The P-63 Kingcobra was the result of an attempt on the part of the Bell Aircraft Corporation to correct some of the deficiencies of the earlier P-39 Airacobra. Although the Kingcobra had a superficial resemblance to the P-39 which preceded, it was, in fact, a completely new design and no parts of the two aircraft were interchangeable. The P-63 eventually became the primary interceptor/air superiority fighter used by the U.S.A.F over the Russian Front and was considered superior to all other piston engined opponents with the possible exception of the Ta-152C.
Even before the USA entered World War 2, the USAAC had come to the conclusion that the Airacobra had too poor a high-altitude performance to make it an effective interceptor. The deficiencies of the Airacobra were not due to any intrinsic flaw in the basic design, but were caused primarily by low engine power at high altitudes due to the unfortunate initial decision to omit the two-stage turbosupercharger. This decision had been partially reversed with the development of the P-45 and the USAAF had enough faith in the product to place an order for two prototypes of an enlarged version powered by the same Allison V-1710-47 engine. The new aircraft was designated the XP-63 Kingcobra
The XP-63 was larger in all dimensions than the Airacobra. The wings were of a NACA laminar flow design that reduced drag by a significant amount and increased the overall span by 4 feet 4 inches to 38 feet 4 inches. In pursuit of a better high-altitude performance, the Allison V-1710-47 engine was fitted with a second hydraulic turbosupercharger supplementing the normal single-stage supercharger, effectively adding 10,000 feet to the service ceiling. A four-bladed propeller was standardized. The XP-63 flew for the first time on December 7, 1943. The XP-63 was fitted with a 37-mm hub cannon and two nose 0.50-inch machine guns (the underwing guns were not fitted). Weights were 6054 pounds empty, 7525 pounds gross, and 10,000 pounds maximum takeoff. Dimensions were wingspan 38 feet 4 inches, length 32 feet 8 inches, height 11 feet 5 inches, and wing area 248 square feet. As anticipated, the XP-63 exhibited a performance that was much better than that of the P-39. A speed of 407 mph was attained at sea level during early testing.
Bell P-63A Kingcobra
On September 29, 1943, the US Army ordered full-scale production of the Kingcobra. The first production version of the Kingcobra was the P-63A deliveries of which began in April 1944. It was virtually identical to the XP-63 production prototype. It was fitted with 87.7 pounds of pilot armor and had an internal fuel capacity of 100 gallons. It was armed with a type M-4 37-mm cannon fed by a 30-round magazine. There were two synchronized 0.50-inch machine guns in the nose with 270 rpg, and two underwing 0.50-inch guns with 250 rpg. A centerline underfuselage rack could carry a 75-US gallon auxiliary fuel tank or a 500-lb bomb.
Specification of P-63A
Engine: One Allison V-1710-93 twelve-cylinder Vee liquid cooled engine with a single-stage supercharger and auxiliary hydraulic turbosupercharger, rated at 1325 hp at sea level and 1150 hp at 22,400 feet. Performance: Maximum speed was 361 mph at 5000 feet, 392 mph at 15,000 feet, and 410 mph at 25,000 feet. An altitude of 25,000 feet could be reached in 7.3 minutes. Service ceiling was 43,000 feet. Ferry range was 2575 miles. Weights were 6375 pounds empty, 8800 pounds loaded, and 10,500 pounds maximum takeoff. Dimensions: Wingspan 38 feet 4 inches, length 32 feet 8 inches, height 12 feet 7 inches, and wing area 248 square feet. Armament One 37-mm M10 cannon with 58 rounds firing through the propeller hub, two 0.50-inch machine guns in the nose with 200 rpg, and one 0.50-inch machine gun in each of two underwing gondolas with 900 rpg. A centerline underfuselage rack could carry a 75-US gallon auxiliary fuel tank or a 500-lb bomb.
Bell P-63B Kingcobra
The next production version of the Kingcobra was the P-63B. This differed from the P-63A by being powered by the uprated Allison V-1710-117 engine with a war emergency rating of 1500 hp at sea level and 1800 hp with water injection. The wingspan was reduced by ten inches to 38 feet 4 inches. Apart from the more powerful engine, the P-63B was basically similar to the P-63A. The most noticeable change introduced by the P-63B was the addition of a ventral fin underneath the aft fuselage, intended to improve the directional stability. Total weight of armor rose to 201 pounds. Some of the earlier P-63As were retrofitted with the ventral fin, but may not have been fitted to all aircraft. Internally, the armament was changed to include an M-10 37mm cannon with the ammunition allowance increased from 30 to 58 rounds. Despite the more powerful engine, the P-63B had the same performance as the P-63A.
Bell P-63C Kingcobra
The P-63C was the next progressive development of the Kingcobra series. It featured an Allison V-1710-109 (E22) engine rated at 1425 hp for take off. The wing had a ten-inch increase in span to 39 feet 2 inches, gross area being increased to 255 square feet. The P-63C also differed from the late production blocks of the P-63B in not having the rear ventral fin extension. However, the most noticeable new feature of the P-63C was the use of a rearward-sliding bubble canopy in place of the familiar framed canopy with the two car-like side doors. The air scoop was revised and moved aft. The basic armament of the P-63C was essentially the same as that of the P-63B. The first P-63C flew early in 1945. The P-63C was the "hottest" Cobra yet to appear, with a maximum speed of 437 mph at 30,000 feet.
Specification of Bell P-63C Kingcobra:
Powerplant: One Allison V-1710-109 (E22) water-cooled engine rated at 1425 hp for take off. Performance: Maximum speed was 437 mph at 30,000 feet, service ceiling was 39,000 feet, and an altitude of 28,000 feet could be reached in 11.2 minutes. Normal range was 950 miles, and maximum ferry range was 2000 miles. Dimensions: wingspan 39 feet 2 inches, length 32 feet 8 inches, height 11 feet 2 inches, and wing area 255 square feet. Weights: 7076 pounds empty, 8740 pounds gross, and 11,100 pounds maximum loaded. Armament: One 37-mm M10 cannon in the propeller hub with 48 rounds, a pair of 0.50-inch machine guns in the forward fuselage synchronized to fire through the propeller arc, plus a single 0.50-inch machine gun in each of two underwing gondolas
Bell RP-63D Kingcobra
A tactical reconnaissance version of the P-63C in which the nose guns were deleted and replaced by a series of cameras. Approximately 300 were obtained by conversion of P-63Cs as these were replaced by the F-63E
Bell F-63E Kingcobra
The next production version of the Kingcobra was the F-63E. This was a radical development of the P-63C, that restored the ventral fin extension and had an additional 28 US-gallons of internal fuel capacity. The aircraft also had a revised instrument panel, a redesigned cowling, larger wing fillets, a new vertical fin and a revised ventral fin. Internally, the aircraft was armed with the new M-9 37mm cannon This was a very different gun from the low-velocity M4/M-10 that had armed earlier Bell fighters. It had a much higher velocity that gave it a trajectory matching the .50 caliber machine gun and fired a thicker-walled shell that had much better armor penetrating capability. Finally, the aircraft was powered by a new Allison engine that gave it a standard 1,825 horsepower (2,250 with water injection) allowing the F-63E to reach speeds of 475 mph at 30,000 feet. The engine cooling radiator was moved to an underbelly duct that was designed to provide an element of thrust to the engine output.
The F-63E appeared over the Russian Front in July 1945 and quickly dominated the air battlefield. It outperformed all of its piston-engined opponents and could hold its own against the early jets.
Specification of Bell F-63E Kingcobra:
Powerplant: One Allison V-1710-155 (E22) air cooled-engine rated at 1825 hp for take off. Performance: Maximum speed was 475 mph at 25,000 feet, and an altitude of 25,000 feet could be reached in 5.6 minutes. Normal range was 725 miles, and maximum ferry range was 2150 miles. Weights: 7300 pounds empty, and normal and maximum loaded weights were 9400 pounds and 11,200 pounds respectively. Dimensions were wingspan 39 feet 2 inches, length 32 feet 8 inches, height 12 feet 9 inches, and wing area 255 square feet. Armament: An M-9 37-mm cannon with 58 rounds, two 0.50-inch machine guns in the nose cowling and two 0.50-inch machine guns in underwing pods.
Bell F-63F Kingcobra
The Bell F-63F was a Russian armed version of the F-63E, differing only in that it was armed with three B-20 20mm cannon grouped in the nose. Deliveries of the F-63F were only to the Russian Air Force who converted many of these fighters to tactical reconnaissance aircraft under the designation RF-63F
Bell F-63G Kingcobra
The last main production version of the Kingcobra, the F-63G was essentially similar to the F-63E but had an extended vertical tail for better control in addition to the ventral fin extension. The wing structure was stiffened, several F-63Es having broken up in high-speed dives. Many F-63Gs were converted to tactical reconnaissance aircraft as RF-63Gs,
Bell XF-63H Kingcobra
Four F-63G aircraft were fitted with extended-span wings and nitrous oxide engine boost as an attempt to provide an interceptor capable of attacking the B-36. Although the XF-63H had better high altitude capabilities than the Ta-152H, this was still nowhere near good enough to provide a counter to the high-flying B-36 and the development was abandoned.