The Lockheed Martin/Boeing F-22 Raptor is an American twin-engine, all-weather, supersonic stealth fighter aircraft. As a product of the United States Air Force's Advanced Tactical Fighter (ATF) program, the aircraft was designed as an air superiority fighter, but also incorporates ground attack, electronic warfare, and signals intelligence capabilities. The prime contractor, Lockheed Martin, built most of the F-22 airframe and weapons systems and conducted final assembly, while program partner Boeing provided the wings, aft fuselage, avionics integration, and training systems.

First flown in 1997, the F-22 descended from the Lockheed YF-22 and was variously designated F-22 and F/A-22 before it formally entered service in December 2005 as the F-22A. Although the U.S. Air Force (USAF) had originally planned to buy a total of 750 ATFs to replace its F-15 Eagles, it later scaled down to 381, and the program was ultimately cut to 195 aircraft — 187 of them operational models — in 2009 due to political opposition from high costs, a lack of air-to-air missions at the time of production, and the development of the more affordable and versatile F-35.[N 2] The last aircraft was delivered in 2012.

The F-22 is a critical component of the USAF's current high-end tactical airpower. While it had a protracted development and initial operational difficulties, the aircraft became the service's leading platform for air-to-air missions against peer adversaries. Although designed for counter-air operations, the F-22 has also performed strike and electronic surveillance, including missions in the Middle East against the Islamic State and Assad-aligned forces. The F-22 is planned to remain a cornerstone of the USAF's fighter fleet until its succession by the crewed Next Generation Air Dominance fighter.

Development
Origins
Main articles: Advanced Tactical Fighter and Lockheed YF-22

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 F-15 Eagle and 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.[3] Code-named "Senior Sky", the ATF would become an air superiority fighter program influenced by these reports; in the potential scenario of a Soviet and Warsaw Pact invasion in Central Europe, the ATF was envisaged to support the air-land battle by spearheading 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 materials, lightweight alloys, 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.[4][5][6]

The USAF initiated 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 proposals (RFP) in September 1985, with requirements placing strong emphasis on stealth, supersonic cruise and maneuver. The RFP would see some alterations after its initial release, including more stringent signature reduction requirements in December 1985 and adding the requirement for flying technology demonstrator prototypes in May 1986.[N 3][8] Owing to the immense investments required to develop the advanced technologies, teaming between companies was encouraged. Of the seven bidding companies,[N 4] Lockheed and Northrop were selected on 31 October 1986.[N 5] 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 YF-22 and the YF-23 respectively; while they represented competing designs, the prototypes were meant for demonstrating concept viability and risk mitigation rather than a competitive flyoff.[N 6] Concurrently, Pratt & Whitney and General Electric competed for the ATF engines.[12][13]

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 in the summer of 1987 due to weight analysis, with notable changes including the wing planform from swept trapezoidal to diamond-like delta and a reduction in forebody planform area.[14][15] The team extensively used analytical and empirical methods including computational fluid dynamics and computer-aided design software, wind tunnel testing (18,000 hours for Dem/Val), and radar cross-section (RCS) calculations and pole testing. Avionics systems were tested in ground and flying laboratories.[16] During Dem/Val, the SPO used trade studies from both teams to review ATF requirements and adjust ones that were significant weight and cost drivers while having marginal value. The short takeoff and landing (STOL) requirement was relaxed to delete thrust-reversers, saving substantial weight. Side looking radars 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 the contractor teams to rein in weight, the takeoff gross weight estimates grew from 50,000 to 60,000 lb (22,700 to 27,200 kg), resulting in engine thrust requirement increasing from 30,000 to 35,000 lbf (133 to 156 kN) class.[17]

Each team built two prototype air vehicles for Dem/Val, one for each of the two engine options. 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 Dem/Val flight test of the demonstrator prototypes at Edwards Air Force Base, the teams submitted the results and their design proposals — or Preferred System Concept — for full-scale development in December 1990; on 23 April 1991, Secretary of the USAF Donald Rice announced the Lockheed team and Pratt & Whitney as the winners of the ATF and engine competitions.[18] 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.[19][20] The press also speculated that the Lockheed team's design was more adaptable to the Navy Advanced Tactical Fighter (NATF) for replacing the F-14 Tomcat, but by fiscal year (FY) 1992, the U.S. Navy had abandoned NATF due to cost.[21]

Full-scale development
As the program moved to full-scale development, or Engineering & Manufacturing Development (EMD), the production F-22 design (internally designated as Configuration 645) evolved to have notable differences from the immature YF-22 demonstrator, despite having similar configuration.[N 7] The external geometry saw significant alterations; the wing's leading edge sweep angle was decreased from 48° to 42°, while the vertical stabilizers were shifted rearward and decreased in area by 20%.[23] The radome shape was changed for better radar performance, the wingtips were clipped for antennas, and the dedicated airbrake was eliminated. To improve pilot visibility and aerodynamics, the canopy was moved forward 7 inches (18 cm) and the engine inlets moved rearward 14 inches (36 cm). The shapes of the fuselage, wing, and stabilator trailing edges were refined to improve aerodynamics, strength, and stealth characteristics. The internal structural design was refined and reinforced, with the production airframe designed for a service life of 8,000 hours.[22][24] The revised shaping would be validated with over 17,000 additional hours of wind tunnel testing and further RCS testing at Helendale, California and the USAF RATSCAT range before first flight. Increasing weight during EMD due to demanding ballistic survivability requirements and added capabilities caused slight reductions in projected range and maneuver performance.[25]

An EMD F-22 alongside the Flying Test Bed
Aside from advances in air vehicle and propulsion technology, the F-22's avionics were unprecedented in terms of complexity and scale for a combat aircraft, with the fusion of multiple sensors systems and antennas, including integrated electronic warfare and integrated communication, navigation, and identification (CNI), and software integration of 1.7 million lines of code written in Ada; the avionics often became the pacing factor of the whole program. In light of rapidly advancing computing and semiconductor technology, the avionics was to employ the Department of Defense's (DoD) PAVE PILLAR systems architecture and Very High Speed Integrated Circuit (VHSIC) program technology; the avionics had computing and processing requirements equivalent to multiple contemporary Cray supercomputers in order to achieve sensor fusion.[26][27] To enable early looks and troubleshooting for mission software development, the software was ground-tested in Boeing's Avionics Integration Laboratory (AIL) and flight-tested on a Boeing 757 modified with F-22 mission systems, called Flying Test Bed, as an avionics laboratory.[28][29] Because much of the F-22's avionics design occurred in the 1990s as the electronics industry was shifting from military to commercial applications as the predominant market, avionics upgrade efforts would initially be difficult and protracted due to changing industry standards; for instance, C/C++ rather than Ada became predominant programming languages.[30]

Manufacturers of the F-22
The roughly equal division of work amongst the team largely carried through from Dem/Val to EMD, with prime contractor Lockheed responsible for the forward fuselage and control surfaces, General Dynamics for the center fuselage, and Boeing for aft fuselage and wings. Lockheed acquired General Dynamics' fighter portfolio at Fort Worth, Texas in 1993 and thus had the majority of the airframe manufacturing, and would merge with Martin Marietta in 1995 to form Lockheed Martin. While Lockheed primarily performed Dem/Val work at its Skunk Works sites in Burbank and Palmdale, California, it would shift its program office and EMD work from Burbank to Marietta, Georgia, where it performed final assembly; Boeing manufactured airframe components, performed avionics integration and developed the training systems in Seattle, Washington. The EMD contract originally ordered seven single-seat F-22As and two twin-seat F-22Bs, although the latter was canceled in 1996 to reduce development costs and the orders were converted to single seaters.[31] The first F-22A, an EMD aircraft with tail number 4001, was unveiled at Air Force Plant 6 in Dobbins Air Reserve Base in Marietta on 9 April 1997 where it was officially named "Raptor".[N 8] The aircraft first flew on 7 September 1997, piloted by chief test pilot Alfred "Paul" Metz.[N 9][33][34] The Raptor's designation was briefly changed to F/A-22 starting in September 2002, mimicking the Navy's McDonnell Douglas F/A-18 Hornet and intended to highlight a planned ground-attack capability amid debate over the aircraft's role and relevance. The F-22 designation was reinstated in December 2005, when the aircraft entered service.[35][36]

Rear/starboard view of aerial refueling tanker transferring fuel to a jet fighter via a long boom. The two aircraft are slightly banking left.
An EMD F-22 refuels from a KC-135 during testing; the attachment on the back top is for a spin recovery chute
The F-22 flight test program consisted of flight sciences, developmental test (DT), and initial operational test and evaluation (IOT&E) by the 411th Flight Test Squadron (FLTS) at Edwards AFB, California, as well as follow-on OT&E and development of tactics and operational employment by the 422nd Test and Evaluation Squadron (TES) at Nellis AFB, Nevada. Nine EMD jets assigned to the 411th FLTS would participate in the test program under the Combined Test Force (CTF) at Edwards. The first two aircraft conducted envelope expansion testing such as flying qualities, air vehicle performance, propulsion, and stores separation. The third aircraft, the first to have production-level internal structure, tested flight loads, flutter, and stores separation, while two non-flying F-22s were built for testing static loads and fatigue. Subsequent EMD aircraft and the Boeing 757 FTB tested avionics, environmental qualifications, and observables, with the first combat-capable Block 3.0 software flying in 2001.[37] Air vehicle testing resulted in several structural design modifications and retrofits for earlier lots, including tail fin strengthening to resolve buffeting at certain conditions.[38] Raptor 4001 was retired from flight testing in 2000 and subsequently sent to Wright-Patterson AFB for survivability testing, including live fire testing and battle damage repair training.[39] Other retired EMD F-22s have been used as maintenance trainers.[40]

An EMD F-22 of the 411th FLTS flies over Edwards AFB, California, in 2018
Because the F-22 had been designed to defeat contemporary and projected Soviet fighters, the end of the Cold War and the dissolution of the Soviet Union in 1991 would have major impacts on program funding; the DoD reduced its urgency for new weapon systems and the following years would see successive reductions in its budget. This resulted in the F-22's EMD being rescheduled and lengthened multiple times. Furthermore, the aircraft's sophistication and numerous technological innovations required extensive testing, which exacerbated the cost overruns and delays, particularly from the mission avionics. Some capabilities were also deferred to post-service upgrades, reducing the initial cost but increasing total program cost.[41][42] The program transitioned to full-rate production in March 2005 and completed EMD that December, after which the test force had flown 3,496 sorties for over 7,600 flight hours.[39] As the F-22 was designed for upgrades throughout its lifecycle, the 411th FLTS and 422nd TES would continue the DT/OT&E and tactics development of these upgrades.[40] Derivatives such as the X-44 thrust vectoring research aircraft and the FB-22 medium-range regional bomber were proposed in the late 1990s and early 2000s, although these were eventually abandoned. In 2006, the F-22 development team won the Collier Trophy, American aviation's most prestigious award.[43] Due to the aircraft's sophisticated capabilities, contractors have been targeted by cyberattacks and technology theft.

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