On this day in aviation history, 61 years ago (October 14, 1965), the North American XB-70 Valkyrie exceeded Mach 3 for the first time. XB-70 AV-1, serial number 62-0001, reached Mach 3.02 at an altitude of 70,000 feet during the flight. The achievement demonstrated the extraordinary performance of an aircraft originally designed to carry nuclear weapons deep into Soviet territory at three times the speed of sound. Development of the B-70 began during the 1950s as the United States Air Force sought a new high-altitude strategic bomber to replace the B-52. North American Aviation developed a massive six-engine delta-wing aircraft capable of sustained Mach 3 flight. The XB-70 utilized compression lift generated by its own shock wave, while its outer wingtips could pivot downward as much as 65 degrees during high-speed flight. Two XB-70A prototypes were ultimately completed.
The October 14 flight demonstrated both the capabilities and challenges of sustained Mach 3 flight. Heat and aerodynamic stresses damaged AV-1’s stainless-steel honeycomb structure, leaving approximately two feet of the left wing’s leading edge missing. Structural problems subsequently resulted in AV-1 being restricted to Mach 2.5. The second Valkyrie, AV-2, later reached Mach 3.08 and sustained Mach 3 for as long as 32 minutes before being lost in a mid-air collision in June 1966. AV-1 survives today at the National Museum of the United States Air Force. The XB-70 measured 185 feet in length with a wingspan of 105 feet and was powered by six General Electric YJ93 afterburning turbojets producing 28,000 pounds of thrust each. The Valkyrie could reach approximately Mach 3.1, or 2,056 mph, had a combat range of 4,287 miles, and a service ceiling of 77,350 feet. Its maximum takeoff weight exceeded 542,000 pounds, making the XB-70 one of the largest and fastest experimental aircraft ever constructed.
