page_title: Benjamin S. Kelsey
section_title: P-39 Airacobra
hierarchical_section_title: Benjamin S. Kelsey / Fighter development / P-39 Airacobra
context_page_description: Benjamin Scovill Kelsey was an American aeronautical engineer and test pilot. Serving as America's chief fighter projects officer, he helped bring success in World War II to the United States Army Air Forces by initiating the manufacture of innovative fighter aircraft designs, and by working to quickly increase American fighter production to meet the needs of the coming war.
  Kelsey co-authored the technical specifications which led to the development of the P-39 Airacobra and the P-38 Lightning. He worked around Air Corps strictures to initiate the development of drop tanks for American fighters. Kelsey was the driving force behind a program of advanced airfoil research which eventually resulted in the P-51 Mustang.
  After the war, Kelsey served in various staff assignments supervising weather operations, personnel and materiel. He was an important committee member of the group that approved and funded the rocket-powered North American X-15.
context_section_description: Kelsey became frustrated by inflexible Air Corps restrictions on pursuit (fighter) aircraft which limited the weight of all guns and ammunition to 500 lbs. He wished for at least 1,000 pounds (450 kg) of armament so that American fighters could dominate their battles. With Lieutenant Gordon P. Saville, Kelsey formulated two new high-altitude fighter specifications in February 1937; one for a single-engine fighter and one for a twin-engine fighter. In Circular Proposal X-608 and X-609, the two men employed the word "interceptor" which had not yet been applied to American military aircraft specifications. In this way, they bypassed the Air Corps limitations. Despite the new term, the proposed aircraft were not fundamentally different in role than traditional pursuit aircraft—just heavier and more powerful. Kelsey specified Allison V-1710 engines with General Electric turbo-superchargers and tricycle landing gear in both proposals, aiming for 360-mile-per-hour (580 km/h) performance, long range, the ability to climb to 20,000 feet (6,100 m) in six minutes, and very heavy armament including a cannon.
  Bell Aircraft won the single-engine X-609 contract with their design of the P-39 Airacobra. After the prototype flew, Kelsey was called to England, and handed oversight of the project off to colleagues who, in keeping with advice from the National Advisory Committee for Aeronautics (NACA), ordered the removal of turbo-superchargers from the aircraft. The P-39 was from that point forward unable to compete in the European Theater against high-altitude German fighters. In Soviet hands, however, the Airacobra excelled in air-to-air combat at low and medium altitudes, racking up the highest individual pilot scores for any American-made fighter type, higher than any other American fighter aircraft ever made.
caption: A P-39C Airacobra at Selfridge Field
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