Duxford: Building 78 (Hangar 5), Duxford, Cambridgeshire

Summary

Aircraft hangar, one of a group of three, built in 1917-18 to the War Office's Directorate of Fortifications and Works Drawing Number 332/17. It was designed by Lieutenant-Colonel BHO Armstrong of the Royal Engineers. The southern annexe was extended in 1930 and the northern annexe in 1935.

Description

MATERIALS: it has brick buttresses, curtain walls and internal piers, all painted, and timber roof trusses covered with profiled steel sheeting. The annex roofs are of corrugated steel sheeting.

PLAN: the hangar forms the westernmost example of a group of three identical and contemporary hangars that stand in-line on an east-north-east to west-south-west axis on the north side of the airfield. Although the building is orientated on a north-north-west to south-south-east alignment cardinal compass points will be used in the following description for simplicity.

The hangar is comprised of paired sheds, each of 100ft span and 25ft clear height, with full-height and full-width sliding/folding doors at the east and west ends. The 15-bay north and south sides, which have an overall length of 170ft, have brick buttresses arranged at 11ft 4inch intervals to support ‘Belfast’ roof trusses. Adjoining the north and south sides are lean-to ancillary annexes.

EXTERIOR: the east and west opening ends have 'Esavian' sliding/folding doors with diagonal timber boarding running to an overhead track with a deep apron above running the full width of the hangar to compact brick pylons at each end. Wicket doors within the aeroplane doors provide personnel access.

The north and south walls have raking buttresses carried up to the eaves soffit, with half-brick curtain walls between. Each end bay is plain while the remaining 13 bays have a full-width steel casement window in 27-panes set as a high clerestory; alternate bays also incorporate a six-pane pivoted opening section. Above these windows is a deep apron band.

At each end the brick pylons that the aeroplane doors slide into are in the form of a square shaft, but that at the north-east corner of the hangar had been modified to form part of a bomb dropping training tower. It has a round-headed open arch on the north side, a corbelled arch on the west side and a brick box superstructure with an open west side and a flat, concrete-slab roof.

The roofs are in profiled steel in flat segmental form, with continuous ridged patent glazing roof lights (to the central 13 bays), and with a line of patent glazing each side of the central valley. The eaves have a plain painted fascia with gutter. Above the horizontal apron to the door track is a flat segmental pediment to each shed, with close-set vertical joint divisions to metal cladding, and a wide central ventilation louvre.

Flanking the sides of the hangar are the lean-to annexes. On the north side, from left to right, bays five to twelve are spanned by a seven-bay annexe, with nine-pane steel casement windows with pivoted central sections to each bay. Bays 13 to 15 are spanned by a three-bay annexe with two-light steel casements with square pane glazing to each bay. Bays four and twelve accommodate late-C20 double doors with glazed top panels and two-light fanlights.

The southern annexe, from left to right, has a four-bay range spanning the width of the first four bays. Built around 1930, it has two three-light steel casements to the left-hand side of an off-centre left doorway and two three-light steel casements with square-pane glazing to its right. Set back to the right-hand side of this addition is the original seven-bay annexe which spans the width of bays five to eleven of the hangar. Its third and fourth bays accommodate double, louvered doors to the boiler house/compressor room, while the other five bays each has a nine-pane steel casement window with pivoted central sections. The hangar’s 12th bay accommodates a late-C20 entrance door with a glazed top panel.

INTERIOR: the paired sheds have a central row of brick oblong piers with narrow central openings to arched heads. On each side there is a moulded stone corbel carrying the roof strutting, and running between the piers to support the gutter and to provide stiffening is a series of ‘diaphragm’ walls, one brick thick, on flat segmental arches.

Each bay is divided by wooden-latticed ‘Belfast’ roof trusses which span from the central row of piers to the buttresses in the outer walls. The trusses, all whitewashed, have a flat bottom chord and a bowed upper profile, formed in a series of straight members. All truss members are small-section softwood, with doubled main members sandwiching a close-spaced diagonal grid infill; at the end supports the trusses are strutted to shaped stone corbels, and this 'knee' area is strengthened by diagonal close-boarded sheeting. Longitudinally there are 5 sets of simple cross bracing, and diagonal sheathing on small purlins carried to the roofing. In the end bays there is extra horizontal bracing to the bottom chord.

A full-height fire curtain of late-C20 date now spans across the four westernmost bays of the south-side shed to partition off an aircraft spray area. The four arched piers at this end have also been infilled with late-C20 protective screens along with two ventilation flues and their associated pipework. Late-C20 fire curtains also protect the aeroplane doors at each end. Floors are in concrete.

History

Duxford’s suitability as a landing field led to its use for military flying during the Military Manoeuvres of 1912. Construction of the Training Depot Station (TDS) started in October 1917, and the first units including Americans arriving in March 1918. It was one of 63 Training Depot Stations in existence in November 1918, and the group of hangars and other buildings on the technical site now constitute one of the best-preserved group of buildings surviving from a First World War airfield in Britain. Training Depot Stations, which comprised the main instructional flying unit for the Royal Flying Corps (RFC) and the Royal Air Force (RAF), were built in pairs, Duxford and its sister station at nearby Fowlmere making one wing. Each TDS comprised three flying units, each having a coupled general service shed and one repair hangar (the Duxford example was demolished in 1968, leaving Old Sarum in Wiltshire and Leuchars in Scotland as the only examples which survive as part of hangar groups). Other specialist buildings, such as carpenters’ shops, dope and engine-repair shops, and technical and plane stores, characterised these sites.

Duxford was one of a core number of stations retained for the RAF after 1918, first as a flying training school and then (from 1 April 1923) as a fighter station with 19 Squadron. This was designated as a mobile (expeditionary) squadron, and they remained on the base until replacement by the Eagle Squadron of American volunteers in August 1941. 19 Squadron’s expertise resulted in the station introducing a number of aircraft into RAF service, such as the Gloster Gauntlet which it received in January 1935 and was displayed along with the prototype of the Gloster Gladiator at George V’s Silver Jubilee in July of that year. The first Spitfire to an RAF squadron was delivered to Duxford by Supermarine’s test pilot in August 1938, and 12,000 visitors caught their first sight of the Spitfire during Empire Day on 20 May 1939. With one exception, the wooden-framed barrack buildings were replaced in a rebuilding campaign that commenced in 1928. A major phase of modernisation was approved in 1931, resulting in the construction of the station headquarters and guardroom on the south camp, and the construction of domestic buildings in the north camp - the sergeants' mess being the first building ready for occupation. In an attempt to achieve parity with Germany’s increasing air strength, the British Government introduced a number of schemes for the expansion of the RAF, which followed in quick succession between 1934 and 1939. The Cabinet (National Government) passed five schemes: ‘A’, ‘C’, ‘F’, ‘L’ and ‘M’, which led to a large-scale re-building programme at existing RAF stations (including Duxford) and to the development of numerous new aerodromes.

During the Battle of Britain (10 Jul – 31 Oct 1940), Duxford was the most southerly airfield in 12 Group, responsible for the defence of the Midlands and East of England but also making it well-placed to reinforce and support 11 Group to the south, which bore the brunt of the Luftwaffe assault. Czech and Polish squadrons operated from Duxford during the battle, and on 15 September - the critical point in the battle - five Duxford squadrons led by Squadron Leader Douglas Bader claimed their highest score of 52 aircraft destroyed (plus 16 probably destroyed and 3 damaged). Bader - Commander of 242 Squadron initially based at Coltishall - was the instigator of what became known as the Duxford Wing, (a strategy whereby he led 3 and later 5 squadrons of Spitfires and Hurricanes into battle), which formed the focus of disagreement concerning fighter defence strategy which continued into the winter of 1940. Some of the pillboxes, air raid shelters and fighter pens installed by 1940 for the purposes of airfield defence and protection against attack have survived.

The arrival of the RAF’s Air Fighting Development Unit at Duxford, in December 1940, saw a wide variety of new aircraft for evaluation and testing, including the replacement of the Hurricane, Hawker Typhoon, Mosquito and Mustang (the most powerful fighter of the Second World War). The airfield was officially handed over to become base 357 of the United States Eighth Air Force on 1 April 1943, the first of 75 P47 Thunderbolts arriving on the same day.. The first of the new Merlin-powered P51 Mustangs, which were to play a critically important role in the European air war, arrived to replace the Thunderbolts after the completion of the steel matting runway in December 1944. The base in its fighter support role was responsible for the destruction of 338 aircraft in the air and a further 358 on the ground, with the loss of 167 aircraft and 113 pilots. Duxford’s post-war service as a jet fighter station, with Meteors, Hunters and then Javelins, was marked by the completion of a replacement runway in concrete (6000 feet long with Operational Readiness Platforms at both ends) in August 1951.

RAF Duxford was closed in 1961, and subsequently chosen as one of the locations for filming of the Battle of Britain in 1968, (when the 1918 repair section hangar was destroyed). In 1969, the Ministry of Defence declared its intention to dispose of Duxford, and the Imperial War Museum duly requested permission to use part of one of the airfield’s hangars as temporary storage. The Imperial War Museum was founded in 1917, and opened to the public at Crystal Palace in Sydenham Hill in 1920, before moving to the Imperial Institute in South Kensington in 1924, and finally the Bethlem Royal Hospital in Southwark in 1936. The museum was originally intended to record the civil and military war effort and sacrifice of Britain and its empire during the First World War. The museum's remit has since expanded to include all conflicts in which British or Commonwealth forces have been involved since 1914. As of 2012, the museum aims to provide for, and to encourage, the study and understanding of the history of modern war and wartime experience. Duxford became the first outstation of the Imperial War Museum in 1976, and Cambridgeshire County Council joined with the Imperial War Museum and the Duxford Aviation Society to purchase the runway in 1977. The construction of the M11 along the east boundary of the site in 1977 shortened the runway by about 1,200ft (366m). The final aircraft to land at Duxford before the runway was shortened was Concorde test aircraft G-AXDN, now on display in the Airspace hangar. In October 2008, an agreement was reached between Cambridgeshire County Council and the Imperial War Museum, under which the runways and 146 acres of surrounding grassland were acquired by the museum.

Building 78 (Hangar 5) is one of three double-span general service aeroplane sheds (hangars) which were built at Duxford between 1917 and 1918. Their design for the Directorate of Fortifications and Works at the War Office corresponds to drawing number 332/17, which is dated 1917 and signed by Lieutenant-Colonel BHO Armstrong of the Royal Engineers.

The three hangars were planned to stand in-line on an east-north-east to west-south-west alignment on the north side of the airfield. A contemporary aeroplane repair section shed which stood between the central and easternmost hangars was destroyed in 1968.

Each hangar is a double shed and of a standard plan with brick-built buttresses arranged at 11ft 4 inch intervals to form 15-bay side walls with an overall length of 170ft. Infilling between the buttresses is of reinforced 4.5 inch temporary brick with each bay, except for those accommodating the main doors, having steel-framed casement windows. The buttresses support 100ft span timber roof trusses manufactured by D Anderson and Son of Belfast.

The side walls of each coupled hangar originally had a 10ft wide annexe covering seven bays. The northern annexes functioned as a small store (a single bay) while the remaining six bays were used as open-plan workshops. The southern annexes were sub-divided into seven individual officers’ dressing rooms with individual doors opening out into the hangar.

In February 1918, with construction having commenced, the Air Ministry decided to alter the design of the hangar door. The traditional brick-built gantries shown on Drawing Number 332/17 with steel-framed doors covered in flat asbestos sheeting were replaced by 'Esavian’ concertina folding doors (a patent of the Educational Supply Association Limited). With this new arrangement, the method of storing the doors when opened required L-shaped, brick-built, door stacking bays of simple design which were quicker to build and used less materials. This subsequently became the new standard and all TDS aeroplane sheds under construction for the newly formed Royal Air Force had doors of this type.

It is not known if the three hangars ever had Anderson ROK roofing (diagonal boarding covered in patent roofing felt) or were clad with 8ft by 4ft flat asbestos sheeting which became the standard roof covering used in conjunction with Belfast roof trusses. Whatever the type of roofing, it was found to be unsatisfactory, as around May 1925 the roofs of all three hangars were recovered in corrugated iron and the ridgelights rebuilt.

Building 78 (Hangar 5) was the only hangar of the three to be built with a bomb dropping training tower, which was located at the north-east corner of the shed. In more recent times it was used as a hose drying tower.

In May 1930 drawings were prepared for the extension of the southern annexe to accommodate the Cambridge University Air Squadron (CUAS). This took the form of a pilots’ locker room and an attached boiler house at the western end of the existing annexe as well as a latrine at the opposite end.

During 1934 it was proposed to extend the northern annexe to a width of 20ft and to build another 20ft wide annexe covering three bays for a gun-cleaning room at the western end of the shed. Although a gun-cleaning room was subsequently built in 1935, its width was the same as the original First World War annexe at 10ft wide. The main extension was never carried out and the annexe was never developed beyond its original length and width.

Building 78 (Hangar 5) now (2018) accommodates the museum's ‘Conservation in Action’ workshop, where its collection of large objects is conserved and prepared for display. To facilitate this a designated spray area and external exhaust duct was installed in around 1994 along with a heating and ventilation system.

Reasons for Listing

Building 78 (Hangar 5), one of a group of three aircraft hangars built at RAF Duxford in 1917-18 to the War Office's Directorate of Fortifications and Works Drawing Number 332/17, is listed at Grade II* for the following principal reasons:

Architectural interest:

* as a rare First World War Hangar which remains largely unaltered since it was built as part of the original layout and design of the Training Depot Station;

* it was designed by Lieutenant-Colonel BHO Armstrong, considered to be the most important War Office architect of the First World War;

* its Belfast roof truss exemplifies the high standard of design achieved against the constraints in cost, efficiency and utility as demanded by the Air Ministry;

* the undivided interior allows for the full impact of its space and construction to be appreciated, with the military experience still being readily captured;

* the inter-war alterations to the annexes are significant in themselves as they illustrate how the hangar was modified to meet the threat posed by Germany's increasing air strength.

Historic interest:

* as an integral component of Duxford Airfield the finest and best-preserved example of a fighter base representative of the period up to 1945 in Britain;

* for Duxford’s important association with the Battle of Britain and the American fighter support for the Eighth Air Force.

Group value:

* for its strong group value with the uniquely complete group of First World War technical and domestic buildings typical of both inter-war Expansion Periods of the RAF;

* for the surviving spatial and functional relationship between the hangar and the flying field which it served.

External Links

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