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Keystone B-3A (S/N 30-281), the first B-3A built.
Role Light bomber
Manufacturer Keystone
Primary user United States Army Air Corps
Number built 63 B-3A/B-5
Variants Keystone B-4
Keystone B-5
Keystone B-6

The Keystone B-3A was a bomber aircraft developed for the United States Army Air Corps in the late 1920s.


Design development

It was originally ordered as the LB-10A (a single-tail modification of the Keystone LB-6), but the Army dropped the LB- 'light bomber' designation in 1930.

Though the performance of the B-3A was hardly better than that of the bombers flown at the end of World War I, it had come a long way. In terms of its safety, it was far superior to its oldest predecessors.

Operational history

The B-3A was the last biplane disbanded by the Army; it remained in service until 1940. A few years after it was first produced, the introduction of all-metal monoplanes rendered it almost completely obsolete.


One LB-6 conversion with re-designed single fin and rudder and two 525hp R-1750E engines.
Production version re-designated B-3A before any delivery made.
Production version with Pratt and Whitney R-1690-3 Hornet engines, 63 ordered. 36 delivered as B-3A.
Production version with Wright R-1750-3 Cyclone engines, 27 delivered.


 United States

Specifications (B-3A)

General characteristics



  • Guns: 3 × .30 in (7.62 mm) machine guns
  • Bombs: 2,500 lb (1,100 kg); 4,000 lb (1,800 kg) on short runs

See also

Related development

Related lists


  • John Andrade, U.S.Military Aircraft Designations and Serials since 1909, Midland Counties Publications, 1979, ISBN 0 904597 22 9 (Page 43 and 135)
  • The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985), 1985, Orbis Publishing, Page 2255

External links



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