US Navy carriers operating in the Pacific during World War II were, like similar vessels of any nation, very vulnerable to air attack. When the changing fortunes of war made it clear to the US Navy that a day could dawn when they would need to attack the Japanese home islands, concern was expressed at the need to deploy these vessels within easy range of large numbers of land-based aircraft. If, however, the US Navy had available a long-range fighter/fighter-bomber, then it might be possible to engage the enemy without the need to bring the carriers within striking range of land-based defence aircraft.
The requirement for such a category of aircraft was communicated to Boeing, which immediately began its design under the designation Boeing Model 400. Submitted to the US Navy, Boeing's design study was sufficiently interesting to warrant the award of a contract for three XF8B-1 prototypes on 4 May 1943. The first of these aircraft made its initial flight during November 1944, and was immediately seen to be the largest single-seat piston-engine fighter to be built in the USA. In fact, it subsequently proved to be one of the most powerful single-engine fighters to be developed by any nation involved in World War II, for its powerplant consisted of a Pratt & Whitney XR-4360-10 radial piston engine, which had four banks of seven cylinders, the 2237kW power output being used to drive two three-blade contra-rotating metal propellers.
Only the first prototype was completed and flown before the end of World War 11, but although the remaining two prototypes were completed and handed over after VJ-Day, the overriding interest in the development of turbine-engined aircraft meant that further test and evaluation of the XF8B-1s was abandoned.
