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The Ryan FR Fireball was a mixed-power (piston and jet-powered) fighter aircraft designed by Ryan Aeronautical for the United States Navy during World War II. It was the Navy's first aircraft with a jet engine.〔 Only 66 aircraft were built before Japan surrendered in August 1945. The FR-1 Fireball equipped a single squadron before the end of the war, but did not see combat. The aircraft ultimately proved to lack the structural strength required for operations aboard aircraft carriers and was withdrawn in mid-1947. ==Design and development== Design of the FR-1 began in 1943 to a proposal instigated by Admiral John S. McCain, Sr. for a mixed-powered fighter because early jet engines had sluggish acceleration that was considered unsafe and unsuitable for carrier operations. Ryan received a contract for three XFR-1 prototypes and one static test airframe on 11 February 1943 with the first two prototypes delivered in 14 months.〔Ginter 1995, p. 2.〕 Another contract was placed for 100 aircraft on 2 December 1943 and a later contract on 31 January 1945 increased the total of FR-1s on order to 700.〔Swanborough and Bowers 1990, p. 402.〕 The XFR-1 was a single-seat, low-wing monoplane with tricycle landing gear. A Wright R-1820-72W Cyclone radial engine was mounted in the fighter's nose while a General Electric I-16 (later redesignated as the J-31) turbojet was mounted in the rear fuselage. It was fed by ducts in each wing root which meant that the wing had to be relatively thick to house the ducts and the outward-retracting main landing gear. To simplify the fuel system, both engines used the same grade of avgas. Two self-sealing fuel tanks were housed in the fuselage, one of and the other of . The cockpit was positioned just forward of the leading edge of the wing and the pilot was provided with a bubble canopy which gave him excellent visibility. The XFR-1 had the first laminar flow airfoil in a navy carrier aircraft.〔Ginter 1995, pp. 5, 30.〕 The Fireball was armed with four .50 in (12.7 mm) M2 Browning machine guns with 300 rounds per gun. They were mounted in the center section of the wing, immediately outboard of the air intakes for the jet engine. Four 5-inch (127 mm) rockets could be carried under each outer wing panel and two hardpoints were provided under the center section for 1,000 lb (454 kg) bombs or drop tanks. Armor plates were provided in front and behind the pilot's seat and for the oil cooler.〔 The first XFR-1 made its first flight on 25 June 1944 without its jet engine, but that was installed shortly afterward. The second prototype first flew on 20 September 1944. Test flights confirmed wind tunnel tests that revealed a lack of longitudinal stability because the center of gravity had been miscalculated. In addition, the circular rear fuselage of the FR-1 gave less stability than the slab-style fuselage of the Grumman F4F Wildcat that was used as a model for the stability calculations. A new tail with enlarged vertical and horizontal stabilizers was designed and retrofitted to the prototypes. The original Douglas double-slotted flaps proved to be unsatisfactory during flight testing, but all three prototypes and the first 14 production aircraft were built with them before they were replaced with a single-slotted flap.〔Ginter 1995, pp. 3, 5.〕 The first prototype was lost in a crash at NAS China Lake on 13 October 1944. Investigation showed that the wing structure was not strong enough to resist compressibility effects. This was cured by doubling the number of rivets in the outer wing panels. The second prototype crashed on 25 March 1945 when the pilot failed to recover from a dive from , probably also due to compressibility effects. The third prototype crashed on 5 April when the canopy blew off during a high-speed pass over Lindbergh Field.〔Ginter 1995, p. 31.〕 Operational testing by the Naval Air Test Center at Naval Air Station Patuxent River that included carrier acceptability tests revealed additional problems. The piston engine tended to overheat until electrically operated cowl flaps were installed, the catapult hooks had to be moved and the nosewheel oleo shock strut had to be lengthened by . Carrier suitability tests began aboard the escort carrier in early January 1945. The aircraft successfully made five catapult takeoffs using the piston engine as well as three takeoffs using both engines. No problems were reported when landing aboard the carrier.〔Ginter 1995, pp. 32–33.〕 The FR-1 Fireball was further developed into the XFR-2 which utilized a 1,425 hp (1,063 kW) Wright R-1820-74W in place of the -72W. One single airframe was converted to this configuration. No prototypes were built for the next proposed variant, the FR-3, which would have used a General Electric I-20 turbojet. Both of these projects were canceled with the end of the war.〔 The fastest Fireball was the XFR-4, which had a Westinghouse J34 turbojet and was approximately 100 mph (161 km/h) faster than the FR-1.〔McDowell 1995, p. 39.〕 The turbojet's air intakes were moved from the wing roots to the fuselage in front of the wing; they were covered by electrically powered doors to lessen drag when the aircraft was flying only on its piston engine. The Fireball's fuselage was lengthened by to accommodate the larger engine and the leading edge extension of the wing root that housed the air intakes was also removed. The XFR-4 was intended to serve as a testbed for the turbojet installation on the XF2R-1 Dark Shark.〔Ginter 1995, pp. 32, 57.〕 This was the final variant; the piston engine was replaced with a General Electric XT31-GE-2 turboprop, but only one prototype was built.〔McDowell 1995, p. 45.〕 On 2 December 1943, orders for 100 production FR-1s were placed, with a follow-up order of 1,000 additional fighters in January 1945. All of the contracts were contingent on the aircraft successfully completing carrier trials. Only 66 Fireballs were completed by November 1945 as orders for 1,044 FR-1s were canceled on VJ Day.〔Green 1969, p. 186.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ryan FR Fireball」の詳細全文を読む スポンサード リンク
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