|National origin||United States|
|First flight||February 1926|
|Number built||1 (possibly 2)|
The Model 64 was built by Boeing at their own expense, and submitted to both the US Army and US Navy as a primary and gunnery training aircraft. The fuselage and tail was constructed of welded steel tubing, with wood wings spars and ribs. The wings used reverted to an earlier two bay design, due to aerodynamic problems with the Model 21/NB. For gunnery training a removable rear cockpit structure was built to carry a gun ring and flexible machine gun. A fixed synchronized gun could also be mounted to fire through the propeller.
The Model 64 first flew in February 1926. Later, the wings were replaced with ones using the thicker NACA Munk M-12 airfoil and which required only one set of struts. The updated plane first flew on 31 August 1926.
Data from Bowers, 1966, pg. 122
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. 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 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.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.
Boeing aircraft model numbers