Boeing XF6B

The Boeing XF6B-1, later redesignated XBFB-1, was the last biplane fighter Boeing designed for the United States Navy. Ordered on 30 June 1931 as Boeing Model 236, it was a derivative of the F4B built almost entirely of metal, with only the wings still covered in fabric, and it was powered by a 625 horsepower Pratt and Whitney R-1535-44 Twin Wasp radial engine. Its rugged structure could take high g-forces, but at 3,704 pounds it was about 700 pounds heavier than the F4B and was not agile enough as a fighter, so in March 1934 it was renamed as a fighter-bomber. Only one prototype was built. It first flew in early 1933 and ran into a crash barrier in 1936, and the Navy chose the Curtiss F11C Goshawk instead.