The Flight Test Hangar, Offices, Fire Station And Control Tower, British Aerospace

The Flight Test Hangar, Offices, Fire Station and Control Tower, British Aerospace

This is a flight hangar with associated offices, fire station and control tower built for the de Havilland Comet jet airliner. The main hangar was constructed in 1952-3, with the offices and tower completed in 1954. The architects were James M Monro and Son, with Structural and Mechanical Development Engineers Ltd designing the aluminium structure, and J Bak as engineer for the foundations.

The hangar is constructed from HE 10 aluminium alloy and clad with an insulated aluminium curtain wall. The north-facing roof slopes are glazed with aluminium glazing bars, whilst the south-facing slopes are covered with insulated aluminium decking topped with bitumen felt. The office block on the west wall incorporates some steel framing and is clad in brick.

The main structure consists of twelve portal frames set at 30-foot centres. They span 217 feet between pinned bases, providing a clear floor area of 200 feet wide by 330 feet long with a clear height of 45 feet. The portal legs are eight feet wide, and the horizontal girder portions maintain a constant depth of ten feet throughout their span, except for increased depth at the knee positions to counteract heavy fixings and loadings. The concrete flooring incorporates prestressed tie beams to resist the side thrust of the portal frames. The entire south elevation is fitted with sliding and folding Esavian doors. The north elevation features saw-tooth profile windows in aluminium frames.

The control tower comprises six storeys and was noted for its early use of non-reflective plate glass and air conditioning. Below this are four floors with curved balcony fronts, the diagonal bracing pattern of which is repeated in the fenestration. The three-bay fire station has a similar curved front with double doors and a deep eaves canopy. The office range has simpler aluminium glazing.

The interior of the main shed is a clear-span space. A staircase to the control tower features a distinctive 1950s contemporary-style steel balustrade with molecule and lightning motifs. The control room retains its original fixed desk and controls.

Historical Context

De Havilland began developing a jet engine called the Goblin in 1941-2, which was incorporated into the Vampire jet fighter design in 1943-4 and further developed as the Ghost. The company's primary focus was on civil aviation, however, and in 1946 they designed the Comet, the world's first jet passenger liner. Sixteen aircraft were ordered as early as 1947, reflecting the aircraft's perceived significance for British aviation. Commercial services commenced in May 1952. Between 1953 and 1954, three Comets exploded in flight, killing 111 people. Investigation revealed the cause to be fatigue of the thin aluminium alloy shell of the pressurised cabin. The two-million-pound analysis that confirmed this fault established a testing model for subsequent jet aircraft. The problem-free Comet 4 was inaugurated in 1958, just ahead of the Boeing 707, and was followed by the DH Trident. The hangar was commissioned for testing and maintaining the Comet.

Architectural and Structural Significance

The aluminium alloy span of 200 feet weighs only one seventh that of an equivalent steel structure. The light weight permitted prefabrication of unusually large sub-assemblies, and the main structure was erected in just thirteen weeks. The Comet hangar represents the most sophisticated example of aluminium construction of its time and was the world's largest permanent aluminium structure at the time of completion. It was comparable with the since-demolished Dome of Discovery at the Festival of Britain and larger and more innovative than the hangar at London Airport, which has also since been demolished. Aluminium construction experienced a boom in the early 1950s, with steel in short supply and aircraft companies with aluminium experience seeking to diversify. British Standards for aluminium buildings and improvements in alloys were recognised by the government in 1953, and the Comet hangar was the first building to employ them.