Main Hangar (Calshot Former Rnas Station Immediately South Of Castle)

The Main Hangar at Calshot, formerly part of the Royal Naval Air Station, was built in 1918 and is a significant flying boat hangar. It features a steel frame with corrugated asbestos or metal cladding and a roof, and has a rectangular plan covering approximately 5,704 square metres. The hangar includes contemporary steel buttresses, with the west elevation showcasing continuous glazing below the eaves and three sets of sliding double doors. The east elevation also has continuous glazing and a single-storey outshut, which is glazed. Both the north and south elevations each have eight lights, and the interior is supported by steel lattice girders.

Historically, this hangar is notable for being the largest built in Britain for fixed-wing aircraft during World War I. It consists of three "F" type hangars introduced in 1917 and is part of a remarkable group of early aircraft structures in the British Isles. This group highlights the significant advancements in aircraft technology during the 1914-1918 period. The site is also linked to the development of RJ Mitchell's Merlin engine, which powered the Spitfire, and was used for RAF speed trials in the inter-war years, as well as hosting British and Italian teams for the Schneider Trophy contest in 1929 and the Supermarine and Gloster racers in 1931.