Aircraft Hangar, Shackleton Barracks, Ballykelly, Limavady, Co Londonderry

Aircraft Hangar, Shackleton Barracks, Ballykelly

A steel-framed and metal-clad structure of anchor-balanced cantilever design, erected in the mid-1960s by the Ministry of Public Buildings and Works. The hangar was designed to house Shackleton maritime reconnaissance aircraft and became operational in 1966. It is unique in the context of Northern Ireland and rare in the wider UK context.

The building is situated to the east of the runways, close to the Spallan Road on flat terrain. It measures 220.7 by 48.3 metres externally. The structure comprises eight identical cantilevered steel frames, each with a clear span of 39.2 metres from the front of the doors to the main upright. The main upright comprises a 660-millimetre square welded steel box, to which a triangulated truss is bolted on the top front and a braced anchor leg at the back. The main components of the trusses and anchor leg are of I-profile rolled steel, 610 by 305 millimetres. Secondary framing comprises braced lengths of L-profile steel. The main frames are set at 27.4-metre centres, with triangulated steel lattices running between them to carry the roof. The roof slopes down slightly towards the rear to facilitate rain run-off.

The external walls consist of a 1.5-metre-high skirting wall in brickwork on three sides, with continuous strip glazing to 2.4 metres high, thereafter profiled aluminium panels. The south elevation is broken up with three large areas of aluminium curtain walling with bands of continuous glazing and blue-coloured infill panels. The roof and its deep fascias are clad in profiled aluminium, consisting of felt on cork on aluminium decking and sides of troughed aluminium sheeting resting on brick walls 660 millimetres wide by 1.5 metres high.

Three catwalks are set within the cantilever frames and run the entire length of the building. The anchor legs are secured to piles driven into the ground some 7.3 metres beyond the south wall. These piles began to move shortly after the building was completed, probably as a result of a change in the local water table. Dead weights were subsequently added to the tops of the piles in the form of mass-concrete blocks of cruciform plan, each measuring 10.5 by 4.3 by 1.2 metres overall.

Along the entire length of the north wall are seven banks of horizontally-moving steel-clad doors, varying from 20.7 to 28.3 metres in width. They are stepped back on either side of the central door to allow for unimpeded movement, enabling the entire length of the hangar to be opened or individual bays to be accessed without opening all doors. The doors were formerly activated by manual winches on metal rails and are no longer operational. Picket gates are set in the front doors, with additional access doors along the south wall.

The roof features windows along the rear pitch and in bays on the south wall. Underground heating pipes, probably low-pressure water, run around the internal perimeter and underneath the floor. The heating steam is generated in a small brick boiler house a short distance beyond the middle of the south wall.

The innovative cantilever design provides a large uninterrupted interior space, allowing aircraft to taxi under their own power without requiring manhandling. The function of the hangar was not to store aircraft but rather to provide shelter, heat and light for their inspection, servicing and repair. In terms of modern aircraft, it is capable of housing four Hercules transport aircraft simultaneously.

Ballykelly airfield originated as an RAF base during the Second World War. Shackletons were the mainstay of RAF Coastal Command at the time and operated out of Ballykelly, Lossiemouth in Invernesshire and St. Magwan in Cornwall. With the development of longer-range Nimrods the base became obsolete as the new aircraft could cover the required area from Lossiemouth and St. Magwan. The hangar was subsequently used for aircraft maintenance and is now used by the Army as a vehicle store and service depot.

The design may have been based on a similar hangar at Orly (1959), to which it is of similar size and construction. Similar, though smaller, hangars were built at RAF Brize Norton, Oxfordshire (1968) and RAF St. Magwan (1968). There had been an intention to build one at RAF Lossiemouth but the idea was dropped on grounds of cost. The original design for Ballykelly had the large doors sliding up into the roof, but this proved too difficult and sliding doors were installed instead.

For its construction, the civil contractor was Kennedy's of Coleraine, with Brims of Newcastle upon Tyne carrying out the erection of the hangar. The steelwork design and fabrication was by Teeside Bridge and Engineering.