Along with its use as a general fighter , the P was used in various aerial combat roles, including as a highly effective fighter-bomber , a night fighter , and a long-range escort fighter when equipped with drop tanks. MacDonald 27 victories. Kelsey and Gordon P. Saville for a twin-engined, high-altitude "interceptor" having "the tactical mission of interception and attack of hostile aircraft at high altitude. Kelsey was looking for a minimum of 1, lb kg of armament.
The unbuilt Vultee XP design was offered to fill this requirement, but was not advanced enough to merit further investigation. A similar proposal for a single-engined fighter was issued at the same time, Circular Proposal X, in response to which the Bell P Airacobra was designed. Lockheed formed a secretive engineering team to implement the project apart from the main factory; this approach later became known as Skunk Works.
The eventual configuration was rare in contemporary production fighter aircraft design, with the Dutch Fokker G. The Lockheed team chose twin booms to accommodate the tail assembly, engines, and turbosuperchargers, with a central nacelle for the pilot and armament. The XP gondola mockup was designed to mount two. Further armament experiments from March to June resulted in the PE combat configuration of four M2 Browning machine guns, and one Hispano 20 mm.
Clustering all the armament in the nose was unusual in U. The P cannon used heavier 20 mm rounds, creating a different trajectory, so it was inclined upward slightly more than the four machine guns such that the trajectories of the cannon rounds and. A Lightning could reliably hit targets at any range up to 1, yd m , whereas the wing guns of other fighters were optimized for a specific range.
Combined rate of fire was over 4, rpm with roughly every sixth projectile a 20 mm shell. The Lockheed design incorporated tricycle undercarriage and a bubble canopy, and featured two 1, hp kW turbosupercharged cylinder Allison V engines fitted with counter-rotating propellers to eliminate the effect of engine torque , with the turbochargers positioned behind the engines, the exhaust side of the units exposed along the dorsal surfaces of the booms.
