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X-1A in flight with flight data superimposed X-1A in flight with flight data superimposed

Photo Number: E-24911
Photo Date: 12 Dec 1953

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This photo of the X-1A includes graphs of the flight data from Maj. Charles E. Yeager's Mach 2.44 flight on December 12, 1953. (This was only a few days short of the 50th anniversary of the Wright brothers' first powered flight.) After reaching Mach 2.44, then the highest speed ever reached by a piloted aircraft, the X-1A tumbled completely out of control. The motions were so violent that Yeager cracked the plastic canopy with his helmet. He finally recovered from a inverted spin and landed on Rogers Dry Lakebed.

Among the data shown are Mach number and altitude (the two top graphs). The speed and altitude changes due to the tumble are visible as jagged lines. The third graph from the bottom shows the G-forces on the airplane. During the tumble, these twice reached 8 Gs or 8 times the normal pull of gravity at sea level. (At these G forces, a 200-pound human would, in effect, weigh 1,600 pounds if a scale were placed under him in the direction of the force vector.) Producing these graphs was a slow, difficult process. The raw data from on-board instrumentation recorded on oscillograph film. Human computers then reduced the data and recorded it on data sheets, correcting for such factors as temperature and instrument errors. They used adding machines or slide rules for their calculations, pocket calculators being 20 years in the future.

Three second generation Bell Aircraft Corporations X-1s were built, though four were requested. They were the X-1A (48-1384); X-1B (48-1385); X-1C (canceled and never built); X-1D (48-1386). These aircraft were similar to the X-1s, except they were five feet longer, had conventional canopies, and were powered by Reaction Motors, Inc. XLR11-RM-5 rocket engines. The RM-5, like the previous engines, had no throttle and was controlled by igniting one or more of the four thrust chambers at will.

The original program outline called for the X-1A and X-1B to be used for dynamic stability and air loads investigations. The X-1D was to be used for heat transfer research while the X-1C was intended as a high-speed armament systems test bed. All of these aircraft like the original X-1s, were launched from a Boeing B-29 or Boeing B-50 "mothership" to take maximum advantage of their limited flying time with a rocket engine.


The Bell X-1A was similar to the Bell 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. The X-1A arrived at Edwards Air Force Base, California on January 7, 1953, with the first glide flight being successfully completed by Bell pilot, Jean "Skip" Ziegler. The airplane also made five powered flights with Ziegler at the controls. The USAF was attempting a Mach 2 flight and USAF test pilot Charles "Chuck" Yeager was eager. He reached speed of Mach 2.435, at a altitude of 75,000 feet on December 12, 1953, a speed record at the time. But all was not well, the aircraft encountered an inertial coupling phenomenon and went out of control. Once the X-1A had entered the denser atmosphere (35,000 feet) it slowly stabilized and Yeager was able to return to Edwards. The aircraft had experienced high-speed roll-coupling, something aerodynamicists had predicted, but this was the first actual encounter.

On August 26, 1954, Major Arthur Murray, USAF test pilot flew the X-1A to an altitude record of 90,440 feet. NACA High-Speed Flight Station received the aircraft in September 1954 and returned it to Bell for the installation of an ejection seat.

NACA test pilot Joseph Walker made a familiarization flight on July 20, 1955 followed by another scheduled flight on August 8, 1955. Shortly before launch the X-1A suffered an explosion. The extent of the damage prohibited landing the crippled aircraft. The X-1A was jettisoned into the desert, exploding and burning on impact. Walker and the B-29 crew returned to base in satisfactory condition. Four pilots had completed 29 flights (including aborts).


The Bell Aircraft Corporation X-1B was similar to the Bell X-1A except for the installation of wingtips extensions for its last three flight. The NACA portion of the X-1B flight test program was for the purpose of aerodynamic heating research, accumulating data during 1956-1958. The X-1B was fitted with special instrumentation for exploratory aerodynamic heating tests. It had over 300 thermocouples installed on it. It was the first aircraft to fly with a reaction control system, a prototype of the control system used on the X-15 and other piloted aircraft. Midway through its flight test program, the X-1B was equipped with an Reaction Motors, Inc. XLR-11-RM-9 engine which differed, from the other XLR-11s, only in having an electric spark, low-tension interrupter type ignition in place of the older high-tension type.

On January 27, 1959 the X-1B was given to the Air Force Museum at Wright-Patterson Air Force Base, Ohio, for preservation and public display. This aircraft completed a total of 27 glide and powered flights made by eight USAF test pilots and two NACA test pilots.


Following the X-1B was the projected X-1C, which was canceled while still in the mock-up stage. The birth of transonic and supersonic-capable aircraft like the North American F-86 Sabre and the North American F-100 Super Sabre eventually eliminated the need for the X-1C.


The X-1D was the first advanced model of the X-1 family to roll from Bell Aircraft Corporation’s plant. It arrived at Edwards, California, in July 1951 suspended from the bomb bay shackles of a Boeing EB-50A, (46-006) aircraft. On July 24, 1951, with Bell test pilot Jean "Skip" Ziegler at the controls, the X-1D had the only successful flight of its career. It was an unpowered glide flight, and on landing the nose gear failed with the plane sliding to a stop. The aircraft was repaired and ready once more for flight when USAF test pilot Frank "Pete" Everest boarded the aircraft for launch on August 22, 1951. The drop from the Boeing B-50 was canceled because of mechanical problems. On the way back to the landing field and after the crew had jettisoned the propellants, an explosion occurred with flames being reported by the chase plane pilot. The X-1D was dropped to crash on the desert near the south end of Rogers Dry Lakebed.

The second generation Bell Aircraft Corporations X-1s increased man’s understanding of the stability and control characteristics, and aerodynamic heating at high-speeds and the environment of high-altitude flight.


Since there had been a loss of several aircraft during the period of the rocket flights, the NACA instituted an investigation. It sent samples of a suspicious looking oily residue from a liquid oxygen tank to a Los Angeles, California, laboratory and to the chemical laboratory at Edwards Air Force Base, California. The Edwards laboratory identified the substance as TCP--tricresyl phosphate--a substance used to impregnate leather. All the destroyed rocket planes--as well as those still flying--had gaskets made of Ulmer leather. The TCP had been the culprit, because it could easily detonate in the presence of liquid oxygen. Armed with this knowledge, the Air Force and the NACA avoided all future catastrophic blasts.

NASA Photo by: NASA photo

Keywords: X-1; Muroc Army Air Field; Muroc Air Force Base; Edwards Air Force Base; NACA Langley Memorial Aeronautical Laboratory; NACA High-Speed Flight Research Station; Pinecastle Army Air Field; Bell Aircraft Corporation; Reaction Motors; Inc.; Army Air Forces; Boeing B-29; Boeing B-50; Chalmers "Slick"Goodlin; USAF Major Charles "Chuck" Yeager; sound barrier; all-moving horizontal stabilizer; XLR-8-RM-5; X-1A; X-1B; X-1D; X-1E; ulmer leather gasket; G-forces; oscillograph; human computers

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