Hughes H-4 Hercules (aka Spruce Goose)
American eight-engine high-wing long-range heavy-load flying boat

Archive Photos 1

Hughes H-4 Hercules (Spruce Goose) (N37602, model) on display (c.1995) at the Western Museum of Flight, Hawthorne, California

Overview 2

The Hughes H-4 Hercules, aka Spruce Goose (NX37602) is a prototype heavy transport aircraft designed and built by the Hughes Aircraft company. The aircraft made its first and only flight on November 2, 1947, and the project never advanced beyond the single example produced. Built from wood because of wartime restrictions on the use of aluminum and concerns about weight, its critics nicknamed it the Spruce Goose, despite it being made almost entirely of birch rather than spruce. The Hercules is the largest flying boat ever built and has the largest wingspan of any aircraft in history. It survives in good condition at the Evergreen Aviation Museum, McMinnville, Oregon, USA.

Design and Development 2

In 1942, the U.S. War Department was faced with the need to transport war materiel and personnel to Britain. Allied shipping in the Atlantic Ocean was suffering heavy losses to German U-boats, so a requirement was issued for an aircraft that could cross the Atlantic with a large payload. Due to wartime priorities, the design was further constrained in that the aircraft could not be made of metal.

The aircraft was the brainchild of Henry J. Kaiser, a leading Liberty ship builder. He teamed with aircraft designer Howard Hughes to create what would become the largest aircraft built at that time. It was designed to be capable of carrying 750 fully equipped troops or one M4 Sherman tank. The original designation HK-1 reflected the Hughes and Kaiser collaboration.

The HK-1 contract was issued in 1942 as a development contract and called for three aircraft to be constructed under a two-year deadline in order to be available for the war effort. Seven configurations were considered including twin-hull and single-hull designs with combinations of four, six, and eight wing-mounted engines. The final design chosen was a behemoth, eclipsing any large transport then built. To conserve metal, it would be built mostly of wood, its elevators and rudder were fabric covered; hence, the Spruce Goose moniker tagged on the aircraft by the media. It was also referred to as the Flying Lumberyard by critics. Hughes himself detested the nickname Spruce Goose.

While Kaiser had originated the flying cargo ship concept, he did not have an aeronautical Background and deferred to Hughes and his designer, Glenn Odekirk. Development dragged on, which frustrated Kaiser, who blamed delays partly on restrictions placed for the acquisition of strategic materials such as aluminum, but also placed part of the blame on Hughes’ insistence on perfection. Although construction of the first HK-1 took place 16 months after the receipt of the development contract, Kaiser withdrew from the project.

Hughes continued the program on his own under the designation H-4 Hercules, signing a new government contract that now limited production to one example. Work proceeded slowly, with the result that the H-4 was not completed until well after the war was over. It was built by the Hughes Aircraft Company at Hughes Airport, location of present day Playa del Rey, Los Angeles, California, employing the plywood-and-resin Duramold process - a form of composite technology - for the laminated wood construction, which was considered a technological tour de force. It was shipped on streets to Pier E in Long Beach, California by a company specializing in house moving. The Spruce Goose was moved in three large sections consisting of the fuselage and each wing, and a fourth smaller shipment containing the tail assembly parts and other smaller assemblies. After final assembly a hangar was erected around the flying boat with a ramp to launch the H-4 into the harbor. This building became the first climate-controlled building in the United States.

In 1947, Howard Hughes was called to testify before the Senate War Investigating Committee over the usage of government funds for the aircraft.

During a Senate hearing on August 6, 1947 (the first of a series of appearances), Hughes said: The Hercules was a monumental undertaking. It is the largest aircraft ever built. It is over five stories tall with a wingspan longer than a football field. That’s more than a city block. Now, I put the sweat of my life into this thing. I have my reputation all rolled up in it and I have stated several times that if it’s a failure I’ll probably leave this country and never come Back. And I mean it.

Operational History 2

During a break in the Senate hearings, Hughes returned to California to run taxi tests on the H-4. On November 2, 1947, the taxi tests began with Hughes at the controls. His crew included Dave Grant as co-pilot, two flight engineers, Don Smith and Joe Petrali, 16 mechanics, and two other flight crew. In addition, the H-4 carried seven invited guests from the press corps and an additional seven industry representatives. Thirty-six were on board.

After the first two taxi runs, four reporters left to file stories, but the remaining press stayed for the final test run of the day. After picking up speed on the channel facing Cabrillo Beach, the Hercules lifted off, remaining airborne at 70 ft (21 m) off the water and a speed of 135 miles per hour (217 km/h) for around a mile (1.6 km). At this altitude, the aircraft still experienced ground effect. Having proven to his detractors that Hughes’ masterpiece was flight-worthy, thus vindicating the use of government funds, the Spruce Goose never flew again. Its lifting capacity and ceiling were never tested. A full-time crew of 300 workers, all sworn to secrecy, maintained the plane in flying condition in a climate-controlled hangar. The crew was reduced to 50 workers in 1962, and then disbanded after Hughes’ death in 1976.

Display 2

In 1980, the Hercules was acquired by the California Aero Club, which put the aircraft on display in a large dome adjacent to the Queen Mary exhibit in Long Beach, California. In 1988, The Walt Disney Company acquired both attractions and the associated real estate. Disney informed the California Aero club that it no longer wished to display the Hercules after its highly ambitious Port Disney was scrapped. After a long search for a suitable host, the California Aero Club awarded custody of the Hughes flying boat to Evergreen Aviation Museum. Under the direction of museum staff, the aircraft was disassembled and moved by barge and truck to its current home in McMinnville, Oregon, where it has been on display ever since. The Flying Boat arrived in McMinnville on February 27, 1993 after a 138-day, 1,055-mile (1,698 km) trip from Long Beach.

By the mid-1990’s, the former Hughes Aircraft hangars at Hughes Airport, including the one that held the Hercules, were converted into sound stages. Scenes from movies such as Titanic, What Women Want and End of Days have been filmed in the 315,000 ft² (29,000 m²) aircraft hangar where Howard Hughes created the flying boat. The hangar will be preserved as a structure eligible for listing in the National Register of Historic Buildings in what is today the large light industry and housing development Playa Vista in suburban Los Angeles.

Specifications (H-4) 2

General Characteristics

Performance (projected)


  1. Shupek, John. Photos, copyright © 2000 Skytamer Images. ALL RIGHTS RESERVED
  2. Wikipedia, the free encyclopedia, Hughes H-4 Hercules


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