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===Origins=== {{main|Advanced Tactical Fighter|Lockheed YF-22}} [[File:Advanced Tactical Fighter Systems Project Office Patch.jpg|thumb|ATF SPO Patch, 1990]] The F-22 originated from the [[Advanced Tactical Fighter]] (ATF) program that the U.S. Air Force (USAF) initiated in 1981 to replace the [[McDonnell Douglas F-15 Eagle|F-15 Eagle]] and [[General Dynamics F-16 Fighting Falcon|F-16 Fighting Falcon]]. Intelligence reports indicated that their effectiveness would be eroded by emerging worldwide threats emanating from the [[Soviet Union]], including new developments in surface-to-air missile systems for integrated air defense networks, the introduction of the [[Beriev A-50]] "Mainstay" airborne warning and control system (AWACS), and the proliferation of the [[Sukhoi Su-27]] "Flanker" and [[Mikoyan MiG-29]] "Fulcrum" class of fighter aircraft.<ref>Jenkins, Dennis R. ''Lockheed Secret Projects: Inside the Skunk Works.'' St. Paul, Minnesota: MBI Publishing Company, 2001. {{ISBN|0-7603-0914-0}}. pp. 70.</ref> Code-named "''Senior Sky''", the ATF would become an air superiority fighter program influenced by these threats; in the potential scenario of a Soviet and [[Warsaw Pact]] invasion in [[Central Europe]], the ATF was envisaged to support the [[AirLand Battle|air-land battle]] by spearheading [[offensive counter air|offensive]] and defensive counter-air operations (OCA/DCA) in this highly contested environment that would then enable following echelons of NATO strike and attack aircraft to perform [[air interdiction]] against ground formations; to do so, the ATF would make an ambitious leap in capability and survivability by taking advantage of the new technologies in fighter design on the horizon, including [[composite material]]s, lightweight [[alloy]]s, advanced flight control systems and avionics, more powerful propulsion systems for supersonic cruise (or [[supercruise]]) around Mach 1.5, and stealth technology for low observability.<ref>{{cite web |url=https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/196040/lockheed-martin-f-22a-raptor/ |title=Lockheed Martin F-22A Raptor |work=National Museum of the U.S. Air Force}}</ref><ref>Pace 1999, pp. 3β4.</ref><ref>Aronstein and Hirschberg 1998, pp. 51-54, 72.</ref> The USAF published an ATF [[request for information]] (RFI) to the aerospace industry in May 1981, and following a period of concept and specification development, the ATF System Program Office (SPO) issued the demonstration and validation (Dem/Val) [[request for proposal]]s (RFP) in September 1985, with requirements placing strong emphasis on stealth, supersonic cruise and maneuver. The RFP saw some alterations after its initial release, including more stringent signature reduction requirements in December 1985 and the addition of the requirement for flying technology demonstrator prototypes in May 1986.{{refn|The greatly increased stealth requirements arose from the SPO's discussions with Lockheed and Northrop, the two companies with prior stealth experience from the "''Senior Trend''"/[[Lockheed F-117 Nighthawk|F-117]] and "''Senior Ice''"/[[Northrop B-2 Spirit|B-2]] respectively.<ref>Aronstein and Hirschberg 1998, pp. 56β57.</ref>|group=N}}<ref>Aronstein and Hirschberg 1998, pp. 82β89.</ref> Owing to the immense investments required to develop the advanced technologies, teaming among companies was encouraged. Of the seven bidding companies,{{refn|The seven bidding companies for Dem/Val were Lockheed, Northrop, General Dynamics, Boeing, McDonnell Douglas, [[Grumman]], and [[Rockwell International|North American Rockwell]].<ref>Miller 2005, pp. 14, 19.</ref>|group=N}} [[Lockheed Corporation|Lockheed]] and [[Northrop Corporation|Northrop]] were selected on 31 October 1986.{{refn|Lockheed's design had considerable variations throughout concept exploration, ranging from [[Lockheed SR-71 Blackbird|SR-71]]/[[Lockheed YF-12|YF-12]]-like, to faceted designs similar to the F-117, to a curved surface design with an arrowhead-like planform as the company became able to design stealthy shapes with curved surfaces.<ref name="f22_evolution_p1">{{cite web |last=Hehs |first=Eric |url=https://www.codeonemagazine.com/article.html?item_id=179 |title=F-22 Raptor Design Evolution, Part 1 |work=Lockheed Martin |date=1998 |access-date=13 March 2023 |archive-date=16 January 2022 |archive-url=https://web.archive.org/web/20220116193649/https://www.codeonemagazine.com/article.html?item_id=179 |url-status=live}}</ref>|group=N}} Lockheed, through its [[Skunk Works]] division at [[Burbank, California]], teamed with [[Boeing]] and [[General Dynamics]] while Northrop teamed with [[McDonnell Douglas]]. These two contractor teams undertook a 50-month Dem/Val phase, culminating in the flight test of two technology demonstrator prototypes, the [[Lockheed YF-22]] and [[Northrop YF-23]]; while they represented competing designs, the prototypes were meant for demonstrating concept viability and risk mitigation rather than a competitive flyoff.{{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}} Concurrently, [[Pratt & Whitney]] and [[General Electric]] competed for the ATF engines.<ref>Jenkins and Landis 2008, pp. 233β234.</ref><ref>Williams 2002, pp. 5β6.</ref> [[File:F-22 design evolution 595 to 645 200x592.png|thumb|upright=0.66|Evolution of the F-22 design from 1987, with the bottom being the production configuration.]] Dem/Val was focused on [[system engineering]], technology development plans, and risk reduction over point aircraft designs; in fact, after down-select, the Lockheed team completely redesigned the airframe configuration in summer 1987 due to weight analysis, with notable changes including the [[Wing configuration#Wing planform|wing planform]] from swept trapezoidal to diamond-like delta and a reduction in forebody planform area.<ref>Aronstein and Hirschberg 1998, p. 119.</ref><ref>Mullin 2019.</ref> The team extensively used analytical and empirical methods including [[computational fluid dynamics]] and [[computer-aided design]], [[wind tunnel]] testing (18,000 hours for Dem/Val), and [[radar cross-section]] (RCS) calculations and pole testing. Avionics were tested in ground prototypes and flying laboratories.<ref>Aronstein and Hirschberg 1998, pp. 104β125.</ref> During Dem/Val, the SPO used [[trade study|trade studies]] from both teams to review the ATF system specifications and adjust or delete requirements that were significant weight and cost drivers while having marginal value. The short takeoff and landing ([[STOL]]) requirement was relaxed to delete [[thrust reversal|thrust-reversers]], saving substantial weight. [[Side looking airborne radar|Side looking radar]]s and the dedicated [[infrared search and track]] (IRST) system were eventually removed as well, although space and cooling provisions were retained to allow for their later addition. The [[ejection seat]] was downgraded from a fresh design to the existing [[ACES II]]. Despite efforts by both teams to rein in weight, the takeoff gross weight estimates grew from {{convert|50000|to|60000|lb|kg|sigfig=3|abbr=on}}, resulting in engine thrust requirement increasing from {{convert|30000|to|35000|lbf|kN|0|abbr=on}} class.<ref>Aronstein and Hirschberg 1998, pp. 105β108.</ref> Each team built two prototype air vehicles for Dem/Val, one for each engine option. The YF-22 had its maiden flight on 29 September 1990 and, in testing, successfully demonstrated supercruise, high angle-of-attack maneuvers, and the firing of air-to-air missiles from internal weapons bays. After the flight test of the demonstrator prototypes at [[Edwards Air Force Base]], the teams submitted the results and their full-scale development design proposals β or Preferred System Concept β in December 1990; on 23 April 1991, the [[United States Secretary of the Air Force|Secretary of the USAF]], [[Donald Rice]], announced the Lockheed team and Pratt & Whitney as the winners of the ATF and engine competitions.<ref>Jenkins and Landis 2008, p. 234.</ref> Both designs met or exceeded all performance requirements; the YF-23 was considered stealthier and faster, but the YF-22, with its thrust vectoring nozzles, was more maneuverable as well as less expensive and risky, having flown considerably more test sorties and hours than its counterpart.<ref name="Goodall_p110">Goodall 1992, p. 110.</ref><ref>Aronstein and Hirschberg 1998, pp. 159β160.</ref> The press also speculated that the Lockheed team's design was more adaptable to the Navy Advanced Tactical Fighter (NATF) for replacing the [[Grumman F-14 Tomcat|F-14 Tomcat]], but by fiscal year (FY) 1992, the [[United States Navy|U.S. Navy]] had abandoned NATF due to cost.<ref name=Miller_p76>Miller 2005, p. 76.</ref>
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