Bell P-39 Airacobra

Ron, e-mail, 28.07.2010 00:52 Just re-engine the P-39 with the new V-1710-93 would have given it a new lease on life by early 1943 without breaking stride. Poof, no more glass ceiling at 15,000'; 1500 hp boosted; 10,000' more altitude performance and 400+ mph! Go ahead and save the water-injected Allison for the P-63 later on for 1800 hp in good time. In one change the P-39 would fly like a real contender in the middle of WW2. It's power of maneuver would perhaps improve it's spin problems too. reply

Ron, e-mail, 27.07.2010 22:56 Edward W, I've read that when gun wear was sufficient, Russian UBS Cowl 12.7-mm guns and a hub ShVAK 20-mm cannon (B-20 for the later P-63) replaced them typically. Then I read that it happened sooner than later on occassion. A few liked the wing guns but mostly they were stripped to unweight the wings for dogfighting. reply

Aaron, e-mail, 04.08.2010 18:56 Found fighter comparison chart showing P-39N reaching 397 mph around 10,000 ft. (338 at S.L.). Climb was 4175 fpm at S.L. and 4425 fpm around 8,000 ft. These figures taken from a graph chart comparing p-39N to others such as p-63, FW-190, ZERO, and others. No test weights or power settings given. reply

Ron, e-mail, 06.08.2010 22:45 Aaron, Where might I find this chart? Was it a stripped Russian version? They were happy with low altitude performance and a big stick, no frills needed. reply

Aaron, e-mail, 07.08.2010 19:13 Hi Ron, I tried to answer your questions earlier but info would not save. I'll try sending this first, then try again. reply

Aaron, e-mail, 08.08.2010 15:32 Ron, I sent you an e-mail on the location of the chart. Appears to be a military chart so I would guess the P-39N to be up to USAAF standards. Imagine how much quicker climbing the VVS Airacobra was. No wing guns and throttle to the wall...WOW! reply

Ron, e-mail, 24.08.2010 00:59 Makes you wonder about that P-39N restoring it's reputation in the West vs P-40 and F4F and dare I say Spitfire at that time. To my knowledge those stats haven't been too well published since. I'd be curious about the power-plant of course. reply

Wulfiewulf, e-mail, 08.05.2010 12:04 what happened to all these Russkie P39 after the war, melted down for Migs I guess? Would be facinating to see any pics of assembled war wearies! reply

Ron, e-mail, 29.04.2010 21:58 Truman, Sorry I don't have the data plates but since you worked at Bell, could you tell me about the synchronized rate of fire for the cowl .50 Cal. MGs? Did the reduction gear dictate a 300 r /m rate each no matter if the cowl gun was a Browning or anything else (faster UBS 12.7mm etc...)? How fast was the rate of fire for cowl mounted Browning .50 Cal. MGs if geared to the Allison engine mounted in the nose like the early P-40 or early P-51 for example? Not that I could expect such details, but thought I'd ask anyway. Seems like the P-63 had the same rate, though later faster Brownings were available for it. But the wing mounted ones were faster than in the earlier P-39Q. Am I wrong? Could you set the record straight? reply

Truman, e-mail, 31.03.2010 23:01 I worked at Bell Aircraft. I like the P-39 Airacobra. I am presently involved with 4 P-39 projects. One is the plane that was pulled out of the Russian lake after 60 years. One is "Cobra I", which crashed into Lake Ontario in 1946. The other two are currently being restored in Australia. I am assisting them by supplying the approximate 180 different stencil information and locations via 1 /12 scale drawings. I have finally rounded up all the info. for all the markings on the inside of the cockpit doors- even to the size and style of lettering. I have all the info. for the data plates on the inside of the cockpit rollover structure. WHAT I DON'T HAVE IS THE INFO. ON THE SMALL (2 1 /2" x 1 1 /4") DATA PLATE THAT IS FOUND ON 17-18 SUB-ASSEMBLIES OF THE PLANE. If anyone has one of these data plates that they could make a GOOD copy of, or they have a GOOD photo of one, I would appreciate it very, very much if you could send me a copy of it. The data plate has spaces for: Serial No.,Dwg. No., A.F.T.O. No.,Inspection, and Modif. No. I am especially interested in knowing what the "stamped /punched" info. is in the space after Serial No. My intention is to replicate all the markings on the doors plus the rollover data plates and the small subassembly data plates. Thanks for all of your help, Truman reply

Aaron, e-mail, 30.08.2010 18:56 From what I have read in many articles and interviews the P-40 was prefered by the USAAF because of its better range and maneuverability (roll rate /turning ability. The P-400 underpowered Airacobra did not help its image either. The P-39D was still underpowered but the pilots in New Guinea and the Russians removed all wing guns to improve overall performance. When the better powered P-39L, M, N and Qs came along the reputation damage was already done. In an interview with Russian ace Nikolay Golodnikov he states that the P-39 was a responsive and dynamic fighter. He further states that the Fokker (FW-190A) was not equal to the Airacobra (P-39Q?) in the verticle plane. He considered the FW-190 weakest characteristic (compaired to the VVS fighters) was its acceleation dynamic. He continued by saying that when they assigned fighters to escort bombers, the "attack group" would comprise of Airacobras or Lavochkins and the direct cover group was comprised of Yaks. He said it was better to have heavier aircraft in the attack group in order to chase down Germans in a dive. reply

Ron, e-mail, 18.03.2010 04:13 Can you imagine a seriously stripped cobra? No added armor (the motor in back of the pilot is plenty). No guns in the wings. Just 1 radio. Take a Mikulin AM-38 in place of the Allison. A ShVAK 20mm and 2 UBS 12.7mm in place of the Olds and Brownings in the nose. Voila! (French, I know. What's the Russian word?) Finally, the interceptor Bell meant it to be! Now you can climb, roll, and turn even better. No more altitude sickness. And the 3 guns are putting out more rounds per second (40+) than the 5 American guns did (37), and they'd have harmonized high-powered ballistics. All the better for dogfighting. Need a 37mm for enemy bombers? Use the Soviet NS-37 for more than twice the firepower of the U.S. Olds 37. Overheat too much? Keep them on the northern front of the Soviet Union. Not enough range? Use drop tanks until engaged with the Luftwaffe. For all we know, many of these things were done, but not by us. What we did was take the P-63 fighter-bomber which was a ton heavier (loaded) than the P-39 fighter, and add more armor (till it could hardly take-off) for target practice. We couldn't see the value of a mid-engine aerobatic fighter to counter the nimble Japanese. The Russians did. They even downed a Nakajima interceptor with a P-63 no less. reply

Aaron, e-mail, 03.09.2010 22:30 ALLISON DIVISION, GENERAL MOTORS CORP., INDIANAPOSIS, INDIANA: December 12, 1942. A letter was sent to the Commanding General of the Army Air Forces, Material Center in Washington, D.C. The subject listed was: Service Use of High Power Outputs on Allison V-1710 Engines. This letter was informing the AAF that Allison was aware that military pilots were using 66" and even 70" of boost in combat. In the letter paragraph No.2 states: While we cannot help but feel pleased that our engines are standing up apparently to the particular squadron's satisfaction under these conditions, we also cannot help but feel that the selection of such high manifold pressures may be based on inadequate testing and that they are very apt to result in occasional failures which may occur some time after the operation at such high horsepowers but when operating normally or even crusing with resultant loss of pilot and aircraft. ENGLISH TRANSLATION: The V-1710-39 and -73 were being pushed to approximately 1780 hp. at 60 degrees F. and they were holding up just fine. The reason for the letter was that the supercharger blowing gear of the -39 and -73 was 8.8:1. The newer V-1710 were being produced with 9.6:1. This new gear would cause earlier detonation in the pistons. 1780hp. out of the engines in the P-40D,E&K and P-51&NA-73. That was in US squadrons. The Russian pilots had no hesitation about pushing their P-39s past the limit. TRANSLATION: 1780hp., match that to the published horsepower ratings of the P-51D, P-63 or Bf.109G. I would really like to see a performance testing of a P-39D being pushed to 66" /+18 lb. of boost. No wonder the Russians loved the plane. reply

Ron, e-mail, 16.02.2010 02:25 WHEN i mentioned intake, I mean in the combustion chamber. It was too undeveloped vs it's peers. The Connie inverted inline became a dead-end unfortunately. The best allied inline should have replaced it on the production line back when it first disappointed Bell. The Merlin or powerful Mikulin AM-38. The Klimov M-105 was not more powerful than the Allison and had the negative 'g' problem of the early Merlins. Failing all that, make an American injected and boosted 'DB-601' style inline for that period. That's what the Italians did well (Alfa Romeo Monsonie) but the Japanese, not so well (perhaps weight reduction made the Ha-40 worse in this case). If Allison and Continental had combined, who knows? All this could have been developed on the Airabonita without delaying the P-39 production. reply

Ron, e-mail, 07.02.2010 08:49 I know it is fantasy to play what if.. But since the basic spin problem was due to a light nose after too much ammo was spent, what if the pilot and weapons swapped places (cockpit forward as in the trainer design but without the back seat) putting the ammo on the c /g. Longer gun barrels wouldn't hurt, improve ballistics if anything (of course the hub gun would go, but 4 synchronized UBS /ShVAK-like guns could be in the sides of the fuselage) If that's not pretty enough, then displace the lost weight as you go, using ballast or something (sliding armor plates). The problems with tail rudder and elevator contact during a spin could be simply avoided by moving the tailplane forward ala Zero or P-51, perhaps enhancing turning time too. P-39s didn't sputter bunting into a negative 'g' dive like the early Merlin powered RAF fighters of the same period (or Yaks too for that matter). So why not install the improved Allison like those in the P-38 (at least a contender vs P-39 /P-40). Why did Bell take so long before fielding a water injected 2 stage supercharged Allison powered P-63C, 1945? Like the early P-51 with a refined Merlin replacing it's Allison engine, Bell (and Curtis too) should have followed suit. Allison should have followed in the steps of Packard which started producing Merlins for the Mustang. At least a few production lines anyway. North American didn't wait around like Bell once the negative 'g' trouble was cured on the Rolls-Royce Merlin. Either way, U.S. fighters being produced from about 1943 on should have only had competitive powerplants, export or not. No excuses. As it was, the P-39 with a 1 stage supercharged Allison would inevitably use too much war emergency to last very long due to overheating. A 3rd point would be this. When the Russian delegation visited the Bell factory to give input for the P-63 they should have installed and demonstrated the Soviet guns of the same caliber like the NS-37 and the UBS 12.7 mm and for the P-400 fans the ShVAK or the later B-20. I know I mentioned this before. But P-39s were faulted for mixed ballistic performance. Switching to these guns at the Bell factory (or something like them) would have addressed this. It's no secret that these powerful weapons found their way into Russian Cobras but certainly U.S. pilots should have benefitted too. Bell should have ceased installing the .30 Cal wing guns long before the P-39Q! At least an American version of the high velocity NS-37 cannon and the others would have almost tripled the total firepower! Thus 3 guns would suffice. Their muzzle velocity was all on the same page too. The complaints by U.S. airmen about the slow synchronized rate of fire for the browning .50 Cal (12.7 mm) P-40B cowl guns averaging around 425 r /m made the P-39 look bad at 300 r /m while the Soviet synchronized 12.7 mm UBS fired over 800 r /m each! And the bullet was even heavier not lighter 48 vs 43 gm. Gone would be the jamming headaches of the Olds T4 37 mm or the Hispano 20 mm cannons. The RAF Hispano was more refined than the American Hispano but both paled in comparison to the ShVAK 20 mm or lightweight B-20 in Russian fighters. All had great ballistics but the Hispano was less reliable. On the other hand it fired a heavier shell 130 vs 98 gm. The Hispano was slower and I don't know if it was ever synchronized like the Russian 20 mm. Even then they were as fast as the Hispano unsynchronized: 600-710 r /m - most; ShVAK /B-20: around 750-850 (708 r /m synchronized). I'll leave the Vya-23 alone for now. The P-39 that the U.S. pilots regarded as a dog could have been so much more. reply

hal, e-mail, 04.02.2010 20:14 Hmmm, where to start. Main reason Soviets were more successful with P-39 was reduced weight by deleting worthless .30 cal wing guns that weighed (with ammo)400 pounds ("good for damaging German paint" said Soviets). At 7100# Airacobra was equal to 109 and 190 at all altitudes up to 26,000'. Turbo was deleted because it wasn't ready or reliable. If not deleted P-39 would not have been ready for WWII. Turbo P-38 didn't see combat until 12 /42, P-39 without turbo was ready in Jan /41. U.S. would have been in trouble without P-39 in 1942. Armament (without .30 cal wing guns) considered excellent and devastating by Soviets. No mechanical problems occurred with 37mm cannon unlike U.S. Soviets used P-39 as air superiority fighter (interceptor /escort) not ground attack resulting in 4 0f top 5 Soviet aces flying Cobra. P-39 was finest fighter in Soviet inventory and was discarded by U.S. much too early. Allison engine with mechanical second stage (in P-63) would have equalled P-51 Merlin performance at high altitude. U.S. gave up on P-39 based on promise of P-47 (somewhat unfulfilled) and gave them to the Soviets who deleted the worthless wing guns and won the war with them. reply

Ron, e-mail, 31.01.2010 08:21 Another problem concerned the P-39's Allison V-1710 engine. The engine's advertized operational life of 250 hours fell short in Russian front combat conditions, where it lasted only around 65% of that. The degraded performance was attributed to excessive boost that overheated the engine oil and fused bearings. Use of poor quality oil and gasoline also contributed to this. When there was a shortage of American spares over 100 P-39s were refitted with hardy Soviet M-105P engines. Can you imagine one of those with Russian weapons installed when the U.S. originals were worn out as well? reply

Ron, e-mail, 31.01.2010 07:49 Soviet P-39 kill ratio against the Luftwaffe was 4 to one in favor of the Cobra to the end of WW 2. Many of it's losses were due to fatal spins when very low on ammo in the nose. Even many top Russian pilots fell victim to this accident. Very quick reaction was necessary to recover. reply

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