Quote:
Originally Posted by horseback
First, and greatest, was that it had limited range and like all Allison powered fighters without a turbosupercharger system, it quickly lost performance above 12,000 to 15,000 ft.
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Good analysis.
It's especially important to recall that early in the war American fighters in the SW Pacific were often called on to be high/middle altitude interceptors against Japanese bombers flying from Rabaul or other bases on or around New Guinea, so high altitude performance and long loiter time were crucial. The P-39 just didn't have the range to be a good bomber escort or long-ranged strike fighter. And it didn't have the high-altitude performance to be a good interceptor.
On New Guinea, offensive missions required pilots to fly over the Owen Stanley Mountains, which are about 12-13,000 feet high - long distances at right about the level where the P-39 starts to lose performance. On Guadacanal, things were even worse, since any offensive operations required long high-altitude flights over water. So, the P-39's "short legs" and poor high altitude performance really grated on pilots, especially since there weren't a whole lot of good places to land.
Another minor issue that Horseback only slightly touched on was the fact that the P-39 was "weird" and "high tech" by the standards of the day. Its tricycle landing gear was different than the typical "tail-dragger" fighters and it's center-mounted engine not only gave it nasty spin recovery characteristics but also made it a maintenance headache (harder to access the engine, the long driveshift for the propeller was a hassle to swap out). Bell made a lot of design trade-offs to put a big cannon in the P-39's nose!
By contrast, the P-40 was longer-ranged, had better high altitude performance, and because it was a progressive development of the P-36, was more familiar to U.S. ground crews and was easier to maintain.
I'd also guess that U.S. pilots were more familiar with the P-40's guns and gun layout, since it had the typical U.S. arrangement of 4-6 wing-mounted 0.50 caliber guns. The 0.50 calibers worked just fine against the lightly-protected Japanese planes of the time, they fired faster, they carried more ammo and they were more or less interchangeable with the 0.50 caliber MG used by the Army ground troops, which made supply and maintenance easier.
By contrast, the Russian Front was perfect for the P-39 - lots of short-ranged, low-level action, mostly fought over land, against more heavily-protected targets where the 20mm cannon was the better weapon. Additionally, while the P-39 was somewhat tricky to maintain, it was inherently a higher-quality product than some of the Soviet fighters available. Soviet pilots appreciated the amenities that Western pilots took for granted, like reflector sights and cockpit heaters, and appreciated its relatively superior reliability.