I once read an article ( on the net - forgot where) about Airacobra and how it was spoiled. It stated that prototype was a good aircraft, but was later ruined by military. Prototype was lighter and was equiped with supercharger. First thing USAAF requested was removal of supercharger ( it was not reliable) and adding a lot of additional armour. It became a lot heavier power/weight ratio was horrible (comparing to prototype). P-63 is said to have similar caracteristics as XP-39, but came much later ( too late for serious fighting). Soviets liked Cobra becouse of armour, firepower and low-level flight caracteristics. What you managed to hit you killed. It made first debut on the eastern front during battles on Kuban peninsular ( ex RAF planes). At the time best fighters soviets had were Yak-1, Yak-7B/Di, Yak-9(early series), LaGG-3 ( ser.35, ser.66) and first La-5. It was mainly used as bomber killer and also as dogfighter. At the beggining it was also used for strafing. It was rearly used as tank killer. Good point is that russians almost never used Cobra (or other planes) at high altitudes, for that work they kept MiG-3 in frontline service up to 1944( production of MiG-3 was discontinued in early 1942)
Yes, the Russians had much better ideas on how to use the P-39 properly. Interestingly enough, a squadron of the export version of the Airacobra, the P-400, was assigned to Henderson Field on Guadalcanal after the USA invaded the island. The planes had a high pressure oxygen system that could not be recharged with the available equipment on the field, so they were used mainly for ground attack. By all accounts, they got very good at it, too.
Good against troops in the open, but less effective than cannon against vehicles, buildings etc. Tony Williams: Military gun and ammunition website and discussion forum
Oh? Are you sure that wasn't a picture of a P-51 that you saw? As far as I know, no Airacobras were ever assigned to Iwo Jima after its capture.