page_title: Lockheed YF-12
section_title: Design and development
hierarchical_section_title: Lockheed YF-12 / Design and development
caption_attribution_description: English: Lockheed YF-12A 60-6934 in Air Defense Command markings 1963. The only YF-12A in ADC markings, its first test flight occurred on 7 August 1963 at Groom Lake, Nevada. It was extensively tested at Edwards Air Force base. The cost of the Vietnam War, and the perceived lessened need for a Mach-3 interceptor led to the F-12 program being canceled by the end of 1967. This aircraft damaged beyond repair by fire at Edwards during a landing mishap on 14 August 1966; its rear half was salvaged and combined with the front half of a Lockheed static test airframe to create the one and only SR-71C 64-17981.
context_page_description: The Lockheed YF-12 is an American prototype interceptor aircraft developed and manufactured by American aerospace company Lockheed Corporation.
  It was developed during the late 1950s and early 1960s as a potential replacement for the F-106 Delta Dart interceptor for the United States Air Force. The YF-12 was a twin-seat version of the then-secret single-seat Lockheed A-12 reconnaissance aircraft operated by the Central Intelligence Agency; unlike the A-12, it was furnished with the Hughes AN/ASG-18 fire-control radar and could be armed with AIM-47 Falcon air-to-air missiles. Performing its maiden flight on 7 August 1963, the YF-12's existence was revealed by President Lyndon B. Johnson on 24 February 1964; this move was to provide plausible deniability for the CIA-operated A-12 fleet, which closely resembled the prototype YF-12.
  During the 1960s, the YF-12 underwent flight evaluations by the USAF, but funding to put it into operational use was not forthcoming partly due to the pressing demands of the Vietnam War and other military priorities.
context_section_description: In the late 1950s, the United States Air Force (USAF) sought a replacement for its F-106 Delta Dart interceptor. As part of the Long Range Interceptor Experimental (LRI-X) program, the North American XF-108 Rapier, an interceptor with Mach 3 speed, was selected. However, the F-108 program was canceled by the Department of Defense in September 1959. During this time, Lockheed's Skunk Works was developing the A-12 reconnaissance aircraft for the U.S. Central Intelligence Agency (CIA) under the Oxcart program. Kelly Johnson, the head of Skunk Works, proposed to build a version of the A-12 named AF-12 by the company; the USAF ordered three AF-12s in mid-1960.
  The AF-12s took the seventh through ninth slots on the A-12 assembly line; these were designated as YF-12A interceptors. The main changes involved modifying the A-12's nose by cutting back the chines to accommodate the huge Hughes AN/ASG-18 fire-control radar originally developed for the XF-108 with two infrared search and track sensors embedded in the chine leading edge, and the addition of the second cockpit for a crew member to operate the fire control radar for the air-to-air missile system. The modifications changed the aircraft's aerodynamics enough to require ventral fins to be mounted under the fuselage and engine nacelles to maintain stability. The four bays previously used to house the A-12's reconnaissance equipment were converted to carry Hughes AIM-47 Falcon (GAR-9) missiles. One bay was used for fire control equipment.
  The first YF-12A flew on 7 August 1963. President Lyndon B. Johnson announced the existence of the aircraft on 24 February 1964. The YF-12A was announced in part to continue hiding the A-12, its still-secret ancestor; any sightings of CIA/Air Force A-12s based at Area 51 in Nevada could be attributed to the well-publicized Air Force YF-12As based at Edwards Air Force Base in California. The first public showing of the aircraft was on 30 September 1964 at Edwards.
  On 14 May 1965, the Air Force placed a production order for 93 F-12Bs for its Air Defense Command (ADC). However, Secretary of Defense Robert McNamara would not release the funding for three consecutive years due to Vietnam War costs. Updated intelligence placed a lower priority on defense of the continental US, so the F-12B was deemed no longer needed. Then in January 1968, the F-12B program was officially ended.
caption: Lockheed YF-12A, Serial# 60-6934, the only YF-12A in ADC markings
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