Lockheed YF-12

YF-12
YF-12A undergoing flight testing.
Type	Interceptor
Manufacturer	Lockheed Corporation
Designed by	Clarence "Kelly" Johnson
Maiden flight	7 August 1963
Status	Cancelled
Primary user	United States Air Force
Number built	3
Unit cost	US$15-18 million (projected)[1]
Developed from	Lockheed A-12

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

Design and development

The United States Air Force (USAF) YF-12 program was a development of the Lockheed A-12 OXCART spy plane designed for the CIA and first flown 26 April 1962, the first YF-12A flew on 7 August 1963.^[2] The existence of the aircraft was not officially revealed until 29 February 1964.^[3] Lockheed was able to interest the Air Force in the project after the United States Air Force had been forced to cancel the XF-108 Rapier, a Mach 3-capable interceptor intended to replace the F-106 Delta Dart in service. It was pointed out that an aircraft based on the A-12 would provide a less costly alternative to the XF-108, since much of the design and development work on the YF-12 had already been done and paid for. In 1960, the USAF agreed to take the 11th through 13th 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 crewmember 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.^[2]

Testing and evaluation

Tests were very impressive: the YF-12As set a speed record of 2,070.101 mph (3331.505 km/h) and altitude record of 80,257.86 ft (24,462.6 m), both on 1 May 1965^[3], 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 74,400 feet (22,677 meters) to a target drone B-47 500 feet (152 m) off the ground. In 1965 the Air Force placed an order for 93 F-12Bs, but this was cancelled due to budget cuts by Secretary of Defense Robert McNamara. The rationale for the cancellation was, in part, the belief that the Soviet Union did not possess a bomber fast enough to warrant the investment in an interceptor of this speed. The program was abandoned at that point, but the YF-12s continued flying for many years with the United States Air Force and with NASA as research aircraft.

Of the three YF-12As, #60-6934 was damaged beyond repair by fire at Edwards AFB 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 (nicknamed "The Bastard" by its pilots, as it did not fly quite straight, and required the pilot to hold some rudder pressure at cruise) today is on display at a museum at Hill AFB, UT. It is unique among all SR-71s as it still carries the ventral fins under its nacelles – an artifact of its YF-12 lineage which does not exist on any other SR-71. 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, it was then flown to the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio on 17 November 1979.^[3] 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 $4 million US dollars. The NASA 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 $14 million US Dollars.^[4]

A fourth YF-12 aircraft, the "YF-12C", was actually the second SR-71A (61-7951). The airplane was loaned to NASA for propulsion testing after the loss of YF-12A (60-6936) in 1971. The SR-71A was re-designated as a YF-12C and given a fictitious serial number 60-6937 (used an A-12). The YF-12C was operated by NASA until September 1978, when it was returned to the Air Force. Today, this aircraft is on display at the Pima Air Museum in Tucson, AZ.^[5]

Specifications (YF-12A)

Data from Lockheed's SR-71 'Blackbird' Family^[6]

General characteristics

• Crew: 2
• Length: 101 ft 8 in (30.97 m)
• Wingspan: 55 ft 7 in (16.95 m)
• Height: 18 ft 6 in (5.64 m)
• Wing area: 1,795 ft² (167 m²)
• Empty weight: 60,730 lb (27,604 kg)
• Loaded weight: 140,000 lb (63,504 kg^[2])
  • Max takeoff weight: 124,000 lb (56,200 kg)
  • Powerplant: 2× Pratt & Whitney JTD11D-20A high-bypass-ratio turbojet with afterburner
    • Dry thrust: 20,500 lbf (91.2 kN) each
    • Thrust with afterburner: 31,500 lbf (140 kN) each

  Performance

  • Maximum speed: Mach 3.35 (2,275 mph, 3,661 km/h^[2]) 80,000 ft
    • Range: 3,000 mi (4,800 km)
    • Service ceiling 90,000 ft (24,000 m)

    Armament

    • Missiles: 3× Hughes AIM-47A air-to-air missiles located internally in fuselage bays

Avionics

• Hughes AN/ASG-18 look-down/shoot-down fire control radar

YF-12 aircraft on display

The sole remaining YF-12A is located:

• National Museum of the United States Air Force, at Wright-Patterson Air Force Base, near Dayton, Ohio.^[3]

  References

  Notes

  1. ^ Knaack, 1978.
  2. ^ ^{a b c d} Green and Swanborough, 1988, page 350.
  3. ^ ^{a b c d} Air Force Museum Foundation, 1983, p. 133.
  4. ^ Drendel 1982, p. 6.
  5. ^ Landis, Tony R. and Jenkins, Dennis R. Lockheed Blackbirds. Specialty Press, 2004. ISBN 1-58007-086-8.
  6. ^ Goodall and Miller, 2002.

  
  

  Bibliography

  • Air Force Museum Foundation Inc. US Air Force Museum. Dayton, Ohio: Wright-Patterson AFB, Ohio, 1983.
  • Drendel, Lou. SR-71 Blackbird in Action. Carrollton, Texas: Squadron/Signal Publications, 1982, ISBN 0-89747-136-9.
  • Goodall, James and Miller, Jay. Lockheed's SR-71 'Blackbird' Family. Midland Publishing, Hinchley, England, 2002. ISBN 1-85780-138-5.
  • Green, William and Swanborough, Gordon. 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.

  See also

  Related development

  • Lockheed A-12
  • M-21/D-21 drone
  • SR-71 Blackbird
    

  Related lists

  • List of military aircraft of the United States
  • List of Lockheed aircraft
  • List of fighter aircraft
    

  External links

  • Mach 3+: NASA/USAF YF-12 Flight Research, 1969-1979 by Peter W. Merlin (PDF book)
  • YF-12A Flight Manual
  • USAF Museum: YF-12
  • SR-71 Online - YF-12A #60-6935 Photos
  • Blackbird Spotting maps the location of every existing Blackbird, with aerial photos from Google Maps
  • USAF Aircraft Serial Numbers for 1960, including all A-12s, YF-12As, and M-21s
  • USAF Aircraft Serial Numbers for 1961, including all SR-71s

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