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The Sikorsky S-52 was a utility helicopter developed by Sikorsky Aircraft in the late 1940s. It was used by the U.S. Navy, Marines, and Coast Guard.〔Donald 1997, p. 840.〕 The S-52 was the first US helicopter with all-metal rotor blades. A two-seater, it was developed into the four-seat S-52-2. It was designated ''HO5S-1'' by the U.S. Navy and Marine Corp; ''HO5S-1G'' by the Coast Guard; and ''YH-18A'' by the Army. ==Design and development== Sikorsky Aircraft began designing the S-52 in late 1945.〔Harding 1990, p. 228.〕 The prototype S-52, first flown in 1947, was a two-seater and used a 178 hp (133 kW) Franklin air-cooled flat-6 piston engine.〔 The two-seat version was modified into the S-52-2, a four-seat helicopter using a 245 hp (183 kW) Franklin O-425-1 air-cooled flat-6. It had a semi-monocoque fuselage of pod-and-boom arrangement with large bubble-like front greenhouse,〔 three-blade rotor, and quadricycle fixed landing gear. The production S-52-3 (HO5S-1) incorporated a downward sloping (anhedral) v-tail stabilizer.〔FAA type certificate〕 It also had sliding doors on the right forward and left rear sides, and a vertically split front bubble, allowing the left half to swing open in a clamshell fashion. The engine was placed at the aft end of the cabin and was canted forward 30 degrees to couple with the clutch and transmission.〔Flight manual, page 5〕 The pilot in command occupied the right front seat. The first American helicopter to have all-metal rotor blades,〔〔 the prototype〔 set several speed and height records in 1948, including 129.6 mph (204.2 km/h) on a 3 km (2 mi) course, 122.75 mph (197.54 km/h) on a 1 km (1,100 yd) circuit, and absolute height 21,220 ft (6,468 m).〔 It was capable of hover out of ground effect at 5,900 ft (1,798 m) or 9,200 ft (2,804 m) in ground effect.〔 The S-52 is widely believed to be the first helicopter to be looped, as flown by Harold E. Thompson in 1949. The S-52 also served as the basis of the turbine-powered S-59, which as the XH-39 competed for and lost the contract that produced the Bell UH-1 Iroquois. This aircraft differed in having a four-bladed rotor (against the S-52's three) and retractable tricycle gear.〔 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「Sikorsky S-52」の詳細全文を読む スポンサード リンク
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