During World War II, engineers in the U.S. and UK studied semi-tailless aircraft, and the German Luftwaffe fielded the semi-tailless Me 163 (one of which is on display in the museum’s World War II Gallery). After the war ended, Northrop built two X-4s to test if this configuration could perform at transonic (near-supersonic) speeds better than conventional aircraft.
Flight testing of the X-4 began in 1948, and in 1950 both X-4s were turned over to the NACA (National Advisory Committee for Aeronautics), predecessor to NASA (National Aeronautics and Space Administration). The first X-4 was grounded after only 10 flights, and only the second X-4 (on display at the museum) was used in the joint USAF/NACA program. Instability of the X-4 at high speed led to the conclusion that semi-tailless aircraft were not suitable for transonic flight (with the technology then available).
The X-4 on display was transferred to the museum shortly after the program ended in 1953. It was restored by the Western Museum of Flight, Hawthorne, Calif.
TECHNICAL NOTES:
Engines: Two Westinghouse XJ30 turbojet engines of 1,600 lbs. thrust each
Maximum speed: 640 mph
Maximum endurance: 44 minutes
Service ceiling: 44,000 feet
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