Hughes Aircraft Company 'Spruce Goose'

The geographic isolation of the US conferred an enormous advantage during the Second World War, but also led to logistic problems with ferrying men and machines to war theatres. Henry Kaiser, a civil engineer who had a habit of thinking big, was building Liberty Ships [5, 6] and had the idea for a large flying boat, which would avoid the U-boat menace in the North Atlantic. He approached Howard Hughes (Video Clip) to build the huge craft, which was called the HK-1, but became known as the ‘Spruce Goose’.

The plane was to be built from wood, had 8 Pratt & Whitney 3 000 hp engines, a wingspan of 320 feet and a length of 218 feet. The payload was to have a mass of 130 000 lbf, loaded through front doors, and it was intended that 3 of the aircraft should be built initially. Hughes was a perfectionist, and his attention to detail was largely responsible for the delay until November 2 1947, of the first and only flight (Taxiing in Water, Video Clip - Flight) of the Spruce Goose, by which time Kaiser had left the project. Part of the time delay was also due to the technological problems which had to be overcome in the design. These included testing of new concepts for the large hull and flying control surfaces, and the incorporation of power boost systems for control.

This flight was probably accidental and was in response to criticism from Congress (one congress man called the craft the ‘flying lumberyard’) which, post-war, had become frugal in outlook as the rationale for the flying boat had disappeared. Whilst it halted the critics, the project was dead and the aircraft was retired to a hangar until after Hughes death in 1976.

It is not clear how well the Spruce Goose would have performed in service, as engine power was limited at the time, and knowledge of aerodynamics was incomplete, whilst the construction method was outdated even for the time (although probably of lower weight than aluminium). This type of aircraft was later resuscitated in the form of the C-5 Galaxy cargo plane [7], as a need for large cargo planes was recognised with the cold war and Vietnam. The figures shows a strong resemblance between outlines of the C-5 and the HK-1.

Design Failure:

Technological problems and a perfectionist attention to detail meant that the prototype was completed after the original need had passed, and before the need was again recognised as important. It was a design which was realised at the wrong moment in history, with the wrong technology.

The existence of the US Military Airlift Command testifies to the current importance of the concept, although with much improved power plant and aircraft technology in examples like the C-5 Galaxy (wingspan 223 feet, length 247 feet, payload mass of 205 000 lb).

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