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).
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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.
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Typical deficiencies for foreign aircraft surfaced from the first days of its use: reduced outflow of oil from the lubrication system, the remnants of which quickly froze in the cold weather. The technicians quickly had to rework the lubrication system by means of installing additional oil taps [as in "faucets"] and also to create a special collector for the simultaneous induction of hot air into the crankcase, reduction box, radiator, and other areas that required warming before starting the engine. This collector successfully withstood testing and was recommended for implementation in the employment of the airplane.
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After completion of testing, approximately in April 1942, the Airacobra I fighter began to be issued to combat units. The procedure for re-equipping a unit with new aircraft was standard. A fighter air regiment that had suffered losses at the front turned over its remaining serviceable aircraft to neighboring units. The personnel of this regiment were sent to the 22d ZAP. Here over the course of 1-2 months the regiment was re-trained, reconstituted in personnel up to TOE [table of organization and equipment] level, issued new equipment, and then returned to the front. Losses in aircraft of the new type were also made up by deliveries from the same 22d ZAP.
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
