hughes H-4

Design and development

Rearward view of the H-4’s fuselage

In 1942, the U.S. Department of War 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, who directed the Liberty ships program. He teamed with aircraft designer Howard Hughes to create what would become the largest aircraft built at that time. When completed, it was 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 in 1942, issued as a development contract, 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 (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 had taken place 16 months after the receipt of the development contract, Kaiser withdrew from the project.

Size comparison between H-4 and a DC-3

Hughes continued the program on his own under the designation “H-4 Hercules” (initially identified as the HFB-1 to signify Hughes Flying Boat, First Design,) 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.

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 in 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

Hughes H-4 Hercules on its maiden flight

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 were begun with Hughes at the controls. His crew included Dave Grant as co-pilot, and two flight engineers, 16 mechanics and two other flight crew. In addition, the H-4 carried seven invited guests from the press corps plus an additional seven industry representatives, for a total of 32 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 near Long Beach, the Hercules lifted off, remaining airborne 70 ft (21 m) off the water at a speed of 135 miles per hour (217 km/h) for around a mile (1.6 km).[14] At this altitude, the aircraft was still experiencing ground effect.[15] The aircraft 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 and legacy

In 1980, the Hercules was acquired by the California Aero Club, who 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 they no longer wished to display the Hercules. 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 to its current home in McMinnville, Oregon (about one hour southwest of Portland) where it has been on display ever since. The Flying Boat arrived in McMinnville at Evergreen International Aviation on February 27, 1993 after a 138-day, 1,055-mile trip from Long Beach.

By the mid-1990s, the former Hughes Aircraft hangars, 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 square foot (29,000 m²) aircraft hangar where Howard Hughes created the flying boat. It also features in the computer Game “Crimson Skies“. The hangar will be preserved as a structure eligible for listing in the National Register of Historic Buildings in what is today the housing development Playa Vista, Los Angeles, California.

Although the project did not move beyond the initial prototype, the H-4 Hercules was a forerunner of the massive transport aircraft of the late 20th century, such as the Lockheed C-5 Galaxy, the Antonov An-124, and the An-225.

Specifications (H-4)

Performance specifications are projected.

Pratt & Whitney R-4360 Wasp Major

General characteristics

  • Crew: 3
  • Length: 218 ft 8 in (66.65 m)
  • Wingspan: 320 ft 11 in (97.54 m)
  • Height: 79 ft 4 in (24.18 m)
  • Fuselage height: 30 ft (9.1 m)


Notable appearances in media


News story on the Hercules

In the film The Rocketeer (1991), hero Cliff Secord uses a large-scale model of the Hercules to escape some eager federal agents and Howard Hughes himself. After Secord glides the model to safety, Hughes expresses astonishment that the craft might actually fly.

The construction and flight of the Hercules was featured in the Hughes 2004 biopic The Aviator. Motion control and remote control models, as well as partial interiors and exteriors of the aircraft, were reproduced for this scene. The motion-control Hercules is on display at the Evergreen Aviation Museum, next to the real Hercules.


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