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F-86A-5-NA 48-257 of the 334th FIS / 4th FIW flown by Capt. James Jabara, 3 April, 1951>
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F-86E-10-NA 51-2764 of the 334th FIS / 4th FIW flown by Capt. Leonard W.Lilley. |
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The North American F-86 Sabre was without question one of the greatest fighter aircraft of all time, ranking right up there with such aircraft as the Fokker D.VII, the Sopwith Camel, the Supermarine Spitfire, the Messerschmitt Bf 109, the Focke Wulf Fw 190, the Mitsubishi Zero, and the North American P-51 Mustang. It first entered service with the USAAF in 1949, and was instrumental in denying air superiority to the Communist forces during the Korean War.>
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After the Korean War ended, many Sabres entered service with dozens of foreign air arms, becoming the primary fighter equipment of many Allied nations. It was built under license in Canada, Japan, Italy, and Australia. Its service was so long-lived that the last operational F-86 was not withdrawn from service until 1993, which must be some sort of record for a combat aircraft. The F-86 Sabre began its life as North American Aviation's company project NA-134, which was originally intended for the US Navy. |
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As the war in the Pacific edged toward its climax, the US Navy was making plans to acquire jet-powered carrier-based aircraft which, it was hoped, could be pressed into service in time for Operation Olympic-Coronet, the invasion of Japan planned for May 1946. The Navy had planned to acquire four jet fighters, the Vought XF6U-1 Pirate, the McDonnell XFD-1 Phantom, the McDonnell XF2D-1 Banshee, and the North American XFJ-1 Fury. Work on the NA-134 project began in the late autumn of 1944. The NA-134 had a straight, thin-section wing set low on a rather tubby fuselage. It featured a straight-through flow of air from the nose intake to the jet exhaust that exited the aircraft under a straight tailplane.> |
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The wing was borrowed directly from the P-51D, and had a laminar-flow airfoil. It was to be powered by a single General Electric TG-180 gas turbine which was a license-built version of the de Havilland Goblin. The TG-180 was designated J35 by the military and was an 11-stage axial-flow turbojet which offered 4000 lb.s.t. at sea level. The Navy ordered three prototypes of the NA-134 under the designation XFJ-1 on January 1, 1945. On May 28, 1945, the Navy approved a contract for 100 production FJ-1s (NA-141).
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At the same time that North American was beginning to design the Navy's XFJ-1, the USAAF issued a requirement for a medium-range day fighter which could also be used as an escort fighter and a dive bomber. Specifications called for a speed of at least 600 mph, since the Republic XP-84 Thunderjet already under construction promised 587 mph. On Nov 22, 1944, the company's RD-1265 design study proposed a version of the XFJ-1 for the Air Force to meet this requirement. This design was known in company records as NA-140.>
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The USAAF was sufficiently impressed that they issued a Letter Contract on May 18, 1945 which authorized the acquisition of three NA-140 aircraft under the designation XP-86. The Navy's XFJ-1 design had to incorporate some performance compromises in order to support low-speed carrier operations, but the land-based USAAF XP-86 version was not so constrained and had a somewhat thinner wing and a slimmer fuselage with a high fineness ratio. However, the XP-86 retained the tail surfaces of the XFJ-1. |
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The XP-86 incorporated several features not previously used on fighter aircraft, including a fully-pressurized cockpit and hydraulically-boosted ailerons and elevators. Armament was the standard USAAF equipment of the era-six 0.50-inch Browning M3 machine guns that fired at 1100 rounds per minute, with 267 rounds per gun. The aircraft was to use the Sperry type A-1B gun/bomb/rocket sight, working in conjunction with an AN/APG-5 ranging radar.Rocket launchers could be added underneath the wings to carry up to 8 5-inch HVARs. Self-sealing fuel tanks were to be fitted, and the pilot was to be provided with some armor plating around the cockpit area. In the XP-86, a ten percent ratio of wing thickness to chord was used to extend the critical Mach number to 0.9.>
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Wingspan was to be 38 feet 2 1/2 inches, length was 35 feet 6 inches, and height was 13 feet 2 1/2 inches. Four speed brakes were to be attached above and below the wings. At a gross weight of 11,500 pounds, the XP-86 was estimated to be capable of achieving a top speed of 574 mph at sea level and 582 mph at 10,000 feet, still below the USAAF requirement. Initial climb rate was to be 5850 feet per minute and service ceiling was to be 46,000 feet. Combat radius was 297 miles with 410 gallons of internal fuel, but could be increased to 750 miles by adding a 170 gallon drop tank to each wingtip. As it would turn out, these performance figures were greatly exaggerated. |
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A mock-up of the XP-86 was built and approved on June 20, 1945. However, early wind tunnel tests indicated that the airframe of the XP-86 would not be able to reach the desired speed of 600 mph. It is highly likely that the XP-86 project would have been cancelled at this time were it not for some unusual developments. After the surrender of Germany in May of 1945, the USAAF (along with a lot of other air forces) was keenly interested in obtaining information about the latest German jet fighters and in learning as much as they could about secret German wartime research on jet propulsion, rocket power, and ballistic missiles.> |
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American teams were selected from industry and research institutions and sent into occupied Germany to investigate captured weapons research data, microfilm it, and ship it back to the USA..
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By the summer of 1945, a lot of German data was pouring in, much of it as yet un-translated into English. As it turned out, German aeronautical engineers had wind-tunnel tested just about every aerodynamic shape that the human mind could conceive of, even some ideas even only remotely promising. A particular German paper dated 1940 reported that wind tunnel tests showed that there were some significant advantages offered by swept wings at speeds of about Mach 0.9. > |
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A straight-winged aircraft was severely affected by compressibility effects as sonic speed was approached, but the use of a swept wing delayed the effects of shock waves and permitted better control at these higher speeds. Unfortunately, German research also indicated that the use of wing sweep introduced some undesirable wing tip stall and low-speed stability effects. American researchers had also encountered similar problem with the swept-wing Curtiss XP-55 Ascender, which was so unstable that it flipped over on its back and fell out of the sky on one of its test flights.
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In 1940, these German studies were of only theoretical interest, since no powerplants were available even remotely capable of reaching such speeds. However, such studies caught the attention of North American engineers trying to figure out ways to improve the performance of their XP-86.
It would do no good to build an aircraft capable of high speeds that would be so unstable that it would fall out of the sky at low speeds. The cure for the low-speed stability problem that was worked out by North American engineers was to attach automatic slats to the wing leading edges. The wing slats were entirely automatic, and opened and closed in response to aerodynamic forces. When the slats opened, the changed airflow over the upper wing surface increased the lift and produced lower stalling speeds. At high speeds, the slats automatically closed to minimize drag.> |
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In August of 1945, project aerodynamicist L. P. Greene proposed to Raymond Rice that a swept-wing configuration for the P-86 be adopted. Wind tunnel tests carried out in September of 1945 confirmed the reduction in drag at high subsonic speeds as well as the beneficial effect of the slats on low speed stability. The limiting Mach number was raised to 0.875.
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“F-86 SABRES”
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