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74 Years Ago This Week in AFLCMC History: Chuck Yeager exceeds sound barrier

1940's -- Chuck Yeager standing in front of the Bell X-1, nicknamed "Glamorous Glennis," 1947. (U.S. Air Force photo)

1940's -- Chuck Yeager standing in front of the Bell X-1, nicknamed "Glamorous Glennis," 1947. (U.S. Air Force photo)

Bell X-1

Bell X-1

Air Force test pilot Maj Charles E. “Chuck” Yeager became the first person to officially exceed the speed of sound (Mach 1) in an aircraft. 

The improvement of aircraft technology spurred by World War II dramatically increased the actual and potential top speeds of airplanes in the 1940s. All metal aircraft, better knowledge of aerodynamics, and particularly improvements in propulsion systems all contributed to raise combat speeds and well above 400mph. In long, powered dives, aircraft approached the speed of sound (~767mph at sea level; the actual speed varies by temperature & air density/altitude). As airplanes entered this transonic region, they experienced the dangerous and little understood phenomenon called compressibility, where shock waves of compressed air form over the wings and flight control surfaces, leading to loss of control, structural damage, and a huge observed increase in drag—the so-called “sound barrier.” 

The advent of turbine (jet) and rocket engines for aircraft, replacing piston engines and propellers, made it both possible and likely that aircraft could push well past the speed of sound. However, the wind tunnels of the day were not able to effectively recreate these speeds, making research into understanding and solving this issue difficult. At Wright Field, engineer Ezra Kotcher conceptualized an aircraft designed specifically to “break the sound barrier.” His counterparts at the civilian National Advisory Committee for Aeronautics (NACA) joined with Wright Field to pursue such a program. 

Kotcher’s idea was novel in many ways, but especially in devising a plane for purely experimental purposes, not as a prototype for an operational aircraft. The resulting X-1 was the first of the X-plane series that continues to this day. Setting the pattern for future x-planes, the acquisition professionals at Wright Field managed the contracting side of the program.

At Kotcher’s insistence, the X-1 used a rocket engine (developed for the Navy) and an airframe based on the shape of a .50 caliber bullet, after consulting with the Wright Field Armament Lab about stable shapes. Bell Aircraft built the X-1 and it was taken to what is now Edwards AFB for secret flight tests. The Air Force’s test pilot cadre (and school) was located at Wright-Patt at the time, where Yeager was chosen for this mission. 

On 14 October, a B-29 took the X-1 aloft. The orange bullet-shaped plane dropped into the clear skies, ignited its rocket engine chambers, and blasted past the speed of sound for the first officially recorded time.