Navigation.

On 21 March 1919, a gyrocompass developed for the Navy was tested in an aircraft, marking the first recorded instance of tests of a device that would become an invaluable navigational instrument for long-range flight.

Development of the Navy's tactical air navigation system (TACAN)--comprising a surface beacon and airborne receiver to determine the direction of the aircraft from the surface station--was initiated by a 1948 contract. On 30 August 1956 the Air Coordinating Committee approved a common military-civil short-range air navigation system called VORTAC, which combined TACAN with the Civil Aeronautic Authority's very high frequency omnirange direction finder.

On 1 January 1943, just nine days after the first successful experimental demonstration of Ground Controlled Approach (GCA) technology, the system was called into emergency use for the first time when a snowstorm closed down the field at NAS Quonset Point, R.I., shortly before a flight of PBY Catalinas was due to arrive. The GCA crew located the incoming aircraft on their search radar and used the control tower as a relay station to "talk" one of them into position for a contact landing. Above, an air traffic controller at NAS Miramar, Calif., demonstrates the military application of GCA, circa 1961.