The Lockheed YF -12 was an experimental aircraft from Lockheed for the United States Air Force, which was derived from the high altitude reconnaissance Lockheed A-12 OXCART. Only three copies of the interceptor were built before the program was terminated. In the Lockheed Advanced Development Projects Unit, better known as Skunk works, chief engineer Clarence Johnson developed the YF- 12th
After the construction of the interceptor North American XF -108 was stopped for reasons of cost, succeeded Lockheed, the Air Force to care for one derived from the A-12 Mach 3 interceptor. The aircraft was intended to replace the Convair F -106 Delta Dart. After the CIA stood by the A-12 program before costs overruns, the Air Force decided to let finish three machines in the configuration for an interceptor. On August 7, 1963, the first YF -12 flew. A purchase of 93 further modified YF -12B in 1965 but was stopped by Defense Secretary Robert McNamara. In addition to cost considerations has also been argued that the Soviet Union already had no bombers that would justify such a fast interceptor.
Of the three built YF -12 still exists a. This is at the National Museum of the United States Air Force at Wright - Patterson Air Force Base. Another plane was in 1966 when a failed landing heavily damaged by a fire at Edwards Air Force Base and later converted to a single SR- 71C Blackbird. The third aircraft was lost on 24 June 1971 by a fire during the flight, the pilots were able to leave the plane by ejection seat.
The YF -12 was essentially an A- 12, that also had a hull which consisted mainly of titanium and as engine two Pratt & Whitney J58, which were the YF -12 to accelerate to speeds in excess of Mach 3. Particularly regarding the equipment, the YF -12 was compared with the OXCART but changed. Thus, the nose was modified to accommodate a radar type Hughes AN/ASG-18 can, also the camera bays were converted to missile bays. Each YF -12 could carry three air - to-air missiles of the type AIM -47 Falcon with it.