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P-63 King Cobra Development History
Designed as a follow-on to the P-39 Airacobra, the P-63 was more powerful and excelled in performance over the P-39. The P-63 became the most produced fighter plane of World War Two to never see combat with the US Army Air Corps. The reasons for this come down primarily to two, it was extremely short-ranged (internal fuel supply was only 122 gallons, enough to fly into combat perhaps, but not enough to return and its performance was not superior to the P-51 Mustang that was already in production and operational. What the Air Force needed was a long-ranged escort fighter with the speed and maneuverability to defeat the Luftwaffe and escort the bombers of the Eighth Air Force to Germany. The P-63, for all of its sensuous curves, was simply a relatively fast climbing point interceptor, cramped, expensive to build, with an engine supercharger that wasn’t overly reliable, and demanding of more maintenance than either the P-51 or P-47. In May 1944, an Air Force report from Eglin Field concluded that the P-63 in its current form cannot be operationally suitable front-line fighter. “Thus, almost all P-63’s were sent to Russia, with 300 being given to the Free French. In the U.S. service, the P-63 was utilised as a “target” in the live-firing Pinball project, hardly an auspicious occupation for a beautiful airplane.

The first P-63A was delivered to the U.S. Army Air Force in October 1943.

At the same time the P-63 was being designed, North American’s Allison powered P-51 fighter was re-engined with a Rolls Royce Merlin engine, which resulted in a dramatic increase in performance and range at high altitude. This was primarily due to the Merlin’s excellent two-stage mechanical supercharger but North American was able to find space for 269 gallons of fuel internally in what became the Mustang, the first true Allied long-range escort fighter.
The Allison V-1710 engine which powered the P-39, P-63 and other fighters was designed from the beginning to use a turbocharger to boost its power at altitude, and when so fitted, as in the P-38 Lightening, gave excellent service. However, when the decision was made to reserve the limited supply of turbochargers primarily for heavy bombers, all but the P-38 were forced to rely on Allison’s mechanical supercharger, which was found wanting in power above 12,000 feet.
Allison’s answer to this problem was the P-63A’s 1,325 horsepower V-1710-93 engine, which featured a second, auxiliary supercharger with an automatic hydraulic drive. All subsequent production P-63’s had versions of this two-stage supercharger, but their performance never matched the Merlin Powered-powered Mustang.
When the Bell P-39 was designed in the late 1930’s, streamlining and small size and weight were one of the few ways to ensure a fast and maneuverable fighter. With the fuselage occupied by the pilot, the mid engine and its cooling system, plus the 37mm cannon and ammunition, the only space left for fuel was in the wings. With the same general layout, the P-63 suffered the same limitation, thus most P-63A’s held only 100 gallons of fuel, and early on pylons were added under the fuselage and later the wings for external fuel tanks or bombs. Thus development of the Kingcobra moved toward a ground attack fighter-bomber, where a heavy ordnance load counted more than long range.
A Total of 1,725 P-63A’s were built by Bell Aircraft between October 1943 and December 1944. Most were armed with the 37mm cannon and two .50 caliber machine guns in the nose, plus two more .50 caliber guns in pods under the wings. Many could also carry two 500 pound bombs, while later production P-63A’s could also mount three air-to-ground rockets under each wing.  Maximum loaded weight was 10,500 pounds and the top speed at 25,000 feet over 400mph. The designation P-63B was reserved for a Merlin-engine variant which was never built, thus the next production model Kingcobra was the P-63C, powered by an Allison V-1710-117 engine with water injection for greater war emergency power. Rated the same as the A model’s engine for normal use, the 117 engine could be boosted from the usual 55 inches of manifold pressure to 78 inches for very short periods using water injection

Internal fuel capacity was slightly increased to 107 gallons, and deliveries of the first of 1,227 P-63C’s began in January 1945.

One P-63D was built, featuring a sliding bubble canopy, longer span wings and 1,425 horsepower – 109 engine. While its performance was an improvement over earlier Kingcobras, it was still behind the North American Mustang which filled its required roll at that particular stage of the war and was thus not developed any further. The longer wings, however, were used on the 13 P-63E’s, which reverted to the automotive style pilot’s compartment but retained the more powerful engine. Two (some sources say only one) E model airframes were completed with a much enlarged vertical find and rudder under the designation P-63F.

One other E series aircraft served as the XP-63H, powered by a turbo compound V-1710-127 engine, which had not only the two-stage supercharger but an exhaust driven gas turbine which fed power mechanically back to the engine. At 29,000 feet, this engine still delivered 1,550 horsepower, and at low altitudes, with special fuel, its output was an amazing 2,900 horsepower. How then did the Kingcobra perform in combat with the U.S. Army Air Forces? It didn’t  - the only American use of the P-63’s as fighters were a few hundred employed as transition trainers in Advanced Training Units. Most, about 2,397, Kingcobras were provided to the Soviet Union under Lend-Lease, ferried by the U.S. and Soviet Pilots via the Alaska Siberia Route. As with the P-39, the Soviets used the P-63’s 37mm cannon for attacks on tanks and other armoured targets and seemed to have good luck with them in air-to-air combat. However few details have been published about the P-63’s combat role in the Soviet Union. It is believed by some sources that an unknown number of the P-63’s supplied by the U.S. were secretly transferred to the Russian front contravening the Lend-Lease agreement and thus seeing combat with the German’s, however no evidence has yet come forward to support this claim. What is known is the P-63 did see combat in the Far East during the brief but fierce fighting that took place when Russia declared war on Japan shortly after and taking advantage of the dropping of the first atom bomb on Hiroshima on August 6th 1945. This conflict became known to the Soviets as Operation Autumn Storm, very little archive information exists about these missions, but it is known that these battles extended beyond the official surrender of Japan which took place on board U.S. battleship Missouri on September 2nd 1945. It is a common misconception that some historians make stating that the last battles of World War Two were fought at Iwo Jima, whilst this might be true when referring the U.S. involvement in the war what is often overlooked was that the Russian’s were still carrying out Operation Autumn Storm well after the last battles of Iwo Jima had finally ended. The P-63’C’s deployed during these operations in the Kuril Islands can surely claim the last combat of World War Two undertaken by any American built aircraft.

P-63C’s also saw action with the Free-French> which were provided with 300 P-63C model Kingcobras, although some sources indicate that the true number delivered was closer to 200. Some sources indicate that these P-63’s operated for a brief period defending the docks at Le Harve during late 1944, however I have not yet seen any actual evidence of this to date. Kingcobras continued to operate with the French forces until about 1951, seeing their last combat in Indochina.
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