DAYTON, Ohio - The cockpit of the Northrop X-4 in the Research & Development Gallery at the National Museum of the U.S. Air Force. (U.S. Air Force photo)
Note: This aircraft is located in the Research & Development Gallery on a secure part of Wright-Patterson Air Force Base. Click here for visiting instructions.
The X-4 was developed for the study of flight characteristics of swept wing semi-tailless aircraft at transonic speeds (about Mach .85). Northrop built two X-4s. The No. 1 aircraft was first flown by Northrop on Dec. 16, 1948, and the second X-4 made its initial flight on June 7, 1949. The No. 1 aircraft was grounded after its 10th flight to provide spare parts for the No. 2 aircraft. Northrop's part of the test program ended on Feb. 17, 1950, with the 20th flight of the remaining X-4.
Although both aircraft were turned over to the Air Force and then to the National Advisory Committee for Aeronautics in May 1950, only the No. 2 X-4 was used in the joint USAF/NACA program to explore stability problems near the speed of sound. The program ended in September 1953 with the 102nd and last flight of the No. 2 aircraft, after proving that swept wing aircraft without horizontal tails were not suitable for transonic flight.
Both aircraft survived the test program without serious incident. The No. 1 X-4 is displayed at the Air Force Academy. The No. 2 aircraft was transferred to the museum shortly after the program ended. It was restored by the Western Museum of Flight, Hawthorne, Calif.
SPECIFICATIONS: Span: 26 ft. 10 in. Length: 23 ft. 3 in. Height: 14 ft. 10 in. Weight: 7,550 lbs. maximum Armament: None Engines: Two Westinghouse XJ-30 turbojet engines of 1,600 lbs. thrust each Crew: One Serial number: 46-677
PERFORMANCE: Maximum speed: 640 mph Cruising speed: 480 mph Maximum endurance: 44 minutes Service ceiling: 44,000 ft.