Building M3 (Type C Hangar), Main Site, Crudwell, Wiltshire

Description

1360/0/10010
01-DEC-05

CRUDWELL
KEMBLE BUSINESS PARK
Building M3 (Type C hangar), Main Site

GV
II

Aircraft storage hangar. 1938/9, to Air Ministry Directorate of Works and Buildings design of 1934. Steel stanchions with in-situ concrete walls, lattice steel roof structure with asbestos-cement slate covering; annexes in rendered brick of block, asphalt flat roof.

PLAN: Located near the main entrance, forming a group with two D type hangars (Main Site, qv). Plain rectangle plan in 12 bays, internal dimensions 300 x 150 x 30ft (91.4 x 45.7 x 9.1), with full width and height doors at each end sliding to external gantries. The roof a series of transverse ridges with hipped ends, behind a parapet, and with deep apron above doors. Low annexe to S side.

EXTERIOR: The long side walls are in plain concrete with slightly worked surface. At mid height are 10 large 32-pane fixed steel casements separated by concrete piers, and with continuous sill and lintel bands. Above the windows a high parapet to flush coping. One bay at each end, also in concrete, is slightly brought forward, and with a higher parapet; a tall single light with horizontal bars is centred to the bay. The short ends have full height and width steel doors, with 12-pane lights at the top, under a deep projecting concrete rail carrying the rolling headgear; beyond the opening a light steel lattice beam projects out and is carried by a light steel strutted support, with steel ground-stops for the doors. Above the doors, and contained by the wing walls of the first bays, a deep apron with asbestos-cement slate hanging. The doors originally had sand or gravel fill between inner and outer sheeting at the lower panels, to enhance blast protection.

INTERIOR: Plain concrete floor, steel stanchions exposed internally carry deep lattice trusses in steel channel, double to top and bottom chords, set to the ridges of the transverse roofs and shaped to the hipped ends. At right angles to these are cantilevered members, in steel angle, at 15ft (4.6m) centres, meeting at and carrying the internal gutters. The bays adjoining the doors have horizontal wind-bracing members. The roof slopes are underlined in softwood square-edged boarding.

HISTORY: The C-type shed was the standard hangar type for the post-1934 Expansion Scheme, originally designed in 1934 and of which 155 examples were built. Its dimensions (300ft long, 150ft span and clear height of 35ft), were intended to accommodate 100-ft span heavy bombers, enabling new specifications to be issued to aircraft manufacturers by the Air Ministry. It evolved from the earlier Type A, and first versions had exposed gabled end to the roofs: after 1935 the hipped version behind parapets, as here, was normal. An internal height of 35ft (10.7) was later reduced to 30ft (9.1), as used in this example. The hangar forms a group with two Type D hangars (qv), immediately N of the axial route through the Main Site. It is retained in commercial use, in fine original condition.

Kemble, by virtue of its range of 5 different hangar types including structurally advanced ones of parabolic form, is the most outstanding and strongly representative of the 24 Aircraft Storage Units planned and built by the Air Ministry for the storage of vital reserve aircraft in the period 1936-1940. The ASUs were all administered by Maintenance Command and were sited to the W of the principal bomber stations and fighter belt, and their function was to receive and store aircraft before they were made ready to be sent to operational bases: some, such as Hullavington to the south, were grafted onto existing Flying Training Schools. Apart from a cluster of 3 hangars on the Main Site, the hangars were planned in pairs around the flying field. The planners of ASUs thus exercised, for the first time, the principle of 'dispersal' in the planning of military airfield landscapes as opposed to fabric, the planning of domestic and technical sites having integrated these requirements from the 1920s. The dispersal of aircraft around the flying field, instead of being concentrated in the hangars, provided further protection against air attack (particularly crucial for the vital supplies of reserve aircraft to front line units) and had a profound influence on airfield layout during the Second World War. This principle also had an effect on hangar design in ASUs, in the use of both concrete and roofs of parabolic form - the latter originally turfed over for additional protection - which housed aircraft in the 'tails-up' position hung from their roofs. The Type D hangar, which combines concrete construction with bow-string trusses, owes its origin to developments in French engineering (as for example at the historic Montaudron airfield at Toulouse). The genesis of the parabolic Lamella type of hangar is the Lamellendach technique, produced by Junkers in Germany from the early 1920s, which utilised a structural grid of short and small-scale steel sections in a diagonal grid in order to create a parabolic vault. This type of hangar was built in England under licence from 1929, and there are four at Kemble (Sites A and B). In addition there are two variants in construction, using the same overall form and dimensions but developed differently: Type L uses close-spaced concrete ribs formed in pressed steel members (Sites F (not included) and C) and Type E uses ribs of small-section steel to support concrete slabs curved to the arc of the frame (Site E). These steel and concrete rib hangars most clearly relate to contemporary experimentation elsewhere in Europe, especially Pierre Luigi Nervi's Lamella-derived forms built for the Italian air force, the Zeiss-Dwidag concrete-ribbed vaults used for side-opening hangars in Germany and the concrete hangars developed for the French air force from the 1920s. All these hangar buildings stretched existing engineering technology in order to clear wide spans, forming the basis for developments in the post-war period. The existence of such a variety of these types of hangars at Kemble, also relating to an advanced type airfield landscape, is certainly unique in a British context, and no such group survives in France or Germany.

RAF Kemble was officially opened in June 1938, but construction continued into 1939 and a Station HQ was not formed until October 1940, under 41 Maintenance Group. By November over 900 personnel were involved, many of them civilians, staffing the Maintenance Unit: most were accommodated off-site, and others were in hutted units, mostly in Kemble Wood to the E. The daily amount of aircraft stored in October was 330, from antiquated Hawker Harts to Bristol Beauforts, Blenheims and Hurricanes. Two runways were built between September 1941 and April 1942, the main one being extended in 1943 in order to accept heavy bombers and accompanied by the building of new taxiways. The station survived aerial attack in 1940/1, it going on to play an important role in the readiness for D-Day with work on Horsa gliders and Typhoons in early 1944. The Fosse Way crosses the site.

(The Royal Air Force Builds for War: A History of Design and Construction in the RAF, 1935-1945, 1956, republished by HMSO in 1997, pp.290-302; Operations Record Book, Public Record Office AIR 28/218; Christopher Ashworth, Action Stations 5 (Military Stations of the South-West), Cambridge, 1982, pp. 115-7; J.S. Allen, 'A short history of 'Lamella' construction', Transactions of the Newcomen Society, 71 (1999-2000), pp. 1-29).

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Building M3 (Type C Hangar), Main Site

A Grade II Listed Building in Crudwell, Wiltshire

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