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Keystone B-6A of the 1st Bomb Squadron, 9th Bomb Group, Mitchel Field, N.Y.
Role Light bomber
Manufacturer Keystone Aircraft
Primary user United States Army Air Corps
Number built 5 Y1B-6 + 39 B-6A
Developed from Keystone B-3

The Keystone B-6 was a biplane bomber developed for the United States Army Air Corps.

Design and development

In 1931, the United States Army Air Corps received five working models (Y1B-6s) of the B-6 bomber. The Y1B- designation, as opposed to a YB- designation, indicates funding outside normal fiscal year procurement. Two of these were redesignations of LB-13s; three were re-engined B-3As. The Air Corps placed an order for 39 production models on 28 April 1931, with deliveries between August 1931 and January 1932.[1]

At the same time, an order was placed for 25 B-4As, the same aircraft but mounting Pratt & Whitney engines instead of Wright Cyclones. Despite their lower sequence number, the B-4As would be delivered last. These were the last canvas-and-wood biplane bombers ordered by the Air Corps.

The performance of the B-6A varied little from the Martin NBS-1 ordered in 1921. Its successor, the monoplane bomber, had a hard time getting accepted. The Douglas Y1B-7 and Fokker XB-8 were originally designed as high-speed reconnaissance aircraft.[1]

Operational history

Keystone B-6 airmail plane in snow storm, 1934

The B-6A together with B-5A were front line bombers of the United States for the period between 1930 and 1934. Afterwards, they remained in service primarily as observation aircraft until the early 1940s.

B-6 aircraft were used, along with many other Army Air Corps planes, as mail planes in what became the Air Mail scandal of 1934.

On December 27, 1935, six B-6 bombers of the 23rd Bomb Squadron based in Hawaii dropped bombs to divert lava flow from the volcano Mauna Loa away from the port of Hilo.


Seven aircraft ordered but delivered as the Y1B-4 and Y1B-6 with different engine installations.
Powered by two 525hp P&W R-1860 Hornet radial engines.
Two pre-production aircraft and three converted B-3As, as the LB-10 but with two 575 hp (429 kW) Wright R-1820-1 engines.
Production version of the Y1B-6, 39 built.


 United States

Specifications (B-6A)

General characteristics

  • Crew: 5
  • Length: 48 ft 10 in (14.9 m)
  • Wingspan: 74 ft 8 in (22.8 m)
  • Height: 15 ft 9 in (4.8 m)
  • Wing area: 1,145 ft² (106.4 m²)
  • Empty weight: 8,057 lb (3,665 kg)
  • Loaded weight: 13,350 lb (6,056 kg)
  • Max. takeoff weight: lb (kg)
  • Powerplant: 2 × Wright R-1820-1 radial engines, 575 hp (429 kW) each


  • Maximum speed: 120 mph (100 kn, 190 km/h)
  • Cruise speed: 103 mph (89 kn, 166 km/h)
  • Range: 825 mi (717 nmi, 1,330 km)
  • Service ceiling: 14,100 ft (6,400 m)
  • Wing loading: 11.66 lb/ft² (56.92 kg/m²)
  • Power/mass: 0.0861 hp/lb (142 W/kg)


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

See also


  1. 1.0 1.1 Baugher, Joe. "Keystone B-6." American Military Aircraft, 11 July 1999. Retrieved: 29 July 2011.

External links

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