Northrop XS-2 Skylancer / X-4 Bantam
The Northrop X-4 was the first example of an X-vehicle intended to research something besides supersonic flight. The jet-powered X-4 was designed to evaluate the characteristics of a tailless aircraft at high subsonic speeds, a configuration believed to hold a great deal of promise for future aircraft.
The final Northrop flying wing design, although it could more accurately be described as a tailless aircraft, was the XS-4 Skylancer, a transonic research vehicle with two 726kg thrust Westinghouse turbojets. Later redesignated X-4, the first of two aircraft flew at Muroc on 16 December 1948, followed by the second on 7 June 1949.
Although not designed for supersonic speeds, the X-4 nevertheless proved that tailless swept-wing aircraft were not well suited for high transonic or supersonic performance. Pitch, roll, and yaw instabilities were very pronounced at speeds in excess of Mach 0.88, and there was no solution to the problem using the technology available at the time. The last flight was made on 29 September 1953. After a total of 102 flights, the highest achieved was 42,300 feet (approx) and fastest Mach 0.90 (630 mph) (approx).
Both aircraft survived the flight test program, and there were no serious accidents during the 102 flights. The first X-4 was on display at Edwards AFB. The second aircraft, after long being displayed at Maxwell AFB, Alabama, moved to the Air Force Museum in Dayton, Ohio.
Engines: 2 x Westinghouse turbojets, 726kg each
Max take-off weight: 3175 kg / 7000 lb
Wingspan: 8.18 m / 26 ft 10 in
Length: 7.1 m / 23 ft 4 in
Wing area: 19 sq.m / 204.51 sq ft
Max. speed: 1000 km/h / 621 mph
Northrop X-4 Bantam