Moffett Field airship hangars

There are three historic airship hangars at Moffett Field, in Mountain View in the southern San Francisco Bay Area, California. Hangar One (built 1931/2) is based on a structure of steel girders, while Hangars Two and Three (built 1941/2) are of wood. They are among the world's largest freestanding structures.

Hangar One was originally built in the 1930s to house US Navy rigid airships, the USS Macon (ZRS-5) in particular. It is 200 feet (61 m) tall and covers 8 acres (3.2 ha).

Moffett Field's Hangars Two and Three were built at the beginning of World War II for a program of coastal defense. They are still among the world's largest freestanding unsupported wood structures.

In 1940, the US Navy proposed to the US Congress the development of a lighter-than-air station program for anti-submarine patrolling of the coast and harbours. This program proposed the construction of new stations in addition to the expansion at Naval Air Stations (NAS) M and Lakehurst.

The original contract was for steel hangars rather than wooden ones, 960 feet (290 m) long, 328 feet (100 m) wide and 190 feet (58 m) high. Included at each site were helium storage and service, barracks for 228 men, power plant, landing apron, and a mobile mooring mast.

The Second Deficiency Appropriation Bill for 1941, passed on 3 July 1941, introduced strict control of strategic materials like steel causing a change in construction material to wood. Standardized plans were drawn up by the Navy Department Bureau of Yards and Docks, with Arsham Amirikian acting as principal engineer.

Hangars Two and Three at Moffett Field are 1,075 ft (328 m) long, 297 ft (91 m) wide and 171 ft (52 m) high, with an extruded parabolic form that reflected the profile of the airship vessels to be accommodated. A total of 51 Douglas Fir heavy-timber trusses resting on concrete bent frames contain the two-story shop and office areas. Two concrete and wood post and lintel structures support 121 ft (37 m) high multi-track rolling doors at either end.

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