from conventional history and I obviously cannot prove that, but it does make sense and other authors have presented this view. I did not make this up.


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## pbehn (Mar 29, 2018)

P-39 Expert said:


> Can you point to one single P-39 performance fact from these official tests that you have "discounted". And there were 10 different P-39 models so there are a lot of facts. My story about the British and the P-400 differs from conventional history and I obviously cannot prove that, but it does make sense and other authors have presented this view. I did not make this up.


I discount all of them showing that it was of any use at all. Trying to sell an aircraft 2 years behind the game in power and down a cul-de sac in airframe design. Your story about the P-400 is a conspiracy theory with nothing for it and much against it, they should have been called P356 for a start.


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## pbehn (Mar 29, 2018)

Shortround6 said:


> Simple, the war started Dec 7th 1941 and the air war ended March of 1944


Ties in nicely with P-39 production, I have the basis of a new conspiracy theory.

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## drgondog (Mar 29, 2018)

P-39 Expert said:


> The P-39Q was burdened with the gondola underwing guns which cost about 15mph top speed and affected climb/ceiling also. Basically the same plane as the N except for the wing guns. Hard to compare the two planes, but the Russians removed the wing guns in both making them both the same plane.


Looking at the Q-1 Operating manual, it is interesting to note that Only 'clean' was any data prepared for long range cruise up to 20K - nothing at 25 K

Fuel consumption data for cruise stops at 14K -----------> 31.7 in MP, 750 HP and 74 g/hr. but the Cruise tables do show 200mph IAS (280 TAS) at 20K w/220RPM and 24" Mp, but no data above 20K.

The max altitude for Cruise tables with 75 gallon external tank is 15K.

Best time to 25K is 10.1 minutes at 7600# GW, 13.1 minutes at 8100 (w/75 gallon tank) using MP @ 44.5" in Military Power.

Single 50 underwing gondola ~ 6-8mph increase in drag at SL

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## Milosh (Mar 29, 2018)

drgondog said:


> The max altitude for Cruise tables with 75 gallon external tank is 15K.



Would this indicate no pressurization of the drop tank?


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## Shortround6 (Mar 29, 2018)

P-39 Expert said:


> Can you point to one single P-39 performance fact from these official tests that you have "discounted". And there were 10 different P-39 models so there are a lot of facts. My story about the British and the P-400 differs from conventional history and I obviously cannot prove that, but it *does make sense and other authors have presented this view*. I did not make this up.



You can find people who claim the earth is flat too. 

It ONLY makes sense *if *you can find actual weight charts that support it. Or memos/memorandum that discus it. 
Existing weight data available to the general public *does not *support this view. 
The British were buying *NO* fighter aircraft without self sealing tanks and armor/BP glass unless for use as trainers at this time (summer of 1940) and strangely enough the USAAF was following suit. NO aircraft without self sealing tanks and armor/BP glass would be categorized as combat capable. Curtiss, Bell, Douglas, Grumman, Brewster and Boeing all got caught by this (and maybe some others). 
Blaming the British sounds like sour grapes or trying to cover up that the P-39 was overweight from the day it rolled out the door as the XP-39. 

Adding a cabin heater should not turn a world beater into a dog. 
Any sales agent worth his salary/commission _should _have been able to at least estimate any performance penalties from extra equipment and have written in suitable adjustments to the performance penalty/cancellations sections of the contract.

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## DarrenW (Mar 29, 2018)

P-39 Expert said:


> My story about the British and the P-400 differs from conventional history and I obviously cannot prove that



Yes views might differ but well established facts normally don't. And why is it fine when you hypothesize but when someone else presents their understanding of something, which has no clear cut answer, you dismiss them outright?


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## DarrenW (Mar 29, 2018)

P-39 Expert said:


> Can you point to one single P-39 performance fact from these official tests that you have "discounted".



Come again???


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## pbehn (Mar 29, 2018)

Shortround6 said:


> You can find people who claim the earth is flat too.
> 
> It ONLY makes sense *if *you can find actual weight charts that support it. Or memos/memorandum that discus it.
> Existing weight data available to the general public *does not *support this view.
> ...


It should also be remembered that the Hurricanes tanks were not able to be completely self sealing and in any case were vulnerable, Hurricane pilots paid a heavy price for it, but not buying and using Hurricane wasn't an option in 1940. Self sealing tanks were not a silly British whim. I don't know what equipment was on the P-39 at the time but things like IFF equipment weighed 40lbs.


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## Shortround6 (Mar 29, 2018)

P-39 Expert said:


> The P-39Q was burdened with the gondola underwing guns which cost about 15mph top speed and affected climb/ceiling also. Basically the same plane as the N except for the wing guns. Hard to compare the two planes, but the Russians removed the wing guns in both making them both the same plane.




Man, somebody screwed the pooch on that one.
Germans claim only 2-4mph loss for a pair of gondolas with 20mm guns under the 109's wings. 
Russians claimed around 12-18mph for the under wing pods on the Mig3 but ti doesn't appear to be the cleanest installation ever seen.





I would also note the pilots manuals show the P-39K doing 300mph at sea level at 2600rpm and 37.5in MAP and burning 97 gallons an hour while a P-39Q doing 300mph at sea level needs the same 2600rpm and a bit higher boost 39in and burns 96 gallons an hour. 
The P-39Q is spinning the supercharger impeller over 2000rpm faster (needs a bit more power to turn the impeller) and needs to use a smaller intake opening (throttle closed a bit more) to make roughly the same power to the prop. 
15mph at top speed should show up as _something_ at max continuous power. 

You have a pair of test results of different airframes with different engines showing one thing and the pilots manuals showing something different.

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## DarrenW (Mar 29, 2018)

P-39 Expert said:


> Every pilots manual for an American WWII fighter had a warning not to snap roll or spin that airplane....



I guess the Hellcat was the exception to this cardinal rule, huh? So will you finally admit that you were completely wrong when you made this outlandish statement? It's ok, we won't hold it against you....

Excerpt from AN 01-85FB-1 Page 38 (Grumman F6F-3/5 Pilot's Handbook - 1 May 1946):

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## Shortround6 (Mar 29, 2018)

Pilots manual for the P-40F & L prohibits spins of more than 3 turns, or any spins with baggage, auxiliary fuel or any other overload.

Snap rolls at speeds over 140mph indicated are also prohibited. 
Page 29.

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## pbehn (Mar 29, 2018)

DarrenW said:


> I guess the Hellcat was the exception to this cardinal rule, huh? So will you finally admit that you were completely wrong when you made this outlandish statement? It's ok, we won't hold it against you....
> 
> Excerpt from AN 01-85FB-1 Page 38 (Grumman F6F-3/5 Pilot's Handbook - 1 May 1946):
> 
> View attachment 487702


I don't know about the USA but in UK from 1917 the ethos of training changed from avoiding dangerous flying events to practicing them in a controlled way. 
This was known as the "Gosport system" pioneered by Robert Smith-Barry. In 1941 at a time when the RAF were clipping the wings of the Spitfire to match the FW190 roll rate the idea that pilots were forbidden to roll or spin an aircraft under any circumstances is fanciful. Maybe just another reason the Brits didn't buy the P-39?

Lieutenant-Colonel Robert Smith-Barry | Taking flight | Exhibitions & Displays | Research | RAF Museum
quote
Smith-Barry taught his students to explore the aircraft's capabilities and to learn the cause and effect of any movement in the air. Instead of avoiding dangerous manoeuvres, such as spins, they were taught how to get out of them safely and, by so doing, developed the skill and confidence to fly their aircraft to the limit.

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## pbehn (Mar 29, 2018)

Shortround6 said:


> Pilots manual for the P-40F & L prohibits spins of more than 3 turns, or any spins with baggage, auxiliary fuel or any other overload.


That of course depends on the pilot being able to correct the spin before 3 turns and on aircraft like the P-39 whether it is possible at all, after all, a test pilot couldn't manage it.

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## Shortround6 (Mar 29, 2018)

Strangely P-40Es were allowed to snap roll at speeds up to 175IAS. Same 3 turn limit on spins


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## pbehn (Mar 29, 2018)

Shortround6 said:


> Strangely P-40Es were allowed to snap roll at speeds up to 175IAS. Same 3 turn limit on spins


I don't know about US training but if you cant do a snap roll in training what do you do if the guy you want to shoot down does? Setting height, speed or load limits isn't the same as a prohibition.

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## tomo pauk (Mar 29, 2018)

Shortround6 said:


> ....
> Germans claim only 2-4mph loss for a pair of gondolas with 20mm guns under the 109's wings.
> ...



Seems like the Bf 109G (early types, with cowl 2 LMGs) were loosing 8 km/h (5 mph) if MG 151/20 gondolas were installed, but, interestingly enough, just 6 km/h with mock-ups of MK 108 gondolas. However, Soviets measued up to 19 km/h difference, with vs. without gondolas.

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## Shortround6 (Mar 29, 2018)

The early P-47 manual is conflicted.
PRACTICE SPINS IN EXCESS OF 1/2 TURN ARE PROHIBITED. 
It is in full caps in the manual, however it says that the pilot should use the recommended control settings for spin recovery for 3 full turns before trying any other combination of control settings. 
Snap rolls are not recommended and should never be performed above 150mph IAS.


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## Shortround6 (Mar 29, 2018)

pbehn said:


> I don't know about US training but if you cant do a snap roll in training what do you do if the guy you want to shoot down does? Setting height, speed or load limits isn't the same as a prohibition.




A lot of this stuff is to keep pilots from killing themselves. 
P-47 manual says it needs 1000ft to enter a spin, it needs 1000ft to recover and it loses 1000ft per turn with the flaps and landing gear up and the canopy closed. It says it loses 3000ft per turn with the landing gear down, flaps up. no mention of canopy? 

Please remember that the US was losing a large number of pilots in training, many due to doing young and dumb things. 
Trying to cover every possible combination of weights and loadings in a short manual was impossible. What you _might_ be able to do with the fuel tanks near empty and with the CG at point X could well be fatal with nearly full tanks and a CG of Y.

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## Shortround6 (Mar 29, 2018)

The FM-2 Wildcat was not permitted to do normal spins or prolonged spins with one or more droppable fuel tanks. 
Without tanks it was allowed to do all standard maneuvers. 
Please note the original F4F was tested by spinning both 10 turns to the right and 10 turns to the left. Two turn inverted spins were also done to both the right and left.


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## DarrenW (Mar 29, 2018)

P-39 Expert said:


> No reduced fuel. If that P-39N had only 87 gallons then it would be only 33 gallons light x 6 pounds/gallon or 198# lighter. The N weighed 7650# loaded with 120 gallons internal, the cannon plus 2 .50 caliber machine guns and 4 .30 caliber wing guns and ammunition, and a 200# pilot with parachute. 7650# less half fuel (60 gal or 360#) resulting in an average weight for that flight of 7290# vs the listed weight of 7274#. Off by 16#. Same for the official performance tests (not different propeller tests etc) of the P-38, and P-47. Look it up.
> 
> Regarding facts, I am quoting the facts from the official government tests.



So you're still hung up on that whole "average" weight thing I see. For your opinion to hold any water the test report author couldn't have been the brightest bulb on the tree. "Gross Weight *at* take-off" means the total weight of aircraft at the moment the wheels left the runway, not average weight *during* the entire flight. Look up the definitions. I'm not making this sh--t up!!!


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## Shortround6 (Mar 29, 2018)

tomo pauk said:


> Seems like the Bf 109G (early types, with cowl 2 LMGs) were loosing 8 km/h (5 mph) if MG 151/20 gondolas were installed, but, interestingly enough, just 6 km/h with mock-ups of MK 108 gondolas. However, Soviets measued up to 19 km/h difference, with vs. without gondolas.



The thing with the P-39 is that you were yanking 2 guns out of each wing





This is a dummied up installation for a Museum on a P-39Q.
and you had two chartridge slots in the bottom of the wing.
And replacing them with the podded .50 cal.
Both the 109 and Mig 3 had nothing coming out or any holes covered over.
The under wing pods could very well have had more drag than the .30 cal installation. But we have no figures on how much drag was saved by pulling and covering the .30s and we have no real figures on a P-39Q with and without pods.

Edit, better picture.


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## Glider (Mar 29, 2018)

Shortround6 said:


> The early P-47 manual is conflicted.
> PRACTICE SPINS IN EXCESS OF 1/2 TURN ARE PROHIBITED.
> It is in full caps in the manual, however it says that the pilot should use the recommended control settings for spin recovery for 3 full turns before trying any other combination of control settings.
> Snap rolls are not recommended and should never be performed above 150mph IAS.


There are many examples of Pilots notes being on the cautious side. On three occasions I have spun a Hunter T8 where the pilots notes state that intentional spinning is forbidden, the notes also tell you what to do in a spin and she behaved perfectly.


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## Graeme (Mar 29, 2018)

Shortround6 said:


> Any sales agent worth his salary/commission _should _have been able to at least estimate any performance penalties from extra equipment and have written in suitable adjustments to the performance penalty/cancellations sections of the contract.



Does the original RAF/Bell contract (worth 9 US million?) still exist somewhere? Love to read it.

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## DarrenW (Mar 29, 2018)

It would seem that snap rolls weren't considered too dangerous to perform in the F6F, as their is no mention of them in the maneuver restriction section of the pilot handbook that I have:


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## pbehn (Mar 29, 2018)

Spitfire instructions are sections 12 and 13 in this pdf.


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## wuzak (Mar 29, 2018)

P-39 Expert said:


> The P-39N pilots manual is not online, or at least I can't find it. I can find manuals for the K/L and the Q.
> 
> 
> 
> ...



Interestingly, that chart shows the 120USG internal fuel is divided into 104USG normal and 16USG overload.

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## DarrenW (Mar 29, 2018)

P-39 Expert said:


> Climb with tank is not shown on P-39N test, so I don't know for sure.
> 
> The graph below is for the P-39K and is representative of the earlier P-39s (D,F,K and L) with the 8.8 supercharger gears and weighing approximately 7650#. As you can see, the dotted line is with belly tank, the solid line is without. This indicates a 300-350fpm lower climb rate with the tank.
> 
> ...



Hey wait a minute, the chicken scratch on that graph looks eerily familiar..... lol!


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## Elmas (Mar 30, 2018)

tomo pauk said:


> Seems like the Bf 109G (early types, with cowl 2 LMGs) were loosing 8 km/h (5 mph) if MG 151/20 gondolas were installed, but, interestingly enough, just 6 km/h with mock-ups of MK 108 gondolas. However, Soviets measued up to 19 km/h difference, with vs. without gondolas.



The problem was not (only) the drag and loss of speed. The problem was that these two weights very far from the CoG augmented substantially the Momentum of Inertia, damaging quite a bit manoeuvers around longitudinal axis.

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## Shortround6 (Mar 30, 2018)

Elmas said:


> The problem was not (only) the drag and loss of speed. The problem was that these two weights very far from the CoG augmented substantially the Momentum of Inertia, damaging quite a bit manoeuvers around longitudinal axis.



There were a number performance problems with the under wing gondola on the Bf 109. Loss of climb being one of them in addition to the loss of roll rate (or loss of roll acceleration/how fast a roll could be started), both being more important than the loss of speed. 
In the case of the P-39 however they were yanking out 50lbs worth of .30 cal guns and 36lbs worth of ammo and replacing it with a 75lb gun and 90lbs worth of ammo. about and 80lb increase (not including weight of the pod) on each side. The Germans were adding about 150lbs not including the pod to each side. P-39 already had some weight in the wings (fuel tanks ) so the percentage change is not as great. Likewise on a percentage basis, the P-39 was a lot heavier than a 109, the weight of the .50s on the P-39 should not affect climb to the extent the under wing pods did to the 109.


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## drgondog (Mar 30, 2018)

Milosh said:


> Would this indicate no pressurization of the drop tank?



Milosh, IMO - yes. That said, a field mod to tap from instrument vacuum system was common - in mid to late 1943. That said, by that time there was not a high altitude requirement for the P-39 and the first Field mods were by Cass Hough in VIII AF ATS for the P-47C/D, then P-51B-1 for external combat tanks.

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## Shortround6 (Mar 30, 2018)

When trying to figure out the weights of some of the test aircraft we have to be careful of some of the minor and not so minor changes between some versions that sometimes are not important enough to make short lists. 
A change in the Aircobras was the propeller shuffle. We have a handle on the difference between the Aero Products prop and the Curtiss prop used on the K and L (and earlier aircraft) finding weights for the later propellers is harder, I don't have any but an 11'7 prop is not going to weigh the same as a 10'3" prop. a minor detail is that at some point they changed nose wheels.




P-39K (?) it is what the caption says with balloon Front tire and small wheel.




P-39N with a low profile tire and bigger wheel.
Maybe they weighed the same and maybe they didn't?
I would work back from the "Q" when figuring weights for the N rather than working forward from the K & L.

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## pbehn (Mar 30, 2018)

Shortround6 said:


> A lot of this stuff is to keep pilots from killing themselves.
> P-47 manual says it needs 1000ft to enter a spin, it needs 1000ft to recover and it loses 1000ft per turn with the flaps and landing gear up and the canopy closed. It says it loses 3000ft per turn with the landing gear down, flaps up. no mention of canopy?
> 
> Please remember that the US was losing a large number of pilots in training, many due to doing young and dumb things.
> Trying to cover every possible combination of weights and loadings in a short manual was impossible. What you _might_ be able to do with the fuel tanks near empty and with the CG at point X could well be fatal with nearly full tanks and a CG of Y.


Perhaps this is just a question of progression in training. Almost every activity requires people to learn the basics before going on to more advanced "stuff". 
From the attached US pilots spent ten weeks each on basic, advanced, advanced single engine, fighter transition and finally operational training and fighter transition this was changed during the war but I presume there was some time when pilots were told to stop "flying by the book" and learn how/when the rules could be broken. 

https://www.quora.com/How-many-hour...required-of-Allied-pilots-during-World-War-II

In the RAF pilots flying a Spitfire needed the permission of their C/O before performing spins regardless of whether they had their "wings" or not, which is similar in principle to the above.


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## P-39 Expert (Mar 30, 2018)

DarrenW said:


> So you're still hung up on that whole "average" weight thing I see. For your opinion to hold any water the test report author couldn't have been the brightest bulb on the tree. "Gross Weight *at* take-off" means the total weight of aircraft at the moment the wheels left the runway, not average weight *during* the entire flight. Look up the definitions. I'm not making this sh--t up!!!


No, you are not making this up. See the post you replied to. If as you say this P-39 had only 87 gallons, then the weight would be reduced by only 198# (33x6).


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## P-39 Expert (Mar 30, 2018)

Shortround6 said:


> When trying to figure out the weights of some of the test aircraft we have to be careful of some of the minor and not so minor changes between some versions that sometimes are not important enough to make short lists.
> A change in the Aircobras was the propeller shuffle. We have a handle on the difference between the Aero Products prop and the Curtiss prop used on the K and L (and earlier aircraft) finding weights for the later propellers is harder, I don't have any but an 11'7 prop is not going to weigh the same as a 10'3" prop. a minor detail is that at some point they changed nose wheels.
> View attachment 487800
> 
> ...


The "Weight and Balance Chart" for the P-39K that I posted earlier was one page before the chart for the P-39L, shows a difference of 50# from the K so I would guess that was the difference in the two props. The only real differences in any of the P-39 models were propellers, (different versions of the same) engines (incl. reduction gears), radios and wing guns.

The front "balloon tire" was on all the P-39s (D,F and K) until the L (and M,N and Q) switched to the slimmer tire.

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## DarrenW (Mar 30, 2018)

Yes, but we never determined what the "official" normal loaded weight of a P-39N-1 truly was. And besides this, how would any of us here really know for sure what equipment was removed or added for that particular flight on 17 October 1942? All we have to go by is what is stated in the report. Gross take-off weight means just that - the weight of the machine at take-off. That's not the same as average weight, which is calculated after the flight is finished.


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## P-39 Expert (Mar 30, 2018)

wuzak said:


> Interestingly, that chart shows the 120USG internal fuel is divided into 104USG normal and 16USG overload.


The fuel capacity was 120 gallons including the 16 gallon reserve. Wasn't actually additional fuel, the inside left fuel tank had two lines to the carburetor, one emptied the tank and the other was shorter forcing the pilot to switch to the "reserve" which was the 16 gallons left over in that tank. Kind of like the "standpipe" reserve the navy used. A standpipe in the bottom of the tank held fuel after the tank was emptied, forcing the pilot to switch tanks to the reserve in the standpipe. In addition to the fuel gauges this arrangement ran the main tank dry and forced the pilot to switch to reserve as a last measure to remind him that fuel was almost gone. Awful description by me, I'll try and find a drawing that explains it better.


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## Shortround6 (Mar 30, 2018)

P-39 Expert said:


> The "Weight and Balance Chart" for the P-39K that I posted earlier was one page before the chart for the P-39L, shows a difference of 50# from the K so I would guess that was the difference in the two props. The only real differences in any of the P-39 models were propellers, (different versions of the same) engines (incl. reduction gears), radios and wing guns.
> 
> The front "balloon tire" was on all the P-39s (D,F and K) until the L (and M,N and Q) switched to the slimmer tire.



EW of P-39L....5733lbs
EW of P-39K....5658lbs
difference...........75lbs

Due to prop, front wheel, pixie dust???

The N and Q had the bigger diameter props. Weight unknown?


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## Shortround6 (Mar 30, 2018)

P-39 Expert said:


> The fuel capacity was 120 gallons including the 16 gallon reserve. Wasn't actually additional fuel, the inside left fuel tank had two lines to the carburetor, one emptied the tank and the other was shorter forcing the pilot to switch to the "reserve" which was the 16 gallons left over in that tank. Kind of like the "standpipe" reserve the navy used. A standpipe in the bottom of the tank held fuel after the tank was emptied, forcing the pilot to switch tanks to the reserve in the standpipe. In addition to the fuel gauges this arrangement ran the main tank dry and forced the pilot to switch to reserve as a last measure to remind him that fuel was almost gone. Awful description by me, I'll try and find a drawing that explains it better.



This is actually quite familiar to anybody who has ridden motorcycles. 






two pipes stick up into tank, you draw fuel from the taller leaving the difference between the taller pipe and the shorter one as the _reserve_.

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## P-39 Expert (Mar 30, 2018)

Shortround6 said:


> The thing with the P-39 is that you were yanking 2 guns out of each wing
> View attachment 487713
> 
> This is a dummied up installation for a Museum on a P-39Q.
> ...


Those .30s in the wing weighed almost 400# total with the original 1000 rounds per gun. Later in the K,L,M and N they reduced the ammo to 300rpg and cut the weight in half to 200# for all 4 guns. Total firing time was about 15 seconds with 300rpg. Then with the Q they switched to the underwing .50cal MGs which weighed 330# including ammo, so the shift to the .50s weighed 130# more. The Q with the underwing .50s was slower than the N by 14mph (399 vs 385). I wish they had discarded the wing armament all together (like the Russians), saved the weight and had the 37mm cannon and the two .50s in the nose.


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## DarrenW (Mar 30, 2018)

I added a P-39N to the chart already provided by Milosh (I know that you really like these ). You can plainly see that, while it could match the early P-47 in range, it's not really a fair contest because the P-39N requires a 75 gallon drop tank to achieve the same results. The P-47 is flying clean from T/O. By the way, before you ask where I got my statistics to chart this, I actually used the information you provided us earlier in this thread......

87 US Gallons internal fuel
75 US Gallon drop tank (only tank available for the Airacobra)
162 US Gallons total fuel
62 gal/hour rate of fuel use equaling roughly 2 hours 40 minutes of flight time
20 minute fuel burned during take-off/climb to altitude/ forming up
20 minute reserve
Actual flight time available for mission = 2 hours
cruise speed = 230 mph
Radius of action (to/from) = 230 miles


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## pbehn (Mar 30, 2018)

After reading a lot I now no longer believe what I am reading. Early test results were never reproduced and by a masterly piece of denial, plausible denial, omission and evasion Bell managed to get a plane that was unsuitable in every way into production and service. Bell's claims about performance and handling were never reproduced in the field, its speed and climb were never satisfactory and the last official test rejected it as a fighter for the US military at all.


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## P-39 Expert (Mar 30, 2018)

Shortround6 said:


> EW of P-39L....5733lbs
> EW of P-39K....5658lbs
> difference...........75lbs
> 
> ...


Yes, I agree and the gross weights are different by 75# also, everything else is the same. My 50# figure is from the original hydromatic prop on the F versus the Curtiss electric on the D. These were 10' props and the extra 25# may have been because of the larger propeller. The hydro prop replaced the Curtiss electric prop from the F model on except for the L (250 mfgd.).


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## Shortround6 (Mar 30, 2018)

DarrenW said:


> cruise speed = 230 mph



Which makes you a target for Luftwaffe fighters, not an escort. 
This is why the escorts "cruised" at 300mph or above and "S" over the bombers. If you are cruising down around 230mph it take around two minutes to accelerate to top speed at which either you are toast or the attackers have come and gone. You are also using up 2 minutes of your 5 min combat power "allowance" just to get up to combat speed.

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## P-39 Expert (Mar 30, 2018)

DarrenW said:


> I added a P-39N to the chart already provided by Milosh (I know that you really like these ). You can plainly see that, while it could match the early P-47 in range, it's not really a fair contest because the P-39N requires a 75 gallon drop tank to achieve the same results. The P-47 is flying clean from T/O. By the way, before you ask where I got my statistics to chart this, I actually used the information you provided us earlier in this thread......
> 
> 87 US Gallons internal fuel
> 75 US Gallon drop tank (only tank available for the Airacobra)
> ...


Can we agree that at least some of the Ns had 120 gals internal and carried a 110gal drop tank? This is absolutely true.

You have figured out how to figure range/endurance from the pilots manual. 120 gal + 110 gal drop = 230gal less 20 gal reserve = 210 gal divided by 62gph = 3.4 hrs less 15 min combat and 20 min reserve for landing = 2.8 hr x 230mph = 644mi divided by 2 = 322mi radius after reserves. The 230mph is the bomber speed TAS and you are weaving to stay at their speed. Drop tank of up to 175 gal was available for the P-39.


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## P-39 Expert (Mar 30, 2018)

Shortround6 said:


> Which makes you a target for Luftwaffe fighters, not an escort.
> This is why the escorts "cruised" at 300mph or above and "S" over the bombers. If you are cruising down around 230mph it take around two minutes to accelerate to top speed at which either you are toast or the attackers have come and gone. You are also using up 2 minutes of your 5 min combat power "allowance" just to get up to combat speed.


Please read my calculations again. I explained that the N with the tank cruised at 281 TAS but since it had to weave to stay with the bombers who were going 230mph TAS that forward progress was at bomber speed. Slow, I know, but that is why you could drop the tank for performance.


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## Milosh (Mar 30, 2018)

That 322 mi is not a straight line but a zig zag line.

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## Milosh (Mar 30, 2018)

So there was no fuel burn during the climb to 25k?

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## Shortround6 (Mar 30, 2018)

Can we please not use ferry tanks or tanks that were not in existence for large parts of 1943 to figure out useful the the P-39 would have been as an escort in early 1943? 
The P-47 first used 200 gallon paper tanks only part filled on July 28th 1943, They couldn't pull the fuel out of them at higher altitudes but they at least got the Planes up to 20-22,000ft. and thus extended the range somewhat. 
Locally made (in the UK) 108 gallon tanks don't show up until Sept, 1943, in the mean time they figured out how to mount 75/85 gallon tanks (and how to pressurize the tank) and by the end of Aug 43 over ten thousand tanks are enroute. 
This is all waaaaaay to late to make any decisions about using the P-39 as an escort in late 1942/very early 1943. 

Allowable take-off weights from hard runways in good conditions for ferrying are often not the same as from grass/unpaved fields in combat areas. overloaded aircraft can lead to broken landing gear and failing to clear the fence. 
going from 7600lb to 8100lbs increased take-off run on a sod runway from 1400ft to 1700ft and adjusting form 32 degrees F to 72 degrees F kicks that up 20%. Take off at 8600lbs would be?????
Yes the P-47 needed a lot of runway.

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## pbehn (Mar 30, 2018)

DarrenW said:


> I added a P-39N to the chart already provided by Milosh (I know that you really like these ). You can plainly see that, while it could match the early P-47 in range, it's not really a fair contest because the P-39N requires a 75 gallon drop tank to achieve the same results. The P-47 is flying clean from T/O. By the way, before you ask where I got my statistics to chart this, I actually used the information you provided us earlier in this thread......
> 
> 87 US Gallons internal fuel
> 75 US Gallon drop tank (only tank available for the Airacobra)
> ...



Informative map but misleading, the P 38 could reach Berlin but could not escort a bomber formation to Berlin, this because of the fuel burned on forming up and weaving which wastes fuel. Also with respect to the map the "THE" on "The Rhein" is where P-51s reached when involved on a raid by the RAF on the Dortmund Ems Canal in October 1942.

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## Peter Gunn (Mar 30, 2018)

P-39 Expert said:


> *Can we agree that at least some of the Ns had 120 gals internal and carried a 110gal drop tank?* This is absolutely true.
> 
> You have figured out how to figure range/endurance from the pilots manual. 120 gal + 110 gal drop = 230gal less 20 gal reserve = 210 gal divided by 62gph = 3.4 hrs less 15 min combat and 20 min reserve for landing = 2.8 hr x 230mph = 644mi divided by 2 = 322mi radius after reserves. The 230mph is the bomber speed TAS and you are weaving to stay at their speed. Drop tank of up to 175 gal was available for the P-39.


No.

Maybe because drgondog post #736...



> The 110 gallon tank was used initially in late 1943 on P-47C/D C/L but AFAIK never on the P-39. First used on P-51B in May 1944.
> 
> I'm unaware that Bell added a tank pressurization capability such as slaving off exhaust or instrument vacuum pump. Did Bell modify the P-39 so that they could carry ANY tank above 20K? Do you have any source documentation of either a mission flown with 110 gallon tank or any mission flown above 20K w/75 gallon combat tank?
> 
> Please point to your sources.



I may have missed it but I do not see a response to this, if so, please point it out for me.


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## P-39 Expert (Mar 30, 2018)

Milosh said:


> That 322 mi is not a straight line but a zig zag line.
> 
> View attachment 487820


I'm not doing a good job of explaining this, my bad. The bombers are going 230mph TAS. Escort is going faster. But escort has to stay with the slower bombers. Bombers fly straight, escort weaves (zig zag) above them. The whole parade is making forward progress at 230mph. 

So you can't use the escort speed to figure range, you have to use the slower bomber speed.

If the mission was not escort, but say patrol or ferry then the TAS of your plane would be used to figure range.


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## Elmas (Mar 30, 2018)

The problem with P-39 was not about a few gallons fuel more or a few gallons less: it was how all the weights of the aeroplane, on the whole, were distributed.
When, for obvious reasons, jets had to install the engine amidship, and to adopt, for aerodynamic reasons, swept back wings, all the problems the P-39 had, not yet fully (if any) understood in the late '30s, were exacerbated. That, added with insufficient thrust of the engines, made some aeroplane really dangerous.


_View: https://youtu.be/Q2qqKwndFW0_

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## pbehn (Mar 30, 2018)

P-39 Expert said:


> I'm not doing a good job of explaining this, my bad. The bombers are going 230mph TAS. Escort is going faster. But escort has to stay with the slower bombers. Bombers fly straight, escort weaves (zig zag) above them. The whole parade is making forward progress at 230mph.
> 
> So you can't use the escort speed to figure range, you have to use the slower bomber speed.
> 
> If the mission was not escort, but say patrol or ferry then the TAS of your plane would be used to figure range.


P39, your flat refusal to read posts and be informed from them is frustrating to say the least. A plane has to take off and form up with its own squadron, then with other squadrons, then rendezvous with the bombers. The airspeed of the bombers was more like 180MPH from what I have read but with headwinds could be down much lower, as low as 120MPH ground speed, which had a big effect when in a flak belt. The Spitfire MkIX could reach the Swiss border with maximum fuel, but this didn't make it any more or less useful than the P-47 which wasn't the answer. It was used to help with bomber withdrawal, now what would you like to be in?


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## Elmas (Mar 30, 2018)

pbehn said:


> P39, your flat refusal to read posts and be informed from them is frustrating to say the least.
> *snip*


_"Whenever a theory seems to you to be the only one possible, take it as a sign that you have not understood either the theory or the problem that you intended to solve. »_
(Karl Popper, Objective Knowledge: an evolutionary point of view.)

This is a typical way of acting of self-taught people: they always look for something that can corroborate their theories, and reject, or even ignore, anything that can challenge them.
The reading of the works of the philosopher Karl Popper (Wien 28 July 1902– London 17 September 1994) would probably be useful, but it seems to me a hopeless thing.

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## DarrenW (Mar 30, 2018)

P-39 Expert said:


> Can we agree that at least some of the Ns had 120 gals internal and carried a 110gal drop tank? QUOTE]



I will agree to your unsubstantiated claim concerning the drop tank when you also agree that "at least some" carrier-based Hellcats were equipped with the ADI jets used during the combat power testing we discussed a few days back. And in reality only the first 166 P-39Ns had the larger internal fuel capacity. ALL P-39N-1s (which is what the test aircraft was) had 33 less gallons available. There's really no wiggle room there. Sorry.


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## DarrenW (Mar 30, 2018)

P-39 Expert said:


> ...322mi radius after reserves



Ok, even it we broke down and gave you the additional 92 miles, according to the chart it's still 53 miles less than the range of the Thunderbolt with drop tanks. So where is the upside to the super duper P-39N again, and why would one EVER select it over the other choices available at the time?


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## wuzak (Mar 30, 2018)

P-39 Expert said:


> The fuel capacity was 120 gallons including the 16 gallon reserve. Wasn't actually additional fuel, the inside left fuel tank had two lines to the carburetor, one emptied the tank and the other was shorter forcing the pilot to switch to the "reserve" which was the 16 gallons left over in that tank. Kind of like the "standpipe" reserve the navy used. A standpipe in the bottom of the tank held fuel after the tank was emptied, forcing the pilot to switch tanks to the reserve in the standpipe. In addition to the fuel gauges this arrangement ran the main tank dry and forced the pilot to switch to reserve as a last measure to remind him that fuel was almost gone. Awful description by me, I'll try and find a drawing that explains it better.



Except the chart didn't say RESERVE, it said OVERLOAD.


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## wuzak (Mar 30, 2018)

P-39 Expert said:


> I'm not doing a good job of explaining this, my bad. The bombers are going 230mph TAS. Escort is going faster. But escort has to stay with the slower bombers. Bombers fly straight, escort weaves (zig zag) above them. The whole parade is making forward progress at 230mph.
> 
> So you can't use the escort speed to figure range, you have to use the slower bomber speed.
> 
> If the mission was not escort, but say patrol or ferry then the TAS of your plane would be used to figure range.



Sure, but you have to base the time aloft figures on the fuel consumption of the fighter's speed.

It will be doing closer to 300mph than 230mph, so the consumption will be significantly higher, meaning shorter time aloft and shorter range when zig-zagging to keep with the bombers.

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## P-39 Expert (Mar 30, 2018)

Shortround6 said:


> This is actually quite familiar to anybody who has ridden motorcycles.
> View attachment 487806
> 
> 
> two pipes stick up into tank, you draw fuel from the taller leaving the difference between the taller pipe and the shorter one as the _reserve_.


That photo tells exactly what I was trying to say. And much better than I said it.


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## Milosh (Mar 30, 2018)

Why is there no data in some of the columns for some of the altitudes?


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## pbehn (Mar 30, 2018)

DarrenW said:


> Ok, even it we broke down and gave you the added 92 mile radius it's still 53 miles less than the range of the Thunderbolt with drop tanks. So where is the upside to the super duper P-39N again, and why would one select it over the other choices available at the time?


This point, like almost every other point has been answered by people with better knowledge than I on this thread, more than once. The range of a fighter is determined by how far a fighter can fly on internal fuel after dropping its external tanks and being in combat on WEP (or its equivalent) for 15 mins (or whatever the maximum is decided). Looking at the chart (previously posted) below it adds up to not very much and puts you in combat with more fuel than the 90 in most tests, don't worry though, it wlll soon be burned down.

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## P-39 Expert (Mar 30, 2018)

wuzak said:


> Sure, but you have to base the time aloft figures on the fuel consumption of the fighter's speed.
> 
> It will be doing closer to 300mph than 230mph, so the consumption will be significantly higher, meaning shorter time aloft and shorter range when zig-zagging to keep with the bombers.


The consumption at 25000' is 62gph at 2600rpm (max continuous). 210 net gallons divided by 62gph = 3.4hr, deduct 15min combat and 20 min landing reserve and you have 2.8 hrs of cruising. Period. Now how far have you gone? You have flown faster than the bombers but you are weaving to keep from passing them. So your forward progress is at their speed of 230mph. So 230mph x 2.8hrs = 644mi divided by 2 = 322mi radius TO ESCORT BOMBERS. On a ferry mission you would use your TAS.


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## P-39 Expert (Mar 30, 2018)

wuzak said:


> Except the chart didn't say RESERVE, it said OVERLOAD.


Yes but it is commonly referred to as the reserve tank in the manual, and it's know as the reserve tank on the fuel tank selector. We're talking about the same thing.


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## DarrenW (Mar 30, 2018)

P-39 Expert said:


> 322mi radius TO ESCORT BOMBERS



_AND _still less than what the Lightning and Thunderbolt was able to provide. Can we also add the Spitfire with a drop tank in for good measure? I read that there were 90 Imperial gallon auxiliary tanks available and actually used on occasion but not sure if they could be jettisoned or not. Anyone with more concise information on this please fill free to chime in....


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## pbehn (Mar 30, 2018)

P-39 Expert said:


> The consumption at 25000' is 62gph at 2600rpm (max continuous). 210 net gallons divided by 62gph = 3.4hr, deduct 15min combat and 20 min landing reserve and you have 2.8 hrs of cruising. Period. Now how far have you gone? You have flown faster than the bombers but you are weaving to keep from passing them. So your forward progress is at their speed of 230mph. So 230mph x 2.8hrs = 644mi divided by 2 = 322mi radius TO ESCORT BOMBERS. On a ferry mission you would use your TAS.


No it doesn't, it just says how far you can go on your imaginary mission. from the moment you are on station escorting the bombers your consumption is in gallons per hour for the time you are in contact at the consumption rate at the height and speed you weave at, that is the speed given previously, and like every other post you ignore. The "range" is how far the bomber group is away from your base at the time you have to head home.


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## P-39 Expert (Mar 30, 2018)

DarrenW said:


> I will agree to your unsubstantiated claim concerning the drop tank when you also agree that "at least some" carrier-based Hellcats were equipped with the ADI jets used during the combat power testing we discussed a few days back. And in reality only the first 166 P-39Ns had the larger internal fuel capacity. ALL P-39N-1s (which is what the test aircraft was) had 33 less gallons available. There's really no wiggle room there. Sorry.


The P-39 obviously could carry a variable amount of fuel. Let's assume that if we're talking about escort duty then we would carry the maximum internal available. Pretend we got one of the kits and put the 33gal tanks back in the wings, or that we had one of the first ones with 120 gallons internal.

How could those experimental ADI jets have been used on combat planes? Did they have an inventory of these experimental parts already on hand while they were testing them? If the parts pass the test then they would go into series production before they could be installed in production planes. They tested these nozzles for a FULL YEAR with the test ending Feb '45. Wouldn't they need to finish the test before they settled on the final configuration for the parts? These parts increased Hellcat speed only 1.5mph. One mile per hour. Climb speed was increased by (per the report) 330fpm. Still this was 450fpm BELOW the P-39N at 20000'. The P-39 still outclimbs the Hellcat.

They were testing non-standard parts, this was not an official performance test. And you didn't even read the report you referenced, or you would have seen the recommendations at the end: 1. Install a carburetor air temp gauge, 2. Modify the derichment valve in the carb, and 3. A new type of water regulator be devised..... DEVISED? How long will that take?

So they had to make the new parts, install them in production planes, and in order for them to work they had to perform the 3 recommendations. 

I'm being honest with you, I just don't see it. Just my opinion.


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## DarrenW (Mar 30, 2018)

pbehn said:


> No it doesn't, it just says how far you can go on your imaginary mission



And according to the Airacobra "Expert", WITH an imaginary never-employed 110 gallon drop tanks as well. And no matter what TAS the Airacobra is flying at (according to P-39 guy, 280 mph) it still will only be able to progress at the speed of the bombers (which will be _at most_ 230 miles in distance) before being forced to turn for home. That sort of range was no real benefit to the bomber crews and that's why external tanks couldn't be added to the Thunderbolt quickly enough.

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## pbehn (Mar 30, 2018)

DarrenW said:


> _AND _still less than what the Lightning and Thunderbolt was able to provide. Can we also add the Spitfire with a drop tank in for good measure? I read that there were 90 Imperial gallon auxiliary tanks available and actually used on occasion but not sure if they could be jettisoned or not. Anyone with more concise information on this please fill free to chime in....


The spitfires maximum internal fuel load reached 164 gallons, and it could carry a 174 gal, external tank all imperial measures.
That doesn't mean that it could carry all at the same time. 
174=209 US 
164=198 US.

Long range escort was a US requirement that appeared very quickly. The Spitfire could have performed a role similar to the P-47, but it was an allied joint effort. All the time US forces were working on the ground on their airplanes they required the same protection as any British forces, that was the job of the RAF and the Spitfire. I would be more than surprised if there was no contingency and involvement of the USAAF in case needed on a massed raid, I just havn't read anything. As previously posted the RAF did assist in withdrawal, from what I remember mainly picking up and escorting stragglers from central/northern France. 

The UK always considered itself under threat, when operation Gisela was launched (at night) by the LW in March 1945, all the equipment was there and procedures in place.

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## Elmas (Mar 30, 2018)

In all these post a thing I did not understand: being P-39 such a formidable weapon, why Luftwaffe, with all the dozens of fancy aircraft designs put on the field, did not copy it by reverse engineering? Quick and simple.
Excellent speed, excellent rate of climb, excellent range, a 37 mm cannon that could destroy a Fortress with a single shot... with the bonus points of having Iron Crosses on the wings ad swastika on the fin. 8th AF would have been wiped out of the skies. And in these posts we have not spoken yet of the outstanding qualities of P-39 as a nightfighter, but soon we will do.
Much, much better of that lousy TA-152s and Me-262s...
Luftwaffe never did something similar, I can't understand why...

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## Milosh (Mar 30, 2018)

Would the Do335 do Elmas?

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## DarrenW (Mar 30, 2018)

P-39 Expert said:


> How could those experimental ADI jets have been used on combat planes? Did they have an inventory of these experimental parts already on hand while they were testing them? If the parts pass the test then they would go into series production before they could be installed in production planes. They tested these nozzles for a FULL YEAR with the test ending Feb '45. Wouldn't they need to finish the test before they settled on the final configuration for the parts? These parts increased Hellcat speed only 1.5mph. One mile per hour. Climb speed was increased by (per the report) 330fpm. Still this was 450fpm BELOW



I have no proof that they were or were not used but the main reason I brought it up is to prove your bias and how quick you are to dismiss others. But your wild-ass claims are not to be challenged, even by those who have a far greater knowledge than you on the subject.

Do you have any proof that they were not used or is that only an assumption on your part? You also assume that only experimental jets were used. Show me the part number and specs of the actual jets fitted to a standard ADI system for the R-2800-10W and then maybe we can clear this up once and for all.

Just calm down and stop attacking everyone here who's trying to help you see the flaws in your theories. It will be an enriching experience for you and one you will eventually be thankful for, I promise.

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## P-39 Expert (Mar 30, 2018)

pbehn said:


> No it doesn't, it just says how far you can go on your imaginary mission. from the moment you are on station escorting the bombers your consumption is in gallons per hour for the time you are in contact at the consumption rate at the height and speed you weave at, that is the speed given previously, and like every other post you ignore. The "range" is how far the bomber group is away from your base at the time you have to head home.


If you read the pilots manual this is how they tell pilots to plan a mission. The consumption rate at 25000' is 62gph at max continuous power from the manual. It is constant throughout the mission, same power setting, same altitude. After reserves you have 2.8hrs to escort. You must use the bomber speed because although you fly faster than them, because of weaving you never pass them. If the escort speed is used, then 2.8hrs x 281mph = 787mi or a radius of 393mi, which is even farther (71mi) than using bomber speed. 

Your consumption is constant at 62gph. The only variable is bomber speed or escort speed. Your forward progress with weaving is the bomber speed.


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## Elmas (Mar 30, 2018)

Milosh said:


> Would the Do335 do Elmas?



Do-335 was twin engine, and while not free from problems, was, at least, statically balanced once ammunition expended. We can not compare P-39 and Do-335, they were different airplanes.
Certainly Do-335 wasn't the best airplane to do a looping, but it wasn't designed with that in mind.

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## pbehn (Mar 30, 2018)

P-39 Expert said:


> If you read the pilots manual this is how they tell pilots to plan a mission. The consumption rate at 25000' is 62gph at max continuous power from the manual. It is constant throughout the mission, same power setting, same altitude. After reserves you have 2.8hrs to escort. You must use the bomber speed because although you fly faster than them, because of weaving you never pass them. If the escort speed is used, then 2.8hrs x 281mph = 787mi or a radius of 393mi, which is even farther (71mi) than using bomber speed.
> 
> Your consumption is constant at 62gph. The only variable is bomber speed or escort speed. Your forward progress with weaving is the bomber speed.


If you knew anything about wartime operations you would know a pilot didn't plan a bomber escort mission, neither did his C/O neither did his group commander, it was an operation involving thousands of aircraft at the most and tens of thousands of people. The idea that you think a pilot just made a plan and waddled off on his own private mission shows how little an "expert" can know before calling himself an "expert".

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## P-39 Expert (Mar 30, 2018)

DarrenW said:


> I have no proof that they were or were not used but the main reason I brought it up is to prove your bias and how quick you are to dismiss others. But your wild-ass claims are not to be challenged, even by those who have a far greater knowledge than you on the subject.
> 
> Do you have any proof that they were not used or is that only an assumption on your part? You also assume that only experimental jets were used. Show me the part number and specs of the actual jets fitted to a standard ADI system for the R-2800-10W and then maybe we can clear this up once and for all.
> 
> Just calm down and stop attacking everyone here who's trying to help you see the flaws in your theories. It will be an enriching experience for you and one you will eventually be thankful for, I promise.


I'm not dismissing anybody, my wild ass claims are straight from the official performance tests. There were other Hellcat tests in the Hellcat section that show basically the same climb rates as your experimental tests. So production Hellcats were climbing at your experimental rate. I just don't think those particular parts could have been used in that time frame. 

I'm not attacking anyone, just discussing.


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## Glider (Mar 30, 2018)

P-39 Expert said:


> If you read the pilots manual this is how they tell pilots to plan a mission. The consumption rate at 25000' is 62gph at max continuous power from the manual. It is constant throughout the mission, same power setting, same altitude. After reserves you have 2.8hrs to escort. You must use the bomber speed because although you fly faster than them, because of weaving you never pass them. If the escort speed is used, then 2.8hrs x 281mph = 787mi or a radius of 393mi, which is even farther (71mi) than using bomber speed.
> 
> Your consumption is constant at 62gph. The only variable is bomber speed or escort speed. Your forward progress with weaving is the bomber speed.


A small point but for the few long range daylight heavy bomber missions the RAF did from May 1944, the favoured UK built escort aircraft was the Tempest. It had a decent range of 740 miles or 1,500 with drop tanks and did escort RAF bombers to the Rhur which is respectable.

Note that the 1,500 range was with two x 45 gallon drop tanks. They rarely but sometimes did use 2 x 90 gallon drop tanks on long range missions but I don't know the range,

Your call P39N or a Tempest

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## pbehn (Mar 30, 2018)

Glider said:


> Your call P39N or a Tempest


P39, it is purely a box art issue, they look cute under attack, with their long range tanks strapped underneath.

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## DarrenW (Mar 30, 2018)

P-39 Expert said:


> Pretend we got one of the kits and put the 33gal tanks back in the wings, or that we had one of the first ones with 120 gallons internal.



If we did that performance would suffer in an escort role so why would anyone do such a thing? I hope you realize that removing a quarter of the internal fuel wasn't done to reduce range (at least I hope you don't think this was the reason). The engineers were trying to keep the Airacobra's speed and climb competitive and range wasn't a primary concern at the time so they cut the fuel load accordingly.

Like everyone has been telling you up to this point, you can't have the extra fuel AND the figures quoted from the army tests as well. It's one or the other so please pick one and be done with it.

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## pbehn (Mar 30, 2018)

DarrenW said:


> Like everyone has been telling you up to this point, you can't have the extra fuel AND the figures quoted from the army tests as well. It's one or the other so please pick one and be done with it.


I believe I read somewhere that sometime in 1941 Bell received a special delivery of solid and liquid anti-gravitum. It is little known in todays world but features a lot in WW2 aircraft discussions.


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## Shortround6 (Mar 30, 2018)

If the bombers are doing 230mph true per hour then and you have two hours of fuel after climb to altitude and allowing for reserve then you have a radius of 230 miles or a bit more, doesn't matter what distance your fighter actually flies in that hour.

However this is NOT the way escort Missions were planned or flown. Please listen to Drgondog, His father Flew P-51s during the war, I beleive he was a squadron commander (?) . He, himself has flown P-51s, He is an aeronautical engineer and and has written at least one book pertaining to the bombing campaign over Germany and is working on another.

Basically it doesn't matter how big a drop tank you can strap on a plane, what matters is what happens after you have to drop said tank/s. How much internal fuel you have to fight for 15-20 minutes and how fast do you have to fly to get back to the channel where you can start to let down/slow down. and then cross the channel. Always keeping that 20-30 minute reserve so you can find an airfield, any airfield in sunny England.

P-39s problem is that it is NOT going to stay at 25,000ft for long in combat. Once you start turning/maneuvering you will lose altitude. 
don'r short change yourself, If you drop 5,000ft your fuel consumption goes up 20 gallons and hour or more, dropping to 15,000ft makes it go up another 20 gallons or more, over a 50% increase in gallons per minute.
P-47s often found themselves at much lower altitudes than when they started.

So lets assume you start with 110 gallons internal ( you got a few gallons back after take-off from vapor return, You need 12-18 gallons reserve depending on requirements. so about 95 gallons. Now can argue about the fuel used in "combat". Later in the war The USAAF figured 5 minutes at WEP and 15 minutes at military power. British figured 15 minutes at times and at other times just equivalents 5 min at combat equeled xx miles at max economy or YY miles at max lean. 

You are counting on using 71 gallons an hour at "military" or full throttle at 25,000ft. Engine is starved for air so it isn't making much power. However, if you drop to 20,000ft and don't throttle back you could be burning close to 90 gallons an hour, drop any lower and the fuel consumption rises even more. The P-39s ability to "fight"at 25,000ft is suspect. You have one test with good climb figures but you have an over 7000lb airplane with about 750hp (or a bit less). While the Mustang (P51-B) isn't available for most of 1943 it has around 1250hp for an airplane a bit over 9000lbs, Early P-47 may have weighed over 12,000lbs but still had 2000hp due the turbo. 
You can't escort/fight flying gentle curves and trying to maintain altitude at all costs. There is no shame in losing altitude in a fight, you just have to plan for it and plan for the power/fuel needed to climb back up. Which cuts into the distance you can fly to get home.

The combat radius of action charts used later in the war were based on.

(a) Warm up and take-off equivalent to 5 minutes at normal rated power.
(b) Climb to 25,000ft, at normal rated power (distance covered in climb is not included in radius)
(c) Cruise out at 25,000ft and 210IAS......(_315 true?)_ 
(d) Drop external tanks and/or bombs before entering combat
(e) combat 5 minutes at war emergency power and 15 minutes at military power
(f) cruise back at 25,000ft and 210 IAS
(g) no account is made of decreased fuel consumption during descent.
(h) Allowance is made for 30 minutes reserve at minimum cruise power
(j) No allowance is made for formation flight or evasive action other than the 20 minutes combat.

Under these conditions (which do not include weaving or time spent with bombers)
the P-38 with 410 gallons internal was rated at 275 miles, the P-47 with 305 gallons internal was rated at 125 miles and the P-51 with 180 gallons was rated at 150 miles. 
some rounding off was going on as all aircraft, with and without tanks all had radiuses that were a multiple of 25. 
Now since we know that a P-39Q with 165 gallons (75 gallon drop tank) is hard pressed to match a clean P-47 with 305 gallons for range the idea that an additional 60-70 gallons is going to turn a P-39 into a long range escort doesn't look good.
BTW a P-47 with 370 gallons internal on this chart is good for 225 miles. Or it used about 30 gallons each way for the extra 100 miles. Granted it was big airplane. 

Remember this is about the maximum radius. No weaving, no dog legs around known flak sites, no allowance for headwinds aside from the built in ones of not counting the climb and not counting the benefit of the descent. 
And remember, beating the crap out of your engines in a "combat" climb right at the beginning of a several hour flight over enemy held territory may not be the smartest thing to do even if it does save a few gallons of fuel.

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## Milosh (Mar 30, 2018)

Glider said:


> A small point but for the few long range daylight heavy bomber missions the RAF did from May 1944, the favoured UK built escort aircraft was the Tempest. It had a decent range of 740 miles or 1,500 with drop tanks and did escort RAF bombers to the Rhur which is respectable.
> 
> Note that the 1,500 range was with two x 45 gallon drop tanks. They rarely but sometimes did use 2 x 90 gallon drop tanks on long range missions but I don't know the range,
> 
> Your call P39N or a Tempest



I have read that there was trouble with the fuel feed from the 90 gal tanks during WW2.


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## DarrenW (Mar 30, 2018)

pbehn said:


> I believe I read somewhere that sometime in 1941 Bell received a special delivery of solid and liquid anti-gravitum. It is little known in todays world but features a lot in WW2 aircraft discussions.


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## eagledad (Mar 30, 2018)

Gentlemen,
Thought I would add more numbers to the mix. Please find a copy of the Tactical Planning chart, which I believe would be used by USAAF planners when planning a mission. Please note that the date is June 1945. Weights include "Basic" + crew, oil, full ammunition, and fuel, Range and endurance includes
1 Allowances for warm up, taxi, run up, take off and landing (Equal to 10 minutes at max cont at SL)
2 Allowance for fuel consumed in climb. Distance and time are included in range and endurance.
3 Allowance for carrying bomb or drop tank ENTIRE flight.
Allowance for 10% net ideal range and endurance for differences in aircraft, pilot techniques etc.






Note that flying at max cruise (max continuous operating at lean mixture setting) at 25000 feet is above the ceiling of the aircraft.
It does not appear that the ranges and endurance given include any allowances for combat.

My 2 cents.

Eagledad

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## Shortround6 (Mar 30, 2018)

trying to use the criteria listed above I come up with

9 gallons for warm up and take-off but since I have no figures for the fuel used climbing at "normal power" =max continuous and since for the P-39Q there is only a 3 gallon difference between the combat climb and the ferry climb (which uses much less than normal power) I am just going to use 40 gallons for take-off and climb to 25,000ft. 
on the other end 30 minutes at minimum cruise seems to be 16 gallons. 
Combat is a bit tricky, at this altitude the P-39 can't even come close to making max continuous power let alone military and WEP. and since fuel consumption fluctuates with altitude (plane might burn 30% more fuel at 20,000ft than at 25,000ft) any number is a WAG. I averaged what I figured was the fuel consumption at 3000rpm (15% higher than the consumption at 2600rpm) for both 25,000ft and 20,000ft at 83 gallons an hour. 20 minutes of that is 28 gallons (rounded up) 
This means that we have 40 gallons for take-off and climb, 28 gallons for combat and 16 gallons for reserve or 84 gallons that cannot be used for cruise. And a minimum 42 of that has to be out of the internal fuel could be as high as 51, depends on how much fuel is returned to main take as vapor/overflow. 
Now we hit the next problem, The P-39 will NOT cruise at the desired 210 IAS with the drop tank. I have no problem with this as a "what if" in early 1943 as tactics and procedures would have been in their infancey and slightly slower plane than desired may have been used anyway. 
However, if 30 gallons of the climb fuel came out of the 75 gallon drop tank ( I am not buying the 110 gallon tank in early 1943) that leaves 45 gallons left and that means roughly 45 minutes to the drop point at 275mph true (I will split the difference between the claimed penalty for the under wing pods) or 206 miles. With over 100 miles of channel to cross before you get to the Belgian/Dutch coast this doesn't look like much of an escort fighter. For getting out of Dodge, you have the 110-120 gallons minus the 42 gallons for combat and reserve. The P-39 is a lot faster without the drop tank. However larger tanks must be looked at carefully as even the 110 gallon tank could get the P-39 further into enemy territory than it could get out. Planes that ditch in the channel are lost. 

However this is best case, no allowances for forming up except the no added radius for the climb ( and no, each fighter does not take-off independently and immediately set course for the rendezvous point) no allowance for having to orbit at a rendezvous point. No allowance for weaving.

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## pbehn (Mar 30, 2018)

eagledad said:


> Gentlemen,
> Thought I would add more numbers to the mix. Please find a copy of the Tactical Planning chart, which I believe would be used by USAAF planners when planning a mission. Please note that the date is June 1945. Weights include "Basic" + crew, oil, full ammunition, and fuel, Range and endurance includes
> 1 Allowances for warm up, taxi, run up, take off and landing (Equal to 10 minutes at max cont at SL)
> 2 Allowance for fuel consumed in climb. Distance and time are included in range and endurance.
> ...


All very well but that is just an historical document on the subject, we prefer made up fantasy from self appointed experts on this particular thread. I am of course joking, that is a great document, sorting out the needs of the many for planning from the needs of the individual to get home must have been a nightmare.

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## wuzak (Mar 31, 2018)

eagledad said:


> Note that flying at max cruise (max continuous operating at lean mixture setting) at 25000 feet is above the ceiling of the aircraft.
> It does not appear that the ranges and endurance given include any allowances for combat.



Regular escort altitude is above maximum cruise setting ceiling!


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## wuzak (Mar 31, 2018)

pbehn said:


> Long range escort was a US requirement that appeared very quickly. The Spitfire could have performed a role similar to the P-47, but it was an allied joint effort.



Spitfires were used as escorts at the start of missions and for withdrawal support.

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## Milosh (Mar 31, 2018)

For comparison with the chart posted earlier on the P-39.

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## Shortround6 (Mar 31, 2018)

So basically a P-39 with 120 gallons internal and 75 gallons external can't fly any further than a P-47 with 305 gallons internal, can't fly as fast and above 20,000ft, can't climb as well. 

And we wonder why they didn't jump all over it as an escort 

I would note that the engine chart for the DB605A as used in the 109 from 1942 on shows around 1100hp at about 25,000ft (7,500 meters) at 2800rpm and around 1000hp at 2600rpm, in a smaller lighter plane. It may have had more drag than the P-39. P-39s at 20-25,000ft ves 109Gs????

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## pbehn (Mar 31, 2018)

The AFDU also did some comparative dog-fighting tests with the Airacobra against a Spitfire VB and a captured Messerschmitt BF 109E. The Airacobra and the Bf 109E carried out mock dog-fighting at 6000 feet and 15,000 feet. The Bf 109E had a height advantage of 1000 feet in each case. The Bf 109, using the normal German fighter tactics of diving and zooming, could usually only get in a fleeting shot. The Bf 109 could not compete with the Airacobra in a turn, and if the Bf 109 were behind the Airacobra at the start, the latter could usually shake him off and get in a burst before two complete turns were completed. If the Bf 109 were to dive on the Airacobra from above and continue the dive down to ground level after a short burst of fire, it was found that the Airacobra could follow and catch up to the Bf 109 after a dive of over 4000 feet. When fighting the Bf 109E below 20,000 feet, the Airacobra was superior on the same level and in a dive.

A similar trial was carried out against a Spitfire V. Although the Airacobra was faster than the Spitfire up to 15,000 feet, it was outclimbed and out-turned by the Spitfire. Unless it had a height advantage, the Airacobra could not compete with the Spitfire. If on the same level or below, at heights up to about 15,000 feet, the Airacobra would have to rely on its superior level and diving speeds and its ability to take negative "G" without the engine cutting out. Above 15,000 feet, the Airacobra lost its advantage in level speed.

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## Shortround6 (Mar 31, 2018)

My criticism of this test is that it is against the 109*E, *which to be fair to the British, was the only airworthy 109 they had at the time and _any_ test was more informative than no test. 
But for telling how the P-39 would have fared against the 109F let alone the G it leaves a lot to be desired.

According to William Green (correction welcome) a 109F-0 with e DB601N engine was compared to a 109E/N also with a DB601N engine. 
a 360 degree turn could be made in 18 seconds compared to the 109Es 25 seconds at 3280ft. Starting at that altitude 2900ft could be gained in a "combat turn"(whatever that is) compared to only 1970ft by the "E". Initial climb rate was 3,730fpm compared to 3420fpm and 16,400ft could be reached in 5.2 minuted compared to 6.1 min.
Starting in early 1942 (?) the 109F got the DB601E engine which made 30 more PS/HP 1600ft higher than the DB601N.

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## pbehn (Mar 31, 2018)

Shortround6 said:


> My criticism of this test is that it is against the 109*E, *which to be fair to the British, was the only airworthy 109 they had at the time and _any_ test was more informative than no test.
> But for telling how the P-39 would have fared against the 109F let alone the G it leaves a lot to be desired.
> 
> According to William Green (correction welcome) a 109F-0 with e DB601N engine was compared to a 109E/N also with a DB601N engine.
> ...


It also doesn't mention that which shouldn't be mentioned, the FW190.


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## drgondog (Mar 31, 2018)

P-39 Expert said:


> Can we agree that at least some of the Ns had 120 gals internal and carried a 110gal drop tank? This is absolutely true.
> 
> You have figured out how to figure range/endurance from the pilots manual. 120 gal + 110 gal drop = 230gal less 20 gal reserve = 210 gal divided by 62gph = 3.4 hrs less 15 min combat and 20 min reserve for landing = 2.8 hr x 230mph = 644mi divided by 2 = 322mi radius after reserves. The 230mph is the bomber speed TAS and you are weaving to stay at their speed. Drop tank of up to 175 gal was available for the P-39.


 Nope. The P-39N was out of deployment when 110 gallon tanks were a.) manufactured in-theater by Brits/Aussies and b.) the P-47 had priority because they WERE used for high altitude escort.

A drop tank FERRY tank, not self sealing, May have been used to Ferry from point A to Point B but not showing up in any Flight Testing.

Kindly point me to ANY document that states the Centerline rack Ever carried anything heavier that 500 pound bomb?

Last but not least, the P-39 Operating manual charts always express the airframe speeds in IAS - which works in your favor if the chart pointed to 230IAS at 20K - but is states Only without drop tank (75G) does recommended 2200 rpm @24"MP ----------> 200mph IAS ------> 298 TAS at 20K. The latter is a good escort speed but in both ETO, escorting 5K under the bombers is not very useful.

You don't seem to get your head around what you are reading.

Gross weigh at T.O. includes all the fuel, all the ammo, all the consumables, the fixed equipment, the pilot, the centerline rack, the guns, etc UNLESS otherwise stated in the report. The Report will further cite special preparations like taping over shell chutes, wing gun ports, the actual ammo/ballast carried if not max combat load, etc.

A well prepared Test report for speed runs and ROC tests will also state the fuel remaining at the altitudes recorded to give us techie/nerds insight to evaluate the actuals against the Analytics in Flight Performance Calcs . (BTW the P-39 nearly always fell short of Poppa Bell's engineering estimates) 

America's One Hundred Thousand by Dean is very rigorous about presenting load outs for 'standard Fighter (less than full load out - but specificity in the actual load and weights) 'Overload fighter' (Full Internal Load), 'Fighter Bomber' (load out when carrying bombs or external fuel tanks'). 

In my own research in which I have the airframe specs from factory for Empty, Basic (w/GFE and other related weights such as residual fuel/oil remaining after mission that is not easily recoverable post flight for 'empty tanks, guns, racks') and the above mentioned load outs which are useful load items - the weights are accurately reproduced.

Weight and Drag increments are Essential reported items when Range, Climb and top speeds for given altitudes and throttle settings - and often insert Horsepower ratings per the manufacturer at those settings and altitude. A Professional report will further reduce the speed data as a function of Mach Number, Standard Temp and Pressure vs altitude. 

ROC is inversely proportional to Gross Weight and proportional to the difference between Power Available less Power Required. Excess Power = Thrust x Velocity - Drag x Velocity ----------> strip weight and climb increases, add drag and climb decreases, run out of excess power and climb ceases (so to constant altitude turns.

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## Shortround6 (Mar 31, 2018)

Getting back to the British and why they didn't want the P-39, the first (and last) operational flight of the P-39/Aircobra I in British service was Oct 9th 1941.
The Germans had introduced the 109F back in March/April on the Channel coast and the first Fw190s were being service tested in July. The British had a pretty good Idea of how these aircraft stacked up against the Spit V and a good idea how the Spit V stacked up against the Aircobra I. They knew the Aircobra I (P-39D) wasn't going to work against either of them in the style of fighting (tactics) the British were using at the time.


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## pbehn (Mar 31, 2018)

Shortround6 said:


> Getting back to the British and why they didn't want the P-39, the first (and last) operational flight of the P-39/Aircobra I in British service was Oct 9th 1941.
> The Germans had introduced the 109F back in March/April on the Channel coast and the first Fw190s were being service tested in July. The British had a pretty good Idea of how these aircraft stacked up against the Spit V and a good idea how the Spit V stacked up against the Aircobra I. They knew the Aircobra I (P-39D) wasn't going to work against either of them in the style of fighting (tactics) the British were using at the time.


Ive just read that there were 4 "missions" two found no targets and the other shot up a trawler, the most involved were three aircraft one time. Initially at least they were taken off operations because of compass problems.
quote
By the end of September, No. 601 Squadron had received permission to take its Airacobras into action. On October 9, two Airacobras took off from RAF Manston and flew across the Channel on a "rhubarb"--a code name for a small-scale raid by fighters against targets of opportunity. On this raid, they shot up an enemy trawler near Gravelines. The next day two Airacobras visited the same area, but found no targets. On October 11, two aircraft flew to Gravelines and Calais and hit some enemy barges and then three Airacobras flew to Ostend, but no targets were found.

After these four missions, the RAF Airacobras were taken off operations because of difficulties encountered with the compass. The compass was too close to the guns in the nose, and when the guns were fired, the compass got thrown out of alignment. Deviations of anything from 7 degrees to 165 degrees were recorded. Without a reliable compass, pilots tend to get themselves lost. In December of 1941, the Airacobra was officially withdrawn from operational service with the RAF.

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## Shortround6 (Mar 31, 2018)

Thank you for the correction.


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## pbehn (Mar 31, 2018)

Shortround6 said:


> Thank you for the correction.


Until yesterday I had read the same as you and posted same, even reading my last post it is not completely clear whether 2 aircraft went to Calais and Gravelines or 2 went to Calais and another 2 went to Gravelines, that would be the 4 that I had previously read about. The two places are only about 10 miles apart but that coast was heavily defended.

From here
joebaugher.com/


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## Just Schmidt (Mar 31, 2018)

I thought I'd try and add something potentially more useful to this thread than my previous Witisism. It has been a most interesting thread, though it's been expanding at a pace that makes me worry i may have missed a few posts along the way. I hope I don't by accident have overlooked something too important. I could never aspire to improve on most of the many informative details that have been under close scrutiny, my efforts are more directed at the greater picture.

I indeed was introduced to the P-39, and many other ww2 planes, by Green - and Swanboroughs - publications on aircraft, I am not sure that Green is too dismissive of the P-39, his assessment of the Ki-43 seem more unfair. In any event, I always felt that the P-39, on paper, looked quite good, especially compared to the P-40. Though the latter was based on a far earlier design, I do think that comparing this aircraft to the P-39 is the fairest that can be done to a contemporary allied aircraft, a little more on this later.

However, to begin 'on thread' (in as far as this isn't the how much superior to any other pane in any mission was the P-39?), I'd site the comparison (fly off) between a P-39D-1 Vs 'The Aleutian Zero', the recovered A6M2 Zero 21. My source is Mikesh, Robert C: 'Zero fighter' Zokeisha Publications 1981 p26f.. It is a picture book, and while I am pretty sure the report referred to (originally from december 1942) is to be found somewhere on this forum, I didn't manage to dig it up, so here goes from the selection in the book:

"takeoff was accomplished in formation on signal to initiate a climb from sea level to 5.000 feet indicated. The P-39D-1 was drawing 3000 rpm and and 70 inches manifold pressure on take off when the engine started to detonate, so manifold pressure was reduced to 52 inches. The airacobra left the ground first and arrived at 5.000 feet indicated just as the zero was passing 4.000 feet indicated. This manifold pressure of 52 inches could be maintained to 4.500 feet indicated. At 5.000 feet from a cruising speed of 230 mph (200 kts) indicated, the P-39 had a marked acceleration away from the Zero. Climb from 5.000 to 10.000 feet at the respective best climbing speeds, (thus eliminating zoom effect) the P-39 reached 10.000 feet approximately six seconds before the Zero.At 10.000 feet indicated, from a crusing speed of 220 mph (191 kts) indicated, the airacobra still accelerated away from the Zero rapidly. Climbing from 10.000 feet to 15.000 feet, both aircrafts maintained equal rates of climb to 12.500 feet. Above this altitude the Zero walked away from the P-39.
Climb from 15.000 to 20.000 feet indicated, the Zero took immidiate advantage and left the Airacobra. The climb from 20.000 feet to 25.000 feet was not completed as the P-39 was running low on fuel.
On a straight climb to altitude rom take off under the same conditions as before, the Airacobra maintained the advantage of the climb until reaching 14.800 feet indicated. Above this altitude the P-39 was left behind reaching 25.000 feet indicated approximately 5 minutes behind the Zero. At 25.000 feet from a cruising speed of 180 mph (156 kts) indicated, the Zero accelerated away from the P-39 for three ship lengths. This lead was maintained by the Zero for one and a half minutes and it took the P-39D-1 another thirty seconds to gain a lead of one ships length."

The comment on the fly off against a P-40F is: "These tests were not completed with the P-40F because it was found impossible to obtain maximum engine operation." To return to an aircraft with the Allison, the early P-51 tested compared worse to the Zero in climb, but better in speed, at least up to the 15.000 feet above which "[t]he P-51's power plant failed to operate properly". Finally it could be remarked that the P-38F had the engines function properly all up to 30.000 feet.

Pity that the Japanese in '42 didn't oblige to the P-39 by coming in at low level. In any event most aircraft still climbing when meeting an escorted raid will be at a distinct disadvantage, but I am not sure whether this example is comparable to the Spitfires problems at Darwin. In any event the P-39 does seem a decent performer down low. Whatever the seriousness of its deficiencies in handling, they did not stop the US itself from operating the type for at least a couple of years, but of course there was a war on. The Soviets (and probably not just Stalin) seem to have really liked the P-39.

Somebody said a few hundred posts ago that it was a niche fighter (not a typo for nice btw) so i can't take credit for that. However I will remark that the eastern front was a pretty big niche, it was hardly a side show. I've expressed my interest in the P-39 in eastern Europe before, in the thread 'How much did Soviet aero-production depend on leand-lease?" Greyman kindly, in post 22, supplied a link that I am not sure i can paste from there. It was most informative, alas also showing some methodological problems, or are we to believe that they shot down no less than 3 He 113? ( Just to be safe: No we're not). Anyway really detailed and reliable data on these operations may never be available. But indeed the Soviets preferred it to the P-40, making it possible that it in some respects not only surpassed this on paper. For these deliberations I'm leaving out the 'Merlin' engined P-40's.

Green does seem to have great responsibility for the myth of the P-39 as mostly a ground attack aircraft, in 'Russia' it was used as an air superiority fighter. Probably too much can be made of specialization in the Red Airforce, as many fighters were equipped for carrying small bombs; however it did possess one of ww2's few dedicated ground attack aircraft in unsurpassed numbers, and apart from the Il-2 several others, including Bostons. So even if the P-40 was a better bomb truck than the P-39, this may have mattered less for Soviet doctrine than Western, making them focus more on effectiveness as a pure fighter, also, as have been remarked, a cannon and two 12,7 weren't as bad in Soviet context. The cannon was useful still for strafing, of course 4 additional light guns were good here too. However, apart from different ballistic properties, 3 kinds of ammo for one fighter does seem a relatively large strain on logistics. Finally, in a P-40 comparison, both aircraft were in the USSR previously unknown properties, in any event making a process of familiarization necessary. Whether they were really considered better than the best Soviet types is another matter, at least after the introduction of Yak-3 and La-5fn.

Ironically The USSR itself had an early plane that failed though it looks good on paper, the MiG-3. It was simply optimized for the wrong altitude, though I have the impression it had numerous other serious issues, I just never came across really detailed and trustworthy accounts of what they were.

Well, just thought I'd sneak in a post while everybody are busy shooting at P-39.

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## Dimlee (Mar 31, 2018)

Just Schmidt said:


> Green does seem to have great responsibility for the myth of the P-39 as mostly a ground attack aircraft, in 'Russia' it was used as an air superiority fighter.



P-39 of Soviet VVS were used for ground(and sea) attacks quite intensively in 1945 and occasionally in 1944. Probably Crimean offensive was the first experience. Whether it was done due to total air superiority and lack of air targets or due to deficit of strike a/c in particular area, it is hard to say. That question was debated for long on some Russian language forums.
Years ago I read interesting materials about P-39s used against German shipping in Danzig Bay in March/April 1945. Over 300 attacks with FAB-250 bombs in about 10 days of operation. Meager results though.

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## P-39 Expert (Mar 31, 2018)

DarrenW said:


> _AND _still less than what the Lightning and Thunderbolt was able to provide. Can we also add the Spitfire with a drop tank in for good measure? I read that there were 90 Imperial gallon auxiliary tanks available and actually used on occasion but not sure if they could be jettisoned or not. Anyone with more concise information on this please fill free to chime in....


Uh, a 90 Imp. gallon tank IS a 110gal American tank.


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## CORSNING (Mar 31, 2018)

[QUOTE="DarrenW, post: 1393614, member: 73711
So for a third time, what are your thoughts on the usefulness of the P-39N in 1944? Could it really deliver the same usefulness as say a P-47D or P-38J/L? As you can see I'm leading up to something here.... [/QUOTE]

*The usefulness of the P-39N to the Russians in 1944 was a very big issue.
It was capable of exceeding the capabilities of the P-47 and P-38 at low
and medium altitudes, within a much shorter distance, agreed.

I am presently pulling up all the info I have on the P-47D and P-38J at the
end of 1943. I intend to compare the actual performance of the P-39N/Q
to these aircrafts and more. But you guys have to seriously slow down.
I am up to posting #765 on page "I haven't a clue".
I work full time and am having a very tough time finding time to keep
up with you wizards of information.*

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## P-39 Expert (Mar 31, 2018)

Just Schmidt said:


> I thought I'd try and add something potentially more useful to this thread than my previous Witisism. It has been a most interesting thread, though it's been expanding at a pace that makes me worry i may have missed a few posts along the way. I hope I don't by accident have overlooked something too important. I could never aspire to improve on most of the many informative details that have been under close scrutiny, my efforts are more directed at the greater picture.
> 
> I indeed was introduced to the P-39, and many other ww2 planes, by Green - and Swanboroughs - publications on aircraft, I am not sure that Green is too dismissive of the P-39, his assessment of the Ki-43 seem more unfair. In any event, I always felt that the P-39, on paper, looked quite good, especially compared to the P-40. Though the latter was based on a far earlier design, I do think that comparing this aircraft to the P-39 is the fairest that can be done to a contemporary allied aircraft, a little more on this later.
> 
> ...


Thank you so much for your post. 

The Green/Swanborough books are unkind to the P-39, especially the N. Their speed and climb numbers are well below the official govt/military tests. But their numbers on other planes sometimes hit the test mark, often not. Same with most reference books. Lots of information, lots doesn't match up. That has contributed to the bad P-39 history.

The test with the Aleutian Zero was with a P-39D-1. The report was dated December '42 and I believe the actual tests were in Oct/Nov. The P-39D-1 was the heaviest and one of the oldest P-39s to that date. There were much better P-39s available and the vastly improved N model would be produced from November. Probably used the D-1 because it was stationed there. The D-1 was also used in tests against the Thunderbolt and Lightning too when much better versions of the P-39 were available. 

P-39N and Q were definitely effective in Russia with 3 of the top 4 Russian aces and scores of 20+ victory aces.

For reference I have attached the govt/military performance charts for the FW190A6 which as we all know is much superior to the Zero in performance with my penciled in P-39N performance. As you can see it was about the same speed above 6km (20000') but climbed substantially better at all altitudes. Standard FW190 vs. standard P-39N from the govt charts.


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## Elmas (Mar 31, 2018)

AFAIK, only another airplane was so much idolized in this Forum by his supporters, FW-187.
But FW-187 had Iron Cross on the wings and swastika on the fin...

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## Stig1207 (Mar 31, 2018)

Dimlee said:


> P-39 of Soviet VVS were used for ground(and sea) attacks quite intensively in 1945 and occasionally in 1944. Probably Crimean offensive was the first experience. Whether it was done due to total air superiority and lack of air targets or due to deficit of strike a/c in particular area, it is hard to say. That question was debated for long on some Russian language forums.
> Years ago I read interesting materials about P-39s used against German shipping in Danzig Bay in March/April 1945. Over 300 attacks with FAB-250 bombs in about 10 days of operation. Meager results though.



At this stage, the Soviets had such a sheer numerical advantage, so it's very likely they were used in an air-to-ground capability; just to have something to use for them. This would naturally extend to all their fighter types, not the P-39 alone.

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## pbehn (Mar 31, 2018)

P-39 Expert said:


> The Green/Swanborough books are unkind to the P-39, especially the N. Their speed and climb numbers are well below the official govt/military tests. But their numbers on other planes sometimes hit the test mark, often not. Same with most reference books. Lots of information, lots doesn't match up. That has contributed to the bad P-39 history.
> 
> .
> View attachment 487986
> View attachment 487987


When you try to disprove field results with lab results the most likely cause is someone fiddling the lab results. Complaints about the actual performance of the P-39 in service being below quoted test results were common. It is as likely that Bell were tweaking the planes sent for test as it was that operators were being unkind or weaseling out of contracts.


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## buffnut453 (Mar 31, 2018)

pbehn said:


> It is as likely that Bell were tweaking the planes sent for test as it was that operators were being unkind or weaselling out of contracts.



Hmmm...so Bell is a direct translation for Volkswagen in American English? 

I know...I'll get my coat!

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## pbehn (Mar 31, 2018)

buffnut453 said:


> Hmmm...so Bell is a direct translation for Volkswagen in American English?
> 
> I know...I'll get my coat!


A better translation would be Triumph motorcycles. When the T160 was given to the press hacks to test, the engine was straight out of the race shop. It was "tested" as doing 127MPH while those actually sold did 110-115, I knew two guys who got them..


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## swampyankee (Mar 31, 2018)

One issue with the P-39, due to its small fuel capacity, was its short range, which largely precluded its use in any kind of offensive role in the European theatre. Part of the reason for restricted fuel capacity was the basic design, in that the best place for fuel tankage is at the aircraft center of gravity, and Bell put the engine right there, in the best place for the fuel tanks.

To a great extent, this made the P-39 useless to the USAAF and Commonwealth air forces in the ETO and Pacific. While I don't think the P-39 was the piece of crap that some histories have made it, I also think that Bell's decision to use the mid-engine configuration with a long drive shaft was basically flawed: it added considerably to the plane's empty weight, as did the choice of tricycle gear, probably caused a net increase in aircraft drag, due to the need to increase the areas of the horizontal and vertical stabilizer to get adequate tail volume, and severely limited fuel capacity.

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## DarrenW (Mar 31, 2018)

P-39 Expert said:


> Uh, a 90 Imp. gallon tank IS a 110gal American tank.



There you go again, spouting off inaccurate information where a cursory internet search will straighten any misconception you may have about a subject. By the way, 90 Imperial gallons equates to approximately 108 US gallons, not 110. It may seem that I'm splitting hairs here but there actually were 108 AND 110 US gallon tanks employed by the AAF during the Second World War. The first was paper and the latter was metal.

I have a suggestion, why don't you research stuff before posting on the forum?

This is a 90 Imperial gallon "slipper" tank used by Spitfires:






How is this EVER the same as this???


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## DarrenW (Mar 31, 2018)

P-39 Expert said:


> Thank you so much for your post.
> 
> The Green/Swanborough books are unkind to the P-39, especially the N. Their speed and climb numbers are well below the official govt/military tests. But their numbers on other planes sometimes hit the test mark, often not. Same with most reference books. Lots of information, lots doesn't match up. That has contributed to the bad P-39 history.
> 
> ...



Nice. Have any "new" information to share with us besides regurgitating the same old charts with penciled in performance figures?


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## Shortround6 (Mar 31, 2018)

P-39 Expert said:


> Uh, a 90 Imp. gallon tank IS a 110gal American tank.


Uh, 90 gal tank for a Spitfire.




models




US 110 gal paper tank




US 110 gal metal tank





I see I was beaten to it.

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## Juha2 (Mar 31, 2018)

Three of the five top Soviet aces (Grigori Rechkalov, Nikolai Gulaev and Dmitri Glinka) got most of their kills while flying P-39s and Rechkalov and D. Glinka ended the war in May 1945 still flying P-39s with Guards units operating inside Germany. Gulaev was badly wounded in Aug 44, still flying P-39 with 129 GIAP. And at least still in March 1945 Airacobras operated with Leningrad area PVO with Guard interceptor units. So guard units used P-39s to the end of the war in Europe in air superiority and interceptor roles.


Juha

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## pbehn (Mar 31, 2018)

DarrenW said:


> By the way, 90 Imperial gallons equates to approximately 108 US gallons, not 110. It may seem that I'm splitting hairs here but there actually were 108 AND 110 US gallon tanks employed by the AAF during the Second World War. The first was paper and the latter was metal.
> This is a 90 Imperial gallon "slipper" tank used by Spitfires:


There were many sizes of slipper tank, some could be dropped but normally weren't, even though they caused a decrease in performance. The issue is not loading up a plane with as much fuel as possible because that doesn't increase range. The Spitfire could have a rear tank fitted, but that changed CoG and like the P 51 had to be burned off first. Fuel could be put in the leading edges 33 Imp. gal. A Spitfire was flown with two 80 imp gal drop tanks and 45 gal rear tank. BUT since you burn off the rear tank first, then the 160 gallons in the drop tanks you only have 85gal (internal fuel) +33 gal(wing edges). to fight 15 mins and then fly home the distance that you just used 205 gals to get to.

The P-51 needed a rear tank and large external drop tanks to do an escort mission to Berlin and back from UK, in peace time it could actually make the trip there and back twice if its only issue was flying as far as possible at the most economical speed and height.
This discusses some of the issues
Escort Spitfire - a missed opportunity for longer reach? - Royal Aeronautical Society

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## DarrenW (Mar 31, 2018)

Shortround6 said:


> I see I was beaten to it.



Only by seconds and your pictorial representations are far prettier than mine....


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## Glider (Mar 31, 2018)

In Malta they came up with their own solution which were 2 x 45 gallon tanks from Hurricanes fitted under the fuselage. They were used to extend the distance from Malta that convoys could get air cover

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## DarrenW (Mar 31, 2018)

Juha2 said:


> Three of the five top Soviet aces (Grigori Rechkalov, Nikolai Gulaev and Dmitri Glinka) got most of their kills while flying P-39s and Rechkalov and D. Glinka ended the war in May 1945 still flying P-39s with Guards units operating inside Germany. Gulaev was badly wounded in Aug 44, still flying P-39 with 129 GIAP. And at least still in March 1945 Airacobras operated with Leningrad area PVO with Guard interceptor units. So guard units used P-39s to the end of the war in Europe in air superiority and interceptor roles.
> 
> 
> Juha



Thanks Juha for the valuable information. Through your research were you able to ascertain the overall validity of the "kills" awarded to these top Soviet fighter pilots? And how much, if any, were their scores "influenced" by the Soviet propaganda machine?


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## pbehn (Mar 31, 2018)

Spitfire with 2x80 gal tanks, note bottomed out suspension.


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## Greyman (Mar 31, 2018)

Glider said:


> In Malta they came up with their own solution which were 2 x 45 gallon tanks from Hurricanes fitted under the fuselage. They were used to extend the distance from Malta that convoys could get air cover

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## fubar57 (Mar 31, 2018)



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## pbehn (Mar 31, 2018)

Greyman said:


> View attachment 488049


Yup, if you put a civil servant in charge of things even a Spitfire can come out fugly.


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## DarrenW (Mar 31, 2018)

fubar57 said:


> View attachment 488050


Thanks for the chart fubar57. Seeing that the majority flew a wide variety of types, is there any way to know which aircraft they were most successful with? Did any score exclusively with the Airacobra?


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## fubar57 (Mar 31, 2018)

This book has 4 pages of Soviet aces who scored with the P-39 though a majority flew other aircraft as well. 




​Its a bit confusing trying to figure out exact numbers, for example...

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## Juha2 (Mar 31, 2018)

Elmas said:


> ...To the Russians, who never were too worried for the lives of their pilots, this did not seem to have been of particular importance, but for the American, British, Australian, Italian pilots, that were particularly attached to their skins, it was...



Strickly speaking that was not true, pilots were specialists, expensive to train, so in normal situations they were valued, Soviet planes had back armour for pilots already in 1939 and at least their fighters and medium DB-3 bombers had self-sealing fuel tanks also at that time. Of course in desperate situations as in 1941 e.g. strafing attacks were ordered regardless the cost.


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## fubar57 (Mar 31, 2018)

Just found out, "Taran" means ramming attack....yikes


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## Juha2 (Mar 31, 2018)

On the soviet aces, the best source is Bykov, e.g. Mellinger's books rely too much on Soviet era books, Bykov had dug out his info from Soviet archives.

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## DarrenW (Mar 31, 2018)

What were the optimum cruise speeds of the Mustang, Thunderbolt, and Lightning while performing escort duties? Was 25,000 feet the optimum mission altitude for US bombers?


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## pbehn (Mar 31, 2018)

Juha2 said:


> Strickly speaking that was not true, pilots were specialists, expensive to train, so in normal situations they were valued, Soviet planes had back armour for pilots already in 1939 and at least their fighters and medium DB-3 bombers had self-sealing fuel tanks also at that time. Of course in desperate situations as in 1941 e.g. strafing attacks were ordered regardless the cost.


I read that Il-2 pilots would be ordered to continue "attacking" German positions even when they had no weapons left, just to keep their heads down. Excluding the material cost of the airplane, it is quite possible for a "dummy attack" to save many more lives than that of a single pilot.


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## Juha2 (Mar 31, 2018)

DarrenW said:


> Thanks Juha for the valuable information. Through your research were you able to ascertain the overall validity of the "kills" awarded to these top Soviet fighter pilots? And how much, if any, were their scores "influenced" by the Soviet propaganda machine?



No, overall Soviet claims were fairly badly inflated but IMHO in most air forces the claim accuracy in the end rested on the claimant, some claimed clearly more accurately and some clearly worse than the national average. And none of those 3 fought here up north.

On the way propaganda machine "influenced" on accepted claims, I don't know. Of course during the "dark days" there was a need for heroes. But IMHO Soviet system has no reason to bring forward especially those who flew LL planes more likely opposite.

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## Elmas (Mar 31, 2018)

Juha2 said:


> Strickly speaking that was not true, pilots were specialists, expensive to train, so in normal situations they were valued, Soviet planes had back armour for pilots already in 1939 and at least their fighters and medium DB-3 bombers had self-sealing fuel tanks also at that time. Of course in desperate situations as in 1941 e.g. strafing attacks were ordered regardless the cost.



Life of Pilots was precious in every Country, of course. I wanted to say that Red Army accepted and was able to sustain unacceptable losses for any other Allied nation.

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## Dimlee (Mar 31, 2018)

Just adding to fubar57's table...
Список лётчиков-асов Второй мировой войны — Википедия
In Russian, but you can scroll down to "CCCP" with red flag and then look for P-39 in the 5th column.
This table includes aces with 30+ kills (except the last one, Safonov).
This is Wiki, so don't consider the data to be very accurate. Pilots with only "P-39" mentioned actually had kills with other types as well.
And of course, all numbers were subject to "overclaim effect". But this is another story.

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## Shortround6 (Mar 31, 2018)

I do not have the skills to plot/chart the results of the tests for the P-39.

What I am referring to is that the test results for the P-39N that form the basis for this argument _seem _to be out of the normal expected results.

That is like testing 10 aircraft and finding 8 are within 2-3% of each other, one is 5% slow and one is 5% fast. The slow one could be checked for poor engine (multiple reasons) or poor airframe causing drag. The fast one has only a few answers, bad test instruments, out of the ordinary weather conditions or an engine that is making more than ordinary power. 
Please note that in many of these tests they had no way of actually _KNOWING _what the engine was making for power, they simply recorded the RPM and manifold pressure and consulted a chart to get the power. Some radial engines had torque meters built into the reduction gearbox and by measuring the RPM and the torque reading they had the actual power that engine was making at the moment. Not what engine XX made on a test stand when they have engine YY in the airplane. 

The P-39N test could be true/accurate. It is just that it is so much better than the P-39M & Q that weren't that different. 
Is the N test accurate and the M & Q tests the result of poor engines?

We also have operational charts showing no difference in performance between the N and Q (or not enough to list) and cruise charts showing little or no difference in the needed by the high drag gunpod Q and the earlier aircraft. 

I would note they hung a 90 imp gallon fuel tank under a MK V Spit (790lbs on a 6695lb plane) and got 560 less fpm at 20,000ft change in rate of climb while the P-39Q lost 430fpm at 20,000ft after adding 600lbs to to 7274lb plane. I would note that the Spitfire was fully tropicalized with that fugly air cleaner and tropical radiator and oil cooler setups.

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## pbehn (Mar 31, 2018)

Shortround6 said:


> I do not have the skills to plot/chart the results of the tests for the P-39.
> 
> What I am referring to is that the test results for the P-39N that form the basis for this argument _seem _to be out of the normal expected results.
> 
> ...


I agree completely, the performance presented shows a wonderful use of the Allison engines power to achieve results no other manufacturer achieved, but actually no one flying a P-39 achieved either. The same goes for the P-400 that the British received, it didn't do 400MPH at any height ever, even the quoted speeds of the P-39D under test were wide of the mark, it should have been slightly slower than the Spitfire V above 15,000 ft in fact it was much slower. The same goes for aerobatic performance, from test pilots taking other pilots word for the plane being satisfactory to "issues being raised" it eventually was barred from use as a front line fighter after it had been used as a front by many nations. To me the issue of spent nose armament is a complete red herring, it progressed into a flat spin while under test by a test pilot, that is all just "plausible denial".


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## Dimlee (Mar 31, 2018)

I searched in my archive and was surprised to find my own 15 year old spreadsheet with Soviet P-39 aces data: names, kills claimed, missions, aircraft type, etc. Let me publish just this shortlist: pilots whom I identified with majority kills (_probably!_) with P-39.
Please treat with a pinch of salt as it was done in 2003 and *never updated* since.
Question marks - where exact numbers were disputed or not available but historians or other sources believed that most victories were with P-39.
Figures in brackets reflected old discussion over actual victories of Pokryshkin. Treat them with another pinch of salt. Or two.

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## Juha2 (Mar 31, 2018)

Glider said:


> The first combat report on WW2aircraft.net for a Spit IX is 28th July 1942 approx. 12 months before the P39N entered service.
> As an aside I believe that the first USAAF units equipped with the Spit VIII started operations in Aug 1943



The first easy to find P-39N kill is the 4th of Fiedler's (the only USAAF P-39 ace) kills, date June 12, 1943. 68 FS


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## Milosh (Mar 31, 2018)

I just remembered something I had read about the P-39. The long drive shaft from the engine to the prop vibrated and cause problems with the reproduction system of the pilot, that is the pilots became sterile. Just a WW2 myth???

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## P-39 Expert (Apr 1, 2018)

DarrenW said:


> Nice. Have any "new" information to share with us besides regurgitating the same old charts with penciled in performance figures?


Just the same old official charts. With the same old P-39 numbers penciled in. Do you have a better method to compare planes?


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## P-39 Expert (Apr 1, 2018)

Shortround6 said:


> Uh, 90 gal tank for a Spitfire.
> View attachment 488043
> 
> models
> ...


So these are the famous non-existant 110 gallon tanks?


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## *SkyChimp* (Apr 1, 2018)

Real world comparison: A6M2 with a 5'3" 120lb pilot who has eaten nothing but rice and a little fish for weeks on end, who is slightly feverish and a bit queasy and may have malaria, versus a P-39 with a 5'10" pilot, 155lb who has diarrhea, lost a card game last night and most of his script, and who can't get a letter to his pregnant wife back home. Oh, and who had 62 cents in nickels, dimes and pennies that fell out of his pocket and is now rattling around in the cockpit. Who wins?

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## Elmas (Apr 1, 2018)

*SkyChimp* said:


> Real world comparison: A6M2 with a 5'3" 120lb pilot who has eaten nothing but rice and a little fish for weeks on end, who is slightly feverish and a bit queasy and may have malaria, versus a P-39 with a 5'10" pilot, 155lb who has diarrhea, lost a card game last night and most of his script, and who can't get a letter to his pregnant wife back home. Oh, and who had 62 cents in nickels, dimes and pennies that fell out of his pocket and is now rattling around in the cockpit. Who wins?



Ben Rich, in his fundamental „Skunk Works“ reminds that Kelly Johnson promised a prize for an idea that that would save a few pounds of weight of an A-12.

Ben Rich proposed to inflate the tyres with helium (that was experimented, but helium very quickly escaped from tyres) and, before each flight, to submit the Pilot to an enema. Kelly replied to Rich to discuss this matter directly with the Pilots.

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## Shortround6 (Apr 1, 2018)

P-39 Expert said:


> So these are the famous non-existant 110 gallon tanks?


Those are the non-existent in early 1943 tanks (Before August/Sept) or the non-existent for most of 1943 in the Pacific tanks. 
Good luck fitting a Spitfire tank on a P-39.

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## P-39 Expert (Apr 1, 2018)

Shortround6 said:


> If the bombers are doing 230mph true per hour then and you have two hours of fuel after climb to altitude and allowing for reserve then you have a radius of 230 miles or a bit more, doesn't matter what distance your fighter actually flies in that hour.
> 
> However this is NOT the way escort Missions were planned or flown. Please listen to Drgondog, His father Flew P-51s during the war, I beleive he was a squadron commander (?) . He, himself has flown P-51s, He is an aeronautical engineer and and has written at least one book pertaining to the bombing campaign over Germany and is working on another.
> 
> ...


Regarding first paragraph, could you distribute this so everyone will know how to plan an escort mission? If you stay with the bombers then your forward progress is at bomber speed. Thank you. If you stay with the bombers, your forward progress is at bomber speed while your TAS is higher. Weaving is accounted for.

My sources are the official tests and the pilot's manuals. I'll stick with those.

Regarding fuel burn at various altitudes, you can also go up a little higher in your P-39N and burn less fuel too. 

Let's do the same exercise for the Thunderbolt. Straight from the pilot's manual. Clean with 305gal internal(no drop tanks, since none were available until August '43). Let's do it your way. Climb to 25000' took 91gal. Cruise at max continuous at 190gph (that big R-2800 used some gas). 305-91gal=214gal divided by 190gph=1.1hr. Take away the 15 min for combat and the 20min landing reserve and you are left with .5hr. That's half an hour, the bombers are going 230mphTAS so you have an escort range of 115mi, divide that by 2 and your escort radius is almost 58mi. That may not even get you TO the English channel from your base.

Lets do this the way the manual says. 305gal less reserve for takeoff and climb to 5000' of 45gal=260gal divided by that 190gph (max continuous)=1.4hr less reserve for combat 15min and landing reserve 20min = .8hr x 230mph (bomber speed) = 184mi divided by 2 = 92mi radius. You may actually see Belgium from there. Remember this includes reserves for combat and finding your airfield to land.

Now let's add the 110gal drop tank. 305+110=415gal less reserve (for T/O&Climb to 5000') 45gal=370gal divided by 190gph = 1.9hr less 15min reserve for combat and 20 minute landing reserve and you are left with 1.4hr at bomber speed 230mph = 322mi divided by 2 = 161mi radius for escort. It's even worse with your method. And you haven't seen Germany before you need to head home.

The whole reason for the 45gal reserve for T/O and climb to 5000' was so the pilot didn't need to use all your calculations. Much easier and very accurate for the pilot. And, if you use 230mph bomber speed (after all, that is your forward progress while weaving) then weaving is accounted for. No combat climb on the initial climb out, just normal climb at 2600rpm max continuous. And sure, if your mission is interrupted by combat you drop your tanks and fight. Then you need to start your journey home then, just like a Thunderbolt.

The ability of the P-39N to fight at 25000' is suspect? What was the P-39s most likely opponent for European bomber escort? The FW190A. At 25000' the combat speed was about the same and the P-39N outclimbed the FW190A by 700fpm. And outturned it too by the way. I think the P-39N would have been successful against the FW190A.

Can we all just admit that you all had not seen these P-39N numbers before now? New information (since late 2012)? If you did see this information then you didn't analyze it. Kind of explains how the Russians did so well with it.


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## P-39 Expert (Apr 1, 2018)

Shortround6 said:


> Getting back to the British and why they didn't want the P-39, the first (and last) operational flight of the P-39/Aircobra I in British service was Oct 9th 1941.
> The Germans had introduced the 109F back in March/April on the Channel coast and the first Fw190s were being service tested in July. The British had a pretty good Idea of how these aircraft stacked up against the Spit V and a good idea how the Spit V stacked up against the Aircobra I. They knew the Aircobra I (P-39D) wasn't going to work against either of them in the style of fighting (tactics) the British were using at the time.


Britain didn't want the P-39 (P-400) because the reason they ordered them in 1940 was in case of a German invasion of Britain. France folded like a deck chair and the British were able to hold the Luftwaffe to a stalemate (effective victory/no invasion) in the fall of 1940 in the Battle of Britain. Lend lease was enacted in early '41 so now Britain (and Russia) will get all the American planes it needs for free. Now the completed P-400s arrived in mid 1941, there is no longer any threat of invasion by Germany. Britain is now supplying their own fighters (Spit & Typhoon) in sufficient quantity that they don't need the P-400s. But these P-400s were PURCHASED under a hard money contract and Bell expected payment. The British were broke and certainly did not want to pay hard cash for planes they could now get for free. 

I'm amused by the British's shock at the P-400 performance. Did they just wake up one morning and realize the P-400 weighed too much? Hardly, they ordered them that way. The purchaser (US Army or British) contractually specified EXACTLY the way the planes were to be equipped down to the last rivet. Bell had no choice but to manufacture the planes as ordered. And I'll wager that there was a British representative (or many) stationed at the Bell plant to make sure their purchase was exactly as ordered. They did the same thing to Lockheed by ordering P-38s without turbochargers and then refused to pay when those planes didn't meet specs. Had Pearl Harbor not happened (US now urgently needed all the planes they could get) then Bell and Lockheed would have sued the pants off the British over those contracts. Plus these were brand new designs and had the normal bugs and glitches any new plane had. This is not what you read in the airplane books, but I have read this exact thing before, I did not make it up. And it makes more sense than the British being surprised by low P-400 and P-38 performance. There was no surprise.

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## michaelmaltby (Apr 1, 2018)

... but watch the Pathe newsreels showing off the "Caribou" to the world ... it was what it was ... but I agree that PH saved the British from legal epics . 
The Eastern Front saved the P-39.
The P-400s that the British contributed to the Soviets were pretty clapped out ... if you believe Soviet sources 
But while the British were operating the P-400s I'm sure they 'trained' with them hard.

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## pbehn (Apr 1, 2018)

P-39 Expert said:


> Britain didn't want the P-39 (P-400) because the reason they ordered them in 1940 was in case of a German invasion of Britain. France folded like a deck chair and the British were able to hold the Luftwaffe to a stalemate (effective victory/no invasion) in the fall of 1940 in the Battle of Britain. Lend lease was enacted in early '41 so now Britain (and Russia) will get all the American planes it needs for free. Now the completed P-400s arrived in mid 1941, there is no longer any threat of invasion by Germany. Britain is now supplying their own fighters (Spit & Typhoon) in sufficient quantity that they don't need the P-400s. But these P-400s were PURCHASED under a hard money contract and Bell expected payment. The British were broke and certainly did not want to pay hard cash for planes they could now get for free.
> 
> I'm amused by the British's shock at the P-400 performance. Did they just wake up one morning and realize the P-400 weighed too much? Hardly, they ordered them that way. The purchaser (US Army or British) contractually specified EXACTLY the way the planes were to be equipped down to the last rivet. Bell had no choice but to manufacture the planes as ordered. And I'll wager that there was a British representative (or many) stationed at the Bell plant to make sure their purchase was exactly as ordered. They did the same thing to Lockheed by ordering P-38s without turbochargers and then refused to pay when those planes didn't meet specs. Had Pearl Harbor not happened (US now urgently needed all the planes they could get) then Bell and Lockheed would have sued the pants off the British over those contracts. Plus these were brand new designs and had the normal bugs and glitches any new plane had. This is not what you read in the airplane books, but I have read this exact thing before, I did not make it up. And it makes more sense than the British being surprised by low P-400 and P-38 performance. There was no surprise.


This is complete, utter tosh, you have been told why it is tosh, but continue to post it. You ignore the attack on Pearl Harbour and what it meant. The USA, understandably, took all planes it needed for itself so the British never received the P-39s they ordered, they never received all the Mustang 1s (P-51A) they ordered either. You continually blather about weight, but weight doesn't have a huge effect on top speed or climb, power and drag do. The P51B was approximately 30MPH faster than the Spitfire Mk IX on the same engine, not only at top speed but on almost any cruise setting, and it also weighed about half a ton more. By 1943, a matter of months after your famous test the P-39 was barred by the US from being used as a fighter, it was an advanced trainer, too dangerous to its own side to be used in anger. That is the opinion of the USA military in official tests, nothing to do with anyone else.


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## Shortround6 (Apr 1, 2018)

P-39 Expert said:


> Regarding first paragraph, could you distribute this so everyone will know how to plan an escort mission? If you stay with the bombers then your forward progress is at bomber speed. Thank you. If you stay with the bombers, your forward progress is at bomber speed while your TAS is higher. Weaving is accounted for.
> 
> My sources are the official tests and the pilot's manuals. I'll stick with those.
> 
> ...




Oh boy, what a load of male bovine excrement. I hardly know where to start. 

Lets try with the P-47 example you gave.

The P-47 doesn't need to cruise at max continuous, so there is *mistake #1* No need to "cruise at 360mph when the P-39 only has to cruise at 275mph (with tank), slowing the P-47 down to 225IAS (337mph true) cuts the fuel burn down to 145 gallons an hour. Gee whiz that kicks the range after taking out 15 minutes of combat and _30 min_ reserve to about 250 miles. EXCEPT 225IAS is still too high. We do have a figure of 200IAS which is 300mph true and a fuel burn of a whopping 95 gallons an hour. That 120 gallons in the P-47 after climb, combat and reserve is now 1.25 hours at 300mph or 375 miles? or escorting the weaving bombers 143 miles, not 58. 

*Mistake #2 *the escorts operated in relays so they did not escort from the shores of Britain to the target or as far as they could go. One group would meet up over the Channel and escort in, another group would meet up part way in after flying in a straight line to the rendezvous point and then start weaving. And so on. ONE Group of fighters did NOT weave both going in and coming out. So radius is actually a bit longer. 

I don't have a chart for a P-47 with a single drop tank. But an extra 110 gallons should be good for about 1 extra hour at about 300mph. Except it doesn't work quite that way. Climb from several thousand ft to 25,000ft is done on the tank and the tank is dropped fairly soon in the flight (maybe, depends on supply) leaving the P-47 with nearly full tanks at 25,000ft. and inbound. 
And as noted the P-47 *DOESN'T NEED *to cruise at max continuous in order perform this mission. 

As for the Fw 190, you know, I have never read where the Bf 109s sat on the ground and let the FW 190s do all the bomber intercepting, can you point me to a source? In fact I have read where they _tried_ to get the 109s to engage the fighters and have the 190s attack the bombers, this is also 1943 so there were a fair number of 5 gun 109s (a 20mm under each wing) also used for bomber intercept so this idea that the P-39s can pick and choose which German fighter they will interact with is *Mistake #3.*

*Mistake #4* I have been a member of this site since 2009, some of the other members have been here much longer, do you really think we have all been ignorant of WW2 Aircraft Performance all that time? There have been a number posts in this forum notifying members about many of the updates as they happened. You are not a modern day Moses coming down from the mount with grand revelations that we unwashed, unbelievers have been ignorant of.

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## pbehn (Apr 1, 2018)

While the YP-39 and the P-39C were being test-flown, Bell Aircraft began work on an export version of the Airacobra known as the Bell Model 14. It was to be powered by a 1150 hp Allison V-1710-E4 engine which had twelve exhaust stacks on each side rather than the usual six. France was sufficiently interested that they ordered 200 Model 14s on October 8, 1939.

All of the media hype surrounding the spectacular performance of the XP-39 prototype had caught the attention of the British Direct Purchase Commission which had visited the USA in 1940 in search of combat aircraft. Seduced by promises of 400 mph top speed, a tricycle undercarriage, heavy cannon armament, and high climb rates, the British ordered 675 examples of the Airacobra. Unfortunately, Bell's glossy advertising brochures did not distinguish between the performance of a lightly-loaded, unarmed, highly-polished experimental prototype and a production fighter heavily-loaded with military equipment and armament, and the British were to rue the day that they ever looked at an Airacobra.

In 1940, the British were desperate for combat aircraft and were willing to consider just about anything that had wings, irrespective of how poor its performance might be. Consequently, when Bell submitted specifications to the British Direct Purchase Commission for a fighter with a top speed of 400 mph, a ceiling of 36,000 feet, and a range of 1000 miles, the Commission literally salivated on the spot and ordered 675 Bell Model 14s sight unseen on April 13, 1940.

The RAF model was at first named Caribou, but the American name of Airacobra was adopted in July 1941. The British Airacobra was virtually identical to the American P-39D, but the slower-firing 37-mm cannon was replaced with the faster-firing and more reliable Hispano 20-mm cannon with 60 rounds. Two 0.50-inch machine guns were mounted in the fuselage, and four 0.30-inch machine guns were mounted in the wings. The engine of the Model 14 was the 1150 hp Allison V-1710-E4 (-35). The British serials of the Airacobras were AH570/AH739 (170 planes), AP264/AP384 (121 planes), BW100/BW183 (84 planes), and BX135/BX434 (300 planes).

Bell began test flying the first Model 14 Airacobra I in April 1941. It carried the British serial number AH570. Tested on the second British Airacobra (AH571) was a revised rudder of more angular shape and less area. Although the aircraft was delivered to England in this form, this rudder was not adopted as standard. A very small dorsal fin just ahead of the rudder became a standard feature of the RAF Airacobras and was also a distinguishing feature of the American P-39D and subsequent versions.

President Roosevelt signed the Lend-Lease Act on March 11, 1941, permitting large quantities of war supplies to be transferred to the Allies. Among the early requisitions under Lend-Lease were three P-39Cs intended for "war tests" plus a batch of 150 Airacobra IAs--the A suffix being used to distinguish between Lend-Lease and Direct Purchase machines, which were otherwise identical. In the event, only the three P-39Cs were ever delivered as British machines, and were assigned the serials DS173/DS175 (USAAF werials 40-2981, -2983, -2984). The P-39Cs could be distinguished from the British Airacobras by the four machine guns in the nose and the lack of wing guns.

The first of these P-39Cs actually arrived at RAF Colerne on July 3, 1941, followed by the other two the next day. It made its first test flight in England on July 6. However, during trials at Duxford, the performance proved disappointing. Although the test pilots praised the general ease of handling of the aircraft, the maximum speed was a shocking 33 mph lower than that anticipated. The fighter proved to be definitely inferior to the Hurricane and Spitfire in climb rate and ceiling, and the 750-yard takeoff run of the Airacobra excluded its operation from some smaller fighter airfields. There was universal shock and dismay among the RAF personnel. What had gone wrong? Bell Aircraft executives later sheepishly admitted that their performance figures had been based on the unarmed and unequipped XP-39 prototype, which weighed a ton less than the armed and equipped P-39C.

The first British-purchased Airacobras began arriving at Colerne before the end of July, joining the three P-39Cs already there. Deliveries of the Airacobra to Britain had to be made by sea, since the Airacobra lacked the range to make the Atlantic crossing. By the end of September, eleven machines had been received. No. 601 "County of London" Squadron was selected to be the first Fighter Command squadron to equip with the Airacobra.

No. 601 Squadron pilots found numerous flaws and weaknesses during their initial work-up with the the Airacobra. Some of them were a question of improving operational efficiency and pilot comfort, but others were considered essential to make the aircraft operational. Numerous modifications were made in the field in an attempt to make the aircraft suitable for combat. A master valve was introduced to allow oxygen to be turned on from the cockpit. The gunsight was modified to improve forward visibility. Changes to the ammunition tanks for the wing guns were made. Modifications were made to the cockpit harness release in order to simplify the operation. The IFF (Identification, Friend or Foe) set was removed from behind the pilot, where it obstructed aft view. A throttle control quadrant friction damper was introduced.

The Air Fighting Development Unit received a British Airacobra I on July 30. They subjected it to tests and completed their report on September 22. They found the aircraft to be pleasant to fly and easy to takeoff and land. Controls were well balanced and although heavier than those of the Spitfire at normal speeds, did not increase appreciably in weight at high speeds as they did in the Spitfire. It was difficult to hold the aircraft in a dive at high speeds unless the aircraft was trimmed nose-heavy. During a turn, the Airacobra would give ample warning of a high-speed stall by severe vibration of the whole airframe. Handling in formation and formation attacks was good, although deceleration was poor because of the plane's aerodynamic cleanliness. Take-offs and landings in close formation were not considered safe, since there was considerable difficulty in bringing the aircraft back to its original path after a swing.

The Airacobra I was powered by an Allison V-1710-E4 twelve-cylinder V in-line engine rated at 1150 hp for takeoff. Weights were 5462 pounds empty and 7845 pounds normal gross. Maximum speeds were 326 mph at 6000 feet, 343 mph at 10,000 feet, 355 mph at 13, 000 feet, 341 mph at 20,000 feet. Initial climb rate was 2040 feet per minute. With an internal fuel capacity of 100 Imp gal the Airacobra had an endurance of 1 hour 20 minutes at maximum continuous cruising speed at 6000 feet, 1 hour 5 minutes at 12,000 feet, and 1 hour 35 minutes at 20,000 feet. The true airspeeds at these altitudes were 287 mph, 327 mph, and 308 mph, respectively. Under most economical cruise conditions, the endurance increased to 3 hours 20 minutes, the relevant speeds being 183 mph at 6000 feet, 217 mph at 12,000 feet, and 215 mph at 20,000 feet. Under maximum continuous climb conditions, it took 15 minutes to reach 20,000 feet. The operational ceiling was considered to be about 24,000 feet, although there was a marked decrease in performance above 20,000 feet. At the Airacobra's rated altitude of 13,000 feet, it was 18 mph faster than the Spitfire VB. However, the speed fell off rapidly above that height, and the two planes were almost exactly matched at 15,000 feet. At 20,000 feet, the Spitfire VB was 35 mph faster and at 24,000 feet it was 55 mph faster. The ground run of the Airacobra during takeoff was 2250 feet, as compared with 1470 feet for the Hurricane II and 1590 feet for the Spitfire V.

The AFDU also did some comparative dog-fighting tests with the Airacobra against a Spitfire VB and a captured Messerschmitt BF 109E. The Airacobra and the Bf 109E carried out mock dog-fighting at 6000 feet and 15,000 feet. The Bf 109E had a height advantage of 1000 feet in each case. The Bf 109, using the normal German fighter tactics of diving and zooming, could usually only get in a fleeting shot. The Bf 109 could not compete with the Airacobra in a turn, and if the Bf 109 were behind the Airacobra at the start, the latter could usually shake him off and get in a burst before two complete turns were completed. If the Bf 109 were to dive on the Airacobra from above and continue the dive down to ground level after a short burst of fire, it was found that the Airacobra could follow and catch up to the Bf 109 after a dive of over 4000 feet. When fighting the Bf 109E below 20,000 feet, the Airacobra was superior on the same level and in a dive.

A similar trial was carried out against a Spitfire V. Although the Airacobra was faster than the Spitfire up to 15,000 feet, it was outclimbed and out-turned by the Spitfire. Unless it had a height advantage, the Airacobra could not compete with the Spitfire. If on the same level or below, at heights up to about 15,000 feet, the Airacobra would have to rely on its superior level and diving speeds and its ability to take negative "G" without the engine cutting out. Above 15,000 feet, the Airacobra lost its advantage in level speed.

The Airacobra was considered to be very suitable for low altitude operations because of the excellent view and controllability, and it was fully maneuverable at speeds above 160 mph. It was not difficult to fly at night, but the exhaust flames could be seen by another aircraft flying three miles to the rear. The flash from the nose guns was blinding, and could cause the pilot to lose not only his target but also his night vision. Firing of the nose guns caused the buildup of carbon monoxide contamination in the cockpit, and this could reach a lethal level very quickly. The guns were fairly inaccessible, and maintenance was troublesome.

By the end of September, No. 601 Squadron had received permission to take its Airacobras into action. On October 9, two Airacobras took off from RAF Manston and flew across the Channel on a "rhubarb"--a code name for a small-scale raid by fighters against targets of opportunity. On this raid, they shot up an enemy trawler near Gravelines. The next day two Airacobras visited the same area, but found no targets. On October 11, two aircraft flew to Gravelines and Calais and hit some enemy barges and then three Airacobras flew to Ostend, but no targets were found.

After these four missions, the RAF Airacobras were taken off operations because of difficulties encountered with the compass. The compass was too close to the guns in the nose, and when the guns were fired, the compass got thrown out of alignment. Deviations of anything from 7 degrees to 165 degrees were recorded. Without a reliable compass, pilots tend to get themselves lost. In December of 1941, the Airacobra was officially withdrawn from operational service with the RAF.

In spite of the problems with the compass and the need for flame dampers for the exhaust and flash suppressors for the nose guns, the RAF concluded that the Airacobra would make an excellent day fighter at altitudes below 20,000 feet and was well suited for the ground-attack role. However, before these plans could be implemented, a decision was made to divert the bulk of the British Airacobra contract to Russia.

By the time this decision was made, production of British-contract Airacobras had reached four a day at Bell's Buffalo plant. The initial contract for 170 planes (RAF serials AH570 thru AH739) had been completed before the end of September, and all but six of these planes had actually been shipped to Britain. However, many of them remained in their crates and were shipped directly to the Soviet Union without being opened. Somewhere between 80 and 100 Airacobras were assembled and flown in Britain by the end of 1941. They were gathered at maintenance units for final modification before being re-crated and shipped to the Soviet Union during 1942. In all, the Soviet Union received 212 of the British Airacobras (some of them shipped direct from the USA), but 49 more were lost at sea en route.

No 601 Squadron relinquished its 13 Airacobras in March of 1942 in favor of Spitfires. One Airacobra was fitted with an arrester hook and was used for deck landing trials at the RAE at Farnborough.

After Pearl Harbor, the USA found itself in desperate need of aircraft to stem the Japanese onslaught in the Pacific. Consequently, nearly 200 of the British direct-purchase Airacobras still in the USA were promptly requisitioned by the USAAC. Although they were similar to the USAAC's P-39Ds, they were not identical and were known by the USAAC under the non-standard designation of P-400. The P-400 designation had, in fact, been associated with the British Airacobras for contractual purposes as early as August 1941. The USAAC P-400s retained their original British serial numbers and their three-color camouflage paint. Most of these planes were used for training stateside, but some of them were rushed to the Southwest Pacific in an attempt to stem the onrushing Japanese advance.

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## pbehn (Apr 1, 2018)

179 of the Airacobras sent to Britain were re-acquired by the USAAF and were sent to North Africa to join the Twelfth Air Force.



*Disposition of RAF Airacobras *
AH573 crashed Feb 11, 1942 from Boscombe Down. Engine failure just after takeoff. Pilot killed.
AH576 in belly landing Aug 29, 1941
AH581 crashed after engine failure Nov 21, 1941.
AH582 crashed during aerobatics Oct 19, 1941. Pilot killed.
AH596 in forced landing at Colchester Sep 29, 1941.
AH602 crashed during aerobatics Jan 12, 1942.
AH603 crashed on takeoff Dec 12, 1941
AH733 delivered to RAF, but transferred to USSR


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## P-39 Expert (Apr 1, 2018)

Milosh said:


> I just remembered something I had read about the P-39. The long drive shaft from the engine to the prop vibrated and cause problems with the reproduction system of the pilot, that is the pilots became sterile. Just a WW2 myth???


Russians had a joke "Pilots over 40 not permitted to fly Aircobra (sic). Balls get caught in propshaft! 

In practice the driveshaft arrangement worked extremely well without vibration even during a wheels up (crash) landing.

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## pbehn (Apr 1, 2018)

". The ground run of the Airacobra during takeoff was 2250 feet, as compared with 1470 feet for the Hurricane II and 1590 feet for the Spitfire V. "

What was the ground run of a P39 with 110 gal. tank? Kent or Suffolk?

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## P-39 Expert (Apr 1, 2018)

pbehn said:


> This is complete, utter tosh, you have been told why it is tosh, but continue to post it. You ignore the attack on Pearl Harbour and what it meant. The USA, understandably, took all planes it needed for itself so the British never received the P-39s they ordered, they never received all the Mustang 1s (P-51A) they ordered either. You continually blather about weight, but weight doesn't have a huge effect on top speed or climb, power and drag do. The P51B was approximately 30MPH faster than the Spitfire Mk IX on the same engine, not only at top speed but on almost any cruise setting, and it also weighed about half a ton more. By 1943, a matter of months after your famous test the P-39 was barred by the US from being used as a fighter, it was an advanced trainer, too dangerous to its own side to be used in anger. That is the opinion of the USA military in official tests, nothing to do with anyone else.


I have heard all the hearsay about the British and the P-400. I did not ignore Pearl Harbor, mentioned it was the reason there were no lawsuits. Weight has more to do with climb rate than any other factor if HP is the same. P51 in all its forms was much more aerodynamic that any mark of the Spitfire. And finally the P-39 was no more dangerous to operate than any other American WWII fighter. Chuck Yeager's favorite plane (prior to Merlin P-51), and he also flatly stated that he did not know any pilots who did not like the P-39. This at a training base where almost all fighter pilots trained on a P-39. And I can tell you either did not know this information existed or did not review it in any detail. Sorry to try and introduce you to anything new since you already know it all. Just keep denying every single fact that I give you.


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## pbehn (Apr 1, 2018)

P-39 Expert said:


> I have heard all the hearsay about the British and the P-400. I did not ignore Pearl Harbor, mentioned it was the reason there were no lawsuits. Weight has more to do with climb rate than any other factor if HP is the same. P51 in all its forms was much more aerodynamic that any mark of the Spitfire. And finally the P-39 was no more dangerous to operate than any other American WWII fighter. Chuck Yeager's favorite plane (prior to Merlin P-51), and he also flatly stated that he did not know any pilots who did not like the P-39. This at a training base where almost all fighter pilots trained on a P-39. And I can tell you either did not know this information existed or did not review it in any detail. Sorry to try and introduce you to anything new since you already know it all. Just keep denying every single fact that I give you.



You have posted yourself that P-400s had British oxygen systems, that wasn't because the British rejected them it was because the USA took them for their own use, it was now at war. Similarly, as previously posted 179 P-39s were re acquired in UK and sent to Africa. At the same time US pilots in UK were flying Spitfire mkVs on reverse lend lease.


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## fubar57 (Apr 1, 2018)

This book has many pilots who did not like the P-39





​

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## pbehn (Apr 1, 2018)

fubar57 said:


> This book has many pilots who did not like the P-39
> 
> View attachment 488132​
> ​


Propaganda by the British secret service, F.Dorr was the nom de plume of J. Bond.


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## P-39 Expert (Apr 1, 2018)

Shortround6 said:


> Oh boy, what a load of male bovine excrement. I hardly know where to start.
> 
> Lets try with the P-47 example you gave.
> 
> ...


Okay, mistake #1. P-47 didn't need to cruise at max continuous power. Okay, then the P-39N didn't need to cruise at max continuous power either. And yes the did need to cruise at max continuous over Europe because the Luftwaffe was the toughest enemy we faced and they controlled the air over Europe. So you went as fast as you could, period. Just to give you an idea of how tough it was, the 8th Air Force had more casualties in WWII than the MARINE CORPS. So yes, you cruised over Europe at max continuous power, if you wanted to come home.

Mistake #2, yes escorts were in relays mainly because there were different types of planes (P-38, P-47 and P-51) that all had different ranges. P-39 would have been extremely useful in the early or intermediate ranges, like the P-47 or earlier P-38.

Mistake #3, the FW 190 was the predominate fighter in the west supplemented by Me109s. Me109s were the predominate fighter in the east supplemented by the FW190. The P-39N performance compared favorably with the Messer also, would you like a graph comparing the two?

Mistake #4, you obviously have not seen this information before or you would not be vehemently denying absolutely every fact that I give you. Straight from the official tests or the pilots manual. You keep coming back with "no altitude performance, no range, tumbled, bad stall, British hated it (that one's true but not for the reasons you claim) and on and on. I'm certainly not Moses but you obviously didn't know this newer information. Try and put all that old P-39 hearsay out of your mind and objectively look at some new information.

I'm enjoying our conversations, maybe someday you will too.


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## buffnut453 (Apr 1, 2018)

P-39 Expert said:


> Chuck Yeager's favorite plane (prior to Merlin P-51), and he also flatly stated that he did not know any pilots who did not like the P-39. This at a training base where almost all fighter pilots trained on a P-39. And I can tell you either did not know this information existed or did not review it in any detail.



Ignoring for a moment the fact that Yeager has a less-than-stellar reputation in many parts, this is just one data point...the opinion of a single pilot. Per Fubar57's Post #957, there were plenty of pilots whose opinions differed vastly from Mr Yeager's. One data point does not disprove hundreds of other contrary data points!

It's not that we didn't know. I'm afraid some of us just don't care because the vast majority of evidence (ie facts) point in a different direction from the selective measures you are providing. 

Yes, there are small individual use cases where a P-39 might be comparable or even better than carefully selected contemporary machines. However, taken as a whole, the P-39 just didn't have the performance when it was needed...ergo it was essentially discarded.

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## Shortround6 (Apr 1, 2018)

P-39 Expert said:


> Britain didn't want the P-39 (P-400) because the reason they ordered them in 1940 was in case of a German invasion of Britain. France folded like a deck chair and the British were able to hold the Luftwaffe to a stalemate (effective victory/no invasion) in the fall of 1940 in the Battle of Britain. Lend lease was enacted in early '41 so now Britain (and Russia) will get all the American planes it needs for free. Now the completed P-400s arrived in mid 1941, there is no longer any threat of invasion by Germany. Britain is now supplying their own fighters (Spit & Typhoon) in sufficient quantity that they don't need the P-400s. But these P-400s were PURCHASED under a hard money contract and Bell expected payment. The British were broke and certainly did not want to pay hard cash for planes they could now get for free.
> 
> I'm amused by the British's shock at the P-400 performance. Did they just wake up one morning and realize the P-400 weighed too much? Hardly, they ordered them that way. The purchaser (US Army or British) contractually specified EXACTLY the way the planes were to be equipped down to the last rivet. Bell had no choice but to manufacture the planes as ordered. And I'll wager that there was a British representative (or many) stationed at the Bell plant to make sure their purchase was exactly as ordered. They did the same thing to Lockheed by ordering P-38s without turbochargers and then refused to pay when those planes didn't meet specs. Had Pearl Harbor not happened (US now urgently needed all the planes they could get) then Bell and Lockheed would have sued the pants off the British over those contracts. Plus these were brand new designs and had the normal bugs and glitches any new plane had. This is not what you read in the airplane books, but I have read this exact thing before, I did not make it up. And it makes more sense than the British being surprised by low P-400 and P-38 performance. There was no surprise.



complete and utter bollocks. 

Just look at the number of books, articles and websites that claim the XP-39 flew at 390-400mph and climbed to 20,000ft in 5 minutes before the NACA ruined it by taking out the turbo charger. The P-39 may have had more complete trash written about it than practically any other fighter if we count the pages of wink and bandwidth. The XP-39 never flew at full power due to a feared drive shaft problem before the turbo was taken out. A new, heavier drive shaft was installed in all later models. What is interesting is that nobody can point to WHEN this supposed flight of 390mph and climb to 20,000f took place, no date is ever given unlike many other planes where early flights and achievements are given. Also no pilots name is mentioned. Some books/accounts even go so far as to claim it was done on the first flight. Which, given the chronic overheating problems the XP-39 had is hardly creditiable let alone the sometimes mentioned flight duration of 20 minutes for the first flight. 
Test pilot took-off retracted landing gear, immediately went into a full power climb to 20,000ft, leveled off, accelerated to 390mph, slowed down, descended to airfield, lowered landing gear and landed, all in 20 minutes and in an airplane that had never flown before?????? 
However this little "fact" did not stop Bell from advertising/ marketing the P-39 as a 400mph fighter. The "fact" that the XP-39 was over 500lbs overweight (about 10%) when delivered to Wright field was exactly pointed out in advertising brochures either. This is for the unarmed prototype with no guns. Bell claimed the performance figures were for a 5500lb gross aircraft. When weighed at Wright field it went 6104lbs. Which makes nonsense out of a lot of the later development weight figures. 
The XP-39B (original XP-39 rebuilt) doesn't fly until Nov 25th 1939. French (desperate) are already trying to buy it. In fact by April of 1940 the French have given Bell a 2 million dollar cash advance. 
Now please note that the first YP-39 (2nd P-39 airframe) to fly does so on Sept 13th 1940 and the first P-400 airframe flies in April of 1941 almost a year after being ordered with contracts signed. This is rather late in the game for the British to start specifying cast iron coal fired cabin heaters or whatever they did to run the weight up to get out of the contract. 
Somethings on the prototypes just did not work very well. Like the first plane had ejection slots in the nose for the machine gun cartridges but these tended to be ingested by the radiator intakes in the wing so the spent cartridges were collected in bins in the weapons bay. 
Bell in 1939 and the first half of 1940 ws promoting the P-39 as a 400mph fighter and that is what the French and British thought they were buying. However the empty weight of the fighter grew by 1026lbs (although this may be debatable, this was based off the 5,849lb gross of the XP-39B which may have been under stated) 
We next have a bit of shall we say "trickery" in which the first P-400 was tested in late April 1941 by both a Bell company pilot and Wing Commander Adams and speeds of 391mph at 14,350 ft are recorded (after corrections). However this aircraft differed from planes on the production line by. 
1.A considerably modified fin/rudder and horizontal stabilizer/elevator assemblies. The moving parts (fabric covered) were made smaller and the fixed parts (metal covered ) made larger but the finished assemblies were a bit smaller over all than standard. 
2. Different fillets were used (or eliminated) on the fixed tail surfaces. 
3. Plastic wood was used around all the edges of all cockpit frame work and sanded smooth.
4. gun access doors were covered over with 0.064 sheet aluminum to prevent partial opening during flight 
5. Stronger landing gear linkage installed to prevent landing gear deflecting up to two in in flight
6. Longer outlet shutters of restricted area installed on oil cooler and radiator ducts to improve local airflow.
7. Standard 6 port exhausts replaced by 12 port exhaust angled down 15 degrees as tuft testing showed local airflow to be 15 degrees below the thrust line.
8. .50 cal gun ports cleaned up
9. removal of antenna mast
10. one piece engine cover and exhaust stack fairing.
11. unspecified other modifications.
12. *20* coats of Dupont grey primer sanded between coats.
13. Standard British camouflage applied but lightly sanded to remove seams from camouflage templates. 

The contract speed was 394mph at rated altitude and thus the test flights were within 1 % . The contract allowed a 4% tolerance. 
However while some of the modifications could be incorporated in production aircraft some could not (like filling the the cockpit structure and the 20 coats of sanded primer) and the production aircraft fell well below this test aircraft. 
A Bell company test report dated Aug 18th 1941 is supposed to show that aircraft AH579 was 20mph slower than AH 571 (the modified aircraft) had a cruise speed 24mph slower, a lower critical altitude by 250 ft and took 2 minutes and 16 seconds longer to get to 26,230 ft. 

This is from "Cobra" Bell Aircraft Corporation 1934-1946 by Brich Mathews.

Now are the British to be blamed for specifying too much "stuff" in order to get out of the contract or did Bell promise way more than it could deliver?

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## pbehn (Apr 1, 2018)

The predominant fighter over Germany in 1942/3 was the Me110, because it was expected allied S/E fighters couldn't reach, the issue was getting S/E fighters over Germany to take them out of the fight. This is also a question of range, since the 110 has twice the range of a 109 the same number of planes can get approx. twice as many 110s to any point of attack.


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## Milosh (Apr 1, 2018)

Actually there was ~100 more Bf109s than Fw190s fighting the Allies in the west (May 1943).
http://www.oocities.org/sturmvogel_66/LWJul42.html#May43

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## Dimlee (Apr 1, 2018)

pbehn said:


> The Airacobra was considered to be very suitable for low altitude operations because of the excellent view and controllability, and it was fully maneuverable at speeds above 160 mph.
> ...
> On October 11, two aircraft flew to Gravelines and Calais and hit some enemy barges and then three Airacobras flew to Ostend, but no targets were found.



When I read that and similar information, I think that one of the reason of P-39's success in VVS was that it was NOT considered suitable for low altitude operations. Instead it developed into "high" (in terms of Eastern front) altitude interceptor or escort. Whatever critics said about Pokryshkin, probably it was very lucky match: his tactical ideas and new aircraft which allowed to try those ideas in practice.

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## Shortround6 (Apr 1, 2018)

P-39 Expert said:


> Okay, mistake #1. P-47 didn't need to cruise at max continuous power. Okay, then the P-39N didn't need to cruise at max continuous power either. And yes the did need to cruise at max continuous over Europe because the Luftwaffe was the toughest enemy we faced and they controlled the air over Europe. So you went as fast as you could, period. Just to give you an idea of how tough it was, the 8th Air Force had more casualties in WWII than the MARINE CORPS. So yes, you cruised over Europe at max continuous power, if you wanted to come home.
> 
> Mistake #2, yes escorts were in relays mainly because there were different types of planes (P-38, P-47 and P-51) that all had different ranges. P-39 would have been extremely useful in the early or intermediate ranges, like the P-47 or earlier P-38.
> 
> ...



Please show any documentation that escort fighters ALL cruised at max continuous?
Or even any documentation that they ALL cruised at max continuous when not escorting?
Most fighters cruised at max lean if that would give them the desired speed. Depending on mission they might fly a bit below that.
Cruising at any throttle setting that used rich mixture could significantly shorten range.
You do have to consider the performance of the aircraft and quite making blanket statements.
A late model P-47 could cruise (at 25,000ft) at 324mph while using auto lean and burning 143 gallons an hour. Pushing things a bit brings it to auto rich and 348mph using 208 gallons a minute. Is the extra 24mph worth 1 extra gallon a minute more?
BTW a late model P-47 can run at 361 mph max continuous vrs the P-39s 371-375mph at full military power (15 minute limit) so if the P-47 is in danger of going the too slow the P-39 shouldn't even be there........Hey, guess what........ it wasn't.

P-39 would have been doing good just to escort a few dozen miles past the coast. It wasn't needed, why devote the airfields, pilots, ground crews and support to such a limited range plane, see earlier discussions about range compared to the P-38 and P-47.

Sure give me a graph showing how well the 1/2 fuel P-39 can climb vs the 109. Of course the 109 doesn't have to shoot the 1/2 fuel P-39 because the P-39 won't make it back to England. You can't have it both ways. You want the speed/climb of the 1/2 fuel P-39 (or what ever it carried in that test) but you want the full range of the 110-120 gallons internal. That doesn't even work in most video games.

I deny the vast majority of your facts because they simply are not true. Just because you didn't make it up doesn't mean somebody else didn't make it up and you are repeating their falsehood.

And now you are calling me a liar as to when I saw this information.
Please look at some of the other threads on the P-39. I have been using some of this information for years. It isn't new to me.
As I have said there is an awful lot of hearsay about the P-39 and lot of it is from it's supporters.
BTW I have been pretty neutral on the P-39 tumbling and in fact tried to post an explanation about why some pilots may have thought it tumbled when it didn't. SO if you can't keep track of _who_ is denying _what_ the likelihood of your understanding some of the other stuff seems to be diminished.

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## P-39 Expert (Apr 1, 2018)

pbehn said:


> While the YP-39 and the P-39C were being test-flown, Bell Aircraft began work on an export version of the Airacobra known as the Bell Model 14. It was to be powered by a 1150 hp Allison V-1710-E4 engine which had twelve exhaust stacks on each side rather than the usual six. France was sufficiently interested that they ordered 200 Model 14s on October 8, 1939.
> 
> All of the media hype surrounding the spectacular performance of the XP-39 prototype had caught the attention of the British Direct Purchase Commission which had visited the USA in 1940 in search of combat aircraft. Seduced by promises of 400 mph top speed, a tricycle undercarriage, heavy cannon armament, and high climb rates, the British ordered 675 examples of the Airacobra. Unfortunately, Bell's glossy advertising brochures did not distinguish between the performance of a lightly-loaded, unarmed, highly-polished experimental prototype and a production fighter heavily-loaded with military equipment and armament, and the British were to rue the day that they ever looked at an Airacobra.
> 
> ...


Thanks for reprinting the company line, we have all read that.

Paragraph 1, Bell actually began work on the P-400 right after the purchase contract in 1940 and was produced on the same assembly line as the P-39Cs and later P-39Ds. British planes differed only slightly (20mm cannon and 4 wing .30s) from production P-39s. 

Paragraph 2, The British read the glossy hype? British know that the prototype P-39s only weighed around 6000# and they also knew that their P-400s would weigh more since they specified EVERY piece of equipment in their contract. This was absolutely no surprise to the British.

Paragraph #3, in 1940 the British (and French) WERE absolutely desperate for aircraft, but in no way did they believe for one second that any P-39 with the 1150HP engine would do 400mph, especially at 7850# after installation of the armor plate/glass and self sealing tanks that were REQUIRED BY THE BRITISH. 

Paragraph 4, agree.

Paragraph 5, note the distinction between Lend Lease planes and Direct Purchase (contracted) planes. The British were paying CASH for the contracted planes. But now free lend lease planes were available. What would you do if you were the British? Well you would do your best to get out of the CONTRACT and get the free lend lease planes.

Paragraph 6 and 7, love this, the British were "shocked and dismayed" at the lack of performance. This from a plane that clearly weighed a lot more than the original because the British had specified that heavier plane in the contract. British were hardly shocked, they knew exactly what they ordered and how it was produced. Bell never "sheepishly" admitted anything, that would be fraud. Again, the British knew exactly what they ordered and received, any "shock and dismay" was for the benefit of publicly weaseling out of the contract. And remember the British found it "pleasant to fly, easy to take off and land, good for formation flying, ample stall warning, and an excellent day fighter at altitudes below 20000'" even at this grossly overweight form.

Paragraph 8,9. These were problems encountered by any brand new plane and were all corrected quickly in production models. No more faulty compasses etc.

Paragraph 10, The British performance tests differed somewhat from Bell's tests. Bell got 371mph at 14000' and a service ceiling of over 35000' from the P-400 at gross weight. Contemporary Spitfire V was good for about 366mph just for comparison and weighed about 6600# instead of 7850#. That's 1200# if you do the math. I probably should prepare a graph for you with the early P-39/P-400 and the Spitfire V so you can see a direct comparison.

If you believe for one second that the British didn't know exactly what they were getting at every stage of P-400 construction, then I have ocean front property in Arizona to show you. Their situation had changed drastically since the 1940 order, they didn't need the planes, and they sure didn't want to pay cash money for them. Believe what you want.

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## pbehn (Apr 1, 2018)

Dimlee said:


> When I read that and similar information, I think that one of the reason of P-39's success in VVS was that it was NOT considered suitable for low altitude operations. Instead it developed into "high" (in terms of Eastern front) altitude interceptor or escort. Whatever critics said about Pokryshkin, probably it was very lucky match: his tactical ideas and new aircraft which allowed to try those ideas in practice.


When fighting is on a land front the simple fact that forces are in contact brings all air fighting down. If you bomb from 20,000 ft you are as likely to hit your own guys as the enemy. Almost all activity is to hit something on the ground and so activity is near the ground. The Tempest was introduced before D-Day but after D-Day there was no need or demand for it to be optimised for high altitude performance.


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## pbehn (Apr 1, 2018)

P-39 Expert said:


> Thanks for reprinting the company line, we have all read that.
> 
> Paragraph 1, Bell actually began work on the P-400 right after the purchase contract in 1940 and was produced on the same assembly line as the P-39Cmn and later P-39Ds. British planes differed only slightly (20mm cannon and 4 wing .30s) from production P-39s.
> 
> ...


Oops sorry, I believe I have committed plagiarism, my post was lifted from this website.
Joe Baugher's Home Page
He quotes the following sources, maybe you should get in touch and put him right, easy enough he lives in the USA.
*Sources:*



War Planes of the Second World War, Fighters, Volume Four, William Green, Doubleday, 1964. 


The American Fighter, Enzo Anguluci and Peter Bowers, Orion Books, 1987. 


United States Military Aircraft since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian Institution Press, 1989. 


P-39 Airacobra in Action, Ernie MCDowell, Squadron/Signal Publications, 1980 


The Calamitous 'Cobra, Air Enthusiast, August 1971. 


Airacobra Advantage: The Flying Cannon, Rick Mitchell, Pictorial Histories Publishing Company, Missoula, Montana 


Airacobra Advantage--The Flying Cannon, Rick Mitchell, Pictorial Histories Publishing Company, 1992 


Bell Cobra Variants, Robert F. Dorr, Wings of Fame, Vol 10, AirTime Publishing , Inc., 1998. 


E-mail from Gordon Birkett on disposition of AP347, BW169, AP361, plus serial numbers on USAAF P-400s. 


E-mail from Terence Geary on P-400 dispositions. 


Andrew Thomas, Bell Airacobra In RAF Service, International Air Power Review, Vol 6, 2002 


E-mail from Franek Grabowski on AH728, AH733, AH737, BW118, BX302. 


E-mail from Nick Jenkins on crash of AH573. 


E-mail from Andrew Linden on loss of BX165

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## Elmas (Apr 1, 2018)

P-39 Expert said:


> *snip*
> Bell had no choice but to manufacture the planes as ordered. And I'll wager that there was a British representative (or many) stationed at the Bell plant to make sure their purchase was exactly as ordered.
> *snip*



In 1939, things did not happen as they do today in 2018.
At that time the bureaucracy and the bureaucrats were reduced to a minimum, and were not running the tons of paper that today run in a public contract.

When the British Commission asked for substantial modifications to Lockheed Super Electra to have a maritime patrol reconnaissance aircraft, the Lockheed team bought a drawing board, paper, pencils a slide rule and put a very young Kelly Johnson at work in his hotel room.

_“I did work continuously for three days”_ Johnson recalls _“and then I slept for twenty four hours…”_
The British signed the contract.

And also the Skyrider was designed overnight ( as a general appearance and main specifications, of course) in a hotel room.

Bell Company had blown the trumpet a lot about the performances of P-39 so the British Commission had no reason whatsoever for not believing to them: the shortcomings of P-39 were by far more subtle to discover.


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## pbehn (Apr 1, 2018)

P-39 Expert said:


> If you believe for one second that the British didn't know exactly what they were getting at every stage of P-400 construction, then I have ocean front property in Arizona to show you. Their situation had changed drastically since the 1940 order, they didn't need the planes, and they sure didn't want to pay cash money for them. Believe what you want.


Can you stop making this ridiculous assertion. It stems from your obsession with the P-39 to the exclusion of all other planes and all other events, even the US declaration of war itself. The "British" you are referring to is the government not some cash strapped airline. In 1942 airfields were being completed at the rate of 1 every three days, a project equal to building a road from UK to China employing 60,000 people. They were building and operating four engine bombers, fighting the battle of the Atlantic etc etc etc. In the midst of this, your tin pot order of 675 fighters amounts to less than a months production, it is zero, zilch, nada in the scheme of things in a war. The needs of Russia in its land war and the needs of the USA defend its own interests abroad and to train pilots were considered much greater than the need of the UK to strafe the "Pas de Calais" which is all the P-39 could do.

On the Schweinfurt Regensburg raid of 1943 the RAF escorted US bombers with Spitfires to Antwerp, the US escorted as far Eupen with P-47s, the idea that the people involved "missed something" with the P-39N is an insult to everyones intelligence,

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## Shortround6 (Apr 1, 2018)

Dimlee said:


> When I read that and similar information, I think that one of the reason of P-39's success in VVS was that it was NOT considered suitable for low altitude operations. Instead it developed into "high" (in terms of Eastern front) altitude interceptor or escort. Whatever critics said about Pokryshkin, probably it was very lucky match: his tactical ideas and new aircraft which allowed to try those ideas in practice.





pbehn said:


> Oops sorry, I believe I have committed plagiarism, my post was lifted from this website.
> Joe Baugher's Home Page
> He quotes the following sources, maybe you should get in touch and put him right, easy enough he lives in the USA.
> *Sources:*
> ...


Sorry to tell you but Mr Baugher (who has for the most part a very excellent site/resource) bought the XP-39 390mph flight.
which never happened and started this whole saga.
As near as I can figure the XP-39 goes like this.
The XP-39 was delivered (in crates) to Wright field Dec 17th, 1939. Assembly, final fitting of details and trying to solve leaks in the integral fuel tanks kept the plane from flying in the Jan fighter trials. The plane was _supposed _to hold 200 gallons of fuel max, I have no idea if this was "normal" or if a lesser mount was considered normal and the 200 gallons was considered overload. I suspect the latter as 1200lbs of fuel would be a tremendous load for a 5500-6100lb airplane.
In any case teh XP-39 began taxi trials on March 1st 1939 and promptly ran into overheating problems (not good in March in Ohio) but the engine was quickly removed by Allison for upgrading and not replaced until March 25th at which point ground testing of the engine and supercharger began.
We then have some conflicting dates. One date of April 5th says that a roughness in engine running was detected between 570 and 1400rpm and only 2650rpm could be reached instead of 3000rpm due to vibrations reaching the magneto drive. Allison had already been working on a new type Hydraulic vibration damper but work went ahead using the original vibration damper to prepare for the first flight. It is at this point that problem with extension shafts to the propeller is discovered. Allison suggests using the original shafts for initial test flying and keeping the engine out of the problem speed range, while they design new ones ( 1/8in larger in diameter with thicker wall sections) Army thinks this is unsafe and this is borne out by tests done on a ground rig at the Allison factory.
In any case the first flight (20 minutes) is done by James Taylor USNR on April 6th.
No record exists for a flight in which either 390mph was reached or 20,000ft achieved in 5 minutes.

Now as flight testing procedes cooling problems with both engine coolant and oil crop up and added/revised scoops are fabricated and fitted along with an enlarged inlet for the turbo-supercharger.
On April 21st General Arnold issues an order that the XP-39 is to be sent to Langley for testing in the wind tunnel as soon as the acceptance tests are completed and these are to be expedited.
among Gen. Arnold's recommendations just 15 days after first flight are.

A. The Fuselage will be streamlined to accommodate a pilot not over 5 feet 8 inches tall and weighing not more than 160lbs.
C. No consideration will be given to a baggage compartments if this adversely affects performance
D. The design fuel load will be for one hour at full throttle at the critical altitude.
F. Flaps will be manually operated.

From this we can reasonably conclude That Gen Arnold was suggesting both drag reduction and weight reduction was needed just 2 weeks after the first flight and well before the XP-39 made it to Langley (which it did in June of 1939).
Hardly what one would expect for plane that demonstrated a 390mph speed in April of 1939.

The heaver drive shafts that allowed full 3000rpm operation were not installed until the plane was being converted to the XP-39B configuration.

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## Glider (Apr 1, 2018)

I do get a little annoyed when you keep saying the British tried to get out of the contract. Have you got any evidence to support that, if so put it up or stop saying it.


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## Glider (Apr 1, 2018)

P-39 Expert said:


> Britain didn't want the P-39 (P-400) because the reason they ordered them in 1940 was in case of a German invasion of Britain. France folded like a deck chair and the British were able to hold the Luftwaffe to a stalemate (effective victory/no invasion) in the fall of 1940 in the Battle of Britain. Lend lease was enacted in early '41 so now Britain (and Russia) will get all the American planes it needs for free. Now the completed P-400s arrived in mid 1941, there is no longer any threat of invasion by Germany. Britain is now supplying their own fighters (Spit & Typhoon) in sufficient quantity that they don't need the P-400s. But these P-400s were PURCHASED under a hard money contract and Bell expected payment. The British were broke and certainly did not want to pay hard cash for planes they could now get for free.


This part of the post is a copy from earlier and as comprehensively proven to be wrong on almost every level and word. Putting it in here is only a distraction adds nothing apart from trying to cause confusion 



> I'm amused by the British's shock at the P-400 performance. Did they just wake up one morning and realize the P-400 weighed too much? Hardly, they ordered them that way.


 Your right but Bell still promised to deliver the performance so your statement should say _I'm amused by Bells shock at the P-400 performance. Did they just wake up one morning and realize the P-400 weighed too much after all they build the aircraft and know the impact of extra weight?_
Interestingly I can see how this happens. I used to work for a major IT company as a senior Project manager/Program Manager and my niche was projects that had gone wrong or were about to go wrong. The number of times the salesmen made a promise to get the contract signed and get their bonus, then leave it up to the developers to sort it out was astonishing.


> The purchaser (US Army or British) contractually specified EXACTLY the way the planes were to be equipped down to the last rivet. Bell had no choice but to manufacture the planes as ordered.


 Fundamentally and legally wrong. Any change to a project has to be agreed and signed off. If Bell had a problem with any extra kit impacting the performance they had every opportunity to change the performance guarantees in the contract.


> And I'll wager that there was a British representative (or many) stationed at the Bell plant to make sure their purchase was exactly as ordered.


 Standard practice in any contract of any nature.


> They did the same thing to Lockheed by ordering P-38s without turbochargers and then refused to pay when those planes didn't meet specs.


 I do hope you can prove that statement as we paid all our obligations even though it almost bankrupted us.


> Had Pearl Harbor not happened (US now urgently needed all the planes they could get) then Bell and Lockheed would have sued the pants off the British over those contracts.


 And they would have lost the case


> Plus these were brand new designs and had the normal bugs and glitches any new plane had. This is not what you read in the airplane books, but I have read this exact thing before, I did not make it up. And it makes more sense than the British being surprised by low P-400 and P-38 performance. There was no surprise.


 The reasons differ but I suspect you know that. The P39 didn't deliver close to what Bell promised, The P38 did deliver the expected performance but we needed high altitude aircraft and wanted to convert a majority of the order to Standard P38E aircraft and it was that change which caused the rancor. Please note that one reason for the British (and French) original order lacking turbochargers wasn't that we didn't want them, we did, but there was a ban on the export of certain technology from America and the Turbochargers were part of that ban. Once the war started for the USA that ban was lifted

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## pbehn (Apr 1, 2018)

Shortround6 said:


> Sorry to tell you but Mr Baugher (who has for the most part a very excellent site/resource) bought the XP-39 390mph flight.
> which never happened and started this whole saga.
> As near as I can figure the XP-39 goes like this.
> The XP-39 was delivered (in crates) to Wright field Dec 17th, 1939. Assembly, final fitting of details and trying to solve leaks in the integral fuel tanks kept the plane from flying in the Jan fighter trials. The plane was _supposed _to hold 200 gallons of fuel max, I have no idea if this was "normal" or if a lesser mount was considered normal and the 200 gallons was considered overload. I suspect the latter as 1200lbs of fuel would be a tremendous load for a 5500-6100lb airplane.
> ...



In all this what I find particularly frustrating are statements on the lines of the British should never have believed that the "P-400" would do 400 MPH, well it was called the P-400 for a reason. You can expect a drop in performance adding BP glass self sealing tanks and guns, but those items don't weigh a ton.

Anyone saying that the British couldn't have believed what they were told unless they were stupid may wish to consider the following.

1. The British believed the claims of NAA and backed them, the plane they built did everything they said it would and hence we had the P51 Mustang, ordered initially off the drawing board.
2 The first twin stage Merlin engine was bench tested in April 1941, work began in March 1940.
3 in Feb 1940 the order for 2 prototype Gloster jets was placed and the first flew in May 1941.

Bells claims, seen by the British were easily believable, it only showed that Bell/Allison were about 6/12 months ahead of RR/Supermarine


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## Dimlee (Apr 1, 2018)

pbehn said:


> When fighting is on a land front the simple fact that forces are in contact brings all air fighting down. If you bomb from 20,000 ft you are as likely to hit your own guys as the enemy. Almost all activity is to hit something on the ground and so activity is near the ground. The Tempest was introduced before D-Day but after D-Day there was no need or demand for it to be optimised for high altitude performance.



Indeed.
But my point is that the tactics applied to P-39 in Soviet VVS has benefited this aircraft "image" overall in USSR. (Until it was somewhat forgotten during Cold War). Should someone decided to use her in the less smart way, this aircraft could get negative publicity among the pilots, with complaints about "another crap Allied plane" which would impact decisions made at the top about further deployment and purchasing. Add to that lobbying efforts of leading Soviet designers who tried hard to prove their worth to the country leadership and who did not shy to tarnish reputations of other aircraft, foreign or made by fellow countrymen.
There were instances in VVS when prospective models were abandoned and left without production lines to develop, - just because they were used in the wrong way and in the wrong time/place.

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## fubar57 (Apr 1, 2018)



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## tomo pauk (Apr 1, 2018)

Glider said:


> ...
> The P39 didn't deliver close to what Bell promised, The P38 did deliver the expected performance but we needed high altitude aircraft and wanted to convert a majority of the order to Standard P38E aircraft and it was that change which caused the rancor. Please note that one reason for the British (and French) original order lacking turbochargers wasn't that we didn't want them, we did, but there was a ban on the export of certain technology from America and the Turbochargers were part of that ban. Once the war started for the USA that ban was lifted



I agree with the rest of the post, but not with some things from this part of the post.
There was no ban on US turbochargers to be exported to the UK. Standard P-38 was with turbo, French and UK ordered the non-turboed Lighning Is. Engine choice were the V-1710 C15 engines for sake of commonality with P-40s ordered. After France folded, UK took over whole order, and changed it to a handful of Lightnig Is and majority of Lightning IIs (with turbos and F series engines).
Lockheed squandered months and months of time, the most precoius comodity, in quest to:
a) redesign the XP-38 into YP-38
b) make the Ligthning I as a sibling of XP-38 (engine series) and YP-38 (rest of the A/C, sans turbo)
Thus, once the Lightning I was tested in Winter of 1941/42 and Spring of 1942 in Britain, RAF saw it as an expensive fighter without a role, incapable to offer anything over the P-40B/C or Spitfire V, while having plenty of shortcomings apart the price.

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## Shortround6 (Apr 1, 2018)

*If* there was a ban it disappeared somewhere between March of 1940 when the British order 143 model 322s without the turbo superchargers and June 5th of 1940 when they order 524 Lighting MK 2s with Turbo Superchargers. 

Mighty short lived if it existed.


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## Shortround6 (Apr 1, 2018)

Dimlee said:


> Indeed.
> But my point is that the tactics applied to P-39 in Soviet VVS has benefited this aircraft "image" overall in USSR. (Until it was somewhat forgotten during Cold War). Should someone decided to use her in the less smart way, this aircraft could get negative publicity among the pilots, with complaints about "another crap Allied plane" which would impact decisions made at the top about further deployment and purchasing. Add to that lobbying efforts of leading Soviet designers who tried hard to prove their worth to the country leadership and who did not shy to tarnish reputations of other aircraft, foreign or made by fellow countrymen.
> There were instances in VVS when prospective models were abandoned and left without production lines to develop, - just because they were used in the wrong way and in the wrong time/place.



In the Soviet Union in 1941-43 there was a real lack of high altitude engines and not from want of trying or desire (they tried turbo-charging everything short of the diesel engine from the T-34 tank) and the two most common fighter engines. The VK-105 and the ASh-82 just weren't very good for several reasons. Getting 1150hp at 12,000ft was beyond the reach of the VK-105 and 1125hp at 15,500 was a miracle. 
For instance the VK-105PA was rated at 1100hp at 6500ft(2000m) and 1050hp at 13200ft (4000M) and when they went to the VK-105PF power went to 1260hp at 2300ft (700m) in low gear and 1180hp at 8900ft (2300M) above 13200ft the performace was the same?
Please note that when pressure in later in engines was increased they went from 1050mm to 1100mm which is about 2in of increased presure or about 1lb. 
The ASh-82F had 1300hp at 17,700ft (5400M) but the radial engine has more drag. The ASh-82FN had 1460hp at 15250(4650m) The Russians constantly worked at reducing drag. 
The only Russian built aircraft with more high altitude performance was the Mig-3 and they were out of production. The P-39 could slide right on in as a medium altitude fighter in Russia.

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## pbehn (Apr 1, 2018)

Shortround6 said:


> *If* there was a ban it disappeared somewhere between March of 1940 when the British order 143 model 322s without the turbo superchargers and June 5th of 1940 when they order 524 Lighting MK 2s with Turbo Superchargers.
> 
> Mighty short lived if it existed.


I don't know if it was a ban or a restriction on who gets what mainly concerned with the far east.

Export Control Act - Wikipedia


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## DarrenW (Apr 1, 2018)

Cast your vote: Best US escort fighter in ETO during 1943?


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## pbehn (Apr 1, 2018)

The performance of the Allison F4R and F20R in a decent airframe is given here.
www.wwiiaircraftperformance.org/mustang/fr893.html

Engine____ Max. TAS (mph)  Height (ft) 
F.4R_____ 401_____________ 4,400
F.20R____ 409_____________ 10,000

Engine Max. r o c __________Time to 20,000 Service ceiling
F.4R_ 4,090 ft/min. at 800 ft__. 8.1 mins____. 31,500 ft.
F.20R 3,800 ft/min. at 6000 ft_. 6.9 mins.____ 34,000 ft.


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## CORSNING (Apr 1, 2018)

*Well, before I get some sort of momentum going, I would like to go on record as saying,
"P-39 Expert, please get off the whole P-39 would have been a good escort fighter at
20,000 ft. in the ETO or anywhere else. It just would not have happened. 
There were too many other aircraft in the works that could do that mission 
so much better. Concentrate on where the P-39 really shined like the 
Russians did."*



pbehn said:


> My head is now hurting. Can someone tell me any area of performance that the latest P-39 was superior to the Spitfire IX or XIV, P-51-B/C, P47 and F4U as of *25 December 1943?[/*QUOTE]
> 
> *1. Spitfire IX*: That would be the LF Mk.IX with the Merlin 66 using +18 lbs./sq. in. boost.
> *2. Spitfire XIV:* *Not Applicable*. It did not fly its first operational sortie until 28 December.
> ...

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## Glider (Apr 1, 2018)

Shortround6 said:


> *If* there was a ban it disappeared somewhere between March of 1940 when the British order 143 model 322s without the turbo superchargers and June 5th of 1940 when they order 524 Lighting MK 2s with Turbo Superchargers.
> 
> Mighty short lived if it existed.


Its my belief that the State department did have a ban on the F engines which is why we had to have the C. Having been forced to have the C we may as well have the same engine as the P40 which is why they weren't handed. Interestingly the tests agreed that having non handed engines wasn't a problem.

I used to live within striking distance of the National Archives but not now that I have moved, so apart from some comments on websites I cannot offer firm evidence to support this


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## pbehn (Apr 1, 2018)

CORSNING said:


> *Well, before I get some sort of momentum going, I would like to go on record as saying,
> "P-39 Expert, please get off the whole P-39 would have been a good escort fighter at
> 20,000 ft. in the ETO or anywhere else. It just would not have happened.
> There were too many other aircraft in the works that could do that mission
> ...


A great post Corsning, but at the end of 1943 what were the requirements in Europe?

1 long range at high altitude.
2 shorter range recon, ground attack, low level escort and air superiority missions.

In the far east almost all missions required range and carrier capability was a price worth paying. 

If you are crossing the Channel in a P-39, what do you do about an Bf109 at 10,000ft? the higher you go the more you are in his territory and he can climb too, the lower you go the more you concede and the closer you are to enemy flak in the place the everyone was trying to convince Adolf that a landing would take place.


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## CORSNING (Apr 1, 2018)

pbehn said:


> A great post Corsning, but at the end of 1943 what were the requirements in Europe?
> 
> 1 long range at high altitude.
> 2 shorter range recon, ground attack, low level escort and air superiority missions.
> ...



*Russia: Short-medium range infantry coop. I was never talking about the requirements in Europe*.


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## Milosh (Apr 1, 2018)

Cornsing, do you have to use *bold* text?


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## buffnut453 (Apr 1, 2018)

P-39 Expert said:


> Paragraph 2, The British read the glossy hype? British know that the prototype P-39s only weighed around 6000# and they also knew that their P-400s would weigh more since they specified EVERY piece of equipment in their contract. This was absolutely no surprise to the British.
> 
> Paragraph #3, in 1940 the British (and French) WERE absolutely desperate for aircraft, but in no way did they believe for one second that any P-39 with the 1150HP engine would do 400mph, especially at 7850# after installation of the armor plate/glass and self sealing tanks that were REQUIRED BY THE BRITISH.



As usual, so much to pull apart in these statements:

The Brits may have specified "EVERY piece of equipment" but it is the obligation of the vendor to determine whether all the requirements of the contract can be met...and if they can't, to work with the customer to determine what, if any, wriggle room there is for compromise. Not all requirements are created equal, hence there may be some wriggle-room on some requirements whereas others are effectively written in stone. Can you please provide evidence that Bell provided the Brits with ANY details of the trade space available? For example "we can't reach the required performance figures with all this extra equipment but we can get with 5% if we remove X, Y and Z." Please show the evidence that this took place rather than assuming that the Brits somehow "knew", through osmosis or otherwise, that the P-400's performance would be lacking.
The armour plate/glass and self sealing tanks weren't just "REQUIRED BY THE BRITISH". They were operational necessities. Why is this so hard for you to comprehend? You seem to be saying that the Brits were wrong for demanding these items. Again, it was Bell's responsibility to identify the performance impacts of these changes and I'd really like you to show that Bell did this rather than dismissing any negative references with helpful trite phrases like "we've all heard this before." Maybe the reason we've heard this before is because they're true?




P-39 Expert said:


> Paragraph 5, note the distinction between Lend Lease planes and Direct Purchase (contracted) planes. The British were paying CASH for the contracted planes. But now free lend lease planes were available. What would you do if you were the British? Well you would do your best to get out of the CONTRACT and get the free lend lease planes.



So instead of facts you're now projecting your own bias and opinions onto the situation. Again, please provide evidence that the British were trying to weasel out of the contract. This comes back to the question of whether Bell was fully open about the performance impacts of the various requirements being levied on the P-400. All evidence to-date suggests they weren't.

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## wuzak (Apr 1, 2018)

CORSNING said:


> 1. Spitfire IX: That would be the LF Mk.IX with the Merlin 66 using +18 lbs./sq. in. boost.
> 2. Spitfire XIV: Not Applicable. It did not fly its first operational sortie until 28 December.
> 3. P-51B: That would be the P-51B-1 with the Packard (Merlin) V-1650-3 using +67" Hg.
> 4. P-47D: That would be the P-47D-2-something(help me here people) using water injection.
> ...



Lucky for the P-39 variant that it did not have to compete with the Spitfire XIV and P-38J-5 because they would not fly operational sorties for 3 days!

Possibly, those aircraft were in squadron service and ready to go on operations at December 25, 1943.

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## Graeme (Apr 1, 2018)

We really do need to see this historic RAF/Bell contract.

Anyone have info on the British pilot Christopher Clarkson, who "evaluated" the P-39 in the USA (December 1940?) prior to delivery to the UK?
His impressions/reports?


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## pbehn (Apr 1, 2018)

wuzak said:


> Lucky for the P-39 variant that it did not have to compete with the Spitfire XIV and P-38J-5 because they would not fly operational sorties for 3 days!
> 
> Possibly, those aircraft were in squadron service and ready to go on operations at December 25, 1943.


The loss of time line and how fast things were changing in 1943 is almost laughable. The first six Griffon Spitfires with 60 series engines were tested by Geoffrey Quill on 20 *January !943* called Mk VIIIGs. That is a month after our P-39N entered production in USA

Changes to the aircraft were restricted to those essential to enable it to accept the new engine ... I found that it had a spectacular performance doing 445 mph at 25,000 ft, with a sea-level rate of climb of over 5,000 ft per minute.[23] I remember being greatly delighted with it; it seemed to me that from this relatively simple conversion, carried out with a minimum of fuss and bother, had come up with something quite outstanding ... The MK VIIIG, with virtually the same tail surfaces both vertical and horizontal as the Merlin MK VIII, was very much over-powered and the handling in the air was unacceptable for an operational type ... I soon realised that a new throttle box would be needed giving a much greater angular travel for the hand lever ... The next essential ... was an improvement in the directional stability and control and a new fin was drawn out with a substantial increase in area (7.42 sq. ft) and a much larger rudder and fitted to the second aircraft _JF317_. This, though not ideal, produced a very marked improvement in directional characteristics and we were able to introduce minor changes thereafter and by various degrees of trimmer tab and balance tab to reach an acceptable degree of directional stability and control. The enlarged fin of _JF317_ had a straight leading edge but for production a more elegant curved line was introduced.

— Quill[24]

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## Greyman (Apr 1, 2018)

Graeme said:


> We really do need to see this historic RAF/Bell contract.
> 
> Anyone have info on the British pilot Christopher Clarkson, who "evaluated" the P-39 in the USA (December 1940?) prior to delivery to the UK?
> His impressions/reports?



I have a data card that has information from the British Air Commission Flight Section and "Bell Report 14-945-001". The card is dated 29 June 1941. I'll compare the figures with A&AEE testing done July '41 to August '42.

*Bell/BAC - A&AEE*

Maximum Speed:
370 mph (approximately) at 15,000 feet - 7,350 lb
355 mph (42", 3000 rpm) at 13,000 feet - 7,845 lb​
Climb to 13,000 feet:
5.3 minutes - 7,350 lb
6.7 minutes - 7,830 lb​
In my opinion (from reading about 601 Squadron during those dark Airacobra days), what killed the aircraft for the RAF was chronic unserviceability, and they were unwilling to put in the mountain of effort that was required to fix it - while the Soviet NII and VVS made a special case out of the P-39 and went all-out to turn it into a real fighter. No small feat - but they sure did it.

A great read here:
Early Cobra's in Soviet Aviation

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## DarrenW (Apr 1, 2018)

_"4. P-47D: That would be the P-47D-2-something(help me here people) using water injection.
at 56"Hg. producing 2,300 hp./T.O.
5. F4U-1a: This would be without water injection. That came along in 1944."_

Just to add more to this:
According to_ America's Hundred Thousand_, Republic Aviation began fitting water injection systems on all P-47D-20RE models in November 1943 and by the end of the year most ADI modifications were complete on older aircraft stationed in England. It also states that on November 25th of the same year the 1,551st F4U-1A built by Vought became the first Corsair equipped with WEP from the factory.


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## Elmas (Apr 2, 2018)

_View: https://youtu.be/MS12isLjS5w_


Look at what Hayabusa is doing at 0' 36"..

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## Dimlee (Apr 2, 2018)

Shortround6 said:


> In the Soviet Union in 1941-43 there was a real lack of high altitude engines and not from want of trying or desire (they tried turbo-charging everything short of the diesel engine from the T-34 tank) and the two most common fighter engines. The VK-105 and the ASh-82 just weren't very good for several reasons. Getting 1150hp at 12,000ft was beyond the reach of the VK-105 and 1125hp at 15,500 was a miracle.
> For instance the VK-105PA was rated at 1100hp at 6500ft(2000m) and 1050hp at 13200ft (4000M) and when they went to the VK-105PF power went to 1260hp at 2300ft (700m) in low gear and 1180hp at 8900ft (2300M) above 13200ft the performace was the same?
> Please note that when pressure in later in engines was increased they went from 1050mm to 1100mm which is about 2in of increased presure or about 1lb.
> The ASh-82F had 1300hp at 17,700ft (5400M) but the radial engine has more drag. The ASh-82FN had 1460hp at 15250(4650m) The Russians constantly worked at reducing drag.
> The only Russian built aircraft with more high altitude performance was the Mig-3 and they were out of production. The P-39 could slide right on in as a medium altitude fighter in Russia.



Hear, hear... Just to add that there were other engines (AM family) with better high alt specs but some were unreliable and other given lower priority when production capacity was in deficit.
By the way, MiG-3 is good example of the aircraft which was abandoned because it was used in wrong way. Pokryshkin, who later became the most famous P-39 "promoter", flew MiG-3 in 1941 and praised it.


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## CORSNING (Apr 2, 2018)

Milosh said:


> Cornsing, do you have to use *bold* text?


Sorry Sir, I was just trying to make a distinction for my reply. I lowered my voice and will take a time-out
until I have learned my lesson.

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## CORSNING (Apr 2, 2018)

DarrenW said:


> _"4. P-47D: That would be the P-47D-2-something(help me here people) using water injection.
> at 56"Hg. producing 2,300 hp./T.O.
> 5. F4U-1a: This would be without water injection. That came along in 1944."_
> 
> ...



I was comparing "Operational" fighters.

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## DarrenW (Apr 2, 2018)

CORSNING said:


> I was comparing "Operational" fighters.



Could you explain further what you mean by "operational"? Both the P-47D and F4U-1A were operational by this time. What am I missing here? Also, you did asked people to "help you out".


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## DarrenW (Apr 2, 2018)

There has been some discussion about how different in performance were the P-39Q and N. They did differ in armament, the two .30 cal. machine guns in each wing being replaced by a .50 cal. mounted in lower-wing gun pods. I checked wind tunnel testing concerning the extra drag of these gun pods in NACA report L5A30 to verify. NACA concluded that the CD of the airplane (in this case, a P-63) was increased by 0.0010, which amounted to a -6 mph change in level speed. So if we add 6 mph to the speed of a P-39Q we will pretty much have the speed of an average P-39N. But then again, those four missing .30 cal. machine guns had to reduce drag slightly as well. So the addition of 4-5 mph is a reasonable amount to add, but never more IMHO.


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## pbehn (Apr 2, 2018)

DarrenW said:


> There has been some discussion about how different in performance were the P-39Q and N. They did differ in armament, the two .30 cal. machine guns in each wing being replaced by a .50 cal. mounted in lower-wing gun pods. I checked wind tunnel testing concerning the extra drag of these gun pods in NACA report L5A30 to verify. NACA concluded that the CD of the airplane (in this case, a P-63) was increased by 0.0010, which amounted to a -6 mph change in level speed. So if we add 6 mph to the speed of a P-39Q we will pretty much have the speed of an average P-39N. But then again, those four missing .30 cal. machine guns had to reduce drag slightly as well. So the addition of 4-5 mph is a reasonable amount to add, but never more IMHO.


.
Altitude SpeedMPH RPM b.h.p. Man.Pr.Hg. Oil Cooler ShutterPosition Prestone Shutter Position

*16,100 389.5 3000 1125 46.7 Flush 6 turns from W.O.
**9,700 398.5 3000 1420 59.8 Flush 6 turns from W.O.
2,700 358.0 3000 1330 57.0 Flush 6 turns from W.O.
30,100 353.0 3000 655 26.7 Flush 6 turns from W.O.


Airplane does not meet Air Corps cooling requirements at any of these powers.


On the test of the P-39N the report says the oil cooler shutters "flush" and Prestone shutter 6 turns from W.O. (as above) followed by "
Airplane does not meet Air Corps cooling requirements at any of these powers. " How is this allowed was a valid test?

​

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## Shortround6 (Apr 2, 2018)

Sounds good, I would even by the 6mph just stop the argument


DarrenW said:


> There has been some discussion about how different in performance were the P-39Q and N. They did differ in armament, the two .30 cal. machine guns in each wing being replaced by a .50 cal. mounted in lower-wing gun pods. I checked wind tunnel testing concerning the extra drag of these gun pods in NACA report L5A30 to verify. NACA concluded that the CD of the airplane (in this case, a P-63) was increased by 0.0010, which amounted to a -6 mph change in level speed. So if we add 6 mph to the speed of a P-39Q we will pretty much have the speed of an average P-39N. But then again, those four missing .30 cal. machine guns had to reduce drag slightly as well. So the addition of 4-5 mph is a reasonable amount to add, but never more IMHO.




Sounds good, I would even go with -6mph to avoid the argument. 
I would say that the increased weight will affect climb more than the drag will affect speed.


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## DarrenW (Apr 2, 2018)

pbehn said:


> .
> Altitude SpeedMPH RPM b.h.p. Man.Pr.Hg. Oil Cooler ShutterPosition Prestone Shutter Position
> 
> *16,100 389.5 3000 1125 46.7 Flush 6 turns from W.O.
> ...



I see your point and it is well taken. I plan to create a speed chart of the N model using the P-39Q test results instead. There is no mention of cooling problems so the results are probably more reliable. I will add 6 mph to the speed at the various heights in order to recreate the actual speeds that a typical P-39N would have attained. Hopefully we will have a better picture of the P-39N's capabilities after that.


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## pbehn (Apr 2, 2018)

DarrenW said:


> I see your point and it is well taken. I plan to create a speed chart of the N model using the P-39Q test results instead. There is no mention of cooling problems so the results are probably more reliable. I will add 6 mph to the speed at the various heights in order to recreate the actual speeds that a typical P-39N would have attained. Hopefully we will have a better picture of the P-39N's capabilities after that.


It was a general question, it seems to me that cooling drag was reduced by not cooling the engine. Overheating on tests and in service seems to be a feature on the P-39.


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## Shortround6 (Apr 2, 2018)

pbehn said:


> On the test of the P-39N the report says the oil cooler shutters "flush" and Prestone shutter 6 turns from W.O. (as above) followed by "
> Airplane does not meet Air Corps cooling requirements at any of these powers. " How is this allowed was a valid test?​




The test may have been valid (unless done on a highly polished, specially prepared aircraft).

It is the conclusions that may not be valid. 

You don't know what is going to work and what won't until you test. 
The P-39 seems to have had chronic cooling problems, get it sorted out for one level of power and the Allison (or the Army) upped the power rating/s the problems came back at the higher power levels.
A number of other planes went through the same thing. Spitfires got ever larger radiators/oil coolers.​


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## DarrenW (Apr 2, 2018)

Shortround6 said:


> Sounds good, I would even by the 6mph just stop the argument
> 
> 
> 
> ...



Good point. So 6 mph it is....


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## Shortround6 (Apr 2, 2018)

DarrenW said:


> I see your point and it is well taken. I plan to create a speed chart of the N model using the P-39Q test results instead. There is no mention of cooling problems so the results are probably more reliable. I will add 6 mph to the speed at the various heights in order to recreate the actual speeds that a typical P-39N would have attained. Hopefully we will have a better picture of the P-39N's capabilities after that.



Climb chart may be harder but just as valuable.


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## pbehn (Apr 2, 2018)

Shortround6 said:


> The test may have been valid (unless done on a highly polished, specially prepared aircraft).
> 
> It is the conclusions that may not be valid.
> 
> ...


Shutters were open in climb and closed in level flight, as a layman I would have thought the engine overheating is as invalid as using uncertified boost or revs on the test.


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## Shortround6 (Apr 2, 2018)

The open during climb and closed for speed was normal, just about all planes did that, what varied was by how much they were open during climb or if they needed to open in level (high speed) flight.
If you are climbing and doing 180mph true you are getting 1/2 the air than if you are doing 360mph in level flight. Some sort of adjustment is needed. And with air being roughly 1/2 the density at 20,000ft that it is at sea level (even though colder) they have to make allowances for that. 

I can easily tests that pushed boundaries or limits and even exceeded them just to find out where they were. Using such results as indicators of operational ability is the problem. 

There are some tests where the climb had to be broken into stages to allow the engine to cool off. That test _might_ tell you what the plane could do for a few minutes in combat. It sure didn't tell you what the plane needed for time to get from sea level to 25-30,000ft for an intercept. Except perhaps it wasn't going to make it.

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## Schweik (Apr 2, 2018)

Greyman said:


> In my opinion (from reading about 601 Squadron during those dark Airacobra days), what killed the aircraft for the RAF was chronic unserviceability, and they were unwilling to put in the mountain of effort that was required to fix it - while the Soviet NII and VVS made a special case out of the P-39 and went all-out to turn it into a real fighter. No small feat - but they sure did it.
> 
> A great read here:
> Early Cobra's in Soviet Aviation



That Lend Lease aircraft site is a fantastic resource, and that article in particular is indeed a good read and it helped me understand how the Soviets did so well with the P-39. The Soviets got their P-39's in December and January of 1941/42, and spent the next 4 moths preparing them, training pilots and doing their workup. Some quotes from the article mentioned:



> _The first party of 20 aircraft (all series AH, from 599 to 677) * arrived in 22d ZAP in the period between late December 1941 and early January 1942*. Their arrival was taken very seriously. The Scientific Research Institute (NII) of the VVS sent a group of specialists to the regiment, from which was formed a separate team (22d ZAP order no. 7 of 2 January 1942).
> *
> The assembly of the first party of aircraft was begun in mid-January. This author does not know the specific site of the assembly and test flight of the first Airacobra. The literature only makes reference to a large airfield on the outskirts of the town. Drawing from the basing of 22 ZAP, the site was one of three airfields: Kineshma, Ivanovo-South, or Ivanovo-North.
> *
> ...



This is one of the key aspects of solving the mystery of why the Soviets got so much mileage out of this aircraft when nobody else could. They liked it initially and recognized it's potential, they had already had experience with Anglo-American fighters and had recognized certain problems they wanted to avoid with the P-39. So they collected all the ones they were sent in some airfield in Siberia, had test pilots fly them, did a complete workup on systematic adjustments, some already widely known like removing the wing-guns to save weight, but others were less widely understood like winterizing and working out maintenance systems in advance. For example they had to modify all Anglo-American fighters so that _all_ fluids could be drained out every night (not just during overhauls) during the Winter, which meant adding plugs and drains on some systems not designed for it - and do it in such a way that would not damage hydraulics, coolant or oil. They did this much more carefully with the P-39's thanks to the work-up, by comparison with the P-40's and Hurricanes this was done in the field, haphazardly, often with damaging results. Another major issue was the "oil culture" and fuel requirements. Finally they trained their pilots to use the new aircraft and worked out tactics (exploiting the radios, among other things) for their optimal use.

One of the big differences between the P-39's and the P-40's and Hurricanes they had gotten earlier was that the P-39's came with spare engines and at least some spare parts. The other parts and supplies were figured out by Soviet engineers, copied as needed added to the Soviet logistics systems. Thus when P-39 engines burned out, as they quickly did in field conditions partly due to using them at high power settings, they could be replaced with new engines. This was much more of a problem with P-40's for example which initially came without any spare engines.

Once all of this was all worked out, and only then, the Soviets committed the P-39 in some numbers, and it caused something of a shock to the Germans.

*Why they liked it so much*

_It was the most similar to Soviet fighters._ The P-39 was the only Anglo-American single-engined fighter with a cannon in the spinner plus nose guns. Their aerial gunnery training was mostly oriented toward nose guns and most (except I-16 pilots or those checked out on P-40's or Hurricanes) were not used to wing-guns. The P-39 was streamlined like a Soviet fighter. It was agile and climbed well. These characteristics endeared it to the Russians and marked it for the careful work-up it got.
_It was fast._ Properly stripped down, the P-39 was faster than a Bf 109E at low altitude and arguably, maybe even Bf 109F. No Soviet planes could match this down low (the MiG 3 could at high altitude only but that really didn't matter in combat along the Russian Front).

_They got some new ones. _Most of the P-40's and Hurricanes they had gotten to that point were already worn out battle veterans with weakened engines. But the British didn't use their P-39's very much at all before sending them on, and the Americans sent new ones.

_It had good radios. _The Soviets had been unable to get enough radios into production and the ones they had suffered from very short range and ineffective transmitters, due to ineffective grounding and other problems. All the Anglo-American planes, the American in particular, had good reliable radios for both transmitting and receiving. This was a huge help for the Soviets!

_It was all -metal. _Soviet planes were mostly made with substantial wooden parts, using new types of plywood which had not in all cases been fully developed and sometimes failed in flight. The P-39 had none of these problems.

_Superior build quality. _All of the newer Soviet fighters - MiG-3 / La GG-3 / Yak 1 / Yak 7 etc., suffered from severe problems with build quality. Many parts which would be interchangeable on a Western fighter were unique one-off's on Soviet planes. Variations in production quality, which in many cases was being done in factories that had just been moved across the Urals and didn't even have roofs, could mean that an aircraft with an official speed of 350 mph was in reality limited to 280 or 290 mph. The early P-39 didn't have the world's best build quality (some serious defects were revealed by British testing such as landing gear doors opening up at speed etc.) but it was better than all of the newer era Soviet planes up until probably 1943.
_The altitude ceiling didn't matter _- almost all of the bombing in the Russian Front zone was tactical and there was often a cloud ceiling at ~4-5,000 feet especially during the long winter. So not only did most of the fighting take place at low altitude the Germans couldn't use their superior climb and ceiling to attack from above all the time like they did so much in North Africa.

_They liked the heavy armament and heavy construction. _The Soviet pilots actually liked the Oldsmobile 37mm as it allowed them 'authority' in a head-on pass with German fighters (who would veer off to avoid what they described as an "anti-aircraft caliber weapon") and the Soviets seemed to be able to get it working, although in some cases it was replaced by 20mm guns. They also felt the P-39 could survive belly landings which would destroy most other aircraft.
_Dive speed and high-G turns. _One effect of the heavy construction was that the P-39 could out-dive most other Soviet planes, which had fairly low speed limits due to their partly wooden construction and typically uneven-build quality. The P-39 could dive very fast and could evade Bf 109's this way. This was key to the survival of Soviet P-39 pilots, the ability to disengage. This also meant that the P-39 could pull higher-G turns (so long as the pilot could keep it out of a Spin) than some other Soviet types.
Most of this of course is well known. So we can see why the Soviets liked the P-39. The question remaining is why they did so well with it compared to say, the British, the Americans, the Free French, the Italian Co-beligerant forces who suffered from it so badly, and whoever else got stuck with it (I think Australians maybe?). This is the biggest question to me.

*Why the Soviets did so well with it compared to others*

_The main reason is I think the big workup described in that article.on Leand Lease P-39's._ In general with early war Anglo-American aircraft, success seemed to hinge on modifying the aircraft appropriately for actual use (as opposed to however they arrived from the factory) usually involving both weight saving and maintenance issues, and *training* on the particular fighter type. Flying a P-39 in combat right out of flight school was a recipe for death. The Soviets solved both of these problems with their extended workup of the P-39.

_The lower altitude ceiling _- the tactical flight ceiling of the Russian Front battlefield really made a difference. It was a low-altitude battlefield, and due to the frequent cloud ceiling, German fighters often could not attack from above. Almost all of the bombing on both sides was dive bombing or close-support (Sturmovik) low altitude attacks. This was one of the main weaknesses of the P-39 for other Theaters but it just didn't matter nearly as much on the Russian Front.

_Range didn't matter as much on the Russian Front-_ I think range is the main reason the P-39s did so poorly in general in the Pacific. Altitude ceiling of course was more important there too, since the Japanese were using level-bombers that were coming in at 20-25,000 feet. But short range exacerbated that problem because short range meant less time to get up to altitude. But the Russians were already operating from forward airfields close to the front and combat was at low altitude, so range wasn't as important.
_The Russians were used to twitchy planes. _I think this is one of the other main factors. Western allied pilots were afraid of the P-39, they didn't trust it, because it was somewhat unstable aircraft which could go into an unforgiving spin (the 'flat spin' and tumble are debated issues, but lets agree a spin in a P-39 could be dangerous). The Soviets had a head start on this due to the 4 month training and evaluation period they did, but they also had a lot of pilots already used to 'twitch' fighters and able to fly well in them and get kills in spite of their touchy handling. The I-16, the LaGG-3, the MiG 3, and the early Yak 1 were all known to be 'twitchy' fighters. Many Soviet pilots assigned to P-39 fighters came directly from flying these somewhat 'difficult" planes. This I suspect is one of the other crucial missing ingredients.
_The Soviets had some input into the aircraft development. _Later model P-39's were adjusted according to feedback from their only happy customer, the Soviets, and the P-63 was basically built to Soviet specifications and under direct Soviet supervision.


I think ceiling and range were the two biggest performance issues preventing the P-39 from doing well in the Pacific. i suspect the 'twitchyness' and training were the major issues in the Med.

Anyway, that's my $.02

S

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## buffnut453 (Apr 2, 2018)

Great post Schweik. The info about the work-up time taken by the Soviets is particularly enlightening. I think your assessments of why the Soviets succeeded when others failed also bang on the money.

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## Shortround6 (Apr 2, 2018)

I would agree with everything except


Schweik said:


> _It was fast._ Properly stripped down, the P-39 was faster than a Bf 109E at low altitude and arguably, maybe even Bf 109F. No Soviet planes could match this down low (the MiG 3 could at high altitude only but that really didn't matter in combat along the Russian Front).



By late spring or early summer of 1942 the Bf109E was fading fast from front line inventory (if it was there at all) and the 109G was starting to be introduced during the summer.
I would also note that the Mig-3 was pretty much out of production in Jan of 1942 with only small numbers trickling out built of spare parts. An overhaul/repair facility did help keep some in operation but one book says only 134 in service (and not all combat capable) in May of 1942. The Mif stayed in service in ever decreasing number until 1943 but there was never any question of it coming back or equipping any new units. 
This makes it's performance vs the P-39 almost irrelevant except for academic purposes.


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## Elmas (Apr 2, 2018)

Schweik said:


> *snip*
> I think ceiling and range were the two biggest performance issues preventing the P-39 from doing well in the Pacific. i suspect the 'twitchyness' and training were the major issues in the Med.
> *snip*
> S



I generally do agree with you but I suspect that the 'twitchyness' affected quite a bit P-39 as a gun platform. That, in pair with the lousy armament, put P-39 clearly at a disadvange in a fighter to fighter combat, unavoidable in ETO and PTO, while in RTO, in which the Luftwaffe lost the vast majority of his transport force, Ju 52 and He 111, flying relatively low and with small escorts, could have been easy game. Luftwaffe had to keep a difficult balance between fighters defending German towns in ETO and fighters escorting transports in RTO. End 1942, with P-39 in numbers, Stalingrad.

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## DarrenW (Apr 2, 2018)

Shortround6 said:


> I would say that the increased weight will affect climb more than the drag will affect speed.



So in your opinion how much extra weight would the P-39N have then? It gained two .50s but lost four .30s. Did one .50 cal machine gun weigh more than twice that of a .30 cal? You know a lot more about this than I do so just curious. Maybe it was the fairings that added the extra weight???


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## Shortround6 (Apr 2, 2018)

You can find the weights on the P-39Q and P-39K/L weight charts. 
Basically it was 99lbs for four .30 cal guns and 150lb for two .50s. 
Weight of ammo was 262lbs for the K/L (300rpg for the .30s) and 370lbs for the Q.


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## DarrenW (Apr 2, 2018)

Shortround6 said:


> You can find the weights on the P-39Q and P-39K/L weight charts.
> Basically it was 99lbs for four .30 cal guns and 150lb for two .50s.
> Weight of ammo was 262lbs for the K/L (300rpg for the .30s) and 370lbs for the Q.



Excellent!


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## Shortround6 (Apr 2, 2018)

Excuse me, that weight is the total weight of ammo for all guns.


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## XBe02Drvr (Apr 2, 2018)

Elmas said:


> I suspect that the 'twitchyness' affected quite a bit P-39 as a gun platform. That, in pair with the lousy armament, put P-39 clearly at a disadvange in a fighter to fighter combat, unavoidable in ETO and PTO, while in RTO, in which the Luftwaffe lost the vast majority of his transport force, Ju 52 and He 111, flying relatively low and with small escorts, could have been easy game.


I beg to differ on the twitchiness angle. Twitchiness is usually a low speed/high AOA phenomenon, unless workmanship or shoddy materials has weakened flight controls. The Soviets praised the high speed controllability of the 'Cobra and used tactics that took advantage of it. The twitchiness comes into play when you are foolish enough to get into a high G, energy draining knife fight with a Zero at tropical air densities and altitudes where your aircraft is running out of steam. This also is where dealing with the three separate trajectories of your gun package is at its most vexing.
Now let's go to the forested plains of NW Russia. (NOT Siberia, BTW). Bitterly cold, air so dense you can cut it with a knife, one less trajectory to deal with, and all your remaining firepower boresighted line of sight. Combat is high speed, down low, and against fighters optimized for altitude, while yours has been carefully adapted and optimized for this environment, and flown by pilots used to living and fighting rough. What more could a poor, maligned venomous snake ask for?
BTW, the victory tallies in the Lend Lease article don't seem to show high kill numbers against LW bombers and transports. Looks like mostly fighters. Also, not many kills against JU-87s. I thought they were pretty numerous on the Eastern Front. Were they depleted by this time, or was it due to their agility and their tail gunner?
Cheers,
Wes

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## Shortround6 (Apr 2, 2018)

We may be getting into arguments about semantics. One man's "twitchy" is another man's "highly responsive" 

I have a brother-in law who owned a Mudry Cap 10 for a number of years






NOT his.
He would fly it when giving rides to other people with his forearm resting on his thigh to avoid over controlling the plane. 
One time some old college buddies wanted to rent a Cessna 172 and have him fly it. He went up for a check ride with an instructor first as it had been years since he flew a 172. After a 1/2 hour he landed and called it off, he had been under controlling the 172 the whole time.

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## CORSNING (Apr 2, 2018)

DarrenW said:


> Could you explain further what you mean by "operational"? Both the P-47D and F4U-1A were operational by this time. What am I missing here? Also, you did asked people to "help you out".



Operational: A fully combat ready aircraft in a fully combat ready unit positioned in an
area capable of putting a hurt on the enemy immediately. And, proven themselves
so by putting their aircraft in hostile air.

Thank you Darren, you are right I did ask for help of which P-47D variant was in fully combat
operational service by 25 December 1943. That was the limiting date that pbehn put on his
post. So I used that limitation. Wuzak is partly right about the P-39N's luck against the P-38J-5.
While I believe the Spitfire 14 would do just fine against the Airacobra at tree top levels, I
believe the J-5 lightning would more than have its hands full in a maneuvering contest.


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## Dimlee (Apr 2, 2018)

Elmas said:


> I generally do agree with you but I suspect that the 'twitchyness' affected quite a bit P-39 as a gun platform. That, in pair with the lousy armament, put P-39 clearly at a disadvange in a fighter to fighter combat, unavoidable in ETO and PTO, while in RTO, in which the Luftwaffe lost the vast majority of his transport force, Ju 52 and He 111, flying relatively low and with small escorts, could have been easy game. Luftwaffe had to keep a difficult balance between fighters defending German towns in ETO and fighters escorting transports in RTO. End 1942, with P-39 in numbers, Stalingrad.



RTO - Eastern Front, I assume. 
P-39 did hunt Ju 52 of course as well as any other fighter. Those were rare operations. Probably the most famous (for P-39): free hunting of 16 GIAP over Black Sea in 1944. 
As for "twitchyness" as of a gun platform - this is one of those questions about Soviet P-39 which were (and probably still are) subject of endless discussions in Russian language community. Same as many other: M4 cannon qualities, flat spin risks, engine overheating, agility, etc. etc.


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## pbehn (Apr 2, 2018)

CORSNING said:


> Operational: A fully combat ready aircraft in a fully combat ready unit positioned in an
> area capable of putting a hurt on the enemy's aircraft immediately. And, proven themselves
> so by putting their aircraft in hostile air.
> 
> ...


 My date of 25 Dec 1943 was itself based on how long a new type aircraft which started to be produced in USA in Dec 1942 would actually be expected to be operational in UK. Shipping and training take much longer than you would think.


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## Schweik (Apr 2, 2018)

Shortround6 said:


> We may be getting into arguments about semantics. One man's "twitchy" is another man's "highly responsive" .



yes, I actually think the two things very much go together. I-16's were considered very maneuverable AND "twitchy" - so were Fw 190's for that matter (though I know some people will disagree with that) and even early Ki-43's. Hurricanes were very stable but not as dynamic, by contrast.

Handling and maneuverability are two different things, and maneuverability can mean multiple different things too. An aircraft can be slightly unstable but also very agile simultaneously. That is actually what I was alluding to - for a pilot experienced with this particular kind of challenge it isn't really a problem at all. Clearly the Soviets had few problems with this aspect of the P-39, comparatively, but it's also very clear that many if not most American, Italian, and French pilots positively dreaded maneuvering with the P-39 and feared that it would go into a spin that would kill them. A lot of them found the P-39 risky to bail out of too due to the 'car type' doors (though some people in New Guinea seemed to have made a career out of bailing out of them).

I think being comfortable with "twitchy" aircraft, and spending more time in familiarization with the type- is one of the main reasons the Soviets did so much better with the P-39, aside from the requirements / conditions of the Theater.

S

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## Elmas (Apr 2, 2018)

The most dreaded thing Italian P-39 pilots feared were the nickname the other pilots, who remained in the Stormo equipped with Macchi gave them: _“the truck drivers”_, for the car style door of their planes...

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## Elmas (Apr 2, 2018)

Dimlee said:


> RTO - Eastern Front, I assume.
> ...



Yes, Russian Teater of Operation.


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## Dimlee (Apr 2, 2018)

Schweik said:


> That Lend Lease aircraft site is a fantastic resource, and that article in particular is indeed a good read and it helped me understand how the Soviets did so well with the P-39. The Soviets got their P-39's in December and January of 1941/42, and spent the next 4 moths preparing them, training pilots and doing their workup. Some quotes from the article mentioned:
> 
> 
> 
> ...



And very valuable $.02, indeed !
Many thanks to Schweik for such detailed commentary. And - especially - for bringing attention to:
1. Massive pre-flight preparations, research and improvements. They continued with later models as well.
2. Advanced training that many pilots received. Human factor should not be underestimated.

Just a couple of small things:
- 22 ZAP and other reserve/training regiments were never based in Siberia. Siberian airfields were just transit points for AlSib route.
- Certainly "not the most similar to Soviet fighters". Actually most, if not all qualities of P-39 praised by VVS pilots were not typical to domestic production. As for nose guns orientation - interesting hypothesis, but it needs to be verified.

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## Dimlee (Apr 2, 2018)

XBe02Drvr said:


> Also, not many kills against JU-87s. I thought they were pretty numerous on the Eastern Front. Were they depleted by this time, or was it due to their agility and their tail gunner?
> Cheers,
> Wes



Good question. I'd suggest both general attrition and (probably) Ju 87 tactics changes after 1941. If they were more and more used at lower altitudes then their typical opposition would be Yak and La, IMHO. P-39 did not excel very low.
One of Rudel's stories was about P-39 on his tail in long ground level chase in 1944...
As for numbers of Ju 87, if someone has enough time to count them from here or from similar source:
http://www.oocities.org/sturmvogel_66/LWJul42.html#May43

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## Schweik (Apr 2, 2018)

Dimlee said:


> And very valuable $.02, indeed !
> Many thanks to Schweik for such detailed commentary. And - especially - for bringing attention to:
> 1. Massive pre-flight preparations, research and improvements. They continued with later models as well.
> 2. Advanced training that many pilots received. Human factor should not be underestimated.
> ...



Interesting, do you know where the 22 ZAP base was exactly? I thought it was Western Siberia / Central Asia.

Similarity I think is mainly regarding the nose gun and overall streamlined appearance, but also small wings and some other features. Admittedly just a theory. I think the nose gun thing is important because so many Soviet pilots mentioned it.

S


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## Schweik (Apr 2, 2018)

Elmas said:


> The most dreaded thing Italian P-39 pilots feared were the nickname the other pilots, who remained in the Stormo equipped with Macchi gave them: _“the truck drivers”_, for the car style door of their planes...



For Italians, pride is very important of course . A lot of them died in accidents in P-39's though including IIRC at least one important ace, so that is pretty tragic.

S


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## Elmas (Apr 2, 2018)

Still, I cannot understand how a plane like P-39 could have had such a good score against Luftwaffe fighters. Difficult handling, not the best suitable armament...

Certainly, while in the Western Front Luftwaffe gave precedence to quality, in the Eastern Front took precedence quantity and, probably, the percentage of unskilled LW pilots there was in the East was higher.

Or was outstandingly high the skill of Russian pilots? Could be, but I doubt: Ulrich Rudel could ride on a Stuka well into 1944, if not 1945 on the Russian Front...


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## Schweik (Apr 2, 2018)

Dimlee said:


> Good question. I'd suggest both general attrition and (probably) Ju 87 tactics changes after 1941. If they were more and more used at lower altitudes then their typical opposition would be Yak and La, IMHO. P-39 did not excel very low.
> One of Rudel's stories was about P-39 on his tail in long ground level chase in 1944...
> As for numbers of Ju 87, if someone has enough time to count them from here or from similar source:
> http://www.oocities.org/sturmvogel_66/LWJul42.html#May43



From reading Black Cross / Red Star it seems like a lot of German bomber sorties were able to take place without fighter opposition, especially during periods when the LW had achieved local air superiority such as during the first part of Stalingrad.

S


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## Elmas (Apr 2, 2018)

Schweik said:


> For Italians, pride is very important of course . A lot of them died in accidents in P-39's though including IIRC at least one important ace, so that is pretty tragic.
> 
> S



Last victory of Teresio Martinoli, top italian Ace in the Regia Aeronautica, was against a P-39 in Tunisia, and then he died in a training flight with an Airacobra. His last victory, a Ju-52 over Jugoslavia, was with a P-39 as well.
Googling "Martinoli, Tunisia" I did find this:

_"In the final chapter in “Fighters over Tunisia” (by Shores, Ring & Hess), “Conclusions”, there are some quite interesting pilot comments on the various fighter planes used. With earlier discussions on the Airacobra in mind, it is interesting to note that there are several pilot remarks on the Airacobra, and none of them is kind. In fact, no fighter type is torn apart to such an extent by the pilots interviewed in “Fighters over Tunisia” as the Airacobra.

Jerry Collingsworth, who flew as a Lieutenant with US 31st FG in Tunisia, is quoted saying:

“The P-39 [Airacobra] was a miserable fighter for Tunisia; we used to have to escort them because the Me 109 and Fw 190 outperformed them in every conceivable way; dive, climb, manoeuvre, speed - you name it!” (p. 416)

Wg.Cdr. M. G. F. Pedley, who served as a Wing Leader in 323 Wing in Tunisia, is quoted on the same subject:

“P-39 Airacobra . . . Its rate of climb was poor, armament inefficient and engine unreliable.” (p. 424)

John L. Bradley of US 33rd FG is quoted to say this on the Airacobra:

“I flew a couple of escorts for P-39s during my tour. Many of the pilots on these aircraft were afraid of them and figured they didn’t have a chance if they were jumped by enemy aircraft without top cover.” (p. 404)

There is not one positive word on the Airacobra among these harsh condemnations. Hardly suprising, since by looking up the two Airacobra units operating in Tunisia (81 FG and 350 FG) in the index of “Fighters over Tunisia”, one gets the impression of a fighter plane which was badly mauled by Luftwaffe fighters without any chance to pay back. In late February 1943 350 FG was withdrawn from first-line service and degraded to coastal patrols with the North-West African Air Force. A little later, the other Airacobra unit, 81 FG, was badly beaten up by II./JG 77.

On 13 March 1943, Bf 109s of II./JG 77 - possibly reinforced by some Bf 109s from III./JG 77 - attacked 12 Airacobras of 81 FG, provided with top cover by Spitfires of 307 and 308 Sqns. In the ensuing combat, seven of the twelve Airacobras were shot down without any loss to the Germans. The shot down Airacobras were piloted by Lt. Murray, Lt. Turkington, Lt. Smith, Lt. Leech, Lt. McCreight, Lt. Lewis, and Lt. Lyons. The Eastern Front veteran Ernst- Wilhelm Reinert scored five victories against Airacobras (at 1744, 1748, 1756, 1756 again, and 1800 hours)

(Earlier that day, II./JG 77 had clashed with 34 P-40 Warhawks of US 57 FG and shot down four of these against one own loss. II./JG 77 claimed to have shot down five Warhawks, including two by Ernst-Wilhelm Reinert; thus, the Eastern Front veteran Reinert scored seven victories against US fighters on 13 March 1943, increasing his total victory tally to 135.)

All of this, including Reinert’s feat, is a perfect illustration of the Luftwaffe Eastern Front veterans repeating what they previously had accomplished on the Eastern Front against the same kind of fighters. 

To compare with the Eastern Front, 216 SAD, equipped with Airacobras and Warhawks, sustained five Airacobras and a Warhawk shot down in a similar outburst of air fighting on 15 April 1943.

However, to be fair, it should be noted that only a few days before II./JG 77’s massacre on US-piloted Airacobras, other Airacobras flown by Soviet pilots of 19 GIAP managed to shoot down three of III./JG 5’s Bf 109s in a single engagement (against only one own Airacobra lost). Lt. Jakob Norz’s Bf 109 F-4 (WNr 13108), Lt. Gerd Grosse-Brauckmann’s WNr 10183, and Fw. Ernst Schulze’s WNr 10122 were all reported destroyed as a result of that combat. Without drawing any far-fetched conclusions, I can only note that AFAIK the American Airacobra pilots never managed to accomplish anything similar against Luftwaffe fighters.

In any case, shortly after it had received such a bad beating by II./JG 77, this US Airacobra unit also was withdrawn from first-line service and joined the other Airacobra unit in coastal patrols with the North-West African Air Force - where they were saved from encountering any Bf 109s or Fw 190s."
_
and also
_
In late February 1943, the Airacobra-equipped 350th FG was withdrawn from first-line service and degraded to coastal patrols with the North-West African Air Force. It is not quite correct to state that "it returned to front line action", as you will see below. 

In fact, the 350th FG Airacobras never were sent back to regular first-line service. From February 1943, their dominant task would remain coastal patrols in the rear area. In November 1943 it was transferred from North Africa to Cagliari/ Elmas, Sardinia."
_
I'm looking if I will be able to find some pics of Airacobra here in Sardinia...

P-39 is certainly a very controversial aircraft.


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## DarrenW (Apr 2, 2018)

CORSNING said:


> Operational: A fully combat ready aircraft in a fully combat ready unit positioned in an
> area capable of putting a hurt on the enemy immediately. And, proven themselves
> so by putting their aircraft in hostile air.
> 
> ...



Thanks Corsning, I just needed the clarification. And just to make clear I enjoy your posts and value your input as always.

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## DarrenW (Apr 2, 2018)

So are we in agreement that the loaded weight of the Q model was roughly 150-200lbs more than the P-39N (extra weight of guns, ammo, and additional fairings) ? How would an increase like that affect the level speed and climb rate?


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## Schweik (Apr 2, 2018)

Elmas said:


> _Earlier that day, II./JG 77 had clashed with 34 P-40 Warhawks of US 57 FG and shot down four of these against one own loss. II./JG 77 claimed to have shot down five Warhawks, including two by Ernst-Wilhelm Reinert; thus, the Eastern Front veteran Reinert scored seven victories against US fighters on 13 March 1943, increasing his total victory tally to 135.)
> 
> All of this, including Reinert’s feat, is a perfect illustration of the Luftwaffe Eastern Front veterans repeating what they previously had accomplished on the Eastern Front against the same kind of fighters._



Good post overall, and yes these were the same quotes included in MAW III which I was referring to about US pilots being "afraid" of their P-39's.

Be careful lumping the P-40 and the P-39, especially the late model P-40's flying with the 57 FG, because based on the newer books by the same author (Shores) which compare actual victories vs. losses on each side, USAAF P-40 squadrons on numerous occasions shot down more Bf 109's than they themselves lost. I cited about ten examples in another thread - I know this too is a controversial topic and I don't want to detail this conversation about the P-39 so if you want to discuss P-40's post in that one probably or create a new thread_.
_
But here are a few examples involving USAAF P-40 F/L vs. Bf 109s specifically:
_*
23 March 1943* (USAAF 79 FG P-40F vs. JG 77 & JG 51)* 2 Bf 109s lost to P-40's / 0 P40's lost
29 March 1943* (USAAF 33 FG P-40L vs. JG 77) *6 Bf 109 lost (4 destroyed +2 crash-landed) *and 3 He 111's and 1 Ju 88* / 2 P-40's lost (1 to AA)
31 March 1943* (USAAF 33 FG P-40L vs. JG 77) *6 Bf 109 lost* *(3 destroyed +3 crash-landed) / 1 P-40 lost*
_


> However, to be fair, it should be noted that only a few days before II./JG 77’s massacre on US-piloted Airacobras, other Airacobras flown by Soviet pilots of 19 GIAP managed to shoot down three of III./JG 5’s Bf 109s in a single engagement (against only one own Airacobra lost). Lt. Jakob Norz’s Bf 109 F-4 (WNr 13108), Lt. Gerd Grosse-Brauckmann’s WNr 10183, and Fw. Ernst Schulze’s WNr 10122 were all reported destroyed as a result of that combat. Without drawing any far-fetched conclusions, I can only note that AFAIK the American Airacobra pilots never managed to accomplish anything similar against Luftwaffe fighters.



Good point and absolutely true. I believe the reasons are as outlined in my previous post. It's certainly a striking contrast.



> In any case, shortly after it had received such a bad beating by II./JG 77, this US Airacobra unit also was withdrawn from first-line service and joined the other Airacobra unit in coastal patrols with the North-West African Air Force - where they were saved from encountering any Bf 109s or Fw 190s."



Quite true but even as the P-39 was relegated to coastal patrol duties, it's worth noting that multiple RAF, Free French and USAAF squadrons were still using the P-40 for front line combat operations, including escort and fighter sweep missions, well into the middle of 1943, with some units continuing until 1944. In Shores MAW P-40 squadrons are still scoring kills against the Luftwaffe well into 1943 as I noted above. it's also worth pointing out that while there was only 1 US ace flying the P-39, and no others in the West that I know of (at least, none who made 5 kills in a P-39) there were at least 80 P-40 aces in the Med Theater alone and something like 15 or 20 double aces. The Soviets also had dozens of P-40 Aces and several double, triple and even quadrouple aces flying the type, including 3 HSU recipients.

_S_


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## pbehn (Apr 2, 2018)

Since most P-39s sent to Russia were the N and Q versions, is it possible these were quite well sorted as far as engine and CoG issues went while the earlier versions just shouldn't have been put into service?


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## Shortround6 (Apr 2, 2018)

DarrenW said:


> So are we in agreement that the loaded weight of the Q model was roughly 150-200lbs more than the P-39N (extra weight of guns, ammo, and additional fairings) ? How would an increase like that affect the level speed and climb rate?


The weight alone has a negligible impact on speed. It is the drag associated with the weight that causes the speed reduction. 
For instance if you were add internal ballast with NO exterior changes the only increase in drag would be a very marginal shift in the angle of attack of the wing and the induced drag, since forces on the plane (both drag and lift) go up with the square of the speed adding a few hundred pounds to an aircraft does very little to the speed. 
However, pods, protruding gun barrels, gun ports/troughs, cartridge ejection slots can cause a much bigger disruption of airflow and increased drag.

When climbing there is a bit of a double whammy. Since climb speed is relatively low, in fact it is a cross/blend between lowest speed with good controllability and the lowest drag speed ( lowest drag caused by lift and lowest drag caused by speed/shape). I am not explaining that well. 





Picture worth 1000 words. Climb is done near the minimum drag speed, an increase in weight is going to cause the lift induced drag to rise at low speed in greater proportion than at high speed. This leaves less power to perform the climb with and when climbing you are lifting every pound. 

Hope that makes sense?

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## Shortround6 (Apr 2, 2018)

pbehn said:


> Since most P-39s sent to Russia were the N and Q versions, is it possible these were quite well sorted as far as engine and CoG issues went while the earlier versions just shouldn't have been put into service?




I am not sure how bad things really were and how much was "hanger talk". The P-39 certainly had a higher landing speed than a P-40 but then so did a P-47. The P-39 may have been more responsive than some other fighters, more results (change of angle of aircraft)for the same movement or effort on the stick/rudder pedals. 
The P-39 may parallel the B-26? Early pilots transitioning from easier to fly aircraft had trouble with it (and inexperienced instructors didn't help) while later pilots had a better training program?
Once a plane gets a bad reputation it takes a LOOOOOOONG time to live it down. 

IN combat in 1942 and early 43 the P-39 was usually going to be the plane being dived down upon and seldom being the plane doing the diving upon others, which means it is at a disadvantage a larger percentage of the time. 

I am not saying the P-39 was a great combat plane in the west, just that some pilot's comments have to be put in context.

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## pbehn (Apr 2, 2018)

Shortround6 said:


> The weight alone has a negligible impact on speed. It is the drag associated with the weight that causes the speed reduction.
> For instance if you were add internal ballast with NO exterior changes the only increase in drag would be a very marginal shift in the angle of attack of the wing and the induced drag, since forces on the plane (both drag and lift) go up with the square of the speed adding a few hundred pounds to an aircraft does very little to the speed.
> However, pods, protruding gun barrels, gun ports/troughs, cartridge ejection slots can cause a much bigger disruption of airflow and increased drag.
> 
> ...


Great post, the proof of that particular pudding is the Mustang Mk I (P51A) bigger and heavier than the P39 but faster, it actually did do 400MPH with and Allison engine, and the P51B bigger and heavier than the Spitfire but faster at all altitudes on the same engine. Rates of climb may have been slightly lower but not seriously behind.

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## pbehn (Apr 2, 2018)

Shortround6 said:


> I am not sure how bad things really were and how much was "hanger talk". The P-39 certainly had a higher landing speed than a P-40 but then so did a P-47. The P-39 may have been more responsive than some other fighters, more results (change of angle of aircraft)for the same movement or effort on the stick/rudder pedals.
> The P-39 may parallel the B-26? Early pilots transitioning from easier to fly aircraft had trouble with it (and inexperienced instructors didn't help) while later pilots had a better training program?
> Once a plane gets a bad reputation it takes a LOOOOOOONG time to live it down.
> 
> ...


The pilots of 601 sqdrn RAF had previously flown Hurricanes, the take off of the P-39 was much longer, so much that it couldn't be used on some RAF bases. The landing speed and I presume take off speed was much higher, the pilots manual says that you can side slip to lose height but the rate of descent means this shouldn't ne necessary. However of the planes used by 601, one crashed after take off with engine failure killing the pilot, another crashed during aerobatics killing the pilot while another had to do a wheels up landing. The actual tests by Boscombe down said it could be used as a low altitude fighter, it just happened that the pilots actually using it hated it. Personally I think Operation Barbarossa and Japanese activities in the Pacific trumped all discussions. The British were already sending planes and tanks to Russia starting June 1941, sending P39s to UK while UK was sending Hurricanes and later Spitfires to Russia makes no sense at all.


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## Vincenzo (Apr 2, 2018)

Schweik said:


> But here are a few examples involving USAAF P-40 F/L vs. Bf 109s specifically:
> _*
> 23 March 1943* (USAAF 79 FG P-40F vs. JG 77 & JG 51)* 2 Bf 109s lost to P-40's / 0 P40's lost
> 29 March 1943* (USAAF 33 FG P-40L vs. JG 77) *6 Bf 109 lost (4 destroyed +2 crash-landed) *and 3 He 111's and 1 Ju 88* / 2 P-40's lost (1 to AA)
> ...


Nikademus time ago posted him sum from Shore's books on war in Africa this give 522 P-40 losses vs 206 109 losses (my sum for both the books)


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## Schweik (Apr 2, 2018)

Vincenzo said:


> Nikademus time ago posted him sum from Shore's books on war in Africa this give 522 P-40 losses vs 206 109 losses (my sum for both the books)



Interesting, do you have a link to the thread where he posted that? I'd like to look at how he added that up - but it is not too far from what I would have expected from reading both books myself. I'm guessing about three-quarters of those losses are all early model P-40s - Tomahawk and Kittyhawk Mark 1, probably at least half of them from the South African squadrons, vs. 109F and G. You can also add ~ 100 shot down MC 202s (guessing the total) to that number as they were fighting the DAF in the same air battles.

But if you ran the numbers from say the middle of 1942 through where MAW III ends (about April of 1943) I think it's basically even.

When I have the time I plan to put all of Shores numbers into a database so I can do a little bit of a deeper dive & break down for example late model p-40s versus the 109's, and specifically USAAF P-40's vs 109F and G - I have been starting that process and I would say at this point it looks like USAAF P-40 units came out ahead of their Luftwaffe adversaries overall.

It gets harder to sort out though because most days there's multiple aircraft types in action including Spitfires and P38, Fw 190 and MC 205 and so on. The specific days that I posted upthread were all days in which either P-40 squadrons were fighting by themselves, or it was clear from the German records that their planes were shot down by P-40's specifically (quite often the Germans specified what aircraft type they took losses too, and usually at least gave the area where their planes went down, making it possible to cross-check against allied claims).

However, you won't find any days where American piloted P-39's shot down 6 Bf 109's for no losses, and I daresay you won't find many of the same with RAF Hurricanes and not too many with Spit V's. My point was that the P-40s were not the pushover we had once been led to believe in the Med, and specifically late model P-40s were fairly evenly matched to the Bf 109 in particular.

P-39s clearly were not in the Med. P-38s didn't do that well either.

Volume IV of MAW should tell us more.

S


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## Juha2 (Apr 2, 2018)

Elmas said:


> ..._In late February 1943, the Airacobra-equipped 350th FG was withdrawn from first-line service and degraded to coastal patrols with the North-West African Air Force. It is not quite correct to state that "it returned to front line action", as you will see below.
> 
> In fact, the 350th FG Airacobras never were sent back to regular first-line service. From February 1943, their dominant task would remain coastal patrols in the rear area. In November 1943 it was transferred from North Africa to Cagliari/ Elmas, Sardinia."
> _
> ...



I agree with your last sentence but in fact 350th returned to first-line service, on 9 Feb. 1944 it moved to Corsica (much nearer to Italian mainland and more importantly north of the frontline there. In fact in early April 1944 the fighter-bomber P-39s made important contributions to the interdiction of German lines of communications, 0n 2 Apr they badly damaged a bridge over the River Ombrone,S of Grosseto and on 11th destroyed the tracks N of Montalto di Castro. They also combat with 109s and 190s during these missions. see e.g.:2-6 April 1944

Juha

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## DarrenW (Apr 2, 2018)

Shortround6 said:


> The weight alone has a negligible impact on speed. It is the drag associated with the weight that causes the speed reduction.
> For instance if you were add internal ballast with NO exterior changes the only increase in drag would be a very marginal shift in the angle of attack of the wing and the induced drag, since forces on the plane (both drag and lift) go up with the square of the speed adding a few hundred pounds to an aircraft does very little to the speed.
> However, pods, protruding gun barrels, gun ports/troughs, cartridge ejection slots can cause a much bigger disruption of airflow and increased drag.
> 
> ...



It makes perfect sense.


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## XBe02Drvr (Apr 2, 2018)

Shortround6 said:


> When climbing there is a bit of a double whammy. Since climb speed is relatively low, in fact it is a cross/blend between lowest speed with good controllability and the lowest drag speed ( lowest drag caused by lift and lowest drag caused by speed/shape). I am not explaining that well.


It's all about L/D, lift over drag. When you're at the speed which gives you the most lift at the least cost in drag, your excess power and your Rate of Climb are maximum. That's the sweet spot in your pretty little graph. The same principle under slightly different circumstances will give you your best glide.
Cheers,
Wes


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## Shortround6 (Apr 2, 2018)

That is true but on some aircraft the "sweet" spot was a little too close to a speed that gave stability problems at the angle of attack needed for max climb. So max climb speed was sometimes a bit faster (by 20mph or so) over the sweet spot to insure good control response in the climb. 
Again, forces acting on the vertical stabilizer or horizontal stabilizer go up with the square of the speed. going from 160mph to 180mph increases these forces by around 26%


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## XBe02Drvr (Apr 2, 2018)

Shortround6 said:


> I am not sure how bad things really were and how much was "hanger talk". The P-39 certainly had a higher landing speed than a P-40 but then so did a P-47. The P-39 may have been more responsive than some other fighters, more results (change of angle of aircraft)for the same movement or effort on the stick/rudder pedals.
> The P-39 may parallel the B-26? Early pilots transitioning from easier to fly aircraft had trouble with it (and inexperienced instructors didn't help) while later pilots had a better training program?
> Once a plane gets a bad reputation it takes a LOOOOOOONG time to live it down.


Why is it so hard to reconcile the differences between P-39 success in USSR and elsewhere? Let me count the ways. SR6 and others bring up a good point in pilot attitude and training. Pilots in MTO and NA were stuck with what was generally considered an also-ran, likely trained by pilots who detested and feared it, and watched in envy as their colleagues got to fly "the good stuff". This doesn't do good things for morale or esprit de corps, and such conditions don't make for confident, aggressive fighter pilots. Chances are their outfits also weren't high in the pecking order for the resources to keep their aircraft up to date. Add to that a hot humid climate with high density altitudes and an overweight plane with a weak supercharger and a reputation for nasty accelerated stalls and it's understandable why its combat performance might be less than stellar against planes optimized for higher altitudes and thinner air.
Now let's go to the Eastern Front. Here we have Airacobras that have been scientifically analyzed and adapted to the conditions flown by pilots who's prior experience has been in relatively primitive, somewhat shoddily constructed domestic aircraft. It must have seemed like a snazzy imported sports car to them. And its real world battlefield performance was a cut above those tired old dogs in the Med because of the carefully analyzed adaptations it received. The cold dense air optimized it's performance and negated any advantages its more elegant opponents might have had, allowing it to give as good as it got, or even better. In all the performance discussion on this thread there's been very little acknowledgement of the huge difference air density makes in comparative performance other than raw altitude.
Cheers,
Wes

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## ssnider (Apr 3, 2018)

A long time ago I had a conversation over a couple of bears with a pilot that had flown the P-39. P-40 and P-51 in combat against the Japanese. He considered the p-39 to be a huge improvement over the P-36 he was fling before the war. He also said the P-40, overall, was equal to the P-39 in combat and not an improvement. The problem with the P-39 was the tropics and the electrical system which never seemed to be 100 percent functional. No one was worried about accelerated stalls or felt the plane was unstable. On the P-51 he said if they had had them sooner "We all would have been F****** heroes"

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## DarrenW (Apr 3, 2018)

Well this is very interesting....

http://www.wwiiaircraftperformance.org/P-39/P-39M-3_42-4706_FS-M-19-1511-A.pdf











_*The two externally mounted caliber .50 wing guns, their fairing, brackets, and equivalent weight of ammunition were removed. Additional ballast was installed to compensate for this removal....*_
*





*
Difference in speed was 12.5 mph for this particular aircraft, with and without gun pods. But at least we can see that the speed of the P-39Q WITHOUT the wing guns was 13.5 mph SLOWER at the critical altitude of our one and only P-39N test aircraft . But to be fair the P-39Q was ballasted for the additional weight of the guns and ammo, and it weighed almost 600 pounds more than the P-39N at take-off. What do you gentlemen make of this?


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## Dimlee (Apr 3, 2018)

Schweik said:


> Interesting, do you know where the 22 ZAP base was exactly? I thought it was Western Siberia / Central Asia.
> S


22nd ZAP was based mainly in Ivanovo (about 250km NE of Moscow). Also in Kineshma for short period in 1942.
P-39 training was done later in other locations as well, for example, in Azerbaijan.


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## Dimlee (Apr 3, 2018)

XBe02Drvr said:


> It must have seemed like a snazzy imported sports car to them.
> Wes



Agree. 
Higher quality equipment boosted morale, indeed. That was said by Soviet veterans and not only pilots. It cured despair caused by catastrophic losses of early war. It helped soldiers to feel themselves not as a cannon meat hastily prepared for another slaughter but as warriors again. It restored self respect. "Human factor" - which is hard to figure out of charts and tables...

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## XBe02Drvr (Apr 3, 2018)

Dimlee said:


> As for nose guns orientation - interesting hypothesis, but it needs to be verified.


What's to verify? It's a known and obvious fact. Getting the highest percentage of bulletstrikes into a target profile is going to occur if your guns are clustered together and shooting down the sightline to the target, even if there are variances in the trajectories. Witness the P-38 or the A-20/B-25/A-26 strafers. Convergence angle is minimal and is only in one plane, resulting in a much longer "sweet spot" rangewise where the bullet density is maximum. All it takes is one 37MM hit. Game over.
Not like "sawing away" at your target with multiple wing mounted .30s.
Cheers,
Wes

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## swampyankee (Apr 3, 2018)

DarrenW said:


> So are we in agreement that the loaded weight of the Q model was roughly 150-200lbs more than the P-39N (extra weight of guns, ammo, and additional fairings) ? How would an increase like that affect the level speed and climb rate?



Assuming no increase in parasitic drag, a 1% increase in weight will cause about a 1.5% increase in power required for flight at the best rate of climb speed (drag coefficient will remain the same but speed will increase 0.5% and power required is proportional to speed cubed). If the plane had a 1,000 shp engine, and needed 500 shp for level flight before, it would have 500 shp to use for climb. Add 1% to its weight, it now needs 508 shp for level flight, and has only 492 shp for climb, a drop of 1.5%.


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## Dimlee (Apr 3, 2018)

XBe02Drvr said:


> What's to verify? It's a known and obvious fact. Getting the highest percentage of bulletstrikes into a target profile is going to occur if your guns are clustered together and shooting down the sightline to the target, even if there are variances in the trajectories. Witness the P-38 or the A-20/B-25/A-26 strafers. Convergence angle is minimal and is only in one plane, resulting in a much longer "sweet spot" rangewise where the bullet density is maximum. All it takes is one 37MM hit. Game over.
> Not like "sawing away" at your target with multiple wing mounted .30s.
> Cheers,
> Wes



Sorry, we are talking about different things.
I'd like to verify this hypothesis (quoting original message of Schweik):
_"Their aerial gunnery training was mostly oriented toward nose guns and most (except I-16 pilots or those checked out on P-40's or Hurricanes) were not used to wing-guns"_
Schweik's argument is valid, I'm just not sure if it's true. It does require verification since not every "pre P-39" fighter type in VVS had only nose MG. 
But this argument reminded me about another and real feature of VVS pre-war training: deficit of gunnery practice. If we assume that pilots who received P-39 were poorly trained in gunnery, then (probably) central mounted guns were easier for them ? For the obvious reason you stated in your post.


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## XBe02Drvr (Apr 3, 2018)

Dimlee said:


> But this argument reminded me about another and real feature of VVS pre-war training: deficit of gunnery practice.


Didn't VVS pre-war training feature a deficit of all kinds of practice, not just gunnery? Didn't the Japanese in Manchuria in 1938 point out some pilot proficiency deficits in the VVS?
Cheers,
Wes


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## Dimlee (Apr 3, 2018)

Elmas said:


> Still, I cannot understand how a plane like P-39 could have had such a good score against Luftwaffe fighters. Difficult handling, not the best suitable armament...
> 
> Certainly, while in the Western Front Luftwaffe gave precedence to quality, in the Eastern Front took precedence quantity and, probably, the percentage of unskilled LW pilots there was in the East was higher.
> 
> *Or was outstandingly high the skill of Russian pilots?* *Could be, but I doubt*: Ulrich Rudel could ride on a Stuka well into 1944, if not 1945 on the Russian Front...



Edited in bold by me.
We probably should define "skill". Soviet pilots could be good in aerobatics but bad in tactics, better or worse in communication, gunnery, individual initiative, etc.. Then there were management skills at squadron and higher levels. And ability of skilled commanders to withstand pressure from less smart superiors (huge issue in Red Army overall). "Average quality" of VVS is hard to define, this is very complex subject and politically sensitive - yes, until today. My humble opinion (some of my fellow Russians will curse me): average qualification of individual in VVS remained below the counterpart in other major air forces, through all WWII (and probably for most period of Cold War as well). But from summer 1943 and on there was enough "higher than average" personnel to gain superiority, step by step.

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## Dimlee (Apr 3, 2018)

XBe02Drvr said:


> Didn't VVS pre-war training feature a deficit of all kinds of practice, not just gunnery? Didn't the Japanese in Manchuria in 1938 point out some pilot proficiency deficits in the VVS?
> Cheers,
> Wes



It did, especially during the rush of mass training in 1940-early 1941. And Finns in Winter War pointed out the same as well.


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## swampyankee (Apr 3, 2018)

XBe02Drvr said:


> Didn't VVS pre-war training feature a deficit of all kinds of practice, not just gunnery? Didn't the Japanese in Manchuria in 1938 point out some pilot proficiency deficits in the VVS?
> Cheers,
> Wes


I think the Japanese provided those lessons to pilots in several air forces.

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## BiffF15 (Apr 3, 2018)

Dimlee said:


> Edited in bold by me.
> We probably should define "skill". Soviet pilots could be good in aerobatics but bad in tactics, better or worse in communication, gunnery, individual initiative, etc.. Then there were management skills at squadron and higher levels. And ability of skilled commanders to withstand pressure from less smart superiors (huge issue in Red Army overall). "Average quality" of VVS is hard to define, this is very complex subject and politically sensitive - yes, until today. My humble opinion (some of my fellow Russians will curse me): average qualification of individual in VVS remained below the counterpart in other major air forces, through all WWII (and probably for most period of Cold War as well). *But from summer 1943 and on there was enough "higher than average" personnel to gain superiority, step by step.*



And if not previously said, quantity has a quality all of its own.

Cheers,
Biff

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## Shortround6 (Apr 3, 2018)

XBe02Drvr said:


> What's to verify? It's a known and obvious fact. Getting the highest percentage of bulletstrikes into a target profile is going to occur if your guns are clustered together and shooting down the sightline to the target, even if there are *variances in the trajectories*. Witness the P-38 or the A-20/B-25/A-26 strafers. Convergence angle is minimal and is only in one plane, resulting in a much longer "sweet spot" rangewise where the bullet density is maximum. All it takes is one 37MM hit. Game over.
> Not like "sawing away" at your target with multiple wing mounted .30s.
> Cheers,
> Wes



This rather depends on the target, both it's size and what it is doing. 

My own belief is that trajectory is somewhat overrated or over valued when dealing with aircraft gunnery. Maybe for shooting at small fighters it matters. When shooting at even medium bombers? you have hundreds of sq ft of wing area and fuselages that are 4 to 6 ft high. 
The British were pretty poor in gunnery training pre-war and in the early part of the war when they instructed their pilots to open fire on target sleeves at 300yds they found that the pilots were sometimes opening fire at 800-1200yds. 
You need a laser beam to to fix that "trajectory problem", not nose mounted guns. 

Unless it is a head on pass or you are sitting directly on the target's "6" deflection shooting will be required to a greater or lesser extent.
for deflection shooting the time of flight is the more important aspect. If you are shooting ahead or behind (much more likely) the target trajectory doesn't matter. 
I will grant that 'flat' trajectory gun will usually have a low time of flight compared to a high trajectory gun and so the terms can be confused. 

Another problem comparing wing mounted guns is that at times "convergence" didn't really happen at any range. The British and perhaps others deliberately aimed the guns in a wide pattern to increase the chances of hit/s to compensate for the poor gunnery. 
One "official" pattern for the Spitfire even had the 20mm cannon hitting at different heights so as the guns "crossed" over they formed a figure 8 pattern and not a circle or oval. And none of the machine guns were pointed where the cannon were pointed. what an individual pilot may have been able to do is different but unless assigned to one plane constantly mucking about with the "patterns" in different aircraft in the squadron wasn't likely to improve things overall. 

Claiming that fuselage mounted guns were so much more accurate than wing mounted guns often does not take this into account. 

When ground strafing the target is essentially stationary (even 30mph trains and trucks compared to 300mph aircraft) and firing starts further away than the convergence planed for air to air combat. You do need to allow for the pull out 

The Russians and Germans had opposite problems with fuselage mounted guns, for the Russians their 12.7mm machine gun/s have a shorter time of flight than the 20mm cannon does. Not a problem at short range but at long range?
For the Germans the machine guns had longer times of flight than the prop mounted 20mm gun and the prop mounted 20mm gun used ammo of rather different ballistics. Again not a problem at short ranges (under 300 meters) but makes long range gunnery a bit of a joke.

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## drgondog (Apr 3, 2018)

XBe02Drvr said:


> I beg to differ on the twitchiness angle. Twitchiness is usually a low speed/high AOA phenomenon, unless workmanship or shoddy materials has weakened flight controls. The Soviets praised the high speed controllability of the 'Cobra and used tactics that took advantage of it. The twitchiness comes into play when you are foolish enough to get into a high G, energy draining knife fight with a Zero at tropical air densities and altitudes where your aircraft is running out of steam. This also is where dealing with the three separate trajectories of your gun package is at its most vexing.
> Now let's go to the forested plains of NW Russia. (NOT Siberia, BTW). Bitterly cold, air so dense you can cut it with a knife, one less trajectory to deal with, and all your remaining firepower boresighted line of sight. Combat is high speed, down low, and against fighters optimized for altitude, while yours has been carefully adapted and optimized for this environment, and flown by pilots used to living and fighting rough. What more could a poor, maligned venomous snake ask for?
> BTW, the victory tallies in the Lend Lease article don't seem to show high kill numbers against LW bombers and transports. Looks like mostly fighters. Also, not many kills against JU-87s. I thought they were pretty numerous on the Eastern Front. Were they depleted by this time, or was it due to their agility and their tail gunner?
> Cheers,
> Wes


Wes - Stuka's were rarely unescorted. Although agile, they were so slow that they could never disengage from a fighter of any current performance. The firepower of a 109E/F or G was far superior in range and destructive power. Any escape maneuver involved a desperate high G turn or even an initial dive which surely hampered the gunner.

If a Stuka initiates a turn too early, he gives the closing fighter a pretty easy (comparably speaking) deflection shot at fuel/pilot/engine. There was a reason that they converted to FW 190 as fast as they could.

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## Shortround6 (Apr 3, 2018)

DarrenW said:


> Difference in speed was 12.5 mph for this particular aircraft, with and without gun pods. But at least we can see that the speed of the P-39Q WITHOUT the wing guns was 13.5 mph SLOWER at the critical altitude of our one and only P-39N test aircraft . But to be fair the P-39Q was ballasted for the additional weight of the guns and ammo, and it weighed almost 600 pounds more than the P-39N at take-off. What do you gentlemen make of this?



What I get is that the tests were done (or at least written) about 2 months apart, in potentially different weather and with an engine that was going south compared to the first test, not to mention any other wear and tear on the aircraft. 

While interesting any data has to be considered in that light. 

I do like the note at the bottom where they say the XP-63A prototype showed a 110fpm difference in climb with and without pods and "Such a figure is close to the limites of climb determination accuracy".


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## Shortround6 (Apr 3, 2018)

drgondog said:


> If a Stuka initiates a turn too early, he gives the closing fighter a pretty easy (comparably speaking) deflection shot at fuel/pilot/engine. There was a reason that they converted to FW 190 as fast as they could.



I believe a fair number of the JU-87s were operating in a night attack role in the last few years of the war, JU-87Gs and a few others excepted which can skew the results as to losses. The FW 190s taking over the day attack role as you say.


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## drgondog (Apr 3, 2018)

Shortround6 said:


> The weight alone has a negligible impact on speed. It is the drag associated with the weight that causes the speed reduction.
> For instance if you were add internal ballast with NO exterior changes the only increase in drag would be a very marginal shift in the angle of attack of the wing and the induced drag, since forces on the plane (both drag and lift) go up with the square of the speed adding a few hundred pounds to an aircraft does very little to the speed.
> However, pods, protruding gun barrels, gun ports/troughs, cartridge ejection slots can cause a much bigger disruption of airflow and increased drag.
> 
> ...


Hi SR - good chart to discuss L/D and level flight characteristics.

Climbing (and turning) introduce Pressure Drag in a big way - mostly attributable to AOA caused Pressure Drag. In addition Cooling Drag escalated during climb and turn.

Total Drag = Parasite Drag (level flight components of Wing, fuselage, empennage, carb and Radiator ducts, gaps in control surfaces and sheet paneling, friction, exhaust stacks - stuff associated with basic airframe) + Delta Parasite Drag (more level flight components such as cannon/gun ports, radio mast, bomb racks, etc) + Vortex/Pressure Drag due to Angle of Attack = Total Drag (almost done).before Compressibility correction and addition of Induced Drag. 

That said a full blown set of forces on the airframe have not yet been calculated. In late 1930s the concept of expressing practical climb, range and turn estimates required that many items be further categorized into attributes that contribute to Power Available and Power Required. This is where the esoteric calcs including equations for Ram Air, Prop design/configuration/efficiencies and Exhaust Thrust all contributed to Power Available as a function of altitude, velocity, throttle/manifold pressure, fuel type and fuel to air ratios.

.In WWII, at least for US airframe designers of piston engine fighters, the calculations for the Cooling drag of both cooling system and carb intake are derived into a delta Power Required. 

For increments to Power Required, calcs for Cooling Drag factors for both high speed and low speed are derived from Wind Tunnel tests and also the increased drag due to the Prop Vortex (all fuselage, approx. 25-30% of wing) for the higher velocity than free stream and immersed in the vortex.

What emerges is the expression Thrust = Drag reorganized into Power Available and Power Required. In balance, there is equilibrium at top speed, top rate of climb, best turn rate, best cruise speed, etc. Otherwise, there is acceleration until equilibrium is once again attained

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## Peter Gunn (Apr 3, 2018)

All I can say is that after reading through this thread, I have a better understanding of the Dunning–Kruger effect...

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## fubar57 (Apr 3, 2018)

John Cleese explains this effect on Youtube


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## pbehn (Apr 3, 2018)

Peter Gunn said:


> All I can say is that after reading through this thread, I have a better understanding of the Dunning–Kruger effect...


Is that like the Bauschinger effect or more akin to the Jule-Thomson effect?


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## P-39 Expert (Apr 3, 2018)

pbehn said:


> My date of 25 Dec 1943 was itself based on how long a new type aircraft which started to be produced in USA in Dec 1942 would actually be expected to be operational in UK. Shipping and training take much longer than you would think.


The first Thunderbolt combat mission is listed at 4/30/43 and was also the first 8thAF bomber mission with at least 100 planes.


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## P-39 Expert (Apr 3, 2018)

pbehn said:


> Since most P-39s sent to Russia were the N and Q versions, is it possible these were quite well sorted as far as engine and CoG issues went while the earlier versions just shouldn't have been put into service?


Absolutely. After the P-400s were sent to Russia from the British, they began getting P-39Ns and Qs in ealy 1943. Almost all airplanes get better during production (initial bugs get sorted out etc) and the N was the ultimate version performance wise. The Q was just an N with gondola wing guns which hurt speed and climb. Since the Russians removed the wing guns on both they were basically the same plane.


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## pbehn (Apr 3, 2018)

P-39 Expert said:


> Absolutely. After the P-400s were sent to Russia from the British, they began getting P-39Ns and Qs in ealy 1943. Almost all airplanes get better during production (initial bugs get sorted out etc) and the N was the ultimate version performance wise. The Q was just an N with gondola wing guns which hurt speed and climb. Since the Russians removed the wing guns on both they were basically the same plane.


The planes that the British got were not sorted then? especially in the area of tail shape/surface area and CoG

The planes delivered to England for test all had a modified non standard rudder.
Tested on the second British Airacobra (AH571) was a revised rudder of more angular shape and less area. Although the aircraft was delivered to England in this form, this rudder was not adopted as standard. A very small dorsal fin just ahead of the rudder became a standard feature of the RAF Airacobras and was also a distinguishing feature of the American P-39D and subsequent versions

CoG was adjusted again even on the P-39N
The 500 P-39Ns were followed by 900 P-39N-1s (Model 26C). These differed only in some minor internal changes which altered the location of the center of gravity.


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## Schweik (Apr 3, 2018)

XBe02Drvr said:


> Didn't VVS pre-war training feature a deficit of all kinds of practice, not just gunnery? Didn't the Japanese in Manchuria in 1938 point out some pilot proficiency deficits in the VVS?
> Cheers,
> Wes



I would say this was the case for most Allied pilots period. American, British, Australian, New Zealand, French, South African and Soviet. Gunnery training seemed to be rare, in fact it was very common for pilots right out of flight school to have barely enough training on their new (much higher performance) fighters to take off and land (and quite often, clearly not enough because there were a huge number of takeoff and landing accidents in the early years of the war especially in 1940-41)

S

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## P-39 Expert (Apr 3, 2018)

Shortround6 said:


> complete and utter bollocks.
> 
> Just look at the number of books, articles and websites that claim the XP-39 flew at 390-400mph and climbed to 20,000ft in 5 minutes before the NACA ruined it by taking out the turbo charger. The P-39 may have had more complete trash written about it than practically any other fighter if we count the pages of wink and bandwidth. The XP-39 never flew at full power due to a feared drive shaft problem before the turbo was taken out. A new, heavier drive shaft was installed in all later models. What is interesting is that nobody can point to WHEN this supposed flight of 390mph and climb to 20,000f took place, no date is ever given unlike many other planes where early flights and achievements are given. Also no pilots name is mentioned. Some books/accounts even go so far as to claim it was done on the first flight. Which, given the chronic overheating problems the XP-39 had is hardly creditiable let alone the sometimes mentioned flight duration of 20 minutes for the first flight.
> Test pilot took-off retracted landing gear, immediately went into a full power climb to 20,000ft, leveled off, accelerated to 390mph, slowed down, descended to airfield, lowered landing gear and landed, all in 20 minutes and in an airplane that had never flown before??????
> ...


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## pbehn (Apr 3, 2018)

P-39 Expert said:


> The first Thunderbolt combat mission is listed at 4/30/43 and was also the first 8thAF bomber mission with at least 100 planes.


Exactly my point, when did they first roll out of the factory in USA?


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## P-39 Expert (Apr 3, 2018)

Glider said:


> I do get a little annoyed when you keep saying the British tried to get out of the contract. Have you got any evidence to support that, if so put it up or stop saying it.


Well, they DID get out of the contract with Bell and Lockheed. Whether it was Pearl Harbor causing a need for planes by the AAF or just refusal to accept, the British did not buy those planes. Lockheed just refitted the undelivered British order with turbos and handed propellers and they became P-38Fs.


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## P-39 Expert (Apr 3, 2018)

pbehn said:


> The planes that the British got were not sorted then? especially in the area of tail shape/surface area and CoG
> 
> The planes delivered to England for test all had a modified non standard rudder.
> Tested on the second British Airacobra (AH571) was a revised rudder of more angular shape and less area. Although the aircraft was delivered to England in this form, this rudder was not adopted as standard. A very small dorsal fin just ahead of the rudder became a standard feature of the RAF Airacobras and was also a distinguishing feature of the American P-39D and subsequent versions
> ...


Only one plane had the modified rudder etc. (SN AH-571) for the performance test.


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## P-39 Expert (Apr 3, 2018)

pbehn said:


> Exactly my point, when did they first roll out of the factory in USA?


The prototype rolled out in Dec '41.


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## pbehn (Apr 3, 2018)

P-39 Expert said:


> Well, they DID get out of the contract with Bell and Lockheed. Whether it was Pearl Harbor causing a need for planes by the AAF or just refusal to accept, the British did not buy those planes. Lockheed just refitted the undelivered British order with turbos and handed propellers and they became P-38Fs.


Can you stop banging on about this, at the time the P39s were on the way to UK, the UK had loaded 40 Hurricane MkIIs and 550 mechanics/pilots to defend Murmansk. In total 3,000 Hurricanes and 1,400 Spitfires were sent. British and Canadian tanks shipped to Russia totalled over 5,000 and were first used in November 1941 on the Volga. The contract for 675 fighters is absolutely utterly insignificant in terms of cost. The significance really was they were available and crated up and of far more use to the USA and the Russians than they were to the British.


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## pbehn (Apr 3, 2018)

P-39 Expert said:


> Only one plane had the modified rudder etc. (SN AH-571) for the performance test.


So the aircraft on the performance test was unique?


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## Shortround6 (Apr 3, 2018)

pbehn said:


> So the aircraft on the performance test was unique?



One might say that 

See post 961 on page 49 for a LIST of differences between the test aircraft and a noraml production aircraft. 

Also consider that fabric covered control surfaces "ballooned" at high speed and created drag so the smaller you could make them the less drag you had.

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## Peter Gunn (Apr 3, 2018)

P-39 Expert said:


> *SNIP*
> 
> Lockheed just refitted the undelivered British order with turbos and handed propellers and they became P-38Fs.


Or you know... they didn't and they actually were taken by the U.S.A.A.F. as the P-322-I and P322-II as advanced trainers ( 143 according to Wiki ). The rest of the French/RAF order were _completed_ as P-38F's ( 420+/- ). Semantics perhaps but still...

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## pbehn (Apr 3, 2018)

Shortround6 said:


> One might say that
> 
> See post 961 on page 49 for a LIST of differences between the test aircraft and a noraml production aircraft.
> 
> Also consider that fabric covered control surfaces "ballooned" at high speed and created drag so the smaller you could make them the less drag you had.


I saw it (good post), now imagine you are the fresh faced bunch of pilots presented with your new steeds and one has a different tail to the others? Imagine you are the clients contract manager and you notice that this cut down version was the one tested?


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## XBe02Drvr (Apr 3, 2018)

P-39 Expert said:


> Lockheed just refitted the undelivered British order with turbos and handed propellers and they became P-38Fs.


Hey guy, it takes more than a "handed propeller" to create a counter rotating airplane. If that's all you do, you're going to have permanent reverse thrust on one side. The prop doesn't determine the engine's direction of rotation.
Cheers,
Wes

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## pbehn (Apr 3, 2018)

XBe02Drvr said:


> Hey guy, it takes more than a "handed propeller" to create a counter rotating airplane. If that's all you do, you're going to have permanent reverse thrust on one side. The prop doesn't determine the engine's direction of rotation.
> Cheers,
> Wes


As far as I can see there was no "cancelling" of contracts they were just re assigned as Lend Lease and sent to wherever needed which is why some ended up operated in the far east with British equipment on board.


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## Shortround6 (Apr 3, 2018)

The order for the P-38s was changed before many of the planes were built. There was NO refitting of already built or even partially built airframes with turbo-chargers. 120 of the P322 were fitted with handed engines (-27/-29 same as P-38D and E )but no turbos as trainers. 
British and American airframes had probably been slotted into a production schedule in alternating batches. So many American planes than so many British then so many American and so one.

In any case according to at least one source the 524 Lighting IIs were broken up as one delivered to the British. 28 delivered as P-38F-13s, 121 delivered as P-38-15s, 174 as P-38G-13s and 200 as P-38G-15s. other accounts may differ or show planes diverted to photo recon? In any case the last of the "British" P-38s were being delivered in the fall/winter of 1942 and the US was glad to get every one of them. This was over 2 years after the initial order.


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## Shortround6 (Apr 3, 2018)

pbehn said:


> I saw it (good post), now imagine you are the fresh faced bunch of pilots presented with your new steeds and one has a different tail to the others? Imagine you are the clients contract manager and you notice that this cut down version was the one tested?


 
Not sure if I am more worried about the modified tail or the 20+ coats of paint sealing up everything or the plastic wood





filling around the cockpit


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## fubar57 (Apr 3, 2018)

Yikes!!!!


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## pbehn (Apr 3, 2018)

Shortround6 said:


> Not sure if I am more worried about the modified tail or the 20+ coats of paint sealing up everything or the plastic wood
> View attachment 488406
> 
> filling around the cockpit


My experience of stuff like that is that after a while it cracks and falls out, I imagine that test aircraft looked very sad by the time they finished with it in UK.


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## tomo pauk (Apr 3, 2018)

P-39 Expert said:


> ...
> Lockheed just refitted the undelivered British order with turbos and handed propellers and they became P-38Fs.



What is source for this?


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## CORSNING (Apr 3, 2018)

pbehn said:


> Great post, the proof of that particular pudding is the Mustang Mk I (P51A) bigger and heavier than the P39 but faster, it actually did do 400MPH with and Allison engine, and the P51B bigger and heavier than the Spitfire but faster at all altitudes on the same engine. Rates of climb may have been slightly lower but not seriously behind.




http://www.wwiiaircraftperformance.org/P-39/P-39Q-30-1400.jpg

I'm just saying,


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## P-39 Expert (Apr 3, 2018)

pbehn said:


> So the aircraft on the performance test was unique?


Oh yes, I think Mr. Shortround detailed it pretty good right out of the book. They had other P-400s but Bell modified this one and got 393mph out of it then the others were going 370mph or so. Actually met the contract for speed. But it was only one plane.


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## tomo pauk (Apr 3, 2018)

pbehn said:


> Great post, the proof of that particular pudding is *the Mustang Mk I (P51A)* bigger and heavier than the P39 but faster, it actually did do 400MPH with and Allison engine, and the P51B bigger and heavier than the Spitfire but faster at all altitudes on the same engine. Rates of climb may have been slightly lower but not seriously behind.



(my bold)
The Mustang I was XP-51, Mustang Ia was P-51 (4 cannons, many times also cameras on the P-51; still no drop tanks), Mustang II was P-51A (1943, better engine, 415 mph, 4 HMGs, drop tanks facility). 
Mustang II joined RAF in June 1943, 1st combat was in September of 1943.

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## P-39 Expert (Apr 3, 2018)

CORSNING said:


> http://www.wwiiaircraftperformance.org/P-39/P-39Q-30-1400.jpg
> 
> I'm just saying,


Yep, 400mph at 16000'.


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## P-39 Expert (Apr 3, 2018)

tomo pauk said:


> What is source for this?


The Lockheed P-38 by Warren M. Bodie. Big book with lots of pictures. Does have a detailed manufacturing schedule though.


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## P-39 Expert (Apr 3, 2018)

pbehn said:


> Can you stop banging on about this, at the time the P39s were on the way to UK, the UK had loaded 40 Hurricane MkIIs and 550 mechanics/pilots to defend Murmansk. In total 3,000 Hurricanes and 1,400 Spitfires were sent. British and Canadian tanks shipped to Russia totalled over 5,000 and were first used in November 1941 on the Volga. The contract for 675 fighters is absolutely utterly insignificant in terms of cost. The significance really was they were available and crated up and of far more use to the USA and the Russians than they were to the British.


Obviously I'm not smart enough to make this up, are you telling me that you never heard any of this before? Honest?


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## P-39 Expert (Apr 3, 2018)

DarrenW said:


> Well this is very interesting....
> 
> http://www.wwiiaircraftperformance.org/P-39/P-39M-3_42-4706_FS-M-19-1511-A.pdf
> 
> ...


Glad you asked. Weight wasn't the important part, it was the drag of the external gunpods that reduced top (and all) speeds.


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## pbehn (Apr 3, 2018)

tomo pauk said:


> (my bold)
> The Mustang I was XP-51, Mustang Ia was P-51 (4 cannons, many times also cameras on the P-51; still no drop tanks), Mustang II was P-51A (1943, better engine, 415 mph, 4 HMGs, drop tanks facility).
> Mustang II joined RAF in June 1943, 1st combat was in September of 1943.


I thought the difference between the Mustang I and IA was the IA was a later order specifying cannon etc the passing of the lease lend act, The Mustang Mk II was with the better engine. Screws everything up when every damned plane is called a Mustang


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## Shortround6 (Apr 3, 2018)

P-39 Expert said:


> Obviously I'm not smart enough to make this up, are you telling me that you never heard any of this before? Honest?


 I have never heard of the British trying to get out of the contract in order to change from cash to lend lease and/or specifying things to reduce the performance in order to do so.


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## tomo pauk (Apr 3, 2018)

P-39 Expert said:


> The Lockheed P-38 by Warren M. Bodie. Big book with lots of pictures. Does have a detailed manufacturing schedule though.



On what page it is said that people at Lockheed just installed turbo system and different engines on existing A/C to come out with P-38Fs? Footnote that proves it?


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## pbehn (Apr 3, 2018)

P-39 Expert said:


> Obviously I'm not smart enough to make this up, are you telling me that you never heard any of this before? Honest?


I have heard all sorts of conspiracy theories before, as I have told you twice before the tin pot contract for 675 underperforming aircraft didn't amount to a bag of beans, there was 1.5 million tons of shipping lost in the "first happy time" which was around this period. Since the USA, UK and Russia were all at war they moved what they had to where it would be most useful. Note the British didn't receive all the Mustang Mk1 or Mk1As they ordered either, were they "weaselling" out of that contract too?


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## pbehn (Apr 3, 2018)

P-39 Expert said:


> Yep, 400mph at 16000'.


Bingo! so it was possible with all the specified equipment, without woodfiller and twenty coats of paint. The British requests were in no way unreasonable or unattainable, just that Bell couldn't do it when they said they could.


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## Vincenzo (Apr 3, 2018)

Schweik said:


> Interesting, do you have a link to the thread where he posted that? I'd like to look at how he added that up - but it is not too far from what I would have expected from reading both books myself. I'm guessing about three-quarters of those losses are all early model P-40s - Tomahawk and Kittyhawk Mark 1, probably at least half of them from the South African squadrons, vs. 109F and G. You can also add ~ 100 shot down MC 202s (guessing the total) to that number as they were fighting the DAF in the same air battles.
> 
> S



I've not the link but i can paste that i've saved

"From Shores' Fighters over the Desert , I calculated the following:

168 x Tomahawk for 47 x Bf-109
223 x Kittyhawk for 97 x Bf-109
11 x P-40F for 4 x Bf-109

summary: 402:148 (3.7:1)

From Shores' Fighters over Tunisia:

62 x Kittyhawk for 25 x Bf-109
58 x P-40F for 33 x Bf-109

summary: 120:58 (2.1:1)"

and that on 202
"I discerned the following from Shores for the 1940-2 fighting: 
the MC-202: (same: P40/202 kills vs each other)

23:35

On the surface, the 202 wins the kill contest. The ratio might be more....or even less because a major issue with the NA fighting was that the similarity in looks between it and the 109. It was suggested more than once in Shores' tombs that some combats credited with "109s" were in fact 202's. Specifically it was suggested in more than one place that kills credited to 109's were in fact 202's."


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## Schweik (Apr 3, 2018)

Vincenzo said:


> I've not the link but i can paste that i've saved
> 
> "From Shores' Fighters over Tunisia:
> 
> ...



Shores seems to have found more data since he wrote those, because the P-40F losses definitely doesn't match the data in MAW II and III

S


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## Shortround6 (Apr 3, 2018)

P-39 Expert said:


> Oh yes, I think Mr. Shortround detailed it pretty good right out of the book. They had other P-400s but Bell modified this one and got 393mph out of it then the others were going 370mph or so. Actually met the contract for speed. But it was only one plane.


 Gee, Bell never had a 390mph prototype, regardless of whether or not it had guns.
The XP-39B first flew on Nov 25th 1939 and belly landed on Jan 6th 1940, repaired and flown some more it crashes after 28 total hours.
The First YP-38 flies in Sept 13th 1940, also unarmed and around 3 month after the French and British order. One day after first flight of YP-38 the US orders 623 AIrcobras with wing guns and leak proof tanks.
Armed YP-38 makes 368mph? with 1090hp.





at 6592 lbs. Please note plane in picture has no guns

who thought an extra 60hp was going to add over 20mph to the plane? especially with extra weight and extra equipment?

WHy did Bell build that one-off special and devote all that time to the drag reduction measures and special paint?

ANd it's the British fault the production machines could not come close to the contract speed?

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## Vincenzo (Apr 3, 2018)

Schweik said:


> Shores seems to have found more data since he wrote those, because the P-40F losses definitely doesn't match the data in MAW II and III
> 
> S



what are the data of MAW II&III?


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## Schweik (Apr 3, 2018)

Vincenzo said:


> what are the data of MAW II&III?



I haven't added it all up yet but I'll try to this weekend. Like I said already though so far it looks like P-40F came out ahead, at least the US units.


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## DarrenW (Apr 3, 2018)

P-39 Expert said:


> Glad you asked. Weight wasn't the important part, it was the drag of the external gunpods that reduced top (and all) speeds.



Hey P-39 man, why haven't you voted yet?

Best US escort fighter in ETO during 1943?

Or have you finally succumbed to the avalanche of facts and voted for something other than the P-39?  And you seriously should consider joining in the conversation as well because the Airacobra is sorely missing it's fan base over there...


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## pbehn (Apr 3, 2018)

Shortround6 said:


> Gee, Bell never had a 390mph prototype, regardless of whether or not it had guns.
> The XP-39B first flew on Nov 25th 1939 and belly landed on Jan 6th 1940, repaired and flown some more it crashes after 28 total hours.
> The First YP-38 flies in Sept 13th 1940, also unarmed and around 3 month after the French and British order. One day after first flight of YP-38 the US orders 623 AIrcobras with wing guns and leak proof tanks.
> Armed YP-38 makes 368mph? with 1090hp.
> ...


In all this much seems to hang on what the British did or didn't, should and shouldn't have believed. Well the Spitfire was about 30MPH faster than the Hurricane so engine power isn't proof of performance. By the time the P-39 arrived the Spitfire MkV was in service with the MkI an Mk II already retired from front line service. For example, along with NAA paying a lot of attention to cooling drag and also low drag wing profiles the method of construction and attention to joints probably meant that Bells filling and painting only achieved what NAA did on every aircraft. This is not unreasonable to expect, there were efforts to do the same on the Spitfire with different rivets etc, but its harder to do when production has started. Things like the Mosquito and P51, FW190 was what most would reasonably expect of a new aircraft in 1941.


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## Shortround6 (Apr 3, 2018)

For me part of the problem is claiming the XP-39 flew at 390mph in April of 1939.
This is around 60mph faster than the XP-40. 
It is almost 30mph faster than MK I Spit with wooden prop and the SPit won't get even a two pitch prop for several more months. 
The only non-race plane in the world that fast is the P-38 using two engine with turbos. 

Now with new evidence (or actually LACK of evidence/documentation) it is very unlikely the XP-39 ever came anywhere near that. 
So basically the Bell sales team was still going by engineering estimates (and wind tunnel data) and darn little flight testing when marketing the P-39 to the French and British. However the 390mph speed had been announced in a number of magazines of the time. 
in fact a Feb 1940 issue of flight magazine describes the P-39 as a 400mph plus machine 
bell aircraft | 1940 | 0526 | Flight Archive

with a picture of the XP-39B.
Granted in war time a bit of exaggeration was good propaganda.


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## pbehn (Apr 3, 2018)

Shortround6 said:


> For me part of the problem is claiming the XP-39 flew at 390mph in April of 1939.
> This is around 60mph faster than the XP-40.
> *It is almost 30mph faster than MK I Spit with wooden prop *and the SPit won't get even a two pitch prop for several more months.
> The only non-race plane in the world that fast is the P-38 using two engine with turbos.
> ...



I agree S/R but I don't think it is unreasonable for it to be believed, bearing in mind the rate of progress at the time.


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## Shortround6 (Apr 3, 2018)

pbehn said:


> I agree S/R but I don't think it is unreasonable for it to be believed, bearing in mind the rate of progress at the time.



Well, the British took the Bell figures on faith, got burned and now we have people blaming the British for not wanting to buy/take delivery of the planes that wouldn't meet the contract specifications.


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## pbehn (Apr 3, 2018)

Shortround6 said:


> Well, the British took the Bell figures on faith, got burned and now we have people blaming the British for not wanting to buy/take delivery of the planes that wouldn't meet the contract specifications.


I don't even believe they did. The British were disappointed with the performance but the test says it could be used at low level. The USA stopped shipments of many types because it wanted planes for themselves, with the invasion of Russia, the Russians they desperately wanted planes. Cancelling the contract is the easiest way to sort things out on paper especially since a lot of them were crated up and could be shipped anywhere. Since Russia's need would obviously be long term the British couldn't rely on it being supplied so took none (Just my opinion)


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## Peter Gunn (Apr 3, 2018)

I said it earlier in this thread but I will say it again.

North American promised a better P-40 and man did they ever deliver!

Bell promised a 400 MPH interceptor and to quote John Wayne "I've been promised a posse, which I figure will be looong on promise and short on posse."

Spin it any way you want, the P-39 had nothing to offer in the ETO for either the 8th and 9th AF or the RAF.

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## buffnut453 (Apr 3, 2018)

Frankly, I think it's time to wind this thread down. We've asked multiple times for evidence of the British "weaseling out of the contract" but all we got in response was "What would you do if you could get the planes for free?" The implausible timelines and overall lack of performance have been discussed ad nauseum and yet we get dragged back to selective opposition airframes and a small subset of performance metrics. In short, we're going nowhere...in fact it's gotten so bad people are repeating info already posted on an entirely separate "P-40 vs Me109" thread. I think it's time I took up knitting, tiddly winks, bus ticket collecting or under-water basket-weaving (full combat version, of course!).

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## Greg Boeser (Apr 3, 2018)

Well, the original Q was whether the P-39 could handle the Zero. 
I think we agree that the P-39D/F/P-400 of 1942 lacked the necessary attributes to overcome the disadvantages of inexperienced pilots, lack of sufficient warning to scramble to intercept altitude, insufficient range, lack of spare parts, lack of coordination within air force, etc. In mid 1943, when the improved performance of the P-39N came available, it was hampered by a lack of opposition because the P-38s had "moved the fight out of the combat radius of shorter ranged fighters."

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## XBe02Drvr (Apr 4, 2018)

Shortround6 said:


> plastic wood
> 
> 
> 
> ...


TSK! TSK! Never say "plastic wood" or "Bondo" within earshot of an airplane!! In mech school we were reprimanded if either of those words were heard. "Airflow smoothing compound" is the professional and approved terminology. If the dirty words were heard by the wrong people you could be asked for the PMA number and official documentation approving its use.
Cheers,
Wes


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## XBe02Drvr (Apr 4, 2018)

I'm with buffnut and Greg Boeser. Let's call it a day. It's been entertaining and educational, but it's degenerating into a Lufberry orbitting around the same repeated arguments. I think any possible convincing has already happened, so what's to gain?
Cheers,
Wes


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## Juha2 (Apr 4, 2018)

Greg Boeser said:


> Well, the original Q was whether the P-39 could handle the Zero.
> I think we agree that the P-39D/F/P-400 of 1942 lacked the necessary attributes to overcome the disadvantages of inexperienced pilots, lack of sufficient warning to scramble to intercept altitude, insufficient range, lack of spare parts, lack of coordination within air force, etc. In mid 1943, when the improved performance of the P-39N came available, it was hampered by a lack of opposition because the P-38s had "moved the fight out of the combat radius of shorter ranged fighters."



More or less so but one can add that at least with V Fighter Command P-39 had its brief period of glory in the summer of 1943, according to John Stanaway in his part of Osprey's P-39 Aces between Feb and Aug 1943 P-39 pilots claimed more than 40 of the 50 kills credited to USAAF units between these months. What they in reality exactly achieved, I cannot check but definitely they gave some bloody noses to the Japanese in Aug 1943.

Juha


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## fubar57 (Apr 4, 2018)

XBe02Drvr said:


> I'm with buffnut and Greg Boeser. Let's call it a day. It's been entertaining and educational, but it's degenerating into a Lufberry orbitting around the same repeated arguments. I think any possible convincing has already happened, so what's to gain?
> Cheers,
> Wes



In agreement but you just know it will be dragged and kicked until we all agree that the P-39N was the best aircraft there ever was


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## XBe02Drvr (Apr 4, 2018)

fubar57 said:


> In agreement but you just know it will be dragged and kicked until we all agree that the P-39N was the best aircraft there ever was


Sorry, I just can't stretch my credulity that far. You know, my dad worked at Bell Niagara in '44 and '45 and he never had anything good to say about the place. He had two part time jobs; afternoons he worked for the government as a DCAS inspector, and evenings he worked for Bell as a roving security patrol. A "double agent" if you will. His comments reminded me of my brief stint at Eastern Airlines: hate and discontent the order of the day. "Do onto others before they can do onto you!"
Cheers,
Wes


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## Elmas (Apr 4, 2018)

P-39 burning at Alghero Airport for a landing accident, 1944.






Another landing accident at Alghero Airport. Pilot arrived short after the engine lost all his oil a few miles from the airport.
The Pilot, on the wing, is fulfilling the accident form...


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## Elmas (Apr 4, 2018)

One question remains: why P-39 (apparently) performed so well with Red Army "in an air-air role" and was so frankly hated by U.S., British, Italian and (possibly, I have no information) French Pilots?
Some answers have been given, but not completely explanatory, by my personal point of view.


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## Peter Gunn (Apr 4, 2018)

buffnut453 said:


> Frankly, I think it's time to wind this thread down. We've asked multiple times for evidence of the British "weaseling out of the contract" but all we got in response was "What would you do if you could get the planes for free?" The implausible timelines and overall lack of performance have been discussed ad nauseum and yet we get dragged back to selective opposition airframes and a small subset of performance metrics. In short, we're going nowhere...in fact it's gotten so bad people are repeating info already posted on an entirely separate "P-40 vs Me109" thread. I think it's time I took up knitting, tiddly winks, bus ticket collecting or under-water basket-weaving (full combat version, of course!).


I agree, there are better things to attend to, after all, it is time to give my goldfish his weekly bath.


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## drgondog (Apr 4, 2018)

tomo pauk said:


> (my bold)
> The Mustang I was XP-51, Mustang Ia was P-51 (4 cannons, many times also cameras on the P-51; still no drop tanks), Mustang II was P-51A (1943, better engine, 415 mph, 4 HMGs, drop tanks facility).
> Mustang II joined RAF in June 1943, 1st combat was in September of 1943.


Tomo - worth noting that all the P-51-1 (and -2) retained by AAF save the two set aside for XP-51B, were modified for Tac Recon. The -1 had the mod performed at Inglewood, all the rest were by Depots.

Also worth noting that the A-36 wing was the precursor for the P-51A/Mustang II. Eliminate the dive brake but all internal plumbing and controls for the bomb/fuel tank rack were passed to the P-51A and B/C with minor changes (landing light, pitot tube, etc).

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## tomo pauk (Apr 4, 2018)

Elmas said:


> One question remains: why P-39 (apparently) performed so well with Red Army "in an air-air role" and was so frankly hated by U.S., British, Italian and (possibly, I have no information) French Pilots?
> Some answers have been given, but not completely explanatory, by my personal point of view.



P-39 offered better performance than contemporary Soviet fighters, fit & finish was better, radios were better while being actually available. Soviets didn't needed long range as much that was required by US, while UK have had better performers to choose from.
I don't think that Western pilots hated P-39 that much.

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## Peter Gunn (Apr 4, 2018)

drgondog said:


> Tomo - worth noting that all the P-51-1 (and -2) retained by AAF save the two set aside for XP-51B, were modified for Tac Recon. The -1 had the mod performed at Inglewood, all the rest were by Depots.
> 
> Also worth noting that the A-36 wing was the precursor for the P-51A/Mustang II. Eliminate the dive brake but all internal plumbing and controls for the bomb/fuel tank rack were passed to the P-51A and B/C with minor changes (landing light, pitot tube, etc).


You see, this is how these threads should progress. P-39 blah blah blah, get the second string junk out of the way and let the thread evolve to the real meat and potatoes of enlightened WWII discussion. The Mustang.

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## Elmas (Apr 4, 2018)

tomo pauk said:


> P-39 offered better performance than contemporary Soviet fighters, fit & finish was better, radios were better while being actually available. Soviets didn't needed long range as much that was required by US, while UK have had better performers to choose from.
> I don't think that Western pilots hated P-39 that much.




Hurricanes, Spitfires and all other western airplanes sent to USSR_ "offered better performance than contemporary Soviet fighters, fit & finish was better, radios were better while being actually available. Soviets didn't needed long range as much that was required by US..."_.

Or Hurricanes and Spitfires were delivered just in the most basical form? It seems we are talking about sports cars, here..._"Where is the coffee cup holder"_?

The only WWII airplane whose Pilots didn't organize an association after the war, AFAIK...

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## Schweik (Apr 4, 2018)

Elmas said:


> Hurricanes, Spitfires and all other western airplanes sent to USSR_ "offered better performance than contemporary Soviet fighters, fit & finish was better, radios were better while being actually available. Soviets didn't needed long range as much that was required by US..."_.
> 
> The only WWII airplane whose Pilots didn't organize an association after the war, AFAIK...



I covered this in an earlier post. in addition to what was mentioned (radios, build quality),


P-39s arrived new unlike most of the Hurricanes, P-40's they got up to that point

P-39 had a nose gun like other Soviet fighters so was familiar to Russian pilots preferred type of gunnery

Soviets did a 4 month training / maintenance workup on the P-39 prior to introducing it to combat (something they didn't do with any other type as far as I know). They did extensive modifications - removing the wing guns but also a lot of maintenance related things.

They had spare engines and spare parts for P-39's (this and the work-up eliminatated most of the problems experienced previously with the P-40 and Hurricane)

Range and ceiling were not really a factor
P-39 could out-dive Bf 109 which no other Soviet fighter could do
Soviet pilots were used to 'twitchy' planes. I-16, Yak 1, LaGG-3, MiG-3, etc.
It's worth noting, the Soviets also did well with P-40's, though they had more maintenance problems with them.

All of this and more is covered in the Lend Lease Aircraft article on the P-39

Early Cobra's in Soviet Aviation



> Or Hurricanes and Spitfires were delivered just in the most basical form? It seems we are talking about sports cars, here..._"Where is the coffee cup holder"_?



Not sure about the Spitfires but the Hurricanes and P-40's were in many cases already worn out from combat when they were sent to the Soviets

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## Schweik (Apr 4, 2018)

On the Spits, see

Spitfires over the Kuban


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## tomo pauk (Apr 4, 2018)

Elmas said:


> Hurricanes, Spitfires and all other western airplanes sent to USSR_ "offered better performance than contemporary Soviet fighters, fit & finish was better, radios were better while being actually available. Soviets didn't needed long range as much that was required by US..."_.
> 
> Or Hurricanes and Spitfires were delivered just in the most basical form? It seems we are talking about sports cars, here..._"Where is the coffee cup holder"_?
> 
> The only WWII airplane whose Pilots didn't organize an association after the war, AFAIK...



There was no Yak-1 association, no La-5 association, no Ki-43 association IIRC. Fiat G.50 association?
Hurricanes certainly did not offered better performance equal to the contemporary Soviet fighters from 1941 on. Stalin was also clamoring for more Spitfires (that was not better under 4 km than P-39), while declaring Hurricanes and P-40s not as good. Most of the Spitfires delivered were with 1-stage Merlin.
There was no such thing as "all other western A/C offering better performance than Soviet fighters", since there was o F4U there, no P-51s were sent to the Soviet Union (apart one Mustang I for tests), no P-38, no Typhoon, no Tempest, not even the F6F. The P-47 was not that good under 4 km, and only 200 were shipped, vs. thousands of P-39s. P-40 will not be as good as P-39 under 4 km, provided same generation of engines is installed. P-63 was probably better, was delivered in numbers, but it was too late to matter, and 1st examples were deemed by Soviets as with too weak fuselage.

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## Schweik (Apr 4, 2018)

tomo pauk said:


> P-40 will not be as good as P-39 under 4 km, provided same generation of engines is installed.



Disagree with that one! Maybe we need to start a P-40 vs. P-39 thread.

Stalin's comments aside, the main issue the Soviets had with the P-40 was with maintenance. They did quite well with the ones they got until the engines wore out ,there were ~40 Russian P-40 aces and 3 double HSU recipients flying them. most of the P-40 units became guards regiments. None of this is true for the Hurricane as far as I know.

Golodnikov noted that the p-40 could out-turn the Yak 7 and could handle the Bf 109 well into 1943.

He was probably flying later (P-40K or M) versions though. And he did still prefer the P-39. Quote from the interview:

"_A. S. Nikolay Gerasimovich, how would you evaluate the speed, rate of climb, acceleration, and maneuverability of the P-40? Did it suit you?

* N. G. * I say again, the P-40 significantly outclassed the Hurricane, and it was far and away above the I-16. 
Personally speaking, the P-40 could contend on an equal footing with all the types of Messerschmitts, almost to the end of 1943. If you take into consideration all the tactical and technical characteristics of the P-40, then the Tomahawk was equal to the Bf-109F and the Kittyhawk was slightly better.

Its speed and vertical and horizontal maneuver were good. It was fully competitive with enemy aircraft.
As for acceleration, the P-40 was a bit heavy, but when one had adjusted to the engine, it was normal.
When the later types Bf-109G and FW-190 appeared, the P-40 Kittyhawk became somewhat dated, but not by much. An experienced pilot could fight an equal fight with it._

_I flew somewhere around 50 combat sorties and participated in 10�12 aerial engagements in the P-40. Then the regiment became the next in line to replace its equipment�for the P-39 Airacobra._"

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## Schweik (Apr 4, 2018)

Some interesting commentary by Golodnikov on the 37mm gun in the P-39
_
Part 3

* A. S. Was a 37mm cannon necessary? Wasn�t this too large a caliber for a fighter? You had so few rounds of ammunition. And wasn�t its rate of fire slow?*

* N. G. * One cannot say that the 37mm cannon was a disadvantage or an advantage. Look at it from this perspective. The M-6 cannon had its strong and weak points. One had to take advantage of the strong points and compensate, as much as possible, for its weaknesses.

These were the weaknesses: 1. Low rate of fire. 8 rounds/second [this is incorrect�the correct rate is slightly over 2 rounds/second (130 rounds/minute) � J.G.] This is indeed a low rate of fire.

2. The ballistics of the projectile were abysmal. The flight trajectory of the projectile was arching, which required large lead angles. But again this was at long ranges, especially when firing at ground targets. When firing at ground targets we had to apply two rings of the sight for lead.

3. Minimal ammunition supply. Thirty rounds.

All these deficiencies could be compensated for by proper selection of firing range. If one fired from 70�50 meters, there was sufficient rate of fire, the ballistics at this range were acceptable, and the lead required was minimal. Thus, all the weaknesses of the 37mm cannon listed above revealed themselves only at long ranges.

Now regarding the strengths: 1. The projectile was very powerful. Normally, one strike on an enemy fighter and he was finished! In addition, we fired this cannon at other types of targets. Bombers, vessels at sea. The 37mm cannon was very effective against these targets.

Here is an example. Our patrol torpedo boats had torn apart a German convoy. The majority of them had in some way or other been damaged, but they were withdrawing. One patrol boat was heavily damaged and lagging behind a bit. German �hunter� boats were closing in on it. One of them moved in either to kill or capture it. There were eight of us; my squadron commander Vitya Maksimovich, had flown out in pair slightly ahead of us to reconnoiter the convoy and I was leading the other six. We were listening to the conversations of the PT boat crews (the PT boats, by the way, were American Higgins craft). The commander of the heavily damaged boat said, �They are on top of us!� My squadron commander said to him, �Don�t worry! I �ll get him now!� He dropped down and fired a burst of 37mm cannon. It was a pleasure to watch the German �hunter� go up in flames. Six Bf-109Fs were covering the convoy and supporting the attack on our PT boats. I engaged them with my group of six Cobras. We circled round and round. I shot down two Messerschmitts and damaged one (intelligence subsequently confirmed the damaged 109). Before we had even landed, the crew of the damaged PT boat reported by radio that one of the Cobras had shot down two Messers and another had set the German �hunter� on fire. This had all happened right in front of their eyes. Later Admiral A. V. Kuzmin, commander of the patrol torpedo boat brigade, personally expressed his appreciation to us. All our damaged PT boats made it back to their base.

Thus, a single burst of several 37mm projectiles was sufficient to set fire to or damage a �hunter-type� patrol vessel.

Here is another example. We were flying on a �free hunt� mission, four of us. I was the leader. We came upon a German tanker that we estimated at 3000�3500 tons. Most importantly, it was proceeding without escort! I gave the command, �Prepare to attack!� I dropped down and made my pass, firing a good burst. I pulled out at an altitude of 25 meters. He also fired back at me. OK, fine. My wingman made his pass on the target, then the leader of the second pair, and the fourth pilot reported, �It�s burning. I can�t see anything!� I responded, �OK, pull out, don�t engage.� We got a look at it, moving toward shore totally engulfed in flames. We flew back to our airfield and reported, �We set a tanker on fire, 3,500 tons.� And he replied, �Right. You set a tanker on fire with all of 38 rounds expended!� He didn�t believe what I was telling them. 38 rounds for 3,500 tons! I said to him, �Isn�t that enough? We put 38 rounds into that box!� At first everyone laughed at us, but later our agent intelligence gave us confirmation of that number. A German tanker of 3,500 tons displacement had been burned out. Everything fit. There you have it�38 rounds of 37mm cannon destroyed a 3,500-ton vessel!

2. The M-6 cannon was very reliable. If it was properly maintained it worked very reliably. We could charge the cannon only one time from the cockpit, but this one re-charging was completely sufficient. If this cannon malfunctioned, it was due entirely to unqualified maintenance.

I was involved in another incident. A young, inexperienced armorer installed the belts upside down, so that the teeth of the links of the belt were on top, for both machine guns and the cannon. We were flying in pair. This was my wingman�s second combat sortie. We spotted a pair of Fokkers[Fw-190 � ed.]. I attacked the lead Fokker, who went into a vertical climb. I fired a shot from my cannon, the glowing ball of the projectile�s tracer crossing the path of the enemy aircraft. The German, naturally, abruptly dove; the range closed rapidly and I had him in my sights. I got off one round from each machine gun and experienced a complete stoppage! I re-charged both guns�to no avail! None of my weapons worked! It was a good thing that I had hit him with these two rounds. The German was smoking heavily and had lost a great deal of speed. I had nothing to kill him with! I called to my wingman, �Get the Fritz!� But he was circling in a merry-go-round with the German�s wingman and continued to circle until the German shot him up. Except for �his own German,� my wingman did not see anything, and the damaged Fokker got away. On the ground it was discovered that my wingman had not fastened his earphones to his helmet, and during the high-G maneuvers his earphones had come off. He had not heard my commands. A month later someone shot down a German pilot in a Fokker, and during his interrogation by the division commander he asked, �Why, a month ago, did a pilot from this regiment not finish me off? Two of my cylinders were shot up.� (The German well knew that only the pilots of 2d GSAP VVS SF flew �red-nosed� Cobras. A. S.) Our division commander replied to him, �Yes, he was something of a screw up, kind of like you, but he didn�t get shot down.�

They badly wanted to send the armorer to a tribunal [courts martial], but he got off with a reprimand. I was categorically opposed to a tribunal. He was a young kid, still a �newbie�. The fault really lay with the armaments mechanic. It was his direct duty to check the correctness of the loading of the rounds. He knew that his armorer was inexperienced, but he did not stop to check and simply took the armorer�s word. �Is it ready?� �Yes, it�s ready.�
_
*Also interesting commentary on the Allison Engines in the P-39's. Problems with them wearing out quickly (~50 hours) just like with the P-40's, though they seem to have been able to get some new ones.*_

"
* A. S. What about the engine in the P-39. Was it weak? They say that it was unreliable, it was never good for the recommended 120 hours, and it �threw� connecting rods. *

* N. G. * We had Allison engines. They were powerful, but . . . the engines in the Cobras were unreliable, especially early on. These were on the English variants, the Q-1 and Q-2. Their engines were weaker. After the first three or four air combats, all ten Cobras were laid up for engine repairs.

These first Allisons did not deliver even one-half of the recommended engine hours. 50 hours was its limit, and frequently less. Normally 10�15 sorties if they were in combat. They seized, the bearings melted; this happened to me once. I sat out for a while with no engine. They monitored these engines closely. As soon as any metal showed up in the oil, they changed out the engine. The supply of replacement engines was plentiful, but it was not always possible to get delivery of them. Sometimes they brought them in on an Li-2 [Soviet-built C-47], four in a load, such was the demand for new power plants. But just the same, despite our best efforts, there were seizures. True, this engine did not �throw� connecting rods, at least this never happened to us. On type-5 and later models the engines were more powerful and reliable.

Now regarding power settings. In principle the RPMs were regulated by a conventional throttle. In the Cobras there were two regimes of throttle operation, �normal� and �war emergency�, which was characterized by increased manifold pressure. The throttle quadrant was mounted in the [left side of the] cockpit and the pilot controlled it. The �war emergency� regime had a lever position that we called �51 inches and 57 inches of boost�. If we were flying on Soviet B-95 fuel, then �war emergency power� was set at 51 inches. If we were using American B-100 fuel, then �war emergency power� was set at 57inches. Although it was mounted in the cockpit, on the throttle quadrant, the pilot did not adjust this setting. The position of the �war emergency power� selector was controlled by a piece of wire that could be broken easily with greater forward pressure on the throttle quadrant.

One time I sensed a lack of power (I needed to get ahead of a German) and I thought, �The hell with it�! I broke the wire and selected �57�. Then I experienced what �57� meant! My airplane leapt forward! The Germans spotted me from above and dove immediately, which was what we wanted.

American gasoline was better than ours. Not more powerful, but better. The anti-detonation qualities of our gasoline came from the addition of tetraethyl lead. After every two or three flights the engine mechanic had to clean the lead from our spark plugs. If he waited too long, a lead droplet would form between the electrodes. But this was not a special problem. Normally our spark plugs were quickly cleaned after every sortie. But with the American gasoline, this did not happen. Either they used higher octane to begin with and added less lead or they raised the octane rating with benzol [another additive]. Perhaps it was just the benzol. Because our gasoline was pink in color and the American gasoline was dark blue.

Incidentally, the Allison �made metal� on any gasoline. Realistically the Allison engine began to live up to its full 100 hours of use only in 1944. These engines came in the Q-25-30. But by this time the intensity of air combat had already fallen somewhat, and the primary distinction of these types was the perceptible decrease in power output. Therefore we removed the wing machine guns. They were heavy [one Browning .50 caliber under each wing], slowed the airplane down, and their recoil was felt in combat."
_

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## Elmas (Apr 4, 2018)

Schweik said:


> *snip*
> 
> Not sure about the Spitfires but the Hurricanes and P-40's were in many cases already worn out from combat when they were sent to the Soviets




This could be certainly a convincing reason.

Furthermore, as has been suggested in a post, politics had a play in that, as relationship between U.S.A. and U.S.S.R. were far better than between U.K. and U.S.S.R. (Or, better, relationship between F.D. Roosevelt and Stalin were better than Churchill and Stalin...)

Could have been some other reasons, mentioned in a very useful link poste before.


Early Cobra's in Soviet Aviation

_“The process of assembly was organized in the best Soviet traditions: foreign specialists, naturally, were absent; instructions, naturally, were in English; of the NII VVS specialists, naturally, no one knew English; the [female] translator, naturally, was an academic to whom "fonar'" [canopy in Russian airplane jargon, in usual sense a light source], for example, was a "light source" only; the aircraft, naturally, was absolutely unfamiliar to the specialists; and the period of time allotted for the work, naturally, was minimal._

_The resourcefulness and ingenuity of the people and "His majesty, chance" helped out. The team leader I. G. Rabkin knew French. At that time, there was a group of British RAF specialists at 22 ZAP, engaged in assisting in the assimilation of the Hurricanes. The leader of this group, an engineer in the rank of captain, fortunately also spoke French. In addition, some of his team members were familiar with the Airacobra. Therefore the consultations went something like this: I. G. Rabkin submitted questions of interest to the British engineer in French. He consulted with his colleagues in English and responded to the questions in French. Our leader passed along the responses to his subordinates in Russian. This process somewhat speeded up the work for translating the instructions._

_The assembly of the aircraft was accomplished directly on the airfield. Despite the severe winter, work went from dawn to dusk, and than for several more hours the team members conducted exercises in classrooms for ZAP specialists or were involved in translating instructions. Thanks to this unstinting effort, the first airplane was assembled and prepared in a minimum amount of time.”_


And, knowing personally the accuracy of the “foolproof manuals” whenever a piece of U.S. built machinery is involved, this probably helped a lot…


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## tomo pauk (Apr 4, 2018)

Schweik said:


> Disagree with that one! Maybe we need to start a P-40 vs. P-39 thread.
> 
> ....
> 
> ...



We have a P-39 that is equal of better than German fighters down low, and P-40N that is worse or equal. That should point out that P-39 was a better A/C for the Soviets.



Schweik said:


> Some interesting commentary by Golodnikov on the 37mm gun in the P-39
> _..._



Too bad that Americans didn't make a shorter and thus lighter HE shell for the M4, with more propellant so the ballistics were less different to the .50 than historically.


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## Schweik (Apr 4, 2018)

tomo pauk said:


> We have a P-39 that is equal of better than German fighters down low, and P-40N that is worse or equal. That should point out that P-39 was a better A/C for the Soviets.



By the time the Russian pilots got P-40N's they (P-40's) were already basically phased out of front line use. P-40Ns mostly saw action in the Pacific, the RAF also used some in Italy. But for the most part that variant was late to the war*.

The Russians were using P-40 B/C / Tomahawk initially, then P-40E, and then P-40K and M, plus a few (I think just a few dozen) P-40F.

Most Russian high scoring Kittyhawk aces (Kuznetzov etc.) got most of their victories while they were flying P-40K, which had a 1,300 hp engine and could reach 1,500 hp at optimal altitude at WEP. P-40K or F/L could handle the German fighters at lower altitude - this is also evident from North Africa. The English tested the P-40K and rated it's top speed as 370 mph.



> Too bad that Americans didn't make a shorter and thus lighter HE shell for the M4, with more propellant so the ballistics were less different to the .50 than historically.



In air to air they mostly shot at very short range anyway, ~150 meters or less. This was true for all the Soviet fighters with nose-mounted guns as well. The drooping arc was more of an issue for strafing, as Golodnikov and others have noted. But P-39's were mostly used for air-to-air.

S


*Most of the P-40Ns produced were 'heavy' lower-powered FB variants, though the early and some later ones were lightened by about 1,000 lbs and with 1,300 hp enginges made 378 mph so probably capable against Luftwaffe fighters. But they were not really used as such.


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## P-39 Expert (Apr 4, 2018)

pbehn said:


> Bingo! so it was possible with all the specified equipment, without woodfiller and twenty coats of paint. The British requests were in no way unreasonable or unattainable, just that Bell couldn't do it when they said they could.


Also had a newer engine with 100HP increase and 200# less weight.


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## pbehn (Apr 4, 2018)

P-39 Expert said:


> Also had a newer engine with 100HP increase and 200# less weight.


Done to death, I will now use the ignore function.

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## Elmas (Apr 4, 2018)

I'm not saying that P-39 could not have been useful in the Russian Front, I'm not convinced that it could have been a Me-109 or a FW-190 destroyer, in spite of her rocket-like appearance...

_“Our Me-109 (G-10s) flew faster and climbed and turned better than a Thunderbolt: but if, even for a few seconds, you were inside the eight MGs trajectory of a Thurderbolt, you were done.”_
M.llo Carlo Cavagliano, II° Gruppo Caccia, 4° Squadriglia “Gigi tre osei”, A.N.R.

My bold. English is a second language for me and certainly I do not master it as I would like to. Sorry.



Schweik said:


> Some interesting commentary by Golodnikov on the 37mm gun in the P-39
> _Part 3
> A. S. Was a 37mm cannon necessary? Wasn�t this too large a caliber for a fighter? You had so few rounds of ammunition. And wasn�t its rate of fire slow?_
> *N. G. *_One cannot say that the 37mm cannon was a disadvantage or an advantage. Look at it from this perspective. The M-6 cannon had its strong and weak points. One had to take advantage of the strong points and compensate, as much as possible, for its weaknesses.
> ...

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## P-39 Expert (Apr 4, 2018)

DarrenW said:


> Hey P-39 man, why haven't you voted yet?
> 
> Best US escort fighter in ETO during 1943?
> 
> Or have you finally succumbed to the avalanche of facts and voted for something other than the P-39?  And you seriously should consider joining in the conversation as well because the Airacobra is sorely missing it's fan base over there...


Sorry I haven't been able to keep up, my day job has been interfering. 

You and I have a running battle about the weight of the P-39N. You say the test plane was lighter than normal. Yes, it was, but so was EVERY other plane in those performance tests.

Below is a little chart that I did just for you. More of my pencil scratch. But as you can see, every one of the tests in wwiiaircraftperformance used a plane that was lighter than standard published gross weight. The gross weight listed in the test was using some form of "average" or "mean" fuel to give an average weight for that particular flight. There are exceptions, like the P-38G tested 2/10/43 that was 2000# light and the test said that only 180gal fuel was carried (normally 300gal), only 50 rounds for the 20MM (normally 150) and only two MGs (normally 4) and the performance of this plane was well above other P-38F and Gs as shown by the performance graphs in the P-38 section.

But the rest of the P-38s, P-39s, P-40s, P-47s and P-51As were ALL lighter than published gross weight to account for "average" fuel. 

So please stop referring the the test P-39N as being "lightened" in any way. Same as the others, that was the way the AAF tested planes back then. And "gross weight" (aka "all up weight") is defined as being the total aircraft weight AT ANY MOMENT DURING THE FLIGHT.

The comparisons that I have made are accurate and the P-39N numbers are accurate. Thanks.

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## Schweik (Apr 4, 2018)

Elmas said:


> I'm not saying that P-39 could not have been useful in the Russian Front, I'm not convinced that it could have been a Me-109 or a FW-190 destroyer, in spite of her rocket-like appearance...
> 
> My bold. English is a second language for me and certainly I do not master it as I would like to. Sorry.



I don't think any of your comments were accurate.

The very close approach before shooting was a standard Soviet practice particularly with all their fighters that had nose-mounted guns (i.e. almost all of them), and whatever you think of Soviet propaganda, the Germans lost quite a few aircraft as well. Obviously it did work at least some of the time.
Quite often with nose mounted cannon, both German and Soviet pilots would get kills with just 1-2 well--placed rounds. Joachim Marseille was famous for this in North Africa. Obviously with the 37mm cannon it didn't even have to be particularly well placed. Also don't forget they also had two heavy machine guns in the nose as well, which was plenty to shoot down a fighter (2 x 12.7mm nose guns was standard armament for early Italian fighters).

At low altitude German speed advantage was not so pronounced, or depending on the type, even apparent against the better P-39 variants (Q-5 for Golodnikov), or for the Yak 1B, Yak 7B, La 5 and 5FN, and Yak 9 and later Yak 3.
Most P-39 victories were against fighters. See Black Cross / Red Star.

If you are one of those people who just assumes that all Soviet victory claims were made up, you probably can't be convinced, but this ground has already been covered.

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## Shortround6 (Apr 4, 2018)

You may want to recheck your figures, 
For example the *design *gross weight for a P-40E was ..............wait..............8011.5 lbs as per the pilots manual.

This included a 180lb pilot instead of the late 200lb pilots but heavier than the 160lb pilots in the P-39 
it included only 120 gallons of fuel, tank behind pilot was not full. But the rear fuselage tank on the P-36/40 has a long and somewhat twisted history/use. 
IF you fly at over 8011lbs you no longer have the 8 "G" service load/12 "G" ultimate load margins. 
BTW a P-40E wvwn with full internal fuel was closer to 8259-8300lbs than to 8400.

I can't be bothered to look up the rest.

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## CORSNING (Apr 4, 2018)

Peter Gunn said:


> You see, this is how these threads should progress. P-39 blah blah blah, get the second string junk out of the way and let the thread evolve to the real meat and potatoes of enlightened WWII discussion. The Mustang.



! Uh, Mmmmm? Here we go...I am not saying that the P-39N was God's gift or anything
like that, but since you brought the P-51 in early/mid+ 1943 into the conversation and assumed
IT was all that:
Atitude / MPH / FPM
P-51A vs. P-39N
S.L.......376/3500 vs. 344/4140
1000m.387/3625 vs. 362/4275
2000m.400/3750 vs. 381/4410
3000m.412/3405 vs. 398/4085
4000m.413/2925 vs. 394/3620
5000m.410/2455 vs. 388/3160
6000m.405/2025 vs. 382/2705
The Russians didn't care up higher altitudes.
The P-39N could outturn the P-51A pretty much at any speed.
The P-39N could out roll the P-51A (probably up to 300 mph.) The D-1 could up to 263 mph.
and I believe the Ns acceleration into the turn was improved from the D's.
Power loading of the two fighters at combat weights= 5.405 vs. 5.122 lb./hp.

P-39 blah, blah, blah... those were not my words.

Truth is guys, I agree that the P-39 was not made for the ETO or the PTO. But it was an
excellent addition to the VVS in 1942-1944.

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## DarrenW (Apr 4, 2018)

P-39 Expert said:


> You and I have a running battle about the weight of the P-39N.
> 
> 
> 
> ...



Geez I hope this hasn't turned into something other than just a good natured disagreement?  And while I haven't seen EVERY test report on the website (I have a life too), I can say that it would be incorrect to lump all of them in together as having "lightened" test aircraft. The only documents that I have examined in great detail are those of the F6F Hellcat (no surprise). And while there have been testing performed at varying weights, the vast majority of Hellcats tested were in a "fighter overload" condition. This means maximum internal fuel and ammunition load (for machine guns only). This amounts to roughly 12,400lbs (the gross weight of an F6F-3 as given by the manufacturer). I do agree that there is test data where the loaded weight of _some _Hellcats was less than this standard, but this situation was more of an exception than the rule.


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## Peter Gunn (Apr 4, 2018)

CORSNING said:


> ! Uh, Mmmmm? Here we go...I am not saying that the P-39N was God's gift or anything
> like that, but since you brought the P-51 in early/mid+ 1943 into the conversation and assumed
> IT was all that:
> Atitude / MPH / FPM
> ...



Two things my friend, first, which would you want to take into combat? Don't quote numbers, if you asked an AAF fighter pilot which he'd prefer I doubt it would be the P-39. No RAF pilot with two brain cells to rub together would, of that I would bet the farm... as did the RAF.

Second, you seemed to have missed my point entirely.

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## Shortround6 (Apr 4, 2018)

When looking at some of these tests the date and purpose of the test (not always stated) have to be taken into account as these were not all standardized tests with same goal/objective in mind. 
And "standards" changed over time. 

You also sometimes have to take into account the original specification of the aircraft. AS I pointed out, the P-40E, had a 'design" weight.
This had gone up from the earlier P-40s. The Original P-40 had a design gross weight of 6782lbs. This included two .50 cal guns and 380rpg of 50 cal ammo. NO .30 cal guns, it included 120 gallons of fuel although tankage was provided for 181 gallons (unprotected).

In order to maintain the load standards, especially in peace time, the aircrafts structure has to be beefed up as it gains weight and the P-40 gained an awful lot of weight. Once the shooting started they didn't pay quite as much attention to the load standards on the older planes. But until they get a good idea of what is going to happen they flew first test flights or performance tests at _DESIGN _weights in order to get baselines. 
It took a while for combat experience to sink in too. For example in the summer of 1942 the US has about zero combat experience with land based fighters fighting anybody or what ranges will be needed. It takes until the Fall/winter of 1942for the combat experience of North Africa, New Guinea and Guadalcanal to sink in.

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## P-39 Expert (Apr 4, 2018)

Shortround6 said:


> You may want to recheck your figures,
> For example the *design *gross weight for a P-40E was ..............wait..............8011.5 lbs as per the pilots manual.
> 
> This included a 180lb pilot instead of the late 200lb pilots but heavier than the 160lb pilots in the P-39
> ...


That's good because most all the sources out there quote different weights. 8400# was most common in my readings.

But every one of the tested planes was light vs. published weights. Had to be something to do with fuel.


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## P-39 Expert (Apr 4, 2018)

Peter Gunn said:


> Two things my friend, first, which would you want to take into combat? Don't quote numbers, if you asked an AAF fighter pilot which he'd prefer I doubt it would be the P-39. No RAF pilot with two brain cells to rub together would, of that I would bet the farm... as did the RAF.
> 
> Second, you seemed to have missed my point entirely.


There's another P-39 graph a few pages back that shows P-39Q (no wing guns) just about 10mph slower. If it was me flying, I will almost always take the highest climb rate. The N outclimbs the P-51A substantially at all altitudes and 650fpm at 20000'. And only 10-15mph slower.


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## Shortround6 (Apr 4, 2018)

P-39 Expert said:


> That's good because most all the sources out there quote different weights. 8400# was most common in my readings.
> 
> But every one of the tested planes was light vs. published weights. Had to be something to do with fuel.



It often was but not because they were testing at 1/2 fuel or average fuel or some other made up condition.

The early (before and part way through 1942) tests were often done at the design weight which is the official contract weight. 
Many of the "published" weights are from latter or as used in combat area weights. And some (like for just about every P-51 built) are over the standard load limits. P-51s weren't 8 G aircraft unless running VERY light.


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## Greg Boeser (Apr 4, 2018)

fubar57 said:


> In agreement but you just know it will be dragged and kicked until we all agree that the P-39N was the best aircraft there ever was


Them's fightin' words! Everybody knows that the B-26 Marauder was the finest aircraft ever produced!
It could fly 326 mph with a full load of 5800 lbs of bombs. Says so right in the pilot's manual.

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## Greg Boeser (Apr 4, 2018)

P-39 Expert said:


> There's another P-39 graph a few pages back that shows P-39Q (no wing guns) just about 10mph slower. If it was me flying, I will almost always take the highest climb rate. The N outclimbs the P-51A substantially at all altitudes and 650fpm at 20000'. And only 10-15mph slower.


I'll take the plane that will get me to where the enemy is and be able to fight there.

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## buffnut453 (Apr 4, 2018)

Greg Boeser said:


> I'll take the plane that will get me to where the enemy is and be able to fight there.



And stands the best chance of bringing me home again.

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## Shortround6 (Apr 4, 2018)

Greg Boeser said:


> Them's fightin' words! Everybody knows that the B-26 Marauder was the finest aircraft ever produced!
> It could fly 326 mph with a full load of 5800 lbs of bombs. Says so right in the pilot's manual.




what page?


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## Greg Boeser (Apr 4, 2018)

Shortround6 said:


> what page?


32.
Oh, wait. it says at design gross weight of 26,734 lbs. Full fuel and 5800 lbs of bombs puts it a bit above that.


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## Shortround6 (Apr 4, 2018)

I always thought the the 5800lb load was a pair of 1600lb AP bombs and a torpedo?
Torpedo hanging on the outside really plays havoc with the speed


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## CORSNING (Apr 5, 2018)

Peter Gunn said:


> Two things my friend, first, which would you want to take into combat? Don't quote numbers, if you asked an AAF fighter pilot which he'd prefer I doubt it would be the P-39. No RAF pilot with two brain cells to rub together would, of that I would bet the farm... as did the RAF.
> 
> *I believe the Russians preferred the P-39 to the Allison powered Mustangs. But then again, I would have to look it up to see
> if they received any P-51As.*
> ...



*I have been known to go brain dead from time to time.*

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## Peter Gunn (Apr 5, 2018)

P-39 Expert said:


> There's another P-39 graph a few pages back that shows P-39Q (no wing guns) just about 10mph slower. If it was me flying, I will almost always take the highest climb rate. The N outclimbs the P-51A substantially at all altitudes and 650fpm at 20000'. And only 10-15mph slower.



Which MUST by why the RAF couldn't get enough P-39s and used them until the end of the war. /sarc



> Second, you seemed to have missed my point entirely.



Seems you have as well.


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## Peter Gunn (Apr 5, 2018)

CORSNING said:


> *I have been known to go brain dead from time to time.*



You're not the only one my friend. 

As I posted waaaaay back earlier in this thread, I agree that the P-39 found its niche as a low altitude fighter with the VVS... yay.

To me that is irrelevant to the needs of the USAAF, RAF, RAAF and RNZAF in the ETO, MTO, PTO and CBI, basically everyone else, everywhere else.


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## P-39 Expert (Apr 5, 2018)

DarrenW said:


> Geez I hope this hasn't turned into something other than just a good natured disagreement?  And while I haven't seen EVERY test report on the website (I have a life too), I can say that it would be incorrect to lump all of them in together as having "lightened" test aircraft. The only documents that I have examined in great detail are those of the F6F Hellcat (no surprise). And while there have been testing performed at varying weights, the vast majority of Hellcats tested were in a "fighter overload" condition. This means maximum internal fuel and ammunition load (for machine guns only). This amounts to roughly 12,400lbs (the gross weight of an F6F-3 as given by the manufacturer). I do agree that there is test data where the loaded weight of _some _Hellcats was less than this standard, but this situation was more of an exception than the rule.


Absolutely just a good natured disagreement, would be better over a couple beers. 

Now, data for the original question posed 1155 posts ago: "Should the P-39 have been able to handle the Zero? Was it training or performance?" The attached performance chart for the P-39K with the Zero (Zeke 32 Hamp) superimposed in pencil. Flame away.


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## Juha2 (Apr 5, 2018)

Peter Gunn said:


> You're not the only one my friend.
> 
> As I posted waaaaay back earlier in this thread, I agree that the P-39 found its niche as a low altitude fighter with the VVS... yay.
> 
> To me that is irrelevant to the needs of the USAAF, RAF, RAAF and RNZAF in the ETO, MTO, PTO and CBI, basically everyone else, everywhere else.




Hello
in fact Soviets saw P-39 as a low- and medium altitude fighter, see my message #197 , according to Soviet tests P-39’s good altitude to fought against Bf 109 G-4 was appr. 3 750 – 5 300 m and against Fw 190 A-5 appr. 2 000 – 6 000 m. That was how the Soviets saw it, not necessarily how it was in reality.

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## Peter Gunn (Apr 5, 2018)

Sometimes I doubt people actually READ what I write, or perhaps they do but can't f#cking comprehend it.

Time for me to stop posting here. See ya round.

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## DarrenW (Apr 5, 2018)

P-39 Expert said:


> Absolutely just a good natured disagreement, would be better over a couple beers.



Now that we are definitely in agreement on! 

But to be totally frank, I'm also in agreement with Peter Gunn and others on this forum. IMHO this thread has long outlasted it's usefulness and except for a minor few nobody really changed their opinion about the P-39. Those who think it was unjustly kept from being a bigger player with the AAF still feel that way, while others will always think of it as a second rate fighter that just held the line until more capable fighters came along. I'm just on the side of history, so other then brushing up on my Airacobra facts, this thread offered me very little if any new information. Sorry but that's just how I feel. But by all means keep the good fight going if you must. I'm certain that there will always be those willing to discuss the topic with you because everyone here has a passion for aviation and in that sense we should at least try to be civil and treat each other with the respect that we all want and deserve. Peace.

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## P-39 Expert (Apr 5, 2018)

DarrenW said:


> Now that we are definitely in agreement on!
> 
> But to be totally frank, I'm also in agreement with Peter Gunn and others on this forum. IMHO this thread has long outlasted it's usefulness and except for a minor few nobody really changed their opinion about the P-39. Those who think it was unjustly kept from being a bigger player with the AAF still feel that way, while others will always think of it as a second rate fighter that just held the line until more capable fighters came along. I'm just on the side of history, so other then brushing up on my Airacobra facts, this thread offered me very little if any new information. Sorry but that's just how I feel. But by all means keep the good fight going if you must. I'm certain that there will always be those willing to discuss the topic with you because everyone here has a passion for aviation and in that sense we should at least try to be civil and treat each other with the respect that we all want and deserve. Peace.


I hear you. My contention is that the 2012 information in wwiiaircraft put a new light on the P-39 and that it was a match for the FW190 and Me109 (as well as contemporary Hellcats, Corsairs, Lightnings etc, but not Merlin Mustangs or Spitfire IX) , but everybody has read and heard all the old information and changing their minds is impossible. Interesting reading anyway, if anyone will actually go there and look. Oh well.

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## b0ned0me (Apr 5, 2018)

P-39 Expert said:


> And by the way, am I a moron? I have a masters degree and I read pretty good. Am I not capable of reading a page of information and commenting on it?


Not sure if you are a moron or a troll, but you are definitely a fanboy. Masters degrees frankly don’t mean a thing, plenty of people on this site have them, even me. Reading you seem to do ok, comprehension not so much. Your alma mater may not be proud. 


P-39 Expert said:


> The upside of the P-39 in general is that it was available from the start of WWII along with the P-40 and F4F Wildcat.
> ..
> I'm comparing the P-39N to other planes in combat in 1943, like the P-38, P-40, P-47 (May '43), Hellcat (Aug '43), Corsair (Feb '43), FW190, Me109G, Zero and Oscar.


Beggars can’t be choosers, which is where the P-39 got its big break. I’m not sure I’d take one over a P-40 or F4F but it was more like P-39 or P-36, and there the AirColon is better.
Choose a P-39 over a P-38, P-47, Hellcat or Corsair? Only if you are deranged. Or if you really needed a sub-par point interceptor that was for all practical purposes just an inferior copy of the spitfire & 109.


pbehn said:


> After reading a lot I now no longer believe what I am reading. Early test results were never reproduced and by a masterly piece of denial, plausible denial, omission and evasion Bell managed to get a plane that was unsuitable in every way into production and service. Bell's claims about performance and handling were never reproduced in the field, its speed and climb were never satisfactory and the last official test rejected it as a fighter for the US military at all.


Sounds about right, IMO. A monument to inspire salesmen everywhere.


P-39 Expert said:


> I hear you. My contention is that the 2012 information in wwiiaircraft put a new light on the P-39 and that it was a match for the FW190 and Me109 (as well as contemporary Hellcats, Corsairs, Lightnings etc, but not Merlin Mustangs or Spitfire IX) , but everybody has read and heard all the old information and changing their minds is impossible. Interesting reading anyway, if anyone will actually go there and look. Oh well.


FFS. In what way is a six year old website sharing public domain Ww2 flight tests “a new light” on the P-39? It’s a marvellous gift to the community, a treasure to the plane geek and an monumental labour of love from an enthusiast, sure. Somewhere probably every visitor of this sub forum has visited many many times.
But the full horrors of P-39 performance have been available to serious researchers and authors for decades. If anything putting it all up in such an accessible form has punctured a lot of the old myths about this particular aircraft being high performing, but clearly your obsessions need a special class of puncturing.

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## DarrenW (Apr 5, 2018)

No hard feelings I hope and I apologize now if it seems that I've treated you unfairly concerning your position. I for one can appreciate what you are trying to do here, really I do. And even if people don't agree with every point you are trying to make at the very least you have fueled discussion on this and other topics as well which is always a good thing.

But we are definitely done here.

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## P-39 Expert (Apr 5, 2018)

DarrenW said:


> No hard feelings I hope and I apologize now if it seems that I've treated you unfairly concerning your position. I for one can appreciate what you are trying to do here, really I do. And even if people don't agree with every point you are trying to make at the very least you have fueled discussion on this and other topics as well which is always a good thing.


No problem at all, I enjoy the discussion. Just thought a little newish information would be fun. Most are comfortable with their long held views. But then facts are facts and most haven't even bothered to look at them. Oh well.


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## Shortround6 (Apr 5, 2018)

Some of us have looked at them, and just like some of the claims Bell was making in 1939-40 and 41, we aren't swallowing them. 
test flights that never happened, specially prepared/modified test planes, planes operating below service weights. These are also facts that some people don't want to acknowledge. Oh well.


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## tomo pauk (Apr 5, 2018)

P-39 Expert said:


> No problem at all, I enjoy the discussion. Just thought a little newish information would be fun. Most are comfortable with their long held views. But then facts are facts and most haven't even bothered to look at them. Oh well.



What are my long-held views? Long held - for how long? Those of Shortround6? Parsifal's? Pbehns?
You are the only one declaring itself as an expert, what are your published works? Peer-reviewed ones? Time spent to bring out new data? Being a fan-boy of an aircraft does not qualify one as expert. We have had a long history of fan-boyism on this site, it will not last long until one is spotted.
Most of the people here are reading about ww2 aviation for long time, myself for perhaps 40 years. While I will not declare me as an expert on the anything, I stil reserve the right to call a mis-information, mud-throwing or cherry-picking as such the very moment I see it.

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## Shortround6 (Apr 5, 2018)

Got my First William Green books before I was 10. almost 55 years. Not saying he was always right, just that I have been reading about aircraft for that long. And finding lots of errors along the way.

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## pbehn (Apr 5, 2018)

I have actually changed my opinion. I thought it was a bad plane, actually it was a badly sorted plane. As S/R pointed out (I believe) it was a new type, higher landing speed, tricycle undercarriage, different performance in stall and sensitive to weight distribution. The Russians perhaps saw that when they flew it with 601 squadron and had the time learn about it and prepare their tactics.

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## DarrenW (Apr 5, 2018)

This was a VERY exhausting thread to say the least. Anyone know if we broke any records with the number of replies?

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## Shortround6 (Apr 5, 2018)

pbehn said:


> I have actually changed my opinion. I thought it was a bad plane, actually it was a badly sorted plane. As S/R pointed out (I believe) it was a new type, higher landing speed, different performance in stall and sensitive to weight distribution. The Russians perhaps saw that when they flew it with 601 squadron and had the time learn about it and prepare their tactics.




The Russian experience is also colored by expectations or previous experience. Figuring out Russian comments is like playing detective. Two comments about the Mig 1 and 3 . !st one says the plane had CG problems and was difficult to handle, 2nd one says all the problems were fixed and that pilots transitioning from I-16s had little or no problem. Then you read comment 3. I-16s had CG problems and were a bit squirrely or had handling problems. Please note that in 1940-41 when the Migs were introduced (ahead of the Laggs and Yaks) a fair number of russian pilots were flying biplanes of some sort. 
Also please note that may LA-5 pilots flew with open canopies due to vision problems or difficulty in bailing out with canopy closed. Some Russian planes didn't have compasses so one that possible screwed up when the nose guns fired was no big deal. 
The Russians would have flown anything that offered a chance against the Germans, they only phased out the last of the I-16s around March of 1943. One of the last missions when 8 I-16s escorted IL-2 in a mission in the breaking of the Leningrad blockade. The eight I-16s were supposed to have successfully stopped an attacking group of FW 190s without loss to themselves and shooting down one Fw 190. Doesn't mean the I-16 really should have been kept in service. 

Or consider the Yak-9D with 650 liters fuel capacity instead of the previous 440 liters. Some were given to the French Normandie squadron who reportedly, plugged the outer wing tanks and flew using the wing root tanks. Experience with the 18th fighter guard regiment showed they using only 270 liters (71 US gallons) per flight on average. Once they figured out that mixing the 9Ds with the shorter ranged 9s wasn't a good idea the 9Ds were used for longer ranged work but were hampered by lack of such things as a gyro horizon or radio compass. Other problems included having a range (not radius) of 562 miles but a two radio range of only 37 miles. 

P-39s would seem like luxury machines.

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## FLYBOYJ (Apr 5, 2018)

b0ned0me said:


> Not sure if you are a moron or a troll, but you are definitely a fanboy.


You're getting one warning, KNOCK OFF THE INSULTS!!!

This warning goes out to all as well

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## Glider (Apr 5, 2018)

DarrenW said:


> This was a VERY exhausting thread to say the least. Anyone know if we broke any records with the number of replies?


Most of the points are repeats so I suggest skipping the first half or even 2/3rds

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## P-39 Expert (Apr 5, 2018)

pbehn said:


> I have actually changed my opinion. I thought it was a bad plane, actually it was a badly sorted plane. As S/R pointed out (I believe) it was a new type, higher landing speed, tricycle undercarriage, different performance in stall and sensitive to weight distribution. The Russians perhaps saw that when they flew it with 601 squadron and had the time learn about it and prepare their tactics.


My opinion if it matters at this point is it was the best plane we had available for combat in 1942, it was grossly overweight (easily corrected) and actually did well at Port Moresby in May considering lack of early warning radar and overwhelming odds. Then in August the P-400s with the wrong oxygen system couldn't fly above 14000' they were relegated to ground attack duty. The AAF turbocharged superplanes (P-38 and P-47) were in production and about to enter combat in late '42-mid '43 and they would be used. The much improved P-39N started production in late '42 but the bad reputation from PM and Guadalcanal got it shipped off to Russia where it shined and not just at low altitudes. And it had a substantial training role in the US. But to this day people still say it was hard to fly and was a low altitude plane.


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## pbehn (Apr 5, 2018)

P-39 Expert said:


> My opinion if it matters at this point is it was the best plane we had available for combat in 1942, it was grossly overweight (easily corrected) and actually did well at Port Moresby in May considering lack of early warning radar and overwhelming odds. Then in August the P-400s with the wrong oxygen system couldn't fly above 14000' they were relegated to ground attack duty. The AAF turbocharged superplanes (P-38 and P-47) were in production and about to enter combat in late '42-mid '43 and they would be used. The much improved P-39N started production in late '42 but the bad reputation from PM and Guadalcanal got it shipped off to Russia where it shined and not just at low altitudes. And it had a substantial training role in the US. But to this day people still say it was hard to fly and was a low altitude plane.


You continually use the royal "we" the British had the Spitfire MkIX in June 1942. The rest of your post is getting back on one of your three main hobby horses and you have done it to death. It is not a discussion, it is you continually stating the same things and disregarding everything everyone else says unless you can bring in one of your hobby horses. It really is beyond tiresome.

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## Peter Gunn (Apr 5, 2018)

Please forgive my last post, got some very troubling news from the youngest son and was in a MAJOR foul mood, it was an insult to all here and my sincerest apologies.

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## KiwiBiggles (Apr 5, 2018)

It is interesting comparing this thread with another one currently taking a revisionist approach, looking instead at the P-40. Both threads endeavour to go against the usual assessments, that the P-39 and P-40 were outdated and out-performed, and were just used as stopgaps until more capable fighters replaced them.

The big difference in the threads, though, is that the P-40 thread asks us to re-evaluate the P-40 using the experiences of the air forces using it at the time, and shows that those using it, while not regarding it as the greatest fighter in the world, were reasonably happy with it, and used it to good effect. In contrast, this thread asks us to disregard the evaluations of fighting pilots at the time, who regarded the P-39 by-and-large as a piece of junk; and instead look solely at some performance figures and so conclude that the P-39 was really a complete world-beater cruelly sidelined, probably by perfidious Albion.

While all received opinion on historical matters should always be open to re-evaluation, we should be very careful in discounting contemporary evaluations, in favour of theoretical results more applicable to a games forum. I am quite prepared to believe that post-war authors were wrong in their assessment of the P-40, and that users at the time were reasonably happy with it. I am not prepared to believe that the users at the time were wrong when they rejected the P-39. They were there, and were the experts; we are not.

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## drgondog (Apr 5, 2018)

P-39 Expert said:


> No problem at all, I enjoy the discussion. Just thought a little newish information would be fun. Most are comfortable with their long held views. But then facts are facts and most haven't even bothered to look at them. Oh well.


The problem is that you source facts that have been systematically refuted by a ton of source material. You just parted with a comment that implies that everybody that you have debated is simply too stupid to comprehend your lofty perspective on 'facts".

As a trump card you threw down a Master's degree? In what - that you consider an intellectual achievement that trumps those 'with an insufficient portfolio of facts' to debate You?

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## XBe02Drvr (Apr 5, 2018)

drgondog said:


> The problem is that you source facts that have been systematically refuted by a ton of source material. You just parted with a comment that implies that everybody that you have debated is simply too stupid to comprehend your lofty perspective on 'facts".
> 
> As a trump card you threw down a Master's degree? In what - that you consider an intellectual achievement that trumps those 'with an insufficient portfolio of facts' to debate You?


Well said, Doctor! A fitting requiem. Adios amigos.


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## DarrenW (Apr 5, 2018)

Is it really truly over????

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## FLYBOYJ (Apr 5, 2018)

DarrenW said:


> Is it really truly over????


It is now


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## FLYBOYJ (Apr 5, 2018)

LOCKED

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## DerAdlerIstGelandet (Apr 6, 2018)

Peter Gunn said:


> Please forgive my last post, got some very troubling news from the youngest son and was in a MAJOR foul mood, it was an insult to all here and my sincerest apologies.



You are good man. We all lose our cool from time to time. God knows I have plenty of times here. I'm finding it hard myself to not lose my cool reading some of the posts in this thread. You would think we are mere peasants among a king...

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## DerAdlerIstGelandet (Apr 6, 2018)

Well so much for that.

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