The X-4 Bantam, a single-place, swept-wing, semi-tailless aircraft, was designed and built by the Northrop Aircraft Company for the National Advisory Committee on Aeronautics, or NACA. With no horizontal tail surfaces, its mission was to obtain in-flight data on the stabil-ity and control of semi-tailless aircraft at high subsonic or transonic speeds. The two X-4 aircraft were 23 feet long, 14 feet high, and had wingspans of 26 feet. They weighed al-most 8,000 pounds at takeoff.

The X-4 was initially powered by two Westinghouse XJ30 turbojet engines and then by J30 turbojet engines with 1,600 pounds of thrust each. These engines boosted the X-4 up to speeds of 630 mph and up to altitudes of 43,300 feet.

The aircraft's maiden flight was on Dec. 16, 1948, with Charles Tucker, a Northrop test pi-lot, at the controls. Once contractor testing was complete, the two X-4 aircraft were turned over to the NACA and the Air Force at Edwards Air Force Base in 1950 for the research program.

The first X-4, tail number 6676, exhibited poor flying characteristics and was taken off flight status after only 10 flights. It was subsequently used for parts to keep the second X-4, tail number 6677, flying. The second X-4's flight characteristics and controllability were much improved, and it flew the remainder of the research program until its completion in 1953.

The X-4 helped demonstrate that tail surfaces are important for proper control effective-ness in the transonic speed range, and was also used to investigate the characteristic problems of tailless airplanes at low speeds, such as marginal longitudinal stability and control.

X-4 Bantam No. 6677 is currently on public display at the National Museum of the Air Force at Wright Patterson Air Force Base near Dayton, Ohio. X-4 No. 6676 is currently in long-term storage awaiting restoration at the Air Force Flight Test Center Museum at Ed-wards Air Force Base, Calif.

Research Airplane Program fact sheet

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