History:
The P-39 Airacobra was one of the most unusual single-seat fighters ever ordered by the Army Air Corps. It had been a standard practice among manufacturers to design an airplane around an engine. However, this was the first time a plane had been designed around a gun; the American Armament Corporation's 37-millimeter cannon.
The Bell engineers wanted to mount the cannon so it would fire directly through the propeller shaft. This meant the engine would have to be located deep in the fuselage, behind the pilot, so he would have access to the breech mechanism of the cannon. This dictated that the machine would have a tricycle landing gear, which was the first such gear ever used on a production fighter.
The Air Corps ordered one XP-39 on October 7, 1937. The plane was ready for flight testing in April 1939, and that same month Bell was contracted to build another 13 for service testing. Meanwhile, various design changes were made in the XP-39 to improve performance. One of these changes was to eliminate the superger, which lowered the effective operating altitude.
Eighty production models of the P-39 were ordered by the Air Corps in August 1939. Before the first of these was delivered, the French ordered the airplane in quantity. When France was defeated in 1940, the order was taken over by the British Purchasing Commission.
Production models of the P-39C started arriving at Air Corps squadrons in January 1941, and six months later, the first Airacobras reached England. The British had planned to order 675 of the planes, but after disappointing combat experience, the order was canceled. At that time, the Royal Air Force needed planes for aerial fighting, and while they found the Airacobra fine for low-level operations, performance fell off sharply at high altitudes.
When Japan attacked the United States, the P-39 and the Curtiss P-40 , were the principal American land based fighters. Airacobras first went into action against the Japanese in April 1942. Three months later, they made their first sorties in Europe and, six of the 12 planes that took off, failed to return to their base.
The Airacobra was never outstanding in combat. Ironically it was extremely difficult to service because of the engine placement. However, it was excellent for low-level operations against ground targets. About 9,560 of the planes were produced, approximately half of which were sent to Russia under the Lend-Lease program. The final model, the P-63 Kingcobra, was considerably improved.
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