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Boeing XF6B-1 / XBFB-1

The Boeing XF6B-1 / XBFB-1 was Boeing’s last biplane design for the United States Navy.

Only the one prototype, Model 236, was ever built, although first flying in early 1933, it rammed into a crash barrier in 1936 and the design was not pursued further.

Ordered by the U.S. Navy on 30 June 1931, the fighter aircraft was a derivative of the Boeing F4B, it was almost entirely of metal construction, with only the wings still fabric-covered.

The aircraft was powered by a 625 hp Pratt & Whitney R-1535-44 Twin Wasp engine.

The intended role of this design turned out to be uncertain.

While its rugged construction was capable of withstanding high g-forces, it weighed in at 3,704 pounds (700 pounds more than the F4B), and did not have the manoeuvrability needed in a fighter aircraft.

It was, however, suitable as a fighter-bomber, and in March 1934 the prototype was redesignated XBFB-1 in recognition of its qualities.

Even so, various ideas were tried to improve its fighter qualifications, such as an improved engine cowling, streamlining around the landing gear, and even a three bladed propeller (two-bladed props being standard).





22 ft 1.5 in (6.73 m)


28 ft 6 in (8.68 m)


10 ft 7 in (3.22 m)

Wing area

252 sq ft (23.41 m2)

Empty weight

2,823 lb (1,281 kg)

Gross weight

3,704 lb (1,680 kg)


1 × Pratt & Whitney R-1535-44,

625 hp (466 kW)


Maximum speed

200 mph (322 km/h, 170 kn)

Cruise speed

170 mph (274 km/h, 150 kn)


525 mi (845 km, 456 nmi)

Rate of climb

1,190 ft/min (6.04 m/s)


2x .30in machine guns

500lb (227kg) bombs.

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