Lockheed YF-12A Blackbird Mach 3 Interceptor Prototype

The Lockheed YF-12A was a three-aircraft Mach 3 interceptor prototype developed from the A-12, with a two-person crew and AIM-47 missiles. Although the interceptor programme ended without production, the type became a major NASA–U.S. Air Force research platform. Two YF-12As entered the joint programme in 1969; aircraft 06935 made the first research flight on December 11. After 06936 was lost in a non-fatal 1971 accident, an SR-71A joined under the administrative designation YF-12C. That aircraft was a different Blackbird variant. Research examined propulsion and inlet control, aerodynamic and thermal loads, boundary layers, handling, and high-speed cruise. The Cold Wall experiment exposed a liquid-nitrogen-cooled cylinder to Mach 3 airflow to study heat transfer. Aircraft 06935 completed its last NASA research flight on October 31, 1979.