On this day in 1967, combat and test pilot William J. Knight broke the world speed record for flight in a winged aircraft—a record that still stands today. He achieved this feat in an X-15A-2, which he flew at the incredible speed of 7,275 kilometres per hour (4,520 mph), Mach 6.72. This was only one of his 16 flights in the X-15A-2. In another notable sortie, he reached an astounding altitude of 280,500 feet (85.5 kilometres), and so he had the unusual triumph of earning his NASA Astronaut Wings by flying an airplane in space.
The X-15A-2, in which Knight set the record, was a North American rocket-powered aircraft, and part of the X-series of experimental planes, which started with the Bell X-1. It was based on a conceptual design for a hypersonic research aircraft by Walter Dornberger, and built by two manufacturers—North American Aviation made the airframe in 1955 and Reaction Motors made the engines in 1956. The X-15A-2 was carried into the sky under the wing of another plane, a NASA B-52 (named the Balls 8), and then released at an altitude of around 8.5 miles and at a velocity of around 500 miles per hour. It was a long and cylindrical aircraft with a flattened appearance, and widened dorsal and ventral fins for stability.
Knight first joined the United States Air Force in 1951. He won an Allison Jet Trophy for flying an F-89 at the National Air Show in 1954, and he started working as a USAF test pilot at Edwards Air Force Base in 1958. There he flew all manner of new and experimental craft: the F-100, the F-101 Voodoo, the F-104 Starfighter, the T-38, F-5 and X-20 Dyna-Soar test programs, and the North American X-15 series.
Flying the X-15A-2 on June 29, 1967, Knight suffered a total electrical failure at a reported 107,000 feet and Mach 4.17—so he arched the plane over at 173,000 feet and then glided all the way down to an emergency landing at Mud Lake, Nevada, for which he was rewarded with a Distinguished Flying Cross.
After 32 years as a pilot, Knight retired in 1982. He holds a Distinguished Flying Cross, NASA astronaut wings, and the world speed record for a flight in a manned aircraft.
Credit: NASA Dryden Flight Research Center
Caption: US Air Force Pilot Pete Knight poses in front of an X-15A-2.