Boeing 81 closeup of 125 hp Fairchild-Caminez 4-cylinder radial engine

The Boeing Model 81 was an American training aircraft built by

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and product ...

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. Operating at a much lower rpm than most engines (1000 rpm) it required the use of a large high-pitch propeller. After initial flight tests with the Fairchild-Caminez, the prototype was refitted with a 145 hp

Axelson Axelson is a surname. Notable people with the surname include: *Jan Axelson (born 1949), American author and conservationist *Joe Axelson (1927–2008), American sports executive *Matthew Axelson (1976–2005), American Navy SEAL See also *Axelso ...

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 The Wright R-540 Whirlwind was a series of five-cylinder air-cooled radial aircraft engines built by the Wright Aeronautical division of Curtiss-Wright. These engines had a displacement of 540 in³ (8.85 L) and power ratings of around ...

, then a 100 hp

Kinner K-5 The Kinner K-5 was a popular engine for light general and sport aircraft developed by Winfield B. 'Bert' Kinner. With the boom in civilian aviation after Charles Lindbergh's transatlantic flight the K-5 sold well. The K-5 was a rough running but ...

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. 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.

Operators

; *Boeing School of Aeronautics

Specifications (XN2B)

References

*Bowers, Peter M. ''Boeing aircraft since 1916''. London: Putnam Aeronautical Books, 1989. {{Boeing model numbers Boeing Model 081 081 Single-engined tractor aircraft Biplanes Aircraft first flown in 1928