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 maneuverability 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).