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The Boeing Model 81 was an American training aircraft built by Boeing in 1928. The Model 81 was a development of the Model 64. It was powered by a newly developed engine, the 125 hp Fairchild-Caminez 4-cylinder radial engine.〔(A diagram of the 4-cylinder Fairchild-Caminez cam engine )〕 Operating at a much lower rpm than most engines (1000 rpm) it required the use of a large high-pitch propeller.〔Bowers, 1989, p. 142〕 After initial flight tests with the Fairchild-Caminez, the prototype was refitted with a 145 hp Axelson engine, redesignated ''Model 81A'' and delivered to the Boeing School of Aeronautics. There, it was re-engined a number of times, first with a 115 hp Axelson engine, redesignated ''Model 81B''. It then received a 165 hp Wright J-6-5, then a 100 hp Kinner K-5 and a redesigned vertical tail. Redesignated ''Model 81C'', it would later be removed from training service, re-engined with an Axelson engine, and used as a classroom trainer.〔Bowers, 1989, pp. 144-145〕 On 21 June 1928, the second Model 81 built was delivered to the US Navy at Anacostia, Maryland for $8,300, and redesignated ''Boeing XN2B''. Its trial with the Fairchild engine was unsatisfactory, and on 10 January 1929 it was refitted by Wright Aeronautical with a 160 hp Wright J-6-5 engine. Despite increased performance, it was not ordered into production.〔Bowers, 1989, pp. 142-144〕 ==Variants== ;81 :Original Caminez-engined aircraft ;81A :145 hp Axelson engine ;81B :115 hp Axelson engine ;81C :100 hp Kinner K-5, redesigned tail. ;XN2B :US Navy designation. 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「Boeing Model 81」の詳細全文を読む スポンサード リンク
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