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H-4 (HK-1) Hercules "Spruce Goose"
Type	Very heavy transport, flying boat
Manufacturer	Hughes Aircraft
Designed by	Howard Hughes (Glenn E. Odekirk) Henry J. Kaiser (concept only)[1]
Maiden flight	2 November 1947
Retired	2 November 1947, stored until 5 April 1976
Status	Project cancelled, sole example still exists
Produced	Prototype only
Number built	1

The Hughes H-4 Hercules (registration NX37602) is a "one-off" heavy transport aircraft designed and built by the Hughes Aircraft company, making its first and only flight on 2 November 1947. Built from wood due to wartime raw material restrictions to the use of aluminium, it was nicknamed the "Spruce Goose" by its critics, some of whom accused Howard Hughes of misusing government funding to build the aircraft. The Hercules is the largest flying boat ever built, and has the largest wingspan and height of any aircraft in history. It survives in good condition at the Evergreen Aviation Museum.

Due to wartime restrictions on the availability of metals, the H-4 was built almost entirely of laminated birch, not spruce as its nickname suggests. The Duramold process,^[2] a form of composite technology, was used in the laminated wood construction. The aircraft was considered a technological tour de force. It married a soon-to-be outdated technology, flying boats, to a massive airframe that required some truly ingenious engineering innovations to function. Ultimately, however, the project was an expensive failure and with the end of the war the project was cancelled.

Contents 1 Design and development 2 Maiden flight 3 Postwar 4 Popular culture 5 Specifications (H-4) 6 References 7 External links 8 Related content

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.

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 or even seriously contemplated at that time. When completed, it was capable of carrying 750 fully-equipped troops or one M4 Sherman tank.^[3] The original designation "HK-1" reflected the Hughes and Kaiser collaboration. ^[4]

The HK-1 contract in 1942, issued as a development contract,^[5] initially called for three aircraft to be constructed under a two-year deadline in order to be available for the war effort.^[6] Seven different configurations were considered including twin-hulled and single-hulled designs with combinations of four, six and eight, wing-mounted engines.^[7] The final design chosen was a behemoth, eclipsing any large transport yet built or even envisioned.^[1][5] To conserve metal, it would be built mostly of wood (elevators and rudder were fabric covered^[8]); hence, the "Spruce Goose" moniker tagged on the aircraft by the media. It was also referred to as the Flying Lumberyard by critics who believed an aircraft of its size physically could not fly. 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 E. Odekirk.^[1] Development dragged on which frustrated Kaiser who blamed delays partly on restrictions placed for the acquisition of strategic materials such as aluminium but also placed part of the blame on Hughes' insistence on "perfection."^[9] Although construction of the first HK-1 had taken place 16 months after the receipt of the development contract, Kaiser withdrew from the project.^[10]

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^[8]), signing a new government contract that now limited production to one example. Work proceeded at a slow pace with the end result that the H-4 was not completed until well after the war was over. There were many reasons for this, not least of which was Hughes' mental breakdown during development.

In 1947, Howard Hughes was called to testify before the Senate War Investigating Committee over the usage of government funds for the aircraft, as Congress was eliminating war-era spending to free up federal funds for domestic projects. Even though he encountered skepticism and even hostility from the committee, Hughes remained unruffled.

In a transcript of a Senate hearing, 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.

”

During a break in the Senate hearings, Hughes returned to California, ostensibly to run taxi tests on the H-4.^[8] On 2 November 1947, after a series of taxi tests with Hughes at the controls with co-pilot Dave Grant and a crew of two flight engineers, accompanied by nine invited guests from the press corps, the Hercules lifted off from the waters off Long Beach, remaining airborne 70 feet (21 m) off the water at a speed of 135 mph (217 km/h or 117 knots) for just under a mile (1.6 km).^[11] At this altitude, the aircraft was still experiencing ground effect and some critics believe it lacked the power necessary to climb above ground effect.^[12]

Hughes had answered his critics, but the justification for continued spending on the project was gone. Congress ended the Hercules project, and the aircraft never flew again. It was carefully maintained in flying condition until Hughes' death in 1976.

After years of storage, in 1980, the Hercules was acquired by the California Aero Club, who successfully 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. Disappointed by the lackluster revenue the Hercules exhibit generated, Disney began to look for another organization to take the exhibit off its hands. After a long search for a qualified buyer, the aircraft was acquired by the Evergreen Aviation Museum in 1995, who disassembled the aircraft and moved it by barge to its current home in McMinnville, Oregon (about an hour southwest of Portland) where it has been on display since.

By the mid-1990s, Hollywood converted the former Hughes Aircraft hangars, including the one that held the Hercules, 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 legendary 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 housing development Playa Vista, Los Angeles, California.

Although the project was a failure, the H-4 Hercules, in some senses, presaged the massive transport aircraft of the late 20th century, such as the Lockheed C-5 Galaxy, the Antonov An-124 and the An-225. The Hercules demonstrated that the physical and aerodynamic principles which make flight possible are not limited by the size of the aircraft, even if the viability of the aircraft itself is, mainly due to the lack (at that time) of powerful enough engines.

In the film The Rocketeer (1991), hero Cliff Secord uses a large-scale model of the Spruce Goose 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 2004 Hughes 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.

Performance specifications are projected.

General characteristics

• Crew: 3
• Length: 218 ft 8 in (66.65 m)
• Wingspan: 319 ft 11 in (97.54 m)
• Height: 79 ft 4 in (24.18 m)

• Fuselage height: 30 ft (9.1 m)

• Loaded weight: 400,000 lb (180,000 kg)
• Powerplant: 8× Pratt & Whitney R-4360 Wasp Major radial engines, 3,000 hp (2,240 kW) each

• Propellers: 8 x four-bladed Hamilton Standard, diameter 17 ft 2 in (5.23 m) each

Performance

• Cruise speed: 220 mph (353.98 km/h)
• Range: 3,000 mi (4,800 km)
• Service ceiling: 20,900 ft (6,370 m)

• Projected endurance (cruise): 20.9 hrs

Notes

Bibliography

• Evergreen Aviation Museum, McMinnville, Oregon, home of the plane
• Spruce Goose: Where Is It Now? A history of the plane following Hughes' death
• The Aviator (2004) Biography/drama movie about Howard Hughes with H-4 Hercules Spruce Goose episode

Comparable aircraft

• Dornier Do X
• Blohm + Voss BV 238
• Boeing Pelican
• Saunders-Roe Princess

Related lists

• List of large aircraft

See also

• Ground effect vehicle
• Ekranoplan

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