Editing Lockheed YF-22

{{Short description|Prototype demonstrator aircraft for the U.S. Air Force Advanced Tactical Fighter program}}
{{redirect|YF-22|the YF-22 rocket engine|YF-20}}
{{use American English|date=September 2019}}
{{Use dmy dates|date=September 2019}}
{{good article}}
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{{Infobox aircraft
 |name= YF-22
 |image= File:YF-22A Advanced Technology Fighter.jpg
 |caption=A YF-22 during a test flight
 |type= [[Stealth aircraft|Stealth]] [[Fighter aircraft|fighter]] technology demonstrator
 |national_origin= United States
 |manufacturer= [[Lockheed Corporation|Lockheed]] / [[Boeing]] / [[General Dynamics]]
 |designer =
 |first_flight= 29 September 1990
 |status= Retired
 |produced= 1989–1990
 |introduction =
 |retired=
 |number_built= 2
 |primary_user= [[United States Air Force]]
 |more_users=
 |unit cost=
 |developed_from=
 |variants=
 |developed_into= [[Lockheed Martin F-22 Raptor]]
}}

The '''Lockheed/<wbr>Boeing/<wbr>General Dynamics YF-22''' is an American single-seat, [[twinjet|twin-engine]], [[stealth aircraft|stealth]] [[fighter aircraft|fighter]] [[technology demonstrator]] prototype designed for the [[United States Air Force]] (USAF). The design team, with Lockheed as the prime contractor, was a finalist in the USAF's [[Advanced Tactical Fighter]] (ATF) competition, and two prototypes were built for the demonstration/validation phase. The YF-22 team won the contest against the [[Northrop YF-23|YF-23]] team for full-scale development and the design was developed into the [[Lockheed Martin F-22 Raptor|Lockheed Martin F-22]].<ref group=N>[[Lockheed Corporation|Lockheed]] merged with [[Martin Marietta]] in 1995 to form [[Lockheed Martin]].</ref> The YF-22 has a similar aerodynamic layout and configuration as the F-22, but with notable differences in the overall shaping such as the position and design of the cockpit, tail fins and wings, and in internal structural layout.

In the 1980s, the USAF began looking for a replacement for its fighter aircraft to counter emerging threats such as the advanced Soviet [[Sukhoi Su-27|Su-27]] and [[Mikoyan MiG-29|MiG-29]]. A number of companies submitted their proposals, with the competition narrowing down to Lockheed and [[Northrop Corporation|Northrop]] as the two finalists for demonstration/validation. Northrop teamed with [[McDonnell Douglas]] to develop the YF-23; Lockheed teamed with Boeing and General Dynamics to develop the YF-22, which, although marginally slower and having a larger [[radar cross-section]], was more agile than the YF-23. The Lockheed team was picked by the Air Force as the winner of the ATF competition in April 1991. The U.S. Navy considered adopting a naval version of the ATF, but these plans were later canceled due to cost.

Following the selection, the first prototype was retired as an exhibit at the [[Air Force Flight Test Museum]], while the second continued flight testing until an accident relegated it to the role of an antenna test vehicle and it was later stored.

== Development ==
{{Main|Advanced Tactical Fighter}}

===Concept definition===
In 1981, the U.S. Air Force (USAF) began exploring concepts and developing requirements for an [[Advanced Tactical Fighter]] (ATF) that would eventually become a new [[air superiority fighter]] to replace the [[McDonnell Douglas F-15 Eagle|F-15 Eagle]] and [[General Dynamics F-16 Fighting Falcon|F-16 Fighting Falcon]]. This was made more crucial by the emerging worldwide threats, including development and proliferation of [[Soviet Union|Soviet]] [[Mikoyan MiG-29|MiG-29 "Fulcrum"]] and [[Sukhoi Su-27|Su-27 "Flanker"]]-class fighter aircraft, [[Beriev A-50|A-50 "Mainstay"]] airborne warning and control system (AWACS), and more advanced surface-to-air missile systems. The ATF would take advantage of the new technologies in fighter design on the horizon including [[composite material]]s, lightweight [[alloy]]s, advanced avionics and flight-control systems, more powerful propulsion systems and [[stealth technology]].<ref name="YF F/S">{{Cite web|title=Fact sheet: Lockheed-Boeing-General Dynamics YF-22|publisher=U.S. Air Force|date=11 February 2009 |url=http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2382|access-date=18 June 2011|archive-url=https://web.archive.org/web/20120119223134/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2382|archive-date=19 January 2012}}</ref>

[[File:F-22 RFI.jpg|thumb|upright=1.25|Diagram of several designs submitted for ATF RFI. Note Lockheed's large CL-2016 design with inspiration from the SR-71 family.]]
The USAF sent out the ATF [[request for information]] (RFI) to the aerospace industry in May 1981 to explore what the future fighter aircraft could look like, and subsequently established a Concept Development Team (CDT) to analyze the results.<ref>Aronstein and Hirschberg 1998, p. 30.</ref> Eventually code-named ''"Senior Sky"'', the ATF at this time was still in the midst of requirements definition with both air-to-air and air-to-ground missions in consideration, and consequently there was substantial variety in the responses from the industry. Lockheed's initial concept was a particularly large aircraft called CL-2016, nicknamed "battlecruiser" for its size, that resembled its [[Lockheed SR-71 Blackbird|SR-71]]/[[Lockheed YF-12|YF-12]] with large [[delta wing]]s and engines mounted in nacelles spaced away from the fuselage and would have had similarly high operating speed and altitude as a missile platform (or "missileer" per Lockheed).<ref name="Hehs1998P1">Hehs 1998, Part 1.</ref><ref>Aronstein and Hirschberg 1998, pp. 39–42.</ref>

In 1983, the ATF Concept Development Team became the System Program Office (SPO) at [[Wright-Patterson Air Force Base]]. After discussions with aerospace companies and [[Tactical Air Command]] (TAC), the CDT/SPO narrowed the requirements to an air superiority fighter with outstanding kinematic performance in speed and maneuverability to replace the F-15.<ref>Sweetman 1991, pp. 10–13.</ref> Additionally, the SPO began to increasingly emphasize stealth for survivability, while still requiring fighter-like speed and maneuverability, due to the Air Force's experience from "[[black project|black world]]" projects such as the [[Lockheed Have Blue|''Have Blue'']]/[[Lockheed F-117 Nighthawk|F-117]] ("''Senior Trend''") and the Advanced Technology Bomber (ATB) program (which would result in the [[Northrop B-2 Spirit|B-2]], or "''Senior Ice''").<ref>Aronstein and Hirschberg 1998, pp. 45–58.</ref> With stealth becoming a core requirement, Lockheed's design team, led by Bart Osborne from its [[Skunk Works]] division at [[Burbank, California]], migrated away from its initial SR-71-like "battlecruiser" concept and instead began drafting a design that resembled the company's F-117. However, the faceted shape, resulting from Lockheed using the same "Echo" computer program that it had used to design the F-117, gave the design very poor aerodynamic performance that would be unsuitable for a fighter. Lockheed would perform poorly throughout the concept exploration phase, placing among the bottom of the competing contractors.<ref name="Hehs1998P1"/>

===Demonstration and validation===
[[File:Lockheed Faceted ATF.jpg|thumb|left|Early Lockheed ATF concept with faceted shape for stealth]]
By November 1984, the SPO had further narrowed the requirements and released the Statement of Operational Need (SON), with requirements calling for a {{convert|50000|lb|kg|-2|abbr=on}} takeoff weight fighter that places strong emphasis on stealth, maneuver, and supersonic cruise without afterburners, or [[supercruise]]; [[radius of action|mission radius]] was expected to be {{convert|500|nmi|mi km|sigfig=2}} mixed subsonic/supersonic or {{convert|700|-|800|nmi|mi km|sigfig=3}} subsonic.<ref name="SON_RFP">Aronstein and Hirschberg 1998, pp. 70–78.</ref> In September 1985, the Air Force sent out technical [[request for proposal]]s (RFP) to a number of aircraft manufacturing teams for demonstration and validation (Dem/Val). In addition to the ATF's demanding technical requirements, Dem/Val also placed a great deal of importance on [[systems engineering]], technology development plans, and risk mitigation. The top four proposals, later reduced to two to reduce program costs, would proceed with Dem/Val as finalists; there was initially no requirement for prototype air vehicles. At the time, the Air Force anticipated procuring 750 ATFs at a unit flyaway cost of $35&nbsp;million in [[fiscal year]] (FY) 1985 dollars (~${{Format price|{{Inflation|index=US-GDP|value=35000000|start_year=1985}}}} in {{Inflation/year|US-GDP}}).<ref name="Hehs1998P1"/><ref name="SON_RFP"/><ref>Aronstein and Hirschberg 1998, pp. 87–88.</ref> Furthermore, under Congressional pressure to combine efforts with the Air Force to reduce costs, the U.S. Navy joined the ATF program initially as an observer and eventually announced in 1988 that it would use a variant/derivative of the winning design to replace its [[Grumman F-14 Tomcat|F-14 Tomcat]] as the Navy Advanced Tactical Fighter (NATF); the service called for the procurement of 546 aircraft.<ref name=Williams_p5>Williams 2002, p. 5.</ref>

[[File:Lockheed Model 090P 300x172.jpg|thumb|Lockheed's submission for Dem/Val RFP, designated Configuration 090P]]
Having performed poorly during ATF concept exploration while also [[Lockheed Senior Peg|losing the ATB]] to [[Northrop Corporation|Northrop]] who had a curved surface design, Lockheed abandoned faceting in 1984 and began incorporating curved shapes and surfaces. Although its analytical tools were initially not able to calculate for such shapes, good empirical results from radar range testing at [[Helendale, California]], gave Lockheed confidence in designing a stealthy aircraft with smooth, curved surfaces, thus greatly improving its aerodynamic characteristics. As Lockheed gradually became able to analyze curved shapes,{{refn|A stealthy curved radome was the last challenge Lockheed overcame in early 1985.<ref name="Hehs1998P1"/>|group=N}} the final design submitted for Dem/Val, designated Configuration 090P, would have an arrowhead-like forward fuselage shape, swept [[trapezoidal wing]]s, four [[empennage]] tail surfaces, [[S-duct|S-shaped]] inlet ducts obscuring the engine face, and an internal rotary missile launcher.<ref name="Hehs1998P1"/> In addition to the change in aircraft design, Lockheed also shifted much more engineering talent and manpower to its ATF effort, appointing Sherman Mullin as the program manager, and had its draft proposals aggressively [[red team|red-teamed]] by a group led by retired Air Force general [[Alton D. Slay]].<ref>Mullin 2012, p. 13.</ref> The resulting proposal improvements were substantial, particularly the systems engineering volume.<ref>Mullin 2012, pp. 18–19.</ref>

The ATF RFP would see some alterations after its first release; the SPO drastically increased all-aspect stealth requirements in December 1985 after discussions with Lockheed and Northrop regarding their experiences with the ''Have Blue''/F-117 and ATB/B-2, and the requirement for flying technology demonstrator prototypes was added in May 1986 due to recommendations from the [[Packard Commission]], a federal commission by President [[Ronald Reagan]] to study [[Department of Defense]] procurement practices.<ref>Aronstein and Hirschberg 1998, pp. 82–85.</ref><ref>Mullin 2012, pp. 19–21.</ref> Seven companies submitted bids in July&nbsp;1986.{{refn|The seven bidding companies were Lockheed, Boeing, General Dynamics, McDonnell Douglas, Northrop, [[Grumman]], and [[Rockwell International|North American Rockwell]].<ref>Miller 2005, pp. 14, 19.</ref>|group=N}} Owing to the immense investments companies were expected to make on their own, teaming was encouraged by the SPO. Following proposal submissions, Lockheed, Boeing, and General Dynamics formed a team to develop whichever of their proposed designs was selected, if any. Northrop and McDonnell Douglas formed a team with a similar agreement.<ref>Goodall 1992, p. 94.</ref>

On [[Halloween|31&nbsp;October&nbsp;]]1986, Lockheed and Northrop, the two industry leaders in stealth aircraft, were selected as the first and second place respectively; Sherman Mullin would credit the Lockheed's top rank to their proposal's system engineering volume, an area other contractors had not emphasized. The two teams, Lockheed/Boeing/General Dynamics and Northrop/[[McDonnell Douglas]], were awarded $691&nbsp;million contracts in FY 1985 dollars (~${{Format price|{{Inflation|index=US-GDP|value=691000000|start_year=1985}}}} in {{Inflation/year|US-GDP}}) and would undertake a 50-month demonstration and validation phase, culminating in the flight test of the two teams' prototypes, the YF-22 and the [[Northrop YF-23|YF-23]]; [[Pratt & Whitney]] and [[General Electric]] had earlier been awarded contracts to develop the competing prototype propulsion systems with the designations [[Pratt & Whitney F119|YF119]] and [[General Electric YF120|YF120]] respectively.<ref name=Miller_p19-0>Miller 2005, pp.&nbsp;19–20.</ref><ref>Jenkins and Landis 2008, pp.&nbsp;233–234.</ref><ref name="Williams 2002, pp. 5–6">Williams 2002, pp.&nbsp;5–6.</ref> Because the requirement for flying prototypes was a late addition due to political pressure, the prototypes were to be "best-effort" vehicles not meant to perform a competitive flyoff or represent a production aircraft, but to demonstrate the viability of its concept and to mitigate risk.{{refn|The contractor teams were to give the SPO "sealed envelope" flight performance predictions against which their prototypes would be evaluated, rather than against each other.<ref>Aronstein and Hirschberg 1998, p. 137.</ref>|group=N}}<ref>Aronstein and Hirschberg 1998, pp. 87–88.</ref>

===Design evolution===
[[File:Lockheed Boeing General Dynamics DemVal Proposal 300x359.jpg|thumb|left|From top to bottom, ATF Dem/Val submissions from Lockheed, Boeing, and General Dynamics (not to scale)]]
Work would be divided roughly equally among the team.{{refn|The division of work was initially 35% Lockheed, 32.5% Boeing, and 32.5% General Dynamics.<ref>Miller 2005, p. 44</ref>|group=N}} Because Lockheed's submission was selected as one of the winners, the company assumed leadership of the program partners. It would be responsible for the forward fuselage, cockpit, and stealthy edge treatments at Burbank as well as final assembly at [[Palmdale]], [[California]]. Meanwhile, the wings and aft fuselage would be built by Boeing at [[Seattle]], [[Washington (state)|Washington]], and the center fuselage, weapons bays, tail and [[landing gear]] would be built by General Dynamics at [[Fort Worth, Texas|Fort Worth]], [[Texas]].<ref name="J&L p. 235"/> The team would also invest $675&nbsp;million (~${{Format price|{{Inflation|index=US-GDP|value=675000000|start_year=1988}}}} in {{Inflation/year|US-GDP}}) combined into their ATF effort during Dem/Val in addition to the government contract awards.<ref>Aronstein and Hirschberg 1998, p. 164.</ref> The partners brought their design experience and proposals with them. Boeing's design was large and long with a chin-mounted inlet, trapezoid wings, [[V-tail]] empennage surfaces (deemed sufficient due to the high operating speed), and palletized internal weapons. General Dynamics' design was smaller with fuselage and delta wings optimized for maneuver and supercruise, shoulder-mounted inlets, a large single vertical tail as the only empennage surface which compromised all-aspect stealth, and weapon bays in the center fuselage. However, much of the team's scrutiny fell on Lockheed's Configuration 090P, which was problematic due to being highly immature as a result of Lockheed's greater focus on systems engineering rather than a point design. Nevertheless, 090P was the initial starting point that the team worked to refine.<ref name="Hehs1998P2">Hehs 1998, Part 2.</ref>

Throughout Dem/Val, the SPO held System Requirement Reviews (SRR) with contractor teams and used the results of their performance and cost [[trade study|trade studies]] to develop the ATF system specifications and adjust or delete requirements that were significant weight and cost drivers while having marginal value.<ref>Mullin 2012, pp. 31–32.</ref> For instance, the requirement for eight internal missiles (represented by the baseline [[AIM-120 AMRAAM|AIM-120A]]){{refn|A clipped-fin variant of the AMRAAM, the AIM-120C, was eventually developed to increase the F-22's internal missile load back to eight.<ref>Aronstein and Hirschberg 1998, pp. 184–185.</ref>|group=N}} was reduced to six. The team continually refined the design, making extensive use of analytical and empirical methods such as wind tunnel testing (18,000 hours by the end of Dem/Val), pole testing at radar ranges, and [[computational fluid dynamics]] (CFD) and [[computer-aided design]] (CAD) software. By early 1987, the design had evolved into Configuration 095, which replaced the rotary launcher with a flatter weapons bay to reduce volume and drag, and the shapes of the forward fuselage and leading-edge root extensions were recontoured to reduce their planform area, preventing uncontrollable pitch-up moments. Around this time, the design had split into two families, the 500 prefix that represents the full system design – or Preferred System Concept (PSC) — to be carried forward for full-scale development and the 1000 prefix that represents the same external airfame shape but designed to be built as prototype air vehicles instrumented for flight testing; Configuration 095 thus became 595 and 1095 respectively.<ref name="Hehs1998P2"/>

[[File:F-22 design evolution 595 to 645 200x592.png|thumb|upright=0.66|From top to bottom, Configuration 595/1095, 614/1114, 632/1132 (YF-22 design), and 645 (EMD/production F-22 design)]]
By mid-1987, detailed weight analysis of Configuration 595/1095 revealed that it was overweight by {{convert|9000|lb|kg|-2|abbr=on}} even if it could still nominally meet maneuver parameters.<ref name="Hehs1998P2"/> With weight likely to increase and compromises not forthcoming, the team chose to completely start over with a new design in July 1987, with Lockheed bringing a new director of design engineering, Richard Cantrell.{{refn|Richard Heppe, president of [[Lockheed Corporation#Aeronautical Systems group|Lockheed California Company]], would also play a major role.<ref>Mullin 2019.</ref>|group=N}}<ref>Mullin 2012, p. 29.</ref> Various different layouts were explored and after an intensive three-month effort, the team chose a new design, Configuration 614/1114, as the starting point in late 1987 with shoulder-mounted inlets and diamond-like delta wings similar to General Dynamics' design, and four empennage tail surfaces; notably, the diamond-like delta's aerodynamic characteristics approached the original swept trapezoidal profile's while offering much lower structural weight due to the longer root chord. The design evolved through the rest of 1987 and into May 1988, when Configuration 632/1132 was frozen as the YF-22. Changes include the shapes of the empennage surfaces to diamond-like and recontouring of the fore and aft fuselage to reduce [[wave drag]] following the deletion of the [[thrust reverser]] requirement after another SRR;<ref name="Miller2005P19-24"/><ref>Mullin 2012, p. 30.</ref> the prototype [[thrust vectoring]] nozzles still retained some thrust reversing hardware provisions however, resulting in the prototype aft fuselage being bulkier than needed. Ultimately, the 50,000-lb takeoff weight still proved to be unachievable for both the Lockheed and Northrop teams, and was adjusted to {{convert|60000|lb|kg|-2|abbr=on}}, resulting in engine [[thrust]] increasing from {{convert|30000|lbf|kN|0|abbr=on|adj=on}} to {{convert|35000|lbf|kN|0|abbr=on|adj=on}} class.<ref>Aronstein and Hirschberg 1998, p. 119.</ref> While the YF-22 configuration was frozen at an immature state relatively soon after the redesign to begin construction of the prototypes, the team continued evolving the configuration and PSC design into the F-22 for full-scale development.<ref name="Hehs1998P2"/>

In addition to the advanced air vehicle and propulsion design, the ATF required an integrated avionics system for sensor fusion to increase the pilot's situational awareness and decrease workload; this demanded a leap in sensor and avionics capability. Avionics development was marked by extensive testing and prototyping and supported by ground and flying laboratories, with Boeing being responsible for avionics integration. As the YF-22 was a technology demonstrator for the airframe and engines, it would not have any of the mission systems avionics. Boeing would build the Avionics Ground Prototype (AGP) and also provide a [[Boeing 757#Government, military, and corporate|Boeing 757]] modified with the mission systems as a flying laboratory for avionics development; this aircraft would later be named the Flying Test Bed.<ref>Aronstein and Hirschberg 1998, pp. 104–121.</ref><ref name="f22_flight_test_update">{{cite journal |last1=Kohn |first1=Lt. Col. Allen E. |last2=Rainey |first2=Lt. Col. Steven M. |author-link2=Steven M. Rainey |journal=SETP 41st Symposium |date=9 April 1999 |publisher=[[Society of Experimental Test Pilots]] |url=http://fas.org/man/dod-101/sys/ac/docs/f-22-emd-paper.htm |title=F-22 Flight Test Program Update |archive-url=https://web.archive.org/web/20140717014716/http://fas.org/man/dod-101/sys/ac/docs/f-22-emd-paper.htm |archive-date=17 July 2014}}</ref> The SPO would similarly adjust avionics requirements as a result of SRRs with contractors. [[Side looking airborne radar|Side-looking radar]] and [[infrared search and track]] (IRST) were deleted from the baseline requirement and became provisions for potential future addition, and a $9&nbsp;million cap in FY 1985 dollars (~${{Format price|{{Inflation|index=US-GDP|value=9000000|start_year=1985}}}} in {{Inflation/year|US-GDP}}) for avionics per aircraft was placed by the SPO in 1989 on the baseline proposal for full-scale development.<ref name="Hehs1998P2"/>

Formally designated as the YF-22A, the first aircraft (PAV-1, [[United States military aircraft serials|serial number]] 87-0700, N22YF), with the GE YF120 engine,<ref>Williams 2002, p.&nbsp;5.</ref><ref name="YF-22 first flight">{{Cite journal|url=http://www.flightglobal.com/pdfarchive/view/1990/1990%20-%203086.html|title=YF-22 flies as ATFs head for deadline|journal=[[Flight International]]|location=London|publisher=Reed Business Information|issue=4237|volume=138|page=6|date=10–16 October 1990|access-date=23 June 2011|archive-url=https://web.archive.org/web/20110521184521/http://www.flightglobal.com/pdfarchive/view/1990/1990%20-%203086.html|archive-date=21 May 2011|issn=0015-3710}}</ref> was rolled out on 29&nbsp;August&nbsp;1990<ref name="J&L p. 235">Jenkins and Landis 2008, p.&nbsp;235.</ref><ref name="YF-22 rollout">Bailey 1990, p. 34.</ref> and first flew on 29&nbsp;September&nbsp;1990, taking off from Palmdale piloted by David L. Ferguson.<ref name="J&L p. 235"/><ref name=Goodall_p99>Goodall 1992, p.&nbsp;99.</ref> The second YF-22A (PAV-2, s/n 87-0701, N22YX) with the P&W YF119 made its [[maiden flight]] on 30&nbsp;October at the hands of chief test pilot Thomas A. Morgenfeld.<ref name="J&L p. 235"/> The aircraft was given the unofficial name "Lightning II" after Lockheed's [[World War II]]-era fighter, the [[Lockheed P-38 Lightning|P-38 Lightning]], which persisted until the mid-1990s when the USAF officially named the production F-22 "Raptor".<ref>{{Cite web|url=http://www.aerospaceweb.org/question/history/q0221.shtml |title=Military Aircraft Names |work=Aerospaceweb.org |access-date=26 September 2010 |archive-url=http://arquivo.pt/wayback/20091012134155/http://www.aerospaceweb.org/question/history/q0221.shtml |archive-date=12 October 2009 |url-status=dead }}</ref> The [[Lockheed Martin F-35 Lightning II|F-35]] later received the "Lightning II" name in 2006.<ref name="jsf_name_announcement">"{{Cite press release|url=http://www.jsf.mil/downloads/documents/JSF_F-35_2006_Inauguration%20Press%20Release.doc|title=Lockheed Martin Joint Strike Fighter Officially Named 'Lightning II'|publisher=Official Joint Strike Fighter program office|date=7 July 2006|access-date=23 June 2011|archive-url=https://web.archive.org/web/20060715214726/http://www.jsf.mil/downloads/documents/JSF_F-35_2006_Inauguration%20Press%20Release.doc|archive-date=15 July 2006}}</ref>

===Naval variant===
Because the NATF, which was to replace the F-14 Tomcat for the U.S. Navy, required a lower landing speed than the ATF for [[CATOBAR|aircraft carrier recovery]] while still attaining Mach 2-class speeds, the Lockheed team's NATF design group went through several configurations to arrive at a suitable design that would achieve acceptable characteristics for carrier operations. Boeing had advocated for a fixed-wing design while General Dynamics favored [[variable-sweep wing]]s. After an internal competition and extensive wind tunnel testing, the team chose to incorporate variable-sweep wings in August 1989. The design retained the thrust vectoring nozzles and four tails.<ref name="Mullin2012P38-39"/> The resulting aircraft would have been heavier, more complex, and more expensive than the Air Force ATF counterpart.<ref name="Miller2005p74">Miller 2005, p. 74.</ref> The Lockheed team would submit its NATF design along with its F-22 full-scale development proposal in December 1990, although the Navy would withdraw from the program shortly afterwards due to cost.<ref name="Mullin2012P38-39">Mullin 2012, pp. 38–39.</ref>

==Design==
[[File:An air-to-air overhead view of the YF-22 advanced tactical fighter aircraft during a test flight DF-ST-92-09938.jpg|thumb|left|The YF-22 design (Configuration 1132) with diamond-like delta wing planform and four tails]]

The YF-22 was a prototype air vehicle intended to demonstrate the viability of the ATF air vehicle and propulsion design, which was ultimately meant to meet USAF requirements for survivability, supercruise, stealth, and ease of maintenance.<ref>{{Cite journal|title=ATF procurement launches new era|journal=[[Flight International]]|location=London|publisher=Reed Business Information|issue=4037|volume=130|pages=10–11|date=9–15 November 1986|url=http://www.flightglobal.com/pdfarchive/view/1986/1986%20-%203004.html|access-date=24 June 2011|archive-url=https://web.archive.org/web/20120724101828/http://www.flightglobal.com/pdfarchive/view/1986/1986%20-%203004.html|archive-date=24 July 2012|issn=0015-3710}}</ref> The airframe has large diamond-like delta wings with leading edge swept back 48°, shoulder-mounted inlets, three internal weapons bays, and four empennage surfaces: canted vertical tails with rudders and all moving horizontal stabilizers. All major edges were aligned at a common set of angles for stealth. It had a tricycle landing gear, an [[aerial refueling]] receptacle centered on its spine, and an airbrake between the vertical tails.<ref>Miller 2005, pp. 90–93.</ref> The cockpit had a completely frameless bubble [[Aircraft canopy|canopy]]. Compared with its Northrop/McDonnell Douglas counterpart, the YF-22 has a more conventional design – its wings have larger [[Flight control surfaces|control surface]]s, such as full-span leading edge,<ref>{{Cite journal|title=Pentagon relaxes ATF design secrecy|journal=[[Flight International]]|location=London|publisher=Reed Business Information|issue=4217|volume=137|page=4|date=23–29 May 1990|url=http://www.flightglobal.com/pdfarchive/view/1990/1990%20-%201446.html|access-date=24 June 2011|archive-url=https://web.archive.org/web/20121105070635/http://www.flightglobal.com/pdfarchive/view/1990/1990%20-%201446.html|archive-date=5 November 2012|issn=0015-3710}}</ref> and, whereas the YF-23 had two tail surfaces, the YF-22 had four, which made it more maneuverable than its counterpart.<ref>{{Cite journal|title=Lockheed's ATF Stresses Agility|journal=[[Flight International]]|location=London|publisher=Reed Business Information|issue=4233|volume=138|pages=46–47|date=12–18 September 1990|url=http://www.flightglobal.com/pdfarchive/view/1990/1990%20-%202770.html|access-date=23 June 2011|archive-url=https://web.archive.org/web/20121105070735/http://www.flightglobal.com/pdfarchive/view/1990/1990%20-%202770.html|archive-date=5 November 2012|issn=0015-3710}}</ref>

[[File:Two Lockheed-Boeing-General Dynamics YF-22s.jpg|thumb|Both YF-22 aircraft on a taxiway at Edwards AFB|alt=Two jet aircraft with outward-canted vertical stabilizers parked on an angle on ramp.]]
The YF-22 was powered by two engines, with the [[General Electric YF120]] mounted on the first aircraft and the second with the [[Pratt & Whitney F119|Pratt & Whitney YF119]].<ref name="YF F/S"/><ref>{{Cite web|url=http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2383|title=YF-23 fact sheet|publisher=National Museum of the U.S. Air Force|access-date=24 June 2011|archive-url=https://web.archive.org/web/20110716073256/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2383|archive-date=16 July 2011}}</ref> The [[intake ramp|fixed-geometry]] caret engine inlets were spaced away from the forward fuselage to divert the boundary layer and generate [[oblique shock]]s with the upper inboard corner for efficient supersonic compression; the serpentine inlet ducts fully shield the engine faces from any exterior view. The two-dimensional thrust vectoring nozzles reduce the [[infrared signature]] by flattening the exhaust plume and facilitating its mixing with ambient air.<ref>Aronstein and Hirschberg 1998, p. 284.</ref><ref>{{cite magazine |last=Katz |first=Dan |url=https://aviationweek.com/defense/physics-and-techniques-infrared-stealth |title=The Physics And Techniques of Infrared Stealth |magazine=Aviation Week |publisher=Penton Media |date=7 July 2017 |access-date=12 April 2019 |archive-url=https://web.archive.org/web/20180814125513/http://aviationweek.com/defense/physics-and-techniques-infrared-stealth |archive-date=14 August 2018 |url-status=live}}</ref> [[chine (aeronautics)|Chines]] run from the nose along the sides of the forward fuselage where they eventually meet the upper edge of the inlets; those then transition to sharp leading edge root extensions of the wings further aft. These produce vortices that improved high [[angle-of-attack]] characteristics. To reduce supersonic drag for supercruise, [[area rule]] was applied to the airframe shape and most of the fuselage volume lies ahead of the wing's trailing edge, although the late configuration redesign meant that the prototype shaping was immature and not quite refined.<ref name="Miller2005P19-24">Miller 2005, pp. 19–24.</ref>

The aircraft had [[relaxed stability|relaxed static stability]] and was controlled via [[fly-by-wire]], integrated into the vehicle management system (VMS). The cockpit had a throttle and [[sidestick]] arrangement similar to the F-16 and simulated an operational fighter layout with a [[heads-up display]] (HUD), two {{Convert|6|x|6|in|cm|abbr=on}} primary [[multifunction display]]s (MFD) and three {{Convert|4|x|6|in|cm|abbr=on}} secondary MFDs. Some of the MFDs could be replaced by instrument panels as needed for specific flight test events. The prototype avionics incorporated a software-controlled stores management system (SMS) to test missile launching from internal weapons bays and its integration into the VMS; the weapons bays were also instrumented to measure vibration and acoustics.<ref>Aronstein and Hirschberg 1998, pp. 131–132, 144.</ref><ref>Miller 2005, p. 83.</ref>

===NATF-22===
[[File:NATF-22 305x170.jpg|thumb|A model of the Lockheed team's NATF design]]
The Lockheed team's design for the Navy Advanced Tactical Fighter (NATF), sometimes referred to as "NATF-22" or "F-22N" (the design was never formally designated), would have differed from the Air Force version in many ways. Because the NATF needed lower landing speeds than the F-22 for [[CATOBAR|aircraft carrier operations]] while still attaining Mach 2-class speeds, the design would have incorporated [[variable-sweep wing]]s; furthermore, the Navy placed greater emphasis on [[Loiter (aeronautics)|loiter]] time for [[fleet air defense]] rather than supercruise, so the variable-sweep wings also improved endurance.<ref name="Mullin2012P38-39"/><ref name="Miller2005p74"/> The fuselage shaping was similar to the Air Force version, while the landing gears and arresting hook were strengthened for aircraft carrier landings; all of these changes would have resulted in a heavier, more complex, and more expensive aircraft. It retained four empennage surfaces and thrust vectoring nozzles, and the avionics would initially have been largely common with the F-22, although additional sensors and mission avionics had also been planned for maritime missions. The design would have had a similar weapons bay arrangement but with expanded weapons carriage, including the [[AIM-152 AAAM]], [[AGM-88 HARM]], and [[Harpoon (missile)|AGM-84 Harpoon]].<ref>{{cite news |title=Naval YF-22 Would Have Swing Wings, But No Prototype Needed |work=Aerospace Daily |page=359 |publisher=McGraw-Hill, Inc |date=31 August 1990}}</ref><ref>Aronstein and Hirschberg 1998, p. 237.</ref>

[[File:Lockheed-Boeing_F-22_NATF-22_A-X_AF-X.jpg|thumb|left|From left to right, PSC F-22, NATF-22, and subsequent Lockheed/Boeing A-X and A/F-X designs; the latter two drew heavily from the NATF-22.]]
While the Lockheed team would submit the NATF-22 design with its F-22 full-scale development proposal in December 1990, the Navy began backing out of the NATF program in late 1990 to early 1991 and fully abandoned NATF by FY 1992 due to escalating cost and thus the design never progressed beyond Dem/Val to full-scale development, or engineering and manufacturing development (EMD). Lockheed and Boeing would leverage aspects of the design, such as the variable-sweep wings and the shaping of the fuselage, for several concepts for the Navy's Advanced-Attack (A-X) program, which later became the Advanced Attack/Fighter (A/F-X) program with added fighter capability, the successor to the canceled [[A-12 Avenger II]]; however, A/F-X would also be canceled as a result of the 1993 Bottom-Up Review due to post-Cold War budget pressure.<ref>Aronstein and Hirschberg, p. 239.</ref><ref>{{cite journal |title=A/F-X Unveiled |journal=[[Flight International]] |publisher=Reed Business Information |pages=12–13 |date=26 January – 1 February 1994}}</ref>

== Operational history ==

=== Evaluation ===
[[File:YF-22 and YF-23.jpg|thumb|The YF-22 (foreground) and YF-23 (background)|alt=Two different jet aircraft in flight towards right of screen.]]
Testing began with the first flight of PAV-1 on 29 September 1990. During the 18-minute flight, PAV-1 reached a maximum speed of {{Convert|250|kn}} and a height of {{Convert|12500|ft}}, before landing at [[Edwards AFB]].<ref name="YF-22 first flight"/> Following the flight, test pilot Dave Ferguson said that the remainder of the YF-22 test program would be concentrated on "the manoeuvrability of the aeroplane, both supersonic and subsonic".<ref name="YF-22 first flight"/>

During the flight test program, unlike the YF-23, weapon firings and high (60°) angle of attack (AoA, or high-alpha) flights were carried out on the YF-22.<ref name="Will p. 6"/> Although not a program requirement, the aircraft fired [[AIM-9 Sidewinder]] and [[AIM-120 AMRAAM]] missiles from internal weapon bays.<ref name="Will p. 6"/><ref>[https://go.gale.com/ps/i.do?p=AONE&sw=w&issn=08890404&v=2.1&it=r&id=GALE%7CA9371744&sid=googleScholar&linkaccess=abs "YF-23 would undergo subtle changes if it wins competition".] ''Defense Daily'', pp. 62–63, 14 January 1991.</ref> Flight testing also demonstrated that the YF-22 with its thrust vectoring nozzles achieved pitch rates more than double that of the F-16 at low-speed maneuvering as well as having excellent high angle-of-attack characteristics, with trimmed alpha of over 60° flown. The first prototype, PAV-1 with the General Electric engines, achieved Mach&nbsp;1.58 in supercruise on 3 November 1990, while PAV-2 with the Pratt & Whitney engines reached a maximum supercruise speed of Mach&nbsp;1.43 on 27 December 1990; maximum speed was in excess of Mach 2.0.<ref>Jenkins and Landis 2008, p.&nbsp;236.</ref><ref name="Goodall_p102-3">Goodall 1992, pp.&nbsp;102–103.</ref> Flight testing continued until 28&nbsp;December&nbsp;1990, by which time 74 flights were completed and 91.6 airborne hours were accumulated.<ref name="Williams 2002, pp. 5–6"/><ref>{{cite AV media |url=https://www.youtube.com/watch?v=nY0j3dmlHec |title=YF-22 – Road to the Raptor with Tom Morgenfeld, Test Pilot |date=17 April 2022 |publisher=Western Museum of Flight |location=Torrance, California |access-date=30 June 2023 |people=Morgenfeld, Thomas A.}}</ref> Following flight testing, the contractor teams submitted proposals for ATF full-scale development, with the Lockheed team's PSC F-22 design being significantly refined and evolving to Configuration 638 for its submission.<ref name=Miller_p38-9>Miller 2005, pp.&nbsp;38–39.</ref>

On 23&nbsp;April&nbsp;1991, the Lockheed team was announced by [[United States Secretary of the Air Force|Secretary of the Air Force]] [[Donald Rice]] as the winner of the ATF competition. The Lockheed team was rated higher on technical aspects, was considered lower risk (the YF-22 flew considerably more hours and sorties than its counterpart), and was considered to have more effective program management.<ref>Jenkins and Landis 2008, p.&nbsp;234.</ref><ref>Miller 2005, p. 38.</ref> Both designs met or exceeded all performance requirements; the YF-23 was stealthier and faster, but the YF-22 was more agile.<ref name="Goodall_p110">Goodall 1992, p.&nbsp;110.</ref> It was speculated in the aviation press that the Lockheed design was also seen as more adaptable to the Navy's NATF, but the Navy abandoned NATF by FY 1992.<ref name="Will p. 6">Williams 2002, p.&nbsp;6.</ref><ref name=Miller_p76>Miller 2005, p.&nbsp;76.</ref> Instead of being retired, as with the case of PAV-1, PAV-2 subsequently flew sorties following the competition – it amassed another 61.6 flying hours during 39 flights.<ref name="Will p. 6"/> On 25&nbsp;April&nbsp;1992, the aircraft sustained serious damage during a [[go-around]] attempt as a result of [[pilot-induced oscillation]]s. It was repaired but never flew again, and instead served as a static test vehicle thereafter.<ref name="Will pp. 6–7">Williams 2002, pp.&nbsp;6–7.</ref><ref>{{Cite journal|last=Warwick|first=Graham|title=Software suspected in YF-22 ATF accident|journal=[[Flight International]]|location=London|publisher=Reed Business Information|issue=4317|volume=141|page=12|date=6–12 May 1992|url=http://www.flightglobal.com/pdfarchive/view/1992/1992%20-%201156.html|access-date=24 June 2011|archive-url=https://web.archive.org/web/20110925145110/http://www.flightglobal.com/pdfarchive/view/1992/1992%20-%201156.html|archive-date=25 September 2011|issn=0015-3710 |ref=none}}</ref> In 1991, it was anticipated that 650 production F-22s would be procured.<ref>{{Cite news |last1=Pearlstein |first1=Steven |author-link=Steven Pearlstein |last2=Gellman |first2=Barton |author-link2=Barton Gellman |date=24 April 1991 |title=Lockheed Wins Huge Jet Contract; Air Force Plans to Buy 650 Stealth Planes At $100&nbsp;million Each |url=https://www.washingtonpost.com/archive/politics/1991/04/24/lockheed-wins-huge-jet-contract/89170285-d2c6-4c36-bb23-74dfae672626/ |newspaper=The Washington Post}}</ref>

=== F-22 production ===
{{Main|Lockheed Martin F-22 Raptor}}
[[File:F-22 Raptor resumes flight testing - 030328-F-0000C-001.jpg|thumb|F/A-22 Raptor test and training flight operations resumed here March 22 after a brief delay following a nose-gear-retraction incident in 2003.]]

As the Lockheed team won the ATF competition, it was awarded the full-scale development, or [[Manufacturing readiness level#Definitions|Engineering & Manufacturing Development]] (EMD) contract in August 1991 initially worth about $11&nbsp;billion (~${{Format price|{{Inflation|index=US-GDP|value=11000000000|start_year=1991}}}} in {{Inflation/year|US-GDP}}), which would ultimately allow it to proceed with production of operational aircraft. The EMD/production design would be further refined and evolve into Configuration 645.<ref name="Hehs1998P2"/> The EMD initially called for seven single-seat F-22A and two twin-seat F-22Bs, although the latter was eventually canceled to save on development costs and the orders were converted to single-seaters. On 9&nbsp;April&nbsp;1997, the first of these, ''Spirit of America'', was rolled out. During the ceremony, the F-22 was officially named "Raptor". Due to limited funding, the first flight, which had previously been scheduled for mid-1996, occurred on 7&nbsp;September 1997.<ref name="Will pp. 6–7"/> Flight testing for the F-22 continued until 2005, and on 15&nbsp;December&nbsp;2005 the USAF announced that the Raptor had reached its [[initial operational capability]] (IOC); with the collapse of the Soviet Union and the Department of Defense focused on counterinsurgency at that time, F-22 production only reached 195 aircraft — 187 of them operational models — and ended in 2011.<ref>{{Cite web|url=https://www.af.mil/News/story/storyID/123013572/ |title=F-22A Raptor goes operational |work=U.S. Air Force |date=15 December 2005 |access-date=24 June 2011 |archive-url=https://archive.today/20120723113239/http://www.af.mil/news/story.asp?storyID=123013572 |archive-date=23 July 2012 |url-status=live }}</ref><ref name="combataircraft">Parsons, Gary. [http://www.combataircraft.net/view_article.asp?ID=4994 "Final F-22 Delivered"]. {{Webarchive|url=https://web.archive.org/web/20160313044134/http://www.combataircraft.net/view_article.asp?id=4994|date=13 March 2016}}. ''Combat Aircraft Monthly'', 3 May 2012. Retrieved 10 April 2014.</ref>

In many respects, the YF-22s were different from EMD/production F-22s as the design progressed from relatively immature Configuration 632/1132 to the final Configuration 645. Contrary to the [[Lockheed F-117 Nighthawk|F-117 Nighthawk]], which was initially difficult to control because of small [[vertical stabilizer]]s, the YF-22 had its fin area over-specified by Lockheed. Therefore, the company reduced the size of those on F-22s by 20–30 percent. Lockheed and its partners recontoured the shape of the wing and [[stabilator]] trailing edges to improve aerodynamics, strength, and stealth characteristics; the wing and stabilitor sweep was reduced by 6° from 48°. The shapes of the [[radome]] and fuselage were changed to improve radar performance and aerodynamics. The dedicated airbrake was eliminated in favor of feathering control surfaces using the control laws. The systems arrangement and structural design were refined. Finally, to improve pilot visibility, the canopy was moved forward {{convert|178|mm|in|0|order=flip}}, and the engine inlets were moved rearward {{convert|356|mm|in|0|order=flip}}.<ref>Williams 2002, p. 5.</ref><ref>Pace 1999, pp.&nbsp;12–13.</ref><ref name="Hehs1998P2"/>

==Accidents==
In April 1992, the second YF-22 crashed on the runway while executing a landing go-around demonstration at Edwards AFB. The test pilot, Tom Morgenfeld, escaped without injury. The cause of the crash was found to be a flight control [[software error]] that failed to prevent a pilot-induced oscillation while performing a low altitude demonstration flight. The aircraft was superficially repaired but never flew again and was later used as an antenna test model. In light of this mishap, the F-22 [[Flight control modes|flight control laws]], the algorithms governing how control inputs translate into aircraft motions and reactions, were altered to better account for non-linear effects of control surface rate/position saturation and PIO triggering mechanisms.<ref>{{cite journal |last1=Harris |first1=Jeffrey |author-link1=Jeffrey K. Harris |last2=Black |first2=G. T. |url=https://www.researchgate.net/publication/269064311_F-22_control_law_development_and_flying_qualities |title=F-22 control law development and flying qualities, AIAA Paper 96-3379 (A96-35101) |journal=21st Atmospheric Flight Mechanics Conference |publisher=American Institute of Aeronautics and Astronautics |location= |page=156 |doi=10.2514/6.1996-3379}}</ref>

==Surviving aircraft==
[[File:Lockheed-Boeing-General Dynamics YF-22 USAF.jpg|thumb|YF-22 on temporary display at the [[National Museum of the United States Air Force]]|alt=Starboard view of jet aircraft in museum among suspended aircraft and an American flag.]]

*YF-22A PAV-1, S/N ''87-0700'', registration number N22YF – on display at the [[Air Force Flight Test Center Museum]], [[Edwards Air Force Base]], [[California]] (was previously loaned to the [[National Museum of the United States Air Force]] near [[Dayton, Ohio]])<ref>{{Cite web |title=YF-22 Raptor/87-700 |url=https://www.aerialvisuals.ca/AirframeDossier.php?Serial=43707 |archive-url=https://web.archive.org/web/20240328042805/https://www.aerialvisuals.ca/AirframeDossier.php?Serial=43707 |archive-date=28 March 2024 |access-date=18 June 2021 |work=aerialvisuals.ca}}</ref>
*YF-22A PAV-2, S/N ''87-0701'', registration number N22YX – stored at [[Rome Laboratory]], [[Rome, New York]].<ref>{{Cite web |title=YF-22 Raptor/87-701 |url=https://www.aerialvisuals.ca/AirframeDossier.php?Serial=25402 |archive-url=https://web.archive.org/web/20240328042709/https://www.aerialvisuals.ca/AirframeDossier.php?Serial=25402 |archive-date=28 March 2024 |access-date=13 May 2022 |work=aerialvisuals.ca}}</ref>

== Specifications (YF-22A) ==
[[File:YF-22 Lightning II "Rzuty" outline drawing.png|right|thumb|Lockheed YF-22 3-view diagram]]
{{Aircraft specs
|ref=Miller,<ref>Miller 2005, p. 102.</ref> Pace,<ref>Pace 1999, pp.&nbsp;14–15.</ref> Baker,<ref name="Baker p28-9, 32">Baker 1995, pp.&nbsp;28–29, 32.</ref> Sweetman,<ref>Sweetman 1991, p. 93.</ref> and Aronstein & Hirschberg<ref>Aronstein 1998, pp. 131, 154.</ref> (note, some specifications are estimated)
|prime units? = kts
<!--   General characteristics
-->
|crew=1
|length ft=64
|length in=2
|length m=19.56
|span ft=43
|span in=0
|span m=13.1
|height ft=17
|height in=8.9
|height m=5.41
|wing area sqft=840
|wing area sqm=78.04
|empty weight lb=31000
|empty weight note=contractor weight (without engines)
|gross weight lb=62000
|gross weight note=takeoff
<!--   Powerplant
-->
|eng1 name=[[Pratt & Whitney F119|Pratt & Whitney YF119]]-PW-100L ''or'' [[General Electric YF120]]-GE-100L
|eng1 type=[[Afterburner|afterburning]] [[turbofan]]s
|eng1 number=2
|eng1 lbf=23500
|eng1 note=(YF120)
|eng1 kn=104
|eng1 lbf-ab=30000 or 35000
|eng1 kn-ab=133 or 156
<!--   Performance
-->
|max speed kts=
|max speed note=
|max speed mach=2.2, {{convert|1452|mph|kn km/h|0|abbr=on}} at altitude
|cruise speed kts=
|cruise speed note=*'''Supercruise:''' Mach 1.58, {{convert|1043|mph|kn km/h|0|abbr=on}} at altitude (military power only)
|range nmi=2000
|range miles=
|range km=
|combat range nmi=700–800
|combat range miles=
|combat range km=
|ferry range nmi=
|ferry range note=
|endurance=<!-- if range unknown -->
|ceiling ft=65000
|ceiling m=19800
|ceiling note=
|g limits=+7.9 ''g'' (highest tested)
|roll rate=
|climb rate ftmin=
|climb rate note=
|time to altitude=
|wing loading lb/sqft=73.8
|wing loading note=(61.9 lb/sq ft at combat weight)
|thrust/weight=1.13 (1.35 at combat weight)
|more performance=
<!--   Armament
-->
|armament=Provisions made for:
* 1 × 20 mm (0.79 in) [[M61 Vulcan]] cannon
* 4 × [[AIM-120 AMRAAM]] medium-range [[air-to-air missile]]s
* 2 × [[AIM-9 Sidewinder]] short-range air-to-air missiles
}}

==See also==
{{Portal|Aviation}}
{{aircontent
|see also=
* {{annotated link|Advanced Tactical Fighter}}
|related= 
* {{annotated link|Lockheed Martin F-22 Raptor}}
* {{annotated link|Lockheed Martin FB-22}}
* {{annotated link|Lockheed Martin X-44 MANTA}}
|similar aircraft= 
* {{annotated link|Northrop YF-23}}
|lists= 
* [[List of Lockheed aircraft]]
}}

==References==
===Notes===
{{reflist|group=N}}

===Citations===
{{Reflist}}

===Bibliography===
{{Refbegin}}
* {{Cite book |author1=Aronstein, David C. |author2=Hirschberg, Michael J. |title=Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter |location=Arlington, Virginia |publisher=American Institute of Aeronautics & Astronomy |year=1998 |isbn=978-1-56347-282-4 |ref=none}}
* {{Cite journal |last=Bailey |first=John |title=YF-22 ATF prototype set for maiden flight |journal=[[Flight International]] |location=London |publisher=Reed Business Information |issue=4232 |volume=138 |page=34 |date=5–11 September 1990 |url=http://www.flightglobal.com/pdfarchive/view/1990/1990%20-%202544.html |access-date=23 June 2011 |archive-url=https://web.archive.org/web/20121105065353/http://www.flightglobal.com/pdfarchive/view/1990/1990%20-%202544.html |archive-date=5 November 2012 |issn=0015-3710 |ref=none}}
* {{Cite journal |author=Baker, David |title=From ATF to Lightning II: A Bolt in Anger: Part Two: Lockheed's YF-22A |journal=[[Air International]] |date=January 1995 |volume=48 |issue=1 |pages=27–38 |issn=0306-5634 |ref=none}}
* {{Cite book |author=Goodall, James C. |chapter=The Lockheed YF-22 and Northrop YF-23 Advanced Tactical Fighters |title=America's Stealth Fighters and Bombers, B-2, F-117, YF-22, and YF-23 |location=St. Paul, Minnesota |publisher=MBI Publishing Company |year=1992 |isbn=0-87938-609-6 |url-access=registration |url=https://archive.org/details/americasstealthf00good |ref=none}}
* {{cite magazine |last=Hehs |first=Eric |title=Design Evolution of the F-22, Part 1 and 2 |url=https://www.codeonemagazine.com/f22_article.html?item_id=179 |archive-url=https://web.archive.org/web/20240518062846/https://www.codeonemagazine.com/f22_article.html?item_id=179 |publisher=Lockheed Martin |archive-date=18 May 2024 |magazine=Code One |date=16 October 1998 |ref=none}}
* {{Cite book |author1=Jenkins, Dennis R. |author2=Landis, Tony R. |title=Experimental & Prototype U.S. Air Force Jet Fighters |location=Minnesota, US |publisher=Specialty Press |year=2008 |isbn=978-1-58007-111-6 |ref=none}}
* {{Cite book |author=Miller, Jay |title=Lockheed Martin F/A-22 Raptor, Stealth Fighter |location=Hinckley, UK |publisher=Midland Publishing |year=2005 |isbn=1-85780-158-X |ref=none}}
* {{cite journal |last=Mullin |first=Sherman N. |title=Winning the ATF |url=https://secure.afa.org/Mitchell/reports/MP9_ATF_0612.pdf |journal=Mitchell Institute for Airpower Studies |location=Arlington, VA |date=June 2012 |archive-url=https://web.archive.org/web/20241005094124/https://secure.afa.org/Mitchell/reports/MP9_ATF_0612.pdf |archive-date=5 October 2024 |ref=none}}
* {{cite interview |last=Mullin |first=Sherman N. |author-mask=------- |interviewer-last1=Westwick |interviewer-first1=Peter |interviewer-last2=Deverell |interviewer-first2=William |title=Oral history interview with Sherman Mullin. Second Interview. |work=Aerospace Oral History Project |date=24 January 2019 |publisher=[[Huntington Library|The Huntington Library, Art Museum, and Botanical Gardens]] |location=San Marino, California |url=https://hdl.huntington.org/digital/collection/p15150coll7/id/45049/ |ref=none |archive-url=https://web.archive.org/web/20240808163832/https://hdl.huntington.org/digital/collection/p15150coll7/id/45049/ |archive-date=8 August 2024}}
* {{Cite book |author=Pace, Steve |title=F-22 Raptor, America's Next Lethal War Machine |location=New York |publisher=McGraw-Hill |year=1999 |isbn=0-07-134271-0 |ref=none}}
* {{cite book |last=Sweetman |first=Bill |title=YF-22 and YF-23 Advanced Tactical Fighters |location=St. Paul, Minnesota |publisher=Motorbooks International Publishing |year=1991 |isbn=0-87938-505-7 |ref=none}}
* {{Cite book |editor-last=Williams |editor-first=Mel |title=Superfighters: The Next Generation of Combat Aircraft |location=London |publisher=AIRtime Publishing |year=2002 |isbn=1-880588-53-6 |ref=none}}
{{Refend}}

===Additional sources===
{{Refbegin}}
* {{cite book |last1=Abrams |first1=Richard |last2=Miller |first2=Jay |title=Lockheed F-22 |publisher=Midland County Publications |location=Leicester, England |year=1992 |isbn=0-942548-53-1 |ref=none}}
* {{Cite book |last=Crosby |first=Francis |title=Fighter Aircraft |location=London |publisher=Lorenz Books |year=2002 |isbn=0-7548-0990-0 |ref=none}}
* {{Cite book |last=Miller |first=Jay |title=Lockheed Martin's Skunk Works: The Official History... |location=Leicester, UK |publisher=Midland Publishing |year=1995 |isbn=1-85780-037-0 |ref=none}}
* {{cite journal |last=Mullin |first=Sherman N. |title=The Evolution of the F-22 Advanced Tactical Fighter |url=https://arc.aiaa.org/doi/abs/10.2514/6.1992-4188 |journal=American Institute of Aeronautics and Astronautics |location=Arlington, VA |doi=10.2514/6.1992-4188 |date=August 1992 |ref=none|url-access=subscription }}
* {{Cite book |last=Pace |first=Steve |title=X-Fighters: USAF Experimental and Prototype Fighters, XP-59 to YF-23 |location=Osceola, Wisconsin |publisher=Motorbooks International |year=1991 |isbn=0-87938-540-5 |ref=none}}
* {{Cite journal |last=Sweetman |first=Bill |author-link=Bill Sweetman |title=Fighter EW: The Next Generation |journal=Journal of Electronic Defense |volume=23 |issue=7 |date=July 2000 |issn=0192-429X |ref=none}}
* {{Cite book |last=Sweetman |first=Bill |author-mask=------- |title=F-22 Raptor |location=St. Paul, Minnesota, USA |publisher=Motorbooks International Publishing |year=1998 |isbn=0-7603-0484-X |ref=none}}
* {{Cite book |editor-last=Winchester |editor-first=Jim |chapter=Northrop/McDonnell Douglas YF-23 |title=Concept Aircraft: Prototypes, X-Planes, And Experimental Aircraft |series=The Aviation Factfile |location=Rochester, Kent, UK |publisher=Grange Books |year=2005 |isbn=1-84013-809-2 |ref=none}}
{{refend}}

==External links==
{{Commons category|Lockheed YF-22}}
* [http://www.f22-raptor.com/ F-22 official team web site]
* [https://web.archive.org/web/20100104193536/http://oea.larc.nasa.gov/PAIS/Partners/F_22.html F-22 page on NASA Langley site]

{{Advanced Tactical Fighter}}
{{Lockheed Martin aircraft}}
{{Boeing combat aircraft}}
{{Convair/GD aircraft}}
{{US fighters}}
{{Stealth aircraft}}

[[Category:Lockheed aircraft|F-022]]
[[Category:1990s United States fighter aircraft]]
[[Category:Twinjets]]
[[Category:Stealth aircraft]]
[[Category:1990s United States experimental aircraft]]
[[Category:Mid-wing aircraft]]
[[Category:Aircraft first flown in 1990]]
[[Category:Aircraft with retractable tricycle landing gear]]
[[Category:Two dimension thrust vectoring aircraft]]