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The Firestone XR-9, also known by the company designation Model 45, was a 1940s American experimental helicopter built by the Firestone Aircraft Company for the United States Army Air Forces. Only two (the military XR-9B and one civil example) were built. ==Development== Originally developed by G & A Aircraft with the co-operation of the United States Army Air Forces' Air Technical Service Command, the G & A Model 45B (designated XR-9 ''Rotocycle'' by the Army)〔("Short Hop Helicopter". ) ''Popular Science,'' April 1946.〕 was a design for a single-seat helicopter of pod-and-boom configuration.〔Andrade 1979, p. 171.〕 It had a fixed tri-cycle landing gear and three-bladed main and tail rotors. Power would have been supplied by a 126 hp (94 kW) Avco Lycoming XO-290-5 engine.〔 The Model 45C (XR-9A) was the same helicopter with a two-bladed rotor. Neither of the two helicopters were built. G & A Aircraft was purchased by Firestone in 1943,〔Merriam 2002, p. 64〕 and was renamed the Firestone Aircraft Company in 1946.〔Lambermont 1958〕 A revised two-seat design the revised Model 45C (or XR-9B) was built with a three-bladed main rotor and two-seat in tandem. The first aircraft procured by the Army Air Forces in 1946,〔 it was powered by an Avco Lycoming O-290-7 engine〔 and first flew in March of that year. A civil version, the Model 45D was also built and flown, in anticipation of a postwar boom in aircraft sales.〔 This differed in having the two occupants side-by-side instead of Tandem as in the 45C, and was equipped with a Lycoming engine.〔 The prototype was demonstrated at the 1946 Cleveland National Air Races.〔'' 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「Firestone XR-9」の詳細全文を読む スポンサード リンク
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