Mid-engined fighter aircraft
The Bell P-63 Kingcobra is an American fighter aircraft that was 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 used during World War II by the Soviet Air Force, which had also been the most prolific user of the P-39.
Design and development.
XP-39E.
While the P-39 had been introduced as an interceptor, later in its development it was decided to reduce the cost and complexity of the engine by removing the turbocharger. High-altitude performance suffered dramatically as a result, and Bell proposed an experimental series to test out a variety of solutions.
The resulting XP-39E featured two primary changes from the earlier P-39D from which it was developed. One was a redesigned wing. The root airfoil, a NACA 0015 on other models of the P-39, was changed to a NACA 0018, to gain internal volume. The other was a switch to the Continental I-1430 engine, which featured an improved overall design developed from the hyper engine efforts, as well as an improved supercharger.
Three prototypes were ordered in April 1941 with serials 41-19501, 41-19502 and 42-7164. The I-1430 had continued development problems and could not be delivered in time, so it was replaced by an Allison V-1710-47, similar to that powering the P-39. Each prototype tested different wing and tail configurations: 41-19501 had a rounded vertical tail, but squared-off tailplane tips; 41-19502, a squared-off fin and rudder and large wing fillets; and 42-7164 had all its flight surfaces squared off. The XP-39E proved faster than standard Airacobra, reaching a maximum speed of at during tests. However, the XP-39E was considered inferior to the stock P-39 Airacobra in all other respects, so it was not ordered into production.
XP-63.
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-63 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 , and wing area was . 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 to the service ceiling. A larger four-bladed propeller was also standardized. A persistent complaint about the Airacobra was that its nose armament was not easily accessible for ground maintenance; 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 M4 cannon firing through the propeller hub, two synchronized machine guns in the cowl, and two 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 at sea level, making this prototype one of the fastest Kingcobras built, attaining at .
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. Most 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 moving the main cannon forward, favorably changing the center of gravity, and increasing its ammunition load from 30 to 58 rounds for the A-9 variant. The P-63 had an impressive roll rate, besting the US P-47, P-40, and P-51—and the Japanese Navy's Kawanishi N1K2 "Shiden-Kai" fighter—with a rate of 110° per second at .
Swept-wing L-39.
After the war, two war surplus P-63Cs were modified by Bell under Navy contract for flight testing of low-speed and stall characteristics of high-speed wing designs. The aircraft received new wings with adjustable leading edge slats, trailing edge flaps and a pronounced sweep of 35 degrees. The wings had no wheel wells; only the nose gear was retractable. L-39-1 first flew 23 April 1946, demonstrating a need for extra tail surface and rear fuselage length to balance the aircraft in flight—the wing repositioning reduced empennage effectiveness and moved the center of lift aft. A lighter three-bladed propeller from a P-39Q-10 was mounted and the necessary changes to the empennage were made. L-39-2 incorporated these adjustments from the start. L-39-1 later went to NACA at Langley for wind tunnel testing, where much valuable data was gathered. L-39-2 also served as a testbed for the Bell X-2 40-degree wing design.
Operational service.
Soviet Union.
The first version to be supplied in quantity to the Soviet Union was the P-63A-7 with a higher vertical tail, and reinforced wings and fuselage. The fuselage proved to need strengthening; consequently, in October 1944 a reinforcement kit for operational P-63s was developed.
Air Transport Command ferry pilots, including U.S. women pilots of the WASP program, picked up the planes at the Bell factory at Niagara Falls, New York, and flew them to Great Falls, Montana and then onward via the Northwest Staging Route through Canada to Alaska, where Soviet ferry pilots, many of them also women, would take delivery of the aircraft at Nome and fly them to the Soviet Union over the Bering Strait via the Alaska-Siberia route (ALSIB). A total of 2,397 (2,672, according to other sources) aircraft were delivered to the USSR, 72.6% of the overall 3,303 production aircraft.
By a 1943 agreement, P-63s were not allowed for Soviet use against Germany and were supposed to be concentrated in the Soviet Far East for an eventual attack on Japan. However, there are many unconfirmed reports from both Soviet and German sources that P-63s did indeed see service against the "Luftwaffe". In memoirs published in the 1990s, one of Pokryshkin's pilots reported that the entire 4th Guards Fighter Aviation Regiment (4 GvIAP) was secretly converted to P-63s in 1944, while officially still flying P-39s. One account states they were in action at Königsberg, in Poland and in the final assault on Berlin. There are German reports of P-63s shot down by both fighters and flak. Hans Rudel, the most-decorated pilot of the Luftwaffe, states in his memoirs, "We often encounter American types of aircraft, especially Airacobras, Kingcobras and Bostons." This was in the Courland front towards the end of the war. Nevertheless, all Soviet records show nothing but P-39s used against Germany.
In general, official Soviet histories played down the role of Lend-Lease supplied aircraft in favor of local designs, but it is known that the P-63 was a successful fighter aircraft in Soviet service. A common Western misconception is that the Bell fighters were used as ground attack aircraft.
 ;templatestyles src="Template:Blockquote/styles.css" / ;One of the enduring myths regarding the P-39/P-63 in Soviet use is that because of its armament, in particular the 37mm nose cannon, it excelled as a ground-attack aircraft, even a 'tank buster'. In translating and preparing this manuscript for publication, I have had the opportunity to peruse several Russian-language sources. Mentions of the employment of this aircraft in the ground-attack role are so rare in these sources as to be exceptional ... The 'tank buster' myth has its roots in the misunderstanding of the general wartime role of the Red Air Force and in the imprecise translation of specific Russian-Language terms that describe this role. The specific Russian-Language term most often used to describe the mission and role of the Airacobra-equipped Red Air Force fighter units, in this manuscript and other Russian-language sources, is "prikrytiye sukhoputnykh voysk" [coverage of ground forces]... Frequent misunderstanding in this country as to the combat role of the P-39 in Soviet use is based in part on imprecise translation of the term "prikrytiye sukhoputnykh voysk" to 'ground support'. The latter term as it is understood by many Western military historians and readers, suggests the attacking of ground targets in support of ground troops, also called 'close air support'. Did a Soviet Airacobra pilot ever strafe a German tank? Undoubtedly. But this was never a primary mission or strong suit for this aircraft.
The Soviets developed successful group aerial fighting tactics for the Bell fighters and scored a surprising number of aerial victories over a variety of German aircraft. Low ceilings, short missions, good radios, a sealed and warm cockpit and ruggedness contributed to their effectiveness. To pilots who had once flown the tricky Polikarpov I-16, the aerodynamic quirks of the mid-engined aircraft were unimportant. In the Far East, P-63 and P-39 aircraft were used in the Soviet invasion of Manchukuo and northern Korea. In the Pacific theatre, the Kingcobras flew escort, close air support and ground attack missions. The Soviet P-63s achieved their first air victory on 15 August 1945, when "Lejtenant" I. F. Miroshnichenko from 17th IAP/190 IAD, shot down a Nakajima Ki-43 "Hayabusa" IJAAS fighter off the coast of North Korea.
Sufficient aircraft continued in use after the war for them to be given the NATO reporting name of Fred. By 9 May 1945, operational units still had 1,148 Kingcobras on strength. On 8 October 1950, two USAF F-80Cs from the 49th Fighter Group breached the USSR's border and attacked Sukhaya Rechka airfield south-west of Vladivostok and from the Soviet-Korean border, making two strafing runs before returning to their home base. Soviet sources say the attack was intentional, but the pilots claimed it was a result of a navigational error. The airfield belonged to the Air Forces of the Pacific Fleet (VVS TOF), but it was occupied by the 821st Fighter Aviation Regiment (821 IAP) of the 190th Fighter Aviation Division (190 IAD). Mostly aircraft of the 1st Squadron of 821 IAP were hit with 12 P-63s damaged, one P-63 burned to the ground while the other damaged aircraft were able to be repaired. There were no human losses.
France.
In 1945, 114 later models were delivered to the French Air Force ("Armée de l'Air"), but they arrived too late to see service in World War II. They did see service during the First Indochina War before being replaced in 1951.
Initially, the French Kingcobras were deployed to Algeria. Fighter