Howard Hughes's famous HK-1 Hercules (#NX37602) is a cargo-type flying boat designed to transport men and materials over long distances. Originally conceived by Henry J. Kaiser, a steelmaker and builder of Liberty ships, the aircraft was designed and constructed by Hughes and his staff. The original proposal for the enormous, 400,000-pound wooden flying boat, with its spectacular 320-foot wingspan, came from the U.S. government in 1942. The goal was to build a cargo and troop carrier that did not require critical wartime materials; in other words, that substituted wood for metal. Throughout its construction, considerable controversy surrounded its funding. After a disgruntled U.S. Senator dubbed the HK-1 a "flying lumberyard," the "Spruce Goose" nickname was coined — Hughes despised the name!
The huge flying boat consists of a single hull, eight radial engines, a single vertical tail, fixed wingtip floats, and full cantilever wing and tail surfaces. The entire airframe and surface structures are composed of laminated wood (primarily birch, not spruce). All primary control surfaces, except the flaps, are fabric covered. The aircraft's hull is divided into two areas: a flight deck for the operating crew and a large cargo hold. Access between the two compartments is provided by a circular stairway. Below the cargo hold are fuel bays divided by watertight bulkheads.
The Hughes/Kaiser flying boat was to be the largest airplane ever built (in fact, after its completion, it was three times larger than the largest aircraft built before it) and probably the most prodigious aviation project of all time. Only the courage and solitary dedication of Howard Hughes and his small development group caused this project to advance resulting in its historic first, and only flight. As Hughes kept meddling in the design, making things more complicated and causing lost time, Kaiser backed out. An urgent government project in 1942, the wooden flying boat had lost all priority by 1944. Hughes's motives for making things so complicated are not clear. They seem to have resolved around his idea for an "aerial freighter beyond anything Jules Verne could have imagined."