Three X-1s were built, the type first being air-launched unpowered, from a Boeing B-29 Superfortress on Jan. 19, 1946. Powered flights began in Dec. of the same year and on Oct. 14 1947 the first X-1, piloted by Capt. Charles E. Yeager, became the first aeroplane to exceed the speed of sound, reaching 670 mph or Mach 1.015 at an altitude of 42,000 ft. The second X-1 was used by the NACA for high speed flight research;the third aircraft was destroyed at Edwards AFB during fueling operations after completing only one unpowered glide flight.
The X-1A was similar to the X-1, except for having turbo-driven fuel pumps (instead of a system using nitrogen under pressure), a new cockpit canopy, longer fuselage and increased fuel capacity. In this aircraft a speed of Mach 2.435 was achieved on Dec. 12, 1953, and the following June an altitude of 90,000 ft. was reached. In Sept. 1954 the aircraft was given to the NACA and on July 20, 1955 it made its first and only flight for the NACA prior to being destroyed on Aug.8 1955.
The X-1B was similar to the X-1A except for having a slightly different wing. This aircraft was used for high speed research by the Air Force prior to being turned over to the NACA in Jan. 1955. This aircraft was flown by the NACA until Jan 1958.
Following the X-1B was the projected X-1C, which was cancelled while still in the mock-up stage and also the X-1D. The latter aircraft was destroyed in Aug. 1951 after being jettisoned from its B-50 carrier plane, following an explosion.
The last of the series was the X-1E. This was the second of the original X-1s fitted with new wings, turbo-driven fuel pumps and a knife-edge windscreen. This aircraft was modified and flown exclusively by the NACA. This aircraft made its first flight on Dec. 12, 1955 and was flown until Nov. 1958.
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