Cobra I, Pilot: Jack Woolams, 1946 Thompson Trophy Race - The Bell P-39 was a revolutionary designed aircraft with the engine placed in the middle of the fuselage just behind the cockpit. The propeller shaft ran under the cockpit floor just beneath the pilotåÕs feet. All this was done to make room for the 37mm M4 canon that fired through the propeller hub. The M4 turned out to have limited ammunition, slow rate of fire and prone to jamming. To add to the poor performance a turbocharger wasnåÕt provided limiting the aircraft to low level duties.