Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained)

[P-39 Expert]

"Could have, would have, should have" once again you're cherry picking. I think you know as well as I the AAF units in the SWP (80th FG, 35th FS for example) that were using P-39Ds and P-400s did not operate with 120 gallon fuel tanks. Even with the extra fuel the P-38 F/G, let alone the J easily outranged the P-39. So please, stop trying to throw "what ifs" into what actually happened. Sorry, all P-39Ds and P-400s had full 120gal internal fuel.


Could have, would have, should have." Easily lightened at forward bases.



The P-38 F/Gs that were replacing the P-39 in front line units were already in theater at the end of 1942 and General Kenney made up his mind because the P-39s performance in that theater was not suitable for what was actually needed and the P-38 was a flat out better aircraft for the mission required. He really didn't want the P-47 either but had to take them because P-38s were being diverted to North Africa and England (That's another story).

If you're going to make comparisons, why don't you compare what was being used at the time?!?!? P-39D or P-400!! The little bit of cherry picked advantage you're trying to show for the P-39N did not make up for the deficiencies in range and high altitude performance when compared to the P-38. For that matter let's compare the P-39M, N or Q to the P-38 J or L! P-39D and P-400 would have significantly better performance if lightened. Compare the M/N/Q with P-38J/L? There were no P-38J/Ls during P-39M/N/Q production. P-38J/L came after the Q had finished production. Better to compare the P-38F/G that were available at the same time.

Now I will give credit were credit is due. The 39th an 9th FS while flying the P-39 really didn't do to badly and their experience carried over when they transitioned to the P-38. Tom Lynch and Curran Jones were two standouts with multiple credits. Pilot skill was probably the main factor of this success as Lynch became one of the top fighter pilots in the SWP and possibly could have scored higher than Richard Bong if he wasn't killed. Bottom Line V Fighter Command aerial victories soared after the P-38 entered combat. Agree with you on the pilot skill. Lynch and Curran were certainly better trained and more experienced that the first squadrons of P-39 pilots in NG, when the P-39s were already well used before they arrived and many of the pilots had not even been trained as fighter pilots (AHT). AAF would have been hard pressed if the P-39 had not been available.

Total agreement with the Soviets and the P-39, it was perfect for them and their operations and their combat record confirmed that despite leaving the gear box armor installed!

 

[pbehn]

Absolutely no earthly idea. Why were the D/F/K/L so heavy for available power when they could have been easily and quickly lightened? Why add external gun pods that produce drag? Especially when the podded 50s weighed almost twice as much as the internal 30s? These are questions I can't answer.

How can you continue to argue this? You say yourself that the P-51 was a ton heavier and it was accepted with any Allison or RR engine put in it. All airforces wanted to increase firepower, if they couldnt put them in the wings they put them in pods, 20mm cannon are much more than 2 times the weight of 0.303mgs, no now you can answer those questions in future, cant you?

 

[P-39 Expert]

A short, incomplete and confusing "history" of the P-400 weight growth.

From Page 120 of "Cobra!" by Birch Mathews.

These are attributed to Bell model specifications. weight in pounds.

date.............................Empty...................useful load...................Gross...........................notes
Feb 1940....................4,524.......................1,325...........................5,849............................1 cannon, two machine guns
March 1940..............4,715.......................1,285............................6,000............................2machine guns added in each wing
May 1940.................5,149........................1,841............................7,000............................wing gun caliber increased
July 1940...................5,383.......................1,974.............................7,350...........................Armour and self-sealing tanks added
Jan 1941....................5,406.......................2,006.............................7,466...........................Minor empty and useful load increases
June 1941.................5,548........................2,087.............................7,635.........................Engine and fixed equipment weight increases
July 1941...................5,550.......................2,087..............................7,637..........................actual weight of Serial number AH 621

Now a few remarks about the 1325lb useful load in the first line. this starts my conclusions
20mm cannon...................................131lb
37mm ammo.....................................32.4lb
2 .50 cal machine guns.................161lbs
.50 cal ammo....................................129lbs
Pilot.......................................................160lbs
oil..............................................................75lbs.
sub total ............................................688lbs

weight left for fuel..........................637lbs=106 US gallons.
Spaces in the wings would hold 170 gallons, the "tanks" were integral (seal up spaces in the wing, no separate tank/s)

The first 165 P-400s were ordered by the French in April of 1940, the French were supposed to supply the guns. 20mm, 13.2mm and 7.5mm.
The British don't get involved until May-June of 1940 when the design has to be redone (converted back to imperial measurements from Metric), use British/American guns and other accessories (radios, etc)
I don't know if the French asked for the four wing machine guns or if Bell offered to make the plane look better?

The 3rd line is rather suspect. The increase in wing gun caliber is from 7.5mm to 7.7mm
The French MAC 34 gun weighed 10.7kg. the Browning weighed about the same. Empty weight does not include the guns although it includes mounts and ammunition bins/tracks/boxes. Increase in useful load and gross weight cannot be blamed on change of guns or change in ammo supply except for around 230lbs.

Line 4 with the added armor and self sealing tanks might well be attributed to the British. US followed in Sept. This also cut the theoretical fuel capacity with full (instead of part filled ) tanks from 170 gallons to 120 galls (US gallons). Not to pick on the P-39. The P-36/Hawk and P-40s were NOT measured for performance with the tank behind the pilot filled at this point in time.

The plane also gained weight due to increases in the engine weight and some of the other parts over which neither Bell or the British had any control over. The book the above list is from claims the weight of the Allison engine and accessories (which were government furnished equipment ) increase 380lbs from the start of design for the P-400 (well before French order) to the production versions.

So I ask again what were the items/equipment that the British asked for in order to reduce the performance of the Aircobra I so they could get out of the contract. Again, 4x30calMGs with 1000rounds per gun (400lbs including mounts, chargers, heaters and ammo boxes), 260lbs of armor plate/glass when 125lbs would have been plenty, and an IFF radio (110lbs) that wouldn't be needed in NG until 1943 because there was no radar until then. Total 645lbs.

every plane escalated in weight.

Please expand above.

 

[pbehn]

So I ask again what were the items/equipment that the British asked for in order to reduce the performance of the Aircobra I so they could get out of the contract.

Again, 4x30calMGs with 1000rounds per gun (400lbs including mounts, chargers, heaters and ammo boxes), 260lbs of armor plate/glass when 125lbs would have been plenty, and an IFF radio (110lbs) that wouldn't be needed in NG until 1943 because there was no radar until then. Total 645lbs.

The British specified 8 x 0.303 mgs for its S/E fighters, this was changed to 4x 20mm cannon in 1940/41. What do you consider to be a reasonable armament for a fighter in 1941? The IFF radio may not have been needed in NG but was in UK, which is the topic of discussion. The P-39 needed armour behind and in front of the pilot because of engine location, how do you come up with a weight for armour?

 

[P-39 Expert]

100% and if you read about Kenny, he was a stickler about performance and logistics. Look what he did to his medium bombers! If any mod "would have" helped the P-39 perfom better in the SWP, it "would have" been done. Actually was done at Guadalcanal. K/L models were reduced by 600lbs+ of unnecessary/redundant equipment and could then fight at 27000ft. But that was in October and P-38s were arriving shortly. Why wait so long?

Agree

Agree 100%. I also believe that during it's development and early deployment the CG issues and false performance claims eventually pissed off the AAF. As we both know having worked a bit around aircraft, if you have an aircraft that is naturally tail heavy, this could be easily adjusted with ballast, but it seems that Bell initially refuse to accept the fact that the aircraft had C/G issues.

Although from Wiki and probably previously posted, sources are identified:

The weight distribution of the P-39 was supposedly the reason for its tendency to enter a dangerous flat spin, a characteristic Soviet test pilots were able to demonstrate to the skeptical manufacturer who had been unable to reproduce the effect. After extensive tests, it was determined the spin could only be induced if the aircraft was improperly loaded, with no ammunition in the front compartment. The flight manual noted a need to ballast the front ammunition compartment with the appropriate weight of shell casings to achieve a reasonable center of gravity.

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. 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.

And as mentioned earlier, Bell never learned from their mistakes:

In February 1944, the Soviet government sent a highly experienced test pilot, Andrey G. Kochetkov, and an aviation engineer, Fyodor P. Suprun, to the Bell factories to participate in the development of the first production variant, the P-63A. Initially ignored by Bell engineers, Kochetkov's expert testing of the machine's spin characteristics (which led to airframe buckling) eventually led to a significant Soviet role in the development. After flat spin recovery proved impossible, and upon Kochetkov's making a final recommendation that pilots should bail out upon entering such a spin, he received a commendation from the Irving Parachute Company. The Kingcobra's maximum aft CG was moved forward to facilitate recovery from spins.

Personally I believe that Bell engineers knew they couldn't get the speeds promised by their management to the AAF so they intentionally kept the aircraft tail heavy to squeeze a few more MPH out of the aircraft and that's why they were so reluctant to listen to the Soviets - this is just my personal opinion.

Now fast forward a bit - the post war Thompson Trophy Races. the P-39s and P-63s operated for racing did real well with a P-39 winning the 1946 race. Although you need the performance, there's a lot more pilot skill involved as you're flying "a line" without cutting a pylon. Aside from souping up engines and modifying airframes, the other thing you're going to do to get the aircraft to fly a little faster is make the aircraft tail heavy.... Keep beating this tail heavy horse to death, it suits your narrative. No P-39 ever went into combat with NO NOSE AMMO. When nose ammo was expended the shell casings remained which achieved a reasonable center of gravity. Chuck Yeager said it had excellent handling characteristics and people who said otherwise had never flown the plane.

Low and tail heavy, the P-39 and P-63 made perfect racers!

Please expand above.

 

[FLYBOYJ]

Sorry, all P-39Ds and P-400s had full 120gal internal fuel.

So then they were even heavier and with worse performance than what we've been working to, right?!?!?!

Easily lightened at forward bases.

P-39D and P-400 would have significantly better performance if lightened.

Could have, would have, should have." If it was easily done why wasn't it?!?!?

Compare the M/N/Q with P-38J/L? There were no P-38J/Ls during P-39M/N/Q production.

Just like there were no P-39Ns in the SWP in late 1942! P-38Js started production in the summer of 43. An even better Lightning was coming and leadership at the time knew it.

P-38J/L came after the Q had finished production. Better to compare the P-38F/G that were available at the same time.

And better compare the P-38F/G with the P-39D and P-400. It's apparent General Kenny did!!!

 

[P-39 Expert]

How can you continue to argue this? You say yourself that the P-51 was a ton heavier and it was accepted with any Allison or RR engine put in it. All airforces wanted to increase firepower, if they couldnt put them in the wings they put them in pods, 20mm cannon are much more than 2 times the weight of 0.303mgs, no now you can answer those questions in future, cant you?

Biggest drawback to 30calMG is effective range was only 200 yards (AHT). All air forces wanted to increase firepower but it had to be used judiciously. Otherwise why not just put 10 50calMGs on every fighter? Because it would have weighed too much. P-51A/B/C, FM2 Wildcat and F8F Bearcat had reduced guns to four from six or eight on previous fighters. Four was deemed sufficient for the time. P-39 nose armament (cannon and twin 50cal MGs) produced more firepower than four 50cal MGs.

 

[FLYBOYJ]

Actually was done at Guadalcanal. K/L models were reduced by 600lbs+ of unnecessary/redundant equipment and could then fight at 27000ft. But that was in October and P-38s were arriving shortly. Why wait so long?

You said it yourself - the P-38s were arriving.

Keep beating this tail heavy horse to death, it suits your narrative.

I'm learning from example!!!!

No P-39 ever went into combat with NO NOSE AMMO.

But as stated, they should have came home with none either

When nose ammo was expended the shell casings remained which achieved a reasonable center of gravity.

And why was that done?!? And why did Bell ignore known issues with the C/G? Why did they ignore the Russians at the beginning of P-63 production?!?!

Chuck Yeager said it had excellent handling characteristics and people who said otherwise had never flown the plane.

And as we know he was arguably one of the best combat pilots of WW2 but he was just one man and didn't have to fly it at Port Moresby against the Zero or Oscar!!

And agree, the aircraft had "excellent handling characteristics " but it had many other issues that caused it to go second string.

Except for the Russians - the Russians liked it! Oh - and it was a great post-war race plane!

 

[pbehn]

Keep beating this tail heavy horse to death, it suits your narrative. No P-39 ever went into combat with NO NOSE AMMO. When nose ammo was expended the shell casings remained which achieved a reasonable center of gravity. Chuck Yeager said it had excellent handling characteristics and people who said otherwise had never flown the plane. .

It is not a dead horse, and Yeager never flew it in combat.

from here The Bell P-39 Airacobra & P-63 Kingcobra
In USAAF hands, its record was mixed: it was sturdy and well-armed, but its high-altitude performance was poor and its centrally-mounted engine led to handling problems. The difficulty was that after ammunition was expended, the aircraft's CG shifted back so that the aircraft was inclined to fly tail-first, throwing it into a flat spin from which recovery was problematic. Bailing out under such conditions was also troublesome, because the pilot had a tendency to hit the tail. Even if recovery were possible, the spin had a tendency to warp the aircraft's tail, rendering the controls useless, which is why the P-39Q-25 introduced a reinforced rear fuselage.




Another reason was that the Red Air Force thoroughly evaluated the Airacobra before putting it into service, finding out the hard way about its vicious spin characteristics, with several test pilots killed. The faults were documented, however, with rules for flying the aircraft written up for operational pilots -- they were warned to never perform aerobatics if they had expended their ammunition -- and training implemented to make sure P-39 pilots knew how to avoid spins and, when possible, head them off before the point of no return. Procedures had to be devised for maintenance in extreme cold conditions. Bell engineers went to the USSR to assist the Soviets in qualifying the P-39, obtaining feedback for refinements to the design.

 

[pbehn]

Biggest drawback to 30calMG is effective range was only 200 yards (AHT). All air forces wanted to increase firepower but it had to be used judiciously. Otherwise why not just put 10 50calMGs on every fighter? Because it would have weighed too much. P-51A/B/C, FM2 Wildcat and F8F Bearcat had reduced guns to four from six or eight on previous fighters. Four was deemed sufficient for the time. P-39 nose armament (cannon and twin 50cal MGs) produced more firepower than four 50cal MGs.

At what time? The Mustang MkI had 4x 0.5" and 4x 0.3" The Mustang MkIA had 4x20mm. Some Spitfires in the Med had 4x20mm cannon and 4x0.303mgs. Only the P-51B/C had 4x0.5 the D went to 6x 0.5"

 

[Thumpalumpacus]

Is it just me or does anyone else wish that P-39 Expert would learn how to use the quoting system properly?

 

[FLYBOYJ]

It is not a dead horse, and Yeager never flew it in combat.

from here The Bell P-39 Airacobra & P-63 Kingcobra
In USAAF hands, its record was mixed: it was sturdy and well-armed, but its high-altitude performance was poor and its centrally-mounted engine led to handling problems. The difficulty was that after ammunition was expended, the aircraft's CG shifted back so that the aircraft was inclined to fly tail-first, throwing it into a flat spin from which recovery was problematic. Bailing out under such conditions was also troublesome, because the pilot had a tendency to hit the tail. Even if recovery were possible, the spin had a tendency to warp the aircraft's tail, rendering the controls useless, which is why the P-39Q-25 introduced a reinforced rear fuselage.




Another reason was that the Red Air Force thoroughly evaluated the Airacobra before putting it into service, finding out the hard way about its vicious spin characteristics, with several test pilots killed. The faults were documented, however, with rules for flying the aircraft written up for operational pilots -- they were warned to never perform aerobatics if they had expended their ammunition -- and training implemented to make sure P-39 pilots knew how to avoid spins and, when possible, head them off before the point of no return. Procedures had to be devised for maintenance in extreme cold conditions. Bell engineers went to the USSR to assist the Soviets in qualifying the P-39, obtaining feedback for refinements to the design.

From your reference;

"The P-39D left something to be desired in service, suffering from a range of teething problems such as gear that was unreliable or froze up and other deficiencies. Deficiencies were addressed in subsequent variants, initially with a confusing list of P-39 variants built in small or relatively limited numbers." and

"However, British expectations of the "Airacobra I" -- as it was designated in Royal Air Force (RAF) service -- had been set by performance figures established by the unarmed and unarmored XP-39 prototype. On evaluation, the P-400 turned out to be about 10% slower than advertised, and of course its high-altitude performance was pathetic. It should be noted, however, that Bell engineers were correct in believing the mid-mounted engine was good for maneuverability, the RAF report concluding that an Airacobra could easily out-turn a Messerchmitt Bf 109."

Give credit where credit is due!

 

[FLYBOYJ]

Is it just me or does anyone else wish that P-39 Expert would learn how to use the quoting system properly?

Agree - this is going to become an issue

 

[SaparotRob]

Is it just me or does anyone else wish that P-39 Expert would learn how to use the quoting system properly?

I still haven't figured it out. Like how to quote just one sentence instead of the whole post.

 

[FLYBOYJ]

And a little more about the C/G and spins:

Another reason was that the Red Air Force thoroughly evaluated the Airacobra before putting it into service, finding out the hard way about its vicious spin characteristics, with several test pilots killed. The faults were documented, however, with rules for flying the aircraft written up for operational pilots -- they were warned to never perform aerobatics if they had expended their ammunition -- and training implemented to make sure P-39 pilots knew how to avoid spins and, when possible, head them off before the point of no return. Procedures had to be devised for maintenance in extreme cold conditions. Bell engineers went to the USSR to assist the Soviets in qualifying the P-39, obtaining feedback for refinements to the design.

Comrade - no victory roll for you!

 

[Thumpalumpacus]

I still haven't figured it out. Like how to quote just one sentence instead of the whole post.

Just put "[/quote]" at the end of the part you want to reference, and delete the rest. Or separate it into another paragraph. If you want to learn that we can take it to PM, it's easy but there's no sense in interrupting the flogging of a deceased equine.

 

[pbehn]

From your reference;

"The P-39D left something to be desired in service, suffering from a range of teething problems such as gear that was unreliable or froze up and other deficiencies. Deficiencies were addressed in subsequent variants, initially with a confusing list of P-39 variants built in small or relatively limited numbers." and

"However, British expectations of the "Airacobra I" -- as it was designated in Royal Air Force (RAF) service -- had been set by performance figures established by the unarmed and unarmored XP-39 prototype. On evaluation, the P-400 turned out to be about 10% slower than advertised, and of course its high-altitude performance was pathetic. It should be noted, however, that Bell engineers were correct in believing the mid-mounted engine was good for maneuverability, the RAF report concluding that an Airacobra could easily out-turn a Messerchmitt Bf 109."

Give credit where credit is due!

I agree, the decision to send P-39s to Russia was political and logistical. On Baughers site it states (to paraphrase) that the British would have taken more, but they were already ordered on Lend Lease but after June 1941 Russias need was greater and after December 1941 the USAs short term need was greatest of all. I wish I could find that article again on the Russians commissioning the P-39, it involved getting the drawings out and stripping one down to the nuts and bolts to decide how to service it and what with (greases lubricants etc) and where to install drains to drain oil coolants etc so they didnt freeze in extreme cold.

 

[pbehn]

I still haven't figured it out. Like how to quote just one sentence instead of the whole post.

Just do the quote and then delete out what you dont want. If quoting something that is already a quote an so doesnt appear, press quote/reply copy what you want to quote into the gap in the brackets.

 

[Milosh]

I still haven't figured it out. Like how to quote just one sentence instead of the whole post.

Just highlight what you want to quote. A popup appears with 'Quote' or 'Reply'.

 

[Dimlee]

Interesting information and something I hadn't heard before. I admit my first thought was the most senior person would probably be the NKVD Commissar, but that's just me.

People of the secret services have accompanied most of the delegations which were sent abroad. But they kept a lower profile usually and their authority was limited to security and ideology. Unless they were stupid.