Boeing Model 81

The Boeing Model 81 was an American training aircraft that Boeing built in 1928, a development of the Model 64. It was powered by the newly developed 125 hp Fairchild-Caminez four-cylinder radial engine, which ran at only about 1,000 rpm and so needed a large high-pitch propeller. The prototype was refitted with a 145 hp Axelson engine as the Model 81A and delivered to the Boeing School of Aeronautics, where it was re-engined several times, becoming the 81B with a 115 hp Axelson and the 81C with a 100 hp Kinner K-5 and a redesigned tail, and was finally used as a classroom trainer. The second aircraft went to the US Navy at Anacostia, Maryland on 21 June 1928 for 8,300 dollars as the XN2B; the Fairchild engine proved unsatisfactory and a 160 hp Wright J-6-5 improved performance, but it was not ordered into production.