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The Lockheed YF-12 was an American prototype interceptor aircraft, which the United States Air Force evaluated as a development of the highly-secret Lockheed A-12 that also spawned the now-famous SR-71 Blackbird.

Design and development

In the late 1950s the United States Air Force (USAF) sought a replacement for the F-106 Delta Dart. As part of the Long Range Interceptor Experimental (LRI,X) program, North American Aviation's F-108 proposal, a Mach 3—capable interceptor was selected. However, the F-108 was canceled in September 1959. During this time Lockheed's Skunk Works was developing the A-12 spy plane for the Central Intelligence Agency (CIA) under the Oxcart program. Skunk Works' Kelly Johnson proposed a version of the A-12 called AF-12 by the company and the USAF ordered three AF-12s in mid-1960.

The AF-12s would take the seventh through ninth slots on the A-12 production line and have them completed in the YF-12A interceptor configuration. The main changes involved modifying the aircraft's nose to accommodate the Hughes AN/ASG-18 fire-control radar originally developed for the XF-108, and the addition of a second cockpit for a crew member to operate the fire control radar. The nose modifications changed the aircraft's aerodynamics enough to require ventral fins to be mounted under the fuselage and engine nacelles to maintain stability. Finally, bays previously used to house the A-12's reconnaissance equipment were converted to carry four Hughes AIM-47 Falcon (GAR-9) missiles.

The first YF-12A flew on 7 August 1963. President Lyndon B. Johnson announced the existence of the plane 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 51marker in Nevada could be attributed to the well-publicized Air Force YF-12As based at Edwards Air Force Basemarker in California.

On 14 May 1965 the Air Force placed a production order for 93 F-12Bs for its Aerospace Defense Command. 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 continental US, so the F-12B was no longer needed. Then in January 1968 the F-12B program was officially ended.

Operational history

USAF testing


During flight tests the YF-12As set a speed record of 2,070.101 mph (3,331.505 km/h) and altitude record of 80,257.86 ft (24,462.6 m), both on 1 May 1965, and demonstrated promising results with their unique weapon system. Six successful firings of the AIM-47 missiles were completed. The last one launched from the YF-12 at Mach 3.2 at an altitude of 74,000 ft (22,677 m) to a JQB-47E target drone 500 ft (152 m) off the ground.

The program was abandoned following the cancellation of the production F-12B, but the YF-12s continued flying for many years with the USAF and with NASAmarker as research aircraft.

NASA testing

YF-12A #60-06935 in the National Museum of the USAF

The initial phase of this program included test objectives aimed at answering some questions about implementation of the B-1. Air Force objectives included exploration of its use in a tactical environment, and how AWACS would control supersonic aircraft. The Air Force portion was budgeted at US$4 million. The NASAmarker tests would answer questions such as how engine inlet performance affected airframe and propulsion interaction, boundary layer noise, heat transfer under high Mach conditions, and altitude hold at supersonic speeds. The NASA budget for the 2.5-year program was US$14 million.

Of the three YF-12As, #60-6934 was 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. That aircraft was nicknamed "The Bastard" by its pilots, as it did not fly quite straight. It is unique among SR-71s as it retained the ventral fins under its nacelles from its YF-12 lineage.

YF-12A #60-6936 was lost on 24 June 1971 due to an inflight fire caused by a failed fuel line; both pilots ejected safely just north of Edwards AFB. YF-12A #60-06935 is the only surviving YF-12A; it was recalled from storage in 1969 for a joint USAF/NASA investigation of supersonic cruise technology, and then flown to the National Museum of the United States Air Forcemarker at Wright-Patterson Air Force Basemarker near Dayton, Ohiomarker on 17 November 1979.

A fourth YF-12 aircraft, the "YF-12C", was actually the second SR-71A (61-7951). This SR-71A was re-designated as a YF-12C and given a fictitious serial number 60-6937 (used an A-12). The airplane was loaned to NASA for propulsion testing after the loss of YF-12A (60-6936) in 1971. The YF-12C was operated by NASA until September 1978, when it was returned to the Air Force.


Pre-production version. Three were built.
Production version of the YF-12A; canceled before production could begin.
Fictitious designation for a SR-71 provided to NASA for flight testing. The YF-12 designation was used to hide the existence of SR-71.

Specifications (YF-12A)

YF-12 aircraft on display

List of YF-12 aircraft
Serial number Model Location or fate
60-6934 YF-12A Transformed into SR-71C 64-17981 after fire damage in 1966
60-6935 YF-12A National Museum of the U.S. Air Force, Wright-Patterson AFB, OH
60-6936 YF-12A Lost, 24 June 1971

The sole remaining YF-12A is located at the National Museum of the United States Air Forcemarker, at Wright-Patterson Air Force Basemarker, near Dayton, Ohiomarker. This aircraft has small patches in its skin, on the starboard side below the cockpit. The patches cover holes caused by the "spurs" of a crewman who had to evacuate the plane after an emergency landing. The "YF-12C" (actually SR-71A, serial 61-7951) is on display at the Pima Air Museum in Tucson, AZ as of 2005.

See also


  1. Pace 2004, pp. 45–46.
  2. Pace 2004, pp. 46–47.
  3. Landis and Jenkins 2005, pp. 40–41.
  4. Green and Swanborough, 1988, p. 350.
  5. Johnson's speech named the plane A-11, the name for the two-seat design.
  6. McIninch 1996, p. 15.
  7. Air Force Museum Foundation, 1983, p. 133.
  8. McIninch 1996, p. 14.
  9. Pace 2004, p. 53.
  10. Donald 2003, pp. 148, 150.
  11. Landis and Jenkins 2005, p. 44.
  12. Drendel 1982, p. 6.
  13. Landis and Jenkins 2005, pp. 49–55.
  14. Landis and Jenkins 2005, p. 40.
  15. Landis and Jenkins 2005, p. 46.
  16. Landis and Jenkins 2005, pp. 49-50.


  • Air Force Museum Foundation Inc. US Air Force Museum. Dayton, Ohio: Wright-Patterson AFB, Ohio, 1983.
  • Donald, David, ed. "Lockheed's Blackbirds: A-12, YF-12 and SR-71". Black Jets. AIRtime, 2003. ISBN 1-880588-67-6.
  • Drendel, Lou. SR-71 Blackbird in Action. Carrollton, Texas: Squadron/Signal Publications, 1982, ISBN 0-89747-136-9.
  • Goodall, James and Jay Miller. Lockheed's SR-71 'Blackbird' Family. Hinchley, England: Midland Publishing, 2002. ISBN 1-85780-138-5.
  • Green, William and Gordon Swanborough. The Complete Book of Fighters. New York: Barnes & Noble Inc., 1988. ISBN 0-07607-0904-1.
  • Jenkins, Dennis R. Lockheed Secret Projects: Inside the Skunk Works. St. Paul, Minnesota: MBI Publishing Company, 2001. ISBN 978-076030914-8.
  • Knaack, Marcelle Size. Encyclopedia of US Air Force Aircraft and Missile Systems: Volume 1 Post-World War II Fighters 1945-1973. Washington, DC: Office of Air Force History, 1978. ISBN 0-912799-59-5.
  • Landis, Tony R. and Dennis R. Jenkins. Lockheed Blackbirds. North Branch, Minnesota: Specialty Press, revised edition, 2005. ISBN 1-58007-086-8.
  • McIninch, Thomas. " THE OXCART STORY". Center for the Study of Intelligence, Central Intelligence Agency, 2 July 1996. Retrieved 10 April 2009.
  • Pace, Steve. Lockheed SR-71 Blackbird. Swindon: Crowood Press, 2004. ISBN 1-86126-697-9.

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