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

[Milosh]

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.

 

[Peter Gunn]

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.

 

[Glider]

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

 

[pbehn]

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.

 

[DarrenW]

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?

 

[Elmas]

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...

 

[DarrenW]

Tell me again how great a dogfighter the Hellcas was.

If we can cruise at less than 2600rpm maximum cruise (not recommended over Europe) then we can go farther. All hail the mighty Thunderbolt.

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....

 

[DarrenW]

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.

 

[P-39 Expert]

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.

The chart below may help. Looks like just about 100hp difference at every altitude.

 

[drgondog]

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

 

[DarrenW]

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!

 

[DarrenW]

Sounds like a winner to me! Good luck and please let us know when it's available for purchase.

 

[P-39 Expert]

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.

 

[Shortround6]

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.

 

[Shortround6]

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.

 

[pbehn]

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

 

[DarrenW]

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.

 

[DarrenW]

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?

 

[Shortround6]

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.

 

[Glider]

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