Boeing Model 81

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Model 81 / XN2B
Role trainer
National origin United States
Manufacturer Boeing
Introduction 1928
Primary user Boeing School
Number built 2
Developed from Boeing Model 64

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[edit]

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[edit]

 United States
  • Boeing School of Aeronautics

Specifications (XN2B)[edit]

Data from Bowers, 1989. p. 144

General characteristics

  • Crew: 2
  • Length: 25 ft 8 in (7.82 m)
  • Wingspan: 35 ft in (10.67 m)
  • Height: 11 ft 2 in (3.40 m)
  • Wing area: 259 ft2 (24.06 m2)
  • Empty weight: 1,652 lb (750 kg)
  • Gross weight: 2,178 lb (988 kg)
  • Powerplant: 1 × Fairchild-Caminez, 125 hp (93 kW) each

Performance

  • Maximum speed: 103.9 mph (167 km/h)
  • Cruise speed: 86 mph (138 km/h)
  • Range: 335 miles (539 km)
  • Service ceiling: 12,000 ft (3660 m)
  • Rate of climb: 515 ft/min (2.62 m/s)

References[edit]

  1. ^ A diagram of the 4-cylinder Fairchild-Caminez cam engine
  2. ^ Bowers, 1989, p. 142
  3. ^ Bowers, 1989, pp. 144-145
  4. ^ Bowers, 1989, pp. 142-144
  • Bowers, Peter M. Boeing aircraft since 1916. London: Putnam Aeronautical Books, 1989. ISBN 0-85177-804-6