View source for Lockheed YF-12

{{Short description|American prototype interceptor aircraft}}
{{Use American English|date=July 2019}}
<!-- This article uses American spelling.-->
{{Use dmy dates|date=December 2019}}
<!-- This article is a part of [[Wikipedia:WikiProject Aircraft]]. Please see [[Wikipedia:WikiProject Aircraft/page content]] for recommended layout, and guidelines. -->
{{Infobox aircraft
 |name= YF-12
 |image= YF-12A.jpg
 |caption= YF-12A
 |type= [[Interceptor aircraft]]
 |manufacturer= [[Lockheed Corporation]]
 |designer= <!-- Only appropriate for one-person designers, not project leaders or chief designers -->
 |first_flight= 7 August 1963
 |introduction=
 |retired=
 |status= Canceled
 |primary_user= [[United States Air Force]]
 |more_users= [[NASA]]
 |produced=
 |number_built= 3
 |unit cost= US$15–18&nbsp;million (projected)<ref name=knaack/>
 |developed_from= [[Lockheed A-12]]
 |developed_into=
 |variants=
}}

The '''Lockheed YF-12''' is an American [[Mach number|Mach]]&nbsp;3+ capable, high-altitude [[interceptor aircraft|interceptor]] [[prototype]], developed and manufactured by American [[aerospace]] company [[Lockheed Corporation]].

The interceptor 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]] (USAF). 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]] (CIA); unlike the A-12, it was furnished with the [[Hughes AN/ASG-18]] [[fire-control radar]] and could be armed with [[AIM-47 Falcon]] (GAR-9) [[air-to-air missile]]s. Its [[maiden flight]] was on 7 August 1963. Its existence was publicly 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.<!--Relatedly, see also [[Lockheed SR-71 Blackbird#Designation as SR-71]], also discussing 1964 public disclosures of Blackbird family members.-->

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. It set and held speed and altitude world records of over {{convert|2000|mph|km/h}} and over {{convert|80000|ft|m}} (later surpassed by the closely related [[Lockheed SR-71 Blackbird|SR-71 Blackbird]]), and is the world's largest, heaviest and fastest crewed interceptor.<ref>{{cite book |url=https://books.google.com/books?id=YoNbTA--HRMC&pg=PA11 |title=X-Planes at Edwards |isbn=978-1-61060786-5 |page=11 |last=Pace |first=Steve |year=1995|publisher=Zenith Imprint }}</ref> Following its retirement by the USAF, it served as a research aircraft for [[NASA]] for a time, which used it to develop several significant improvements in control for future supersonic aircraft.

==Design and development==
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 [[United States Department of Defense|Department of Defense]] in September 1959.<ref name=Pace_p45-6>Pace 2004, pp. 45–46.</ref> 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 (engineer)|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.<ref name=Pace_p46-7>Pace 2004, pp. 46–47.</ref>

[[File:YF-12 Forward Chine.jpg|thumb|Picture of the modified chine to accommodate the AN/ASG-18 radar]]
The AF-12s took the seventh through ninth slots on the A-12 assembly line; these were designated as ''YF-12A'' interceptors.<ref name=Land_Jenk_p40-1>Landis and Jenkins 2005, pp. 40–41.</ref> 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 located 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.<ref name=airforcemag>{{cite magazine |last=Jn. |first=J. S. B. |date=November 1964 |title= Nine Times Better |url=http://www.airforcemag.com/MagazineArchive/Magazine%20Documents/1964/November%201964/1164YF-12.pdf |magazine=Air Force Magazine |publisher=USAF }}</ref> The modifications changed the aircraft's aerodynamics enough to require ventral fins to be mounted under the fuselage and engine nacelles to maintain stability. Three of the four bays previously used to house the A-12's reconnaissance equipment were converted to carry Hughes [[AIM-47 Falcon]] (GAR-9) missiles.<ref name=fighter/> One bay was used for fire control equipment.<ref>{{Cite web |url= http://www.designation-systems.net/dusrm/m-47.html |title= Hughes AIM-47 Falcon |publisher= Designation systems}}</ref>

[[File:Lockheed YF-12A 60-6934 in Air Defense Command markings 1963.jpg|thumb|Lockheed YF-12A, Serial# 60-6934, the only YF-12A in ADC markings]]
The first YF-12A flew on 7 August 1963.<ref name=fighter>Green and Swanborough, 1988, p. 350.</ref> President [[Lyndon B. Johnson]] announced the existence of the aircraft{{efn-ua|Johnson's speech named the plane A-11, the name for the two-seat design.}}<ref name=oxcartstory_p15>McIninch 1996, p. 15.</ref> on 24 February 1964.<ref name=museum>Air Force Museum Foundation, 1983, p. 133.</ref><ref name=oxcartstory_p14>McIninch 1996, p. 14.</ref> 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.<ref name=oxcartstory_p15/> The first public showing of the aircraft was on 30&nbsp;September 1964 at&nbsp;Edwards.<ref name=srapunv>{{cite news |url=https://news.google.com/newspapers?id=PjlWAAAAIBAJ&sjid=regDAAAAIBAJ&pg=7229%2C11473 |work=Spokesman-Review |location=(Spokane, Washington) |agency=Associated Press |title=Super jet fighter unveiled by U.S. |date=1 October 1964 |page=1}}</ref>

On 14 May 1965, the Air Force placed a production order for 93 F-12Bs for its [[Aerospace Defense Command|Air Defense Command]] (ADC).<ref name=Pace_p53>Pace 2004, p. 53.</ref> However, [[United States Secretary of Defense|Secretary of Defense]] [[Robert McNamara]] would not release the funding for three consecutive years due to [[Vietnam War]] costs.<ref name=Pace_p53/> 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.<ref>Donald 2003, pp. 148, 150.</ref>

==Operational history==

===Air Force testing===
[[File:Lockheed YF-12.jpg|thumb|YF-12A over mountainous terrain.|alt=Sideview of black jet aircraft overflying mountain towards right of photo.]]

During flight tests the YF-12As set a speed record of {{convert|2070.101|mph|km/h}}<ref>{{Citation |title=Could This Change Air Travel Forever? | date=5 January 2024 |url=https://www.youtube.com/watch?v=C_dNt4UEVZQ |access-date=2024-01-05 |language=en}}</ref> and altitude record of {{convert|80257.86|ft|m}}, both on 1 May 1965,<ref name=museum/> and demonstrated promising results with its unique weapon system. Six successful firings of the [[AIM-47]] missiles were completed, and a seventh failed due to a gyro failure on one of the missiles. The last one was launched from the YF-12 at Mach&nbsp;3.2 at an altitude of {{convert|74000|ft|m}} to a [[Boeing B-47 Stratojet#Variants|JQB-47E target drone]] {{convert|500|ft|m}} off the ground.<ref name=Land_Jenk_p44>Landis and Jenkins 2005, p. 44.</ref> The missile did not have a warhead but still managed to hit the B-47 directly and take a {{convert|4|ft|cm|adj=on}} section off its tail. The Air Force considered it a success and ordered 96 aircraft and had an initial budget of $90 million to further testing, but this was withheld by Secretary of Defense McNamara, who on 23 November 1967<ref name=knaack>Knaack, 1978.</ref> put it towards the much less successful [[Convair F-106 Delta Dart#Variants|F-106X]] program that nearly failed.<ref>SR-71 Blackbird By Paul F Crickmore. Bloomsbury. {{ISBN|9781472813176}}</ref>

The successful AIM-47 Falcon missile was increased in size and performance and became the [[AIM-54 Phoenix]] missile for the [[Grumman F-14 Tomcat|F-14 Tomcat]]. The AN/ASG 18 radar was upgraded to become the [[AN/AWG-9]] and APG-71, which added the ability to track multiple targets.

One of the Air Force test pilots, [[James Irwin|Jim Irwin]], would go on to become a NASA astronaut and [[List of Apollo astronauts#People who have walked on the Moon|walk on the Moon]].

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 NASA as research aircraft.

===NASA testing===
{{Listen
| type        = video
| image       = [[File:Video Camera Icon.png|50px]]
| help        = no
| filename    = NASA YF-12 Overview.ogv
| title       = NASA Overview of the YF-12, circa 1974
}}
The initial phase of the test program included objectives aimed at answering some questions about implementation of the [[Rockwell B-1 Lancer|B-1]]. Air Force objectives included exploration of its use in a tactical environment, and how [[airborne early warning and control]] (AWACS) would control supersonic aircraft. The Air Force portion was budgeted at US$4&nbsp;million. 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 US$14&nbsp;million (~${{Format price|{{Inflation|index=US-GDP|value=14000000|start_year=1982}}}} in {{Inflation/year|US-GDP}}).<ref>Drendel 1982, p. 6.</ref>

The YF-12 and SR-71 originally suffered from severe control issues that affected both the engines and the physical control of the aircraft. Wind testing at NASA Dryden and YF-12 research flights developed computer systems that nearly completely solved the performance issues. Testing revealed vortices from the nose chines interfering with intake air, which led to the development of a computer control system to open the forward bypass doors. A computer system to reduce [[unstart]]s was also developed. They also developed a flight engineering computer program called Central Airborne Performance Analyzer (CAPA) that relayed engine data to the pilots and informed them of any faults or issues with performance and indicated the severity of malfunctions.<ref name="nasa.gov">{{Cite web|url=https://www.nasa.gov/centers/dryden/about/Organizations/Technology/Facts/TF-2004-17-DFRC.html|title=NASA - NASA Dryden Technology Facts - YF-12 Flight Research Program|website=www.nasa.gov|language=en|access-date=2020-04-24|archive-date=12 September 2019|archive-url=https://web.archive.org/web/20190912045121/https://www.nasa.gov/centers/dryden/about/Organizations/Technology/Facts/TF-2004-17-DFRC.html|url-status=dead}}</ref>

Another system called Cooperative Airframe-Propulsion Control System (CAPCS) greatly improved the control of supersonic aircraft in flight. At such high speeds even minor changes in direction caused the aircraft to change position by thousands of feet, and often had severe temperature and pressure changes. CAPCS reduced these deviations by a factor of 10. The overall improvements increased range of the SR-71 by 7 percent.<ref name="nasa.gov"/>

Of the three YF-12As, AF Ser. No. 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 only [[Lockheed SR-71 Blackbird#Variants|SR-71C]].<ref>Landis and Jenkins 2005, pp. 62, 75.</ref><ref>Pace 2004, pp. 109–10.</ref>

YF-12A, AF Ser. No. 60-6936 was lost on 24 June 1971 due to an in-flight fire caused by a failed fuel line; both pilots ejected safely just north of Edwards AFB. YF-12A, AF Ser. No. 60-6935 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 Force]] at [[Wright-Patterson Air Force Base]] near [[Dayton, Ohio]] on 17 November 1979.<ref name=museum/>

[[File:YF-12C on ramp.jpg|thumb|YF-12C on ramp]]
A fourth YF-12 aircraft, the "YF-12C", was actually the second SR-71A (AF Ser. No. 61–7951). This SR-71A was re-designated as a YF-12C and given the fictitious Air Force Serial Number 60-6937 from an A-12 to maintain SR-71 secrecy. The aircraft was loaned to NASA for propulsion testing after the loss of YF-12A (AF Ser. No. 60–6936) in 1971. The YF-12C was operated by NASA until September 1978, when it was returned to the Air Force.<ref name=Land_Jenk_p49-55>Landis and Jenkins 2005, pp. 49–55.</ref>

The YF-12 had a real-field sonic-boom overpressure value between 33.5 and 52.7 N/m<sup>2</sup> (0.7 to 1.1&nbsp;lb/ft<sup>2</sup>) – below 48 was considered "low".<ref name="dugan">Dugan, James F. Jr. [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730009312_1973009312.pdf "Preliminary study of supersonic-transport configurations with low values of sonic boom"], p. 18. [[NASA]] [[Lewis Research Center]], March 1973. Retrieved: March 2012. (PDF)</ref>

==Variants==
;YF-12A: Pre-production version. Three were built.<ref>Landis and Jenkins 2005, p. 40.</ref>
;F-12B: Production version of the YF-12A with various improvements such as an increased combat radius from 1,200 to 1,350 nautical miles and an improved fire control system with increased bomber detection range from 100 to 125 miles;<ref>{{cite report |author= Robert P. Lyons |date= 30 April 1986 |title=THE SEARCH FOR AN ADVANCED FIGHTER: A HISTORY FROM THE XF-108 TO THE ADVANCED TACTICAL FIGHTER |url=https://apps.dtic.mil/dtic/tr/fulltext/u2/a166724.pdf |archive-url=https://web.archive.org/web/20190121174102/https://apps.dtic.mil/dtic/tr/fulltext/u2/a166724.pdf |url-status=live |archive-date=21 January 2019 |publisher=Defense Technical Information Center |page=10}}</ref> canceled before production could begin.<ref>Landis and Jenkins 2005, p. 46.</ref>
;YF-12C: Fictitious designation for an SR-71 provided to NASA for flight testing. The YF-12 designation was used to keep SR-71 information out of the public domain.<ref name=Land_Jenk_p49-0>Landis and Jenkins 2005, pp. 49–50.</ref> From 1971 to 1978, 61-7951 was temporarily loaned to NASA from the Air Force as "YF-12C #06937".<ref>{{cite web |title=61-7951 |url=http://www.habu.org/sr-71/17951.html |website= habu.org}}</ref>

==Operators==
;{{USA}}
*[[United States Air Force]]
*[[NASA]]

==Accidents and incidents==
*24 July 1971 YF-12A 60-6936 (Article 1003) was lost in an accident near Edwards Air Force Base, California, United States.

==Aircraft on display==
[[File:YF-12A NMUSAF.jpg|thumb|YF-12A AF Ser. No. ''60-6935'' in the National Museum of the USAF]]

;YF-12A
* YF-12A, AF Ser. No. 60-6935 (Article 1002) – at the [[National Museum of the U.S. Air Force]], [[Wright-Patterson AFB]], [[Dayton, Ohio]]. 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.<ref>[http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=590 "YF-12A/60-6935."] {{webarchive|url=https://web.archive.org/web/20130404155730/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=590 |date=4 April 2013 }} National Museum of the USAF. Retrieved: 16 April 2013.</ref>
* SR-71C, AF Ser. No. 61-7981 (portion of the former YF-12A AF Ser. No. 60-6934) is on display at the [[Hill Aerospace Museum]], [[Hill AFB]], [[Utah]].<ref>[http://www.hill.af.mil/library/factsheets/factsheet.asp?id=5757 "YF-12A/60-6934."] {{webarchive|url=https://web.archive.org/web/20130423192348/http://www.hill.af.mil/library/factsheets/factsheet.asp?id=5757 |date=23 April 2013 }} Hill Aerospace Museum. Retrieved: 16 April 2013.</ref>

==Specifications (YF-12A)==
[[File:Lockheed YF-12A 3view.png|right|300px|Orthographically projected diagram of the Lockheed YF-12.]]

{{Aircraft specs
|ref=''Lockheed's SR-71 'Blackbird' Family''<ref>Goodall and Miller, 2002.</ref>
|prime units?= imp
<!--   General characteristics
-->
|crew=2; pilot and fire control officer (FCO)
|length m= 30.97
|length ft= 101
|length in= 8
|span m= 16.95
|span ft= 55
|span in= 7
|height m= 5.64
|height ft= 18
|height in= 6
|wing area sqm= 167
|wing area sqft= 1795
|wing area note=
|aspect ratio= 1.7
|airfoil=
|empty weight kg= 27604
|empty weight lb= 60730
|empty weight note=
|gross weight kg= 56200
|gross weight lb= 124000
|gross weight note=
|max takeoff weight lb= 140000
|max takeoff weight kg= 63504
|fuel capacity=
|more general=
<!--   Powerplant
-->
|eng1 number=2
|eng1 name=[[Pratt & Whitney J58]] (JTD11D-20A)
|eng1 type=[[afterburning turbojet]] with compressor bleed bypass
|eng1 kn= 91.2
|eng1 lbf= 20500
|eng1 kn-ab= 140
|eng1 lbf-ab= 31500
<!--   Performance
-->
|max speed kmh= 3661
|max speed mph= 2275
|max speed kts=
|max speed note=at {{cvt|80000|ft}}<ref name=fighter/>
|max speed mach= 3.35
|cruise speed kmh=<!-- if max speed unknown -->
|cruise speed mph=<!-- if max speed unknown -->
|cruise speed kts=
|never exceed speed kmh=
|never exceed speed mph=
|never exceed speed kts=
|range km=
|range miles=
|range nmi=
|combat range km=
|combat range miles= 3000
|combat range nmi=
|endurance=<!-- if range unknown -->
|ceiling m=27400
|ceiling ft=90000
|g limits=<!-- aerobatic -->
|roll rate=<!-- aerobatic -->
|climb rate ms=60
|climb rate ftmin= 11820
|lift to drag=
|wing loading kg/m2=
|wing loading lb/sqft=
|wing loading note=
|thrust/weight= 0.44
|more performance=
<!--   Armament
-->
|missiles=3× [[AIM-47 Falcon|Hughes AIM-47A]] [[air-to-air missile]]s located internally in fuselage bays
|avionics=
* Hughes [[AN/ASG-18]] look-down/shoot-down fire control radar
}}

==See also==
{{Portal|Aviation}}
{{aircontent
|see also=
|related=
*[[Lockheed A-12]]
*[[Lockheed A-12#M-21|M-21 drone carrier]]
*[[Lockheed SR-71 Blackbird]]
|similar aircraft=
|lists=
*[[List of military aircraft of the United States]]
*[[List of Lockheed aircraft]]
*[[List of fighter aircraft]]
}}

==References==
===Notes===
{{notelist-ua}}

===Citations===
{{Reflist|30em}}

===Bibliography===
{{Refbegin|45em}}
* Air Force Museum Foundation Inc. ''US Air Force Museum''. Dayton, Ohio: Wright-Patterson AFB, 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, 1988, {{ISBN|0-7607-0904-1}}.
*Jenkins, Dennis R. ''Lockheed Secret Projects: Inside the Skunk Works''. St. Paul, Minnesota: MBI Publishing, 2001, {{ISBN|978-0-7603-0914-8}}.
*Jenkins, Dennis R. and Tony R. Landis. ''Experimental & Prototype U.S. Air Force Jet Fighters.'' Minnesota, US: Specialty Press, 2008, {{ISBN|978-1-58007-111-6}}.
*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 ed., 2005, {{ISBN|1-58007-086-8}}.
*McIninch, Thomas. "[https://web.archive.org/web/20090311152540/https://www.cia.gov/library/center-for-the-study-of-intelligence/kent-csi/vol15no1/html/v15i1a01p_0001.htm 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}}.
{{Refend}}

==External links==
{{Commons category|Lockheed YF-12}}
*[http://www.nasa.gov/centers/dryden/pdf/88796main_YF-12.pdf ''Mach 3+: NASA/USAF YF-12 Flight Research, 1969–1979'' by Peter W. Merlin (PDF book)]
*[http://www.sr-71.org/blackbird/yf-12a-1/ YF-12A Flight Manual] and [http://www.sr-71.org/photogallery/blackbird/06935/ YF-12A #60-6935 Photos on SR-71.org]
*[https://web.archive.org/web/20081215111103/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2380 YF-12 fact sheet on USAF Museum site]
*[https://web.archive.org/web/20131109203034/http://gmaps.tommangan.us/blackbirds/index.html Where are they now? Map of the location of every Blackbird]
*[https://web.archive.org/web/20061219200835/http://home.att.net/~jbaugher/1960.html USAF Aircraft Serial Numbers for 1960, including all A-12s, YF-12As, and M-21s]
* NASA videos: [https://www.youtube.com/watch?v=5SwyJTJagq8 Take-off], [https://www.youtube.com/watch?v=Ol7Tcza6wi0 Mid-air Refueling] <!--more at https://www.youtube.com/user/DrydenTV/videos -->
*[https://www.youtube.com/watch?v=x15UOSYf9Mo The Lockheed Martin YF-12 NASA documentary]

{{Lockheed}}
{{US fighters}}
{{Authority control}}

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[[Category:1960s United States fighter aircraft|Lockheed F-12]]
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