Boeing Model 81 Explained

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.[1] Operating at a much lower rpm than most engines (1000 rpm) it required the use of a large high-pitch propeller.[2]

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.[3]

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.[4]

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.

    Operators

    References

    Notes and References

    1. Web site: A diagram of the 4-cylinder Fairchild-Caminez cam engine . 2011-11-12 . https://web.archive.org/web/20171005113859/http://www.aqpl43.dsl.pipex.com/MUSEUM/POWER/unusualICeng/cam-IC/cam-IC.htm#fcam . 2017-10-05 . dead .
    2. Bowers, 1989, p. 142
    3. Bowers, 1989, pp. 144-145
    4. Bowers, 1989, pp. 142-144