page_title: Bell P-63 Kingcobra
section_title: XP-63
hierarchical_section_title: Bell P-63 Kingcobra / Design and development / XP-63
caption_attribution_description: P-59A (S/N 44-22609, first production -A model) and P-63 (S/N 42-69417) in flight.
context_page_description: The Bell P-63 Kingcobra is an American fighter aircraft developed by Bell Aircraft during World War II. Based on the preceding Bell P-39 Airacobra, the P-63's design incorporated suggestions from P-39 pilots and was superior to its predecessor in virtually all respects. The P-63 was not accepted for combat use by the United States Army Air Forces. However, it was deployed during World War II by the Soviet Air Force, which had also been the most prolific user of the P-39.
context_section_description: Although the XP-39E proved disappointing, the USAAF was nevertheless interested in an even larger aircraft based on the same basic layout. Even before its first flight, the USAAF placed an order on 27 June 1941 for two prototypes of an enlarged version powered by the same V-1710-47. The new design was given the designation XP-63 and serials were 41-19511 and 41-19512. A third prototype was also ordered, 42-78015, using the Packard V-1650, the U.S.-built version of the Rolls-Royce Merlin engine.
  The XP-87897 was larger in all dimensions than the Airacobra. The wing was redesigned again, this time with new NACA laminar flow airfoils, 66(215)-116 a=0.6 at the root and a NACA 66(215)-216 a=0.6 at the tip. The wing taper ratio was approximately 2:1, span was 38 ft 4 in (11.68 m), and wing area was 248 sq ft (23.0 m²). The engine was fitted with a second remotely mounted supercharger, supplementing the normal single-stage supercharger. At higher altitudes, when additional boost was required, a hydraulic clutch would engage the second supercharger, adding 10,000 ft (3,000 m) to the service ceiling. A larger four-bladed propeller was also standardized. A persistent complaint against the Airacobra was that its nose armament was not easily accessible for ground maintenance, and in order to cure this problem, the XP-63 airframe was fitted with larger cowling panels.
  In September 1942, even before the prototype flew, the USAAF ordered it into production as the P-63A (Model 33). The P-63A's armament was to be the same as the current P-39Q, a single 37 mm (1.46 in) M4 cannon firing through the propeller hub, two synchronized .50 caliber (12.7 mm) machine guns in the cowl, and two .50 cal (12.7 mm) machine guns in underwing gondolas.
  The first prototype, 41-19511, flew for the first time on 7 December 1942. It was destroyed on 28 January 1943 when its landing gear failed to extend. The second prototype, 41-19512, followed on 5 February 1943. It, too, was destroyed, this time due to an engine failure. The Merlin-engined 42-78015 (as Merlins were primarily needed for the P-51 Mustang) was delivered with another Allison instead, a -93, which had a war emergency rating of 1,500 hp (1,120 kW) at sea level, making this prototype one of the fastest Kingcobras built, attaining 421 mph (678 km/h) at 24,100 ft (7,300 m).
  Deliveries of production P-63As began in October 1943. The USAAF concluded the Kingcobra was inferior to the Mustang, and declined to order larger quantities. American allies, particularly the Soviet Union, had a great need for fighter aircraft, however, and the Soviets were already the largest users of the Airacobra. Therefore, the Kingcobra was ordered into production to be delivered under Lend-Lease. In February 1944, the Soviet government sent a highly experienced test pilot, Andrey G. Kochetkov, and an aviation engineer, Fyodor P. Suprun, to the Bell factories to participate in the development of the first production variant, the P-63A. Initially ignored by Bell engineers, Kochetkov's expert testing of the machine's spin characteristics (which led to airframe buckling) eventually led to a significant Soviet role in the development. After flat spin recovery proved impossible, and upon Kochetkov's making a final recommendation that pilots should bail out upon entering such a spin, he received a commendation from the Irving Parachute Company. The Kingcobra's maximum aft CG was moved forward to facilitate recovery from spins.
  P-63A-8, SN 269261, was extensively tested at TsAGI in what was then the world's largest wind tunnel. Soviet input was significant. With the Soviet Union being the largest buyer of the aircraft, Bell was quick to implement their suggestions. The vast majority of the changes in the A sub-variants were a direct result of Soviet input, e.g. increased pilot armor and fuselage hardpoint on the A-5, underwing hardpoints and extra fuel tanks on the A-6, etc. The Soviet Union even experimented with ski landing gear for the P-63A-6, but this never reached production. Most significantly, Soviet input resulted in mov
caption: First production P-59A with a P-63 behind.
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