Lockheed Martin F/A-22 Raptor

Last revised May 30, 2004


The F/A-22 Raptor has its origin as far back as the early 1970s with a Tactical Air Command (TAC) study known as TAC-85. In 1969-70, even before the F-15, F-16 and A-10 had entered service with the USAF, the TAC-85 study begin exploring the question of what their successor might look like. The results of this study led to TAC issuing a Concept of Operations in 1971 for what they called the Advanced Tactical Fighter (ATF).

At that time, the ATF concept was still fairly vague, and there were only some relatively small-scale studies that were carried out during the early 1970s. In early 1975, the USAF Systems Command actually developed a plan to build two sets of ATF prototypes in 1977-81, but there was no money available to fund such a project at that time.

In 1978, the USAF split the ATF concept into two separate projects, one known as the Enhanced Tactical Fighter (ETF) and the other known as the Advanced Tactical Attack System (ATAS). The ETF would be a near-term project, whereas the ATAS would be a longer-term project which would concentrate on the development of new weapons and other advanced technologies. Initially, the emphasis was to be on the ground-attack mission, since it was assumed that the F-15 and F-16 would be able to deal adequately with the Soviet fighters then in service. However, the appearance of new Soviet fighters such as the MiG-29, Su-27, and the MiG-31 caused the USAF to reconsider its philosophy and to contemplate the development of air-to-air and air-to-ground aircraft in parallel. In April of 1980, the ETF project was shelved, and the ATAS project was redesignated the ATF. It was hoped that both air-to-air and air-to-ground roles could be incorporated in the same aircraft. In addition, it was decided that the possibility of incorporating Short Take-Off and Landing (STOL) capability into the design should also be explored.

The first Request For Information (RFI) for the Advanced Tactical Fighter was issued to the industry in June of 1981. In the RFI, nine companies were invited to submit bids: Boeing, Fairchild, General Dynamics, Grumman, Lockheed, McDonnell Douglas, Northrop, Rockwell, and Vought. An RFI for the engine was issued a month later. Since the USAF had really not yet decided on what kind of aircraft they wanted, RFI was basically a request from the Air Force for the industry to tell them what the requirements for the new aircraft should be.

Seven companies actually responded to the RFI. By October 1982, the USAF had digested the RFI responses that came in and decided that supercruise capability should be an important requirement for the future ATF. NATO commanders had expressed pessimism about the survivability of its forward-based fighter and attack forces in the event that a war broke out in Europe. Control of the skies above central Europe would probably have to be maintained by fighters based in the Benelux countries or in the United Kingdom. In such a scenario, the ability of an aircraft to fly at supersonic speed without afterburning and thus to fly supersonically for the entire mission segment that lay over hostile territory would, it was hoped, reduce the fighter's exposure to enemy SAMs. It was also recommended that the aircraft should have a greater range than that of the F-15, which would allow it to operate from more distant, safer airbases. Short Take-Off and Landing (STOL) capabilities would also be important, since STOL would make it easier to continue operations from damaged airfields.

In addition, the Air Force wanted an attempt to be made to reverse the trend of rapidly increasing cost and complexity that seemed to occur with every new generation of fighters. In support of this goal, the Air Force wanted to set a limit on the size and weight of the ATF aircraft, and strongly recommended the use of new technology to reduce the cost of acquiring and supporting the new fighter.

By the early 1980s, the air-to-ground mission for the ATF began to appear less urgent, since the projected F-117A "stealth fighter" that was currently under development should be able to penetrate the air defenses of the Warsaw Pact in the event of a European war. Also, the F-111 would, it was thought, still remain effective even into the 1990s. In addition, General Dynamics and McDonnell Douglas had both demonstrated that both the F-15 and F-16 fighters could be successfully modified into strike aircraft, which meant that it would probably be safe to optimize the ATF for an air-to-air role. By mid-1983, the USAF had adopted this philosophy and had reoriented the ATF concept as a primarily air-to-air fighter, and had defined the ATF concept as an F-15 replacement that would be capable of supersonic flight without afterburning, with a greater range than the F-15 but with a similar armament, and with thrust vectoring and reversing engine nozzles provided for STOL performance.

At that time, it was anticipated that the ATF would be ready in time to start entering service in the late 1990s, with the ATF being the primary fighter in service with the USAF by the time the new century began.

In October of 1982, representatives from most of the American fighter manufacturers met with USAF representatives in Anaheim, California to discuss the ATF project. They came up with a concept for an aircraft capable of supersonic cruise performance, a combat radius of 600-800 nautical miles, and the ability to take off and land in a 2000-foot runway. The normal takeoff weight should be no greater than 60,000 pounds in the air-to-air mission and 80,000 pounds for the strike mission. In late 1982, a Request For Proposals (RFP) was issued for the Concept Definition Investigation (CDI) stage of the ATF program. It was still hoped that the ATF could be introduced into service by the mid-1990s.

In May of 1983, the final RFP for the CDI phase was issued. At that time, the ATF project was still in the "white" unclassified world, and a lot of the project officers working on the ATF were unaware of the "black" stealth technology that was being developed. Once this project officers were made aware of this work, the ATF RTP was amended to include the incorporation of stealth technology.

In September 1983, concept definition contracts were issued to all of the companies which had responded to the RFP-Boeing, General Dynamics, Lockheed, McDonnell Douglas, Northrop, and Rockwell. The final reports were expected by May 1984.

A parallel program was initiated for the engine that would power the ATF, the project being known as the Joint Advanced Fighter Engine (JAFE). In May of 1983, even before it had released the RFP for the aircraft itself, the Air Force released its Request For Proposals (RFP) for the development of the engines for the ATF. The power plant for the ATF had to be self-starting, with autonomous ground check-out equipment based around very high thrust/weight ratios and high reliability values.

In September of 1983, Pratt & Whitney and General Electric were awarded contracts to design and build engines for the ATF. The Pratt & Whitney engine was known as the PW5000 by the manufacturer and as F119 by the Air Force. The General Electric engine was known as the GE37 by the company and as F120 by the Air Force. The engines were to be interchangeable in the ATF airframe, leaving either one of them to be applicable to the definitive fighter. There was to be a contest between these two manufacturers to see which one of them would build the engine for the production ATF.

By the end of 1984, the ATF requirement had reached a more definitive form. The requirement now called for a fighter with a Mach 1.5 cruising speed, a takeoff roll of only 2000 feet, a gross takeoff weight of no greater than 50,000 pounds and a combat radius of more than 700 nautical miles. The aircraft was to be capable of performing 5g turns at Mach 1 and 6g turns at Mach 1.5 at 30,000 feet. At 10,000 feet, the ATF was to be capable of pulling instantaneous turning acceleration loads as high as 9 gs at Mach 0.9 and was to be capable of performing sustained 2g turns at Mach 1.5 at 50,000 feet. At sea level, the ATF was to be capable of accelerating from Mach 0.6 to Mach 1.0 in 20 seconds. At 20,000 feet or 30,000 feet, the aircraft was to be capable of accelerating from Mach 0.8 to Mach 1.8 in 50 seconds. The unit flyaway cost was to be no more than $40 million in 1985 dollars (later reduced to only $35 million), and the life-cycle cost was to be no more than that of the F-15.

At first, the USAF wanted to develop the ATF through a "Demonstration and Validation" (Dem/Val) process rather than by having a flyoff competition between prototypes as was done in the case of the LWF contest that resulted in the F-16. The Dem/Val process would cover everything short of flight testing. Complete avionics systems would be tested in simulators, and the design would be tested in wind tunnels and on radar cross-section ranges. Full-scale mockups would be built, but flyable aircraft would not be. The winner of the Dem/Val phase would then be awarded a full-scale development (FSD) contract for a flyable aircraft.

In September of 1985, the Air Force issued a full Dem/Val Request for Proposals (RFP) for the ATF, specifying a submission deadline of January of 1986. At this time, the Air Force indicated the possibility of a procurement buy of as many as 750 aircraft. As part of the Dem/Val approach, full and reduced scale wind tunnel models would be built, with computational analysis being made of radar cross sections for low visibility. The deadline for the response to the RFP was later extended to April of 1986.

All seven competitors responded to the Dem/Val RFP. Boeing proposed a V-tailed, diamond-shaped wing design with a single shark-mouth chin-type intake to feed both engines. General Dynamics proposed a delta-winged design that reflected some of the work it had done on the F-16XL. There were two intakes, one located on each of the fuselage sides, just ahead of the leading edge of the wing. There was a single large vertical tail. There were two separate radar arrays fitted behind the cockpit, one over each of the air intakes. Lockheed's design closely paralleled that of the F-117 that was currently under development. It had an arrowhead planform and a leading-edge glove which extended in a straight line to the nose. It had conventional trapezoidal wings, vectored thrust, and a horizontal tail. The design had an internal weapons bay, and featured twin outward-canted vertical tails. The McDonnell Douglas design had a single wedge-shaped chin inlet and sharply swept wings. Northrop's design had a diamond-shaped wing and an internal weapons bay, but did not have thrust vectoring. The Rockwell design had a large, highly blended delta wing. The Grumman design has never been described in any detail, but might have featured a forward-swept wing.

In April of 1986, the US Navy decided to get involved in the ATF program, and agreed that they would use the ATF as the basis for a replacement for the F-14D Tomcat. At the same time, it was agreed that the Air Force would develop an F-111 replacement from the Navy's Advanced Tactical Aircraft (ATA) program. The concept of a navalized ATF was especially attractive to a Congress that was keen to extract maximum utilization from an already strained defense budget.

In May of 1986, the USAF changed its mind and announced that instead of proceeding toward a single contractor at the end of the Dem/Val phase, two contractors would be selected to build prototypes for flight test. The two winning contractors would then compete against each other for a Full Scale Development (FSD) contract. The Packard Commission had strongly advocated the flight testing of prototypes in military procurement contests, and the USAF was under strong pressure to accept its recommendations, with the cost overruns and delays involved in the C-5A and F-111 projects being still fresh in the memories of many.

At first sight, Lockheed would seem to be an unlikely entrant into the ATF contest, and even less likely to have won. Lockheed had not built a successful fighter aircraft since the F-104 Starfighter of the mid-1950s. It is true that Lockheed had successfully integrated the first lookdown pulse-Doppler radar and shoot-down missile into the YF-12, but the company had not been a contender in the F-15 competition. However, Lockheed's Advanced Development Projects Division, better known as the "Skunk Works", had made a series of breakthroughs in low-observability technology during the mid-1970s. These culminated in the Senior Trend low-observability strike aircraft, which eventually emerged as the F-117A Nighthawk.

One of the first responses by Lockheed to the RFI had been a proposal for a high-altitude, highly supersonic aircraft that would be able to cruise well above its adversaries and shoot them down with long-range missiles. This concept was rejected as being too costly. In 1984-85, the Skunk Works went to work to see if it was possible to combine the newly-emergent stealth technology with supersonic speed and excellent maneuverability, something that was considered virtually impossible at the time. However, advances in computer technology had made it possible to do the mathematical modeling and simulations that were needed to design a stealthy aircraft which was also supersonic and capable of good maneuverability. The computers of the mid-1970s could only model the radar-scattering properties of flat surfaces, but the Cray supercomputer of the 1980s made it possible to handle the much more complex problem of curved surfaces. In addition, much more capable radar absorbent materials (RAM) were now available.

Early in 1985, before the final Dem/Val RFP was issued, Lockheed decided that it was unlikely that it could win the competition for full-scale development all by itself. In June of 1986, it was announced that Lockheed would form a team with Boeing and General Dynamics to develop an ATF entry. It was agreed that the company whose design won the Dem/Val contest would lead the team. Boeing would seem to be as unlikely an entrant in the ATF contest as Lockheed--Boeing had never built a manned supersonic aircraft nor had it ever even built a jet fighter, the company having specialized since the early 1930s in bombers, transports, tankers, and large commercial airliners. The last fighter built by Boeing was the unsuccessful F8B carrier-based fighter of World War 2 vintage. However, Boeing had always recognized that there was a large market for tactical fighters and had kept a design team working on these types of aircraft all throughout the 1970s.

At the same time, Northrop had announced that it would be teaming with McDonnell Douglas in the ATF competition.

Seven manufacturers responded to the RFP--Boeing, General Dynamics, Grumman, Lockheed, McDonnell Douglas, Northrop, and Rockwell. Grumman and Rockwell pulled out of the competition at an early phase. On October 31, 1986, Lockheed and Northrop were announced as the winners and were awarded contracts for the demonstration and validation phase of the program. Each group was to build two flyable prototypes. The designation YF-22A was assigned to the aircraft that would be built by the Lockheed-led team, with YF-23A being assigned to the plane to be built by the Northrop-lead team. Each aircraft would be capable of flying with either a pair of Pratt & Whitney F119 or a pair of General Electric F120 engines. At the completion of the competition, one of the teams would be awarded a Full-Scale Development (FSD) contract.

In 1987, the requirement for the use of thrust reversers was eliminated. The thrust reversers were designed to be used in flight, for deceleration in combat, and for speed control during approach and landing. During development, tests with the F-15 STOL/Maneuver Technology Demonstrator had found that these thrust reversers would be heavier and would require more cooling air than had been predicted. Consequently, late in 1987, the thrust reversers were eliminated from the ATF requirements. Without thrust reversers, the aircraft would land in 3000 feet rather than the 2000 feet that had been originally specified, but the additional weight and complexity needed for the extra 1000 feet of stopping space were deemed not to be worth the cost.

Lockeed assumed responsibility for the overall design of the YF-22A, and was to supply the forward part of the fuselage, including the cockpit. It would also handle most of the specialized stealth development work. Lockheed would also handle the final assembly in its facility at Palmdale, California. Boeing would build the wings and the aft fuselage and would install the engines. General Dynamics of Fort Worth, Texas would handle the center fuselage, the weapons bays, the empennage, and the undercarriage. The entire team would build a complete avionics system.

In mid-1987, the YF-22A design had to be significantly changed because of weight problems. A diamond-shaped wing replaced the less-tapered trapezoidal wing that had originally been planned. The long glove extending all the way to the nose was eliminated, since wind tunnel testing had revealed that the pitch-up forces generated by the glove could not be controlled by the tail surfaces. In addition, the horizontal tails were enlarged in area. The originally-proposed rotary weapons bay was replaced by a flat weapons bay. This redesign coincided with the elimination of the thrust reversers, which meant that the fuselage afterbody could now be made slimmer and lighter.

These extensive redesigns meant that the YF-22A would have to be delayed. By early 1989, it became clear that the YF-22A would not be ready to fly by the beginning of 1990. However, the Air Force agreed to extend the demonstration and validation program by six months.

In 1988, declining budgets forced the Air Force to cut the number of tactical fighter wings from 38 to 35. In 1988, USAF modernization plans now included 750 ATFs, to be delivered at a rate of 72 per year. Following the FSD go-ahead scheduled for 1991, deliveries of the first FSD aircraft were to begin during 1993, with the first aircraft entering service with the USAF in 1996. By late 1988, the ATF program had been extended by one year and the USAF declared a pilot production lot of 24 aircraft.

A draft request for proposals on the FSD phase was issued during August of 1989. On October 6, 1989, the Defense Acquisition Board approved a six-month delay in early design work, extending the Dem/Val phase to mid-1991. This delayed the FSD phase by one year. The Air Force agreed to issue the RFP for FSD at the end of October 1990 and to move to FSD in April 1991, at which time a single contractor would be selected.

The aircraft that finally emerged from the Lockheed/Boeing/General Dynamics team had a forward fuselage that was essentially diamond-shaped in cross-section, merging into a pentagonal mid-fuselage and a tapered flat rear fuselage. The body shape was designed with large flat sides which reflected the "faceting" philosophy that was used in the F-117A. However, the facet breaks are not nearly as sharp as they are on the F-117A, the facets are fewer in number, and curved surfaces are used on the aerodynamic surfaces and above and below the fuselage. The use of curved surfaces was made possible by the advent of Cray supercomputers to do the simulation of the radar reflectivity of various geometries. Air intakes flanked a short, tapered nose which accommodated the cockpit and most of the avionics. The inlet ducts curved inwards and upwards, shielding the front faces of the engines from direct illumination by hostile radars. In the critical front quadrant, it is estimated that the radar cross-section of the YF-22A is about 100 times smaller than that of the F-15.

The aircraft is about the same size as an F-15, but is heavier, weighing about 62,000 pounds in clean condition.

Since variable-geometry intake ramps would be incompatible with stealthy design, the wedge-shaped air intakes were designed to be of fixed geometry with no moving parts. The inlets were of the two-shock variety, and the ramp angles were chosen for optimal efficiency at Mach 1.5. There were spill doors mounted immediately behind the top lip which dump excess air from the inlet at low speeds and low power settings. The intakes ensure low airflow distortion with good recovery and provide low observable characteristics as well as comprehensive boundary layer air bleed. The intakes were offset from the fuselage wall by several inches for effective boundary layer control. S-shaped intake tunnels carried air to the engines, the shape of the intake tunnels being deliberately designed so that the engine faces were completely invisible from any external look-angle. There were a pair of auxiliary blow-in inlets above the body just forward of the vertical tails which provided the engines with extra air for starting and takeoff.

The wing was designed with a diamond-shaped planform, which was actually fairly close to that of a delta with a 48 degree sweep on the forward edge, a nearly straight trailing edge, and a very small tip chord. The sharp taper reduces the bending loads across the wing because most of the lift is generated close to the root. The wing root chord at the fuselage centerline is 34 feet 6 inches, and the wing tip chord is 4 feet 2 1/2 inches. The wing has no twist or pronounced camber, and there are no foreplanes or leading-edge root extensions. Large integral fuel tanks are built into the wing structure.

The wing was fitted with full-span leading edge flaps. The trailing edge has large plain flaps inboard and smaller, tapered flaperons outboard. All of the wing surfaces droop at low speed to reduce takeoff and landing runs.

The forebody of the fuselage was provided with a sharp edge, or hard chine running from the tip of the nose to the upper inlet lip, and there was a small aerodynamic lip attached to the top outside corner of each inlet. These were designed to cause the formation of vortices at high angles of attack. As a result of these chines and lips, at high angles of attack a pair of strong vortices form over the fuselage center section and another pair form over the wings. Because of low pressure inside these vortices, additional lift can be generated, improving the controllability at high angles of attack. However, these vortices can have an adverse affect on the vertical tails-- they can cause aerodynamically buffeting, they can blanket the vertical tails so that they become aerodynamically ineffective, or they can form asymmetrically so that there is a destabilizing effect. Careful computational fluid dynamics calculations using supercomputers were needed to avoid these unwanted side effects.

A large speedbrake was installed on the upper fuselage between the two vertical tails. Like most of the other doors on the aircraft, the airbrake panel had serrated, dogtooth edges to suppress unwanted radar reflections.

The horizontal tail was set on two booms which extend beyond the ends of the engine exhausts. The stabilizers were located in the same plane as the wing and were so close to the wing that the wing and tailplane planforms actually merge smoothly together--the stabilizer leading edges fit neatly into cutouts at the roots of the wing flaps. In accordance with stealth principles, the horizontal tail has the same planform as the wing.

The twin vertical tails were canted outward by 27 degrees. When viewed from the sides, the large fins mask thermal images of the aircraft's tail and engine-exhaust areas and help to block infrared search scans from all but the rear and high elevation angles. The twin vertical tail surfaces are located well forward (like those on the F/A-18). They are unusually massive, and are 70 percent larger than those on the F-15. Because of anticipated problems with structural stresses caused by vortexes from the wing, it was decided not to use an all-flying vertical tail format, and there are two fixed vertical stabilizers with moveable rudders. The rudders account for almost a third of the total area.

Throughout the entire fuselage, all internal and external metal areas were coated with radar absorbent materials (RAM) and with radar absorbent paint (RAP). Considerable progress has been made in this area. When the first F-117A was flown, the RAP was expensive to apply and came off easily. The design of the various doors that are cut into the sides and top of the fuselage (e.g. for landing gear, weapons stowage, blow-in intakes, maintenance access, etc) posed a major challenge for designers trying to achieve low observability. Serrated edges were added to the doors to reflect radar returns in harmless directions. Intake and cooling vents which must remain open at all times are covered with a low-observable wire mesh to prevent enemy radar emissions from getting inside.

The F-22 was to be powered by a pair of advanced technology engines, mounted close together on the fuselage centerline, between the two booms that carry the tail surfaces. The AFF engines are of an advanced type, designed to make it possible to cruise for extended periods of time at supersonic speeds. Conventional fighter engines reach their compressor-exit temperature (CET) limits at speeds of about Mach 1, because of the rise in inlet temperature and pressure. At higher speeds, the engine must be throttled back to hold down the CET, and the extra thrust must come from the afterburner. The afterburner consumes fuel very rapidly, and supersonic flight must of necessity be fairly brief. In contrast, the ATF engines are designed to run at full throttle at speeds of up to Mach 1.5.

Both the YF119 and the YF120 engines are counter-rotating dual-spool, low bypass turbofans with single turbine disks in both low and high compression stages. Both engines have improved blade aerodynamics and structures, reducing the number of stages as well as the number of parts, and making it easier to cool. Both engines also make use of advanced materials and techniques such as composites, ceramic seals, hollow fan blades, and new heat-resistant coatings. The General Electric YF120 engine was apparently the more advanced of the two. The YF120 is a double-bypass variable-cycle powerplant that operates as a turbofan at subsonic speeds and as a turbojet at supersonic speeds. The F120 engine has a low pressure rotor consisting of a two-stage fan and a single-stage high-pressure turbine with a triplex digital control unit mounted on the power plant itself. The YF119 is based around a conventional cycle with an advanced fuel control and management system. It is basically a low-bypass ratio (0.2 to 1) turbofan. The F119 incorporates a three-stage fan as the low-pressure rotor with a singe-stage high-pressure turbine stage and a six-stage high pressure compressor, also driven by a single-stage turbine. Exit guide vanes are cast as an integral part of the strutless diffusers, and a fully-modulating cooling diffuser is located ahead of the two-dimensional convergent-divergent nozzle.

The two-dimensional engine nozzles of the YF-22A can be vectored 20 degrees up or down at any power setting. Vectored thrust is most effective at high engine power and is most useful at each end of the speed range. Continuous vectored thrust can also be used for high-speed turns (e. g. 6 g at Mach 1.8 is an ATF objective), where horizontal tail authority might not be sufficient. Vectored thrust also improves roll control. An afterburner is incorporated for use in combat or for Mach 2 plus dash speeds.

Combining low-observable technology with the requirement for high maneuverability required the use of fly-by-wire controls. The FBW system for the F-22 was developed by General Dynamics. Air data sensors, rate gyroscopes, and accelerometers feed information into the computer, where it is integrated with inputs from the pilot's controls. The central computer then coordinates the operation of leading-edge flaps, ailerons, tailplanes, rudders, airbrake, and thrust-vectoring nozzles.

Roll and yaw is effected by a combination of differential movement of the ailerons, flaperons, and the tailplane. The rudders also provide directional control and feed coordination functions during complex integrated maneuvers. Pitch control is provided by coupled commands to the tailplane and to the thrust-vectored nozzles. The leading edge surfaces operate automatically according to angle of attack, airspeed, altitude, and data inputs from the FBW system.

There is a receptacle for a boom-type midair refuelling probe in the upper fuselage, located between the blow-in auxiliary intake doors that are just forward of the vertical tails. This receptacle is covered by a door when not in use.

In the interest of achieving low-observability, all of the air-to-air weapons are carried internally. There are three weapons bays. Two of the weapons bays are located on the sides of the fuselage (one on each side) immediately aft of the cheek intakes, the rear wall of each bay forming the forward wall of the main undercarriage bays. Each side bay can accommodate two AIM-9 Sidewinder infrared-homing air-to-air missiles and is covered by two separate doors. When a Sidewinder missile is fired, the weapons bay doors snap open, the Sidewinder missile swings outward on a trapeze, the missile's infrared seeker locks onto its target, the missile is fired, the trapeze swings back in and the doors close. The quicker this is done, the less likely it is than an enemy could pick up a radar return from the open weapons bay. A third weapons bay is located underneath the fuselage and can carry four or six AIM-120C AMRAAM radar-guided air-to-air missiles. The main bay is covered by two hinged doors, each consisting of two lengthwise fold-back panels. When an AMRAAM is fired, the door is opened and the missile is dropped. The door can be closed right away, because the missile's engine does not ignite until it drops free of the aircraft. The leading and trailing edges of the main weapons bay doors carry serrated edges for low observability.

Although designed largely for internal weapons carriage in the interest of stealth, the F-22 can be fitted with four external weapons pylons under the wings. These could be used for ferry purposes or for operations in which stealth is unnecessary.

The main landing gear members retract forward into bays in the fuselage sides immediately aft of the side weapons bays underneath the wings. These doors have serrated edges for low radar observability. The steerable nosewheel retracts forward into a well between the air intakes. All three undercarriage units are operated via independent hydraulic rams and each wheel has an anti-skid disc brake unit.

About 23 percent of the structure of the prototypes is made up of composite materials, and it is planned for about 40 percent of the production F-22 to be made of composite materials. Some of the high-temperature structural components are made from carbon fibres embedded in a bismaleimide matrix, which can supposedly tolerate higher thermal stresses then the epoxy materials that are currently used. Wing skins are made from carbon fibers in a thermoplastic matrix. The advantage of thermoplastics is that they can be reheated and reformed, lowering the cost of manufacturing and repairing complex components.

The pilot's cockpit is what has come to be known as a "glass" cockpit. The control panel has no dials or gauges, and all information is presented to the pilot on screens or as holographic images on the heads-up display (HUD). The cockpit has two 8x8 inch primary multifunction displays, flanked by three 6x6 inch secondary MFDs, all in full color. There is a three-color up-front control underneath the HUD. All of the displays are liquid-crystal-display (LCD) panels, which replace the conventional cathode-ray tubes used by previous "glass"-cockpit aircraft. The F-22 is the first military aircraft to feature this technology. At first, the liquid crystal displays were provided with finger-on-glass (FOG) panels, but a lack of tactile feedback during tests led to a decision to revert to pushbutton switches surrounding the screens.

In the production aircraft which will carry a full avionics suite, the primary screens will provide tactical situation information while the secondary screens will provide offensive and defensive systems data. Voice annunciators will present vital advisory and cautionary information to the pilot. It will be arranged so that these voice annunciators will present only the most urgent information and will avoid overloading the pilot with things he or she does not need to know.

Control of all aircraft functions is handled by a hands-on throttle and stick (HOTAS) that gives the pilot access to all the selection modes he or she needs to complete an attack. The YF-22A has a central control column, but this will be replaced by a sidestick controller in production machines.

The cockpit canopy is frameless and is shaped and coated to eliminate radar reflections. The single-piece acrylic laminate canopy was only for the prototypes. Indium tin oxide will be added to the laminate in production machines to reduce the radar return. Great emphasis was placed on the design of the cockpit for low observability, and careful selection of proper materials for the control panel, ejector seat, and canopy was a vital part of achieving a stealthy interior.

The pilot's seat is upright, studies having shown that the inclination would have to be at least 65 degrees to provide any significant benefit to a pilot's g-tolerance. The two YF-22A prototypes have the ACES II ejector seat, but the production machines will have a modified Weber seat.

Not many details have been published about the avionics suite that will be fitted to production F-22s. It is known that the avionics suite will include a Northrop Grumman/Raytheon APG-77 active-array, electronically-scanned radar and a Sanders/General Electric ALR-94 integrated electronic warfare system. The sensor antennae for the ALR-94 system are smoothly blended into the skin, and the system can positively identify the target, determine its bearing and its range. The avionics systems are tied together by a computer system. The radar is designed to provide the pilot with a first-look, first-launch, first-kill capability. It has long range and high resolution for the early detection of enemy fighters. It has a low passive-detection signature which is designed to allow the F-22 to approach very close to its target before being detected. The Lockheed Martin AAR-65 Missile Launch Detector comprising six IR focal plane arrays located around the nose is used to warn of immediate treats from enemy missile launches.

Two YF-22A prototypes had been ordered, one to be powered by a pair of F120 engines and the other to be powered by F119 engines. The first YF-22A was ready by June 1990. However, at that time the General Electric F120 engines that were to power the aircraft had not yet been qualified for flight by the Air Force. Lockheed briefly considered switching its initial efforts to the second prototype, which was to be powered by the competing Pratt & Whitney F119 engine, but decided to stick with the original schedule.

The two YF-22As were integrated and assembled at Lockheed's facility at Palmdale, California. The first YF-22A was officially unveiled at a ceremony at Palmdale on August 29, 1990. Rather unusually, the aircraft bore a civilian registration number N22YF rather than a USAF serial number. It flew for the first time on September 29, 1990, with Lockheed test pilot Dave Ferguson at the controls. It was powered by a pair of General Electric YF120 engines. The first flight was a short hop from Palmdale to Edwards AFB. The flight was considerably shorter than planned because of a minor fault with telemetry equipment which required repair at the end of Palmdale's runway, reducing the fuel load available and curtailing the opportunity to perform a number of tests.

The YF-22A achieved supersonic speed for the first time on October 25.

The second YF-22 followed on October 30, with Lockheed test pilot Tom Morgenfeld at the controls. It bore the civilian registration of N22YX and was powered by a pair of Pratt & Whitney YF119 engines. Neither of the two test aircraft carried any radar, nor were they equipped with cannon armament. However, they were capable of carrying and launching AMRAAM and Sidewinder air-to-air missiles.

Early in November of 1990, YF-22 N22YF achieved one of the important milestones of the ATF program, when it attained a speed of Mach 1.58 without using afterburners. Optimal supercruise speed was Mach 1.58 for N22YF and Mach 1.43 for N22YX. With afterburning, both aircraft could easily exceed Mach 2 at 50,000 feet.

The first thrust-vectoring by the YF-22A was performed by N22YF on November 15, with test pilot Dave Ferguson exploring the roll response enhancement that this feature could afford. With 2-dimensional thrust vectoring, the aircraft could achieve supersonic roll and pitch rates in excess of those that can be achieved by a conventional fighter at subsonic speeds. At speeds above Mach 1.4, the two-dimensional nozzles improved turning rates by about 35 percent. The YF-22A was able to perform maneuvers when it was far beyond the stall angle of attack and could perform bank-to-bank rolls at speeds as low as 80 knots and angles of attack as high as 60 degrees. Enhanced agility at high angles of attack will give the F-22A an important edge over other fighters, allowing weapons lock-on with a conventional aircraft that is unable to avoid flick-pointing. The nozzles give a four-fold improvement in pitch-down nose recovery, allowing the aircraft to resume normal flight attitudes within a second.

On November 28, 1990, YF-22 number two achieved another first for the ATF program when test pilot Jon Beesley test-fired an AIM-9M Sidewinder during a flight over the Navy's China Lake range. On December 20, test pilot Tom Morgenfeld fired an AIM-120 AMRAAM from YF-22 number two during a flight over the Pacific Missile Test Center range at Point Mugu, California.

On April 23, 1991, the Air Force announced that the Lockheed group had won the Demonstration/Validation phase of the ATF contest. At the same time, the Pratt & Whitney F119 entry was selected as the winning engine. On August 3, 1991, the Air Force formally awarded an Engineering, Manufacture, and Development (EMD) contract to the Lockheed team. The first of 11 EMD aircraft (including two F-22B two-seaters) was due to fly in 1995. Initial operating capability (IOC) was set for 2001.

N22YX with its YF119 engines went back into the air on October 30, 1991 for more flight tests. N22YF was stripped of its General Electric engines and was moved to Lockheed's Marietta, Georgia facility for EMD systems mock-up tests.

Unfortunately, N22YX was involved in a major accident on May 25, 1992 when it belly-flopped onto the runway after 8 seconds of violent pilot-induced oscillations. It slid several thousand feet down the runway and caught fire, destroying some 25 percent of the airframe. Pilot Tom Morgenfeld was uninjured, but the aircraft was deemed too badly damaged for economical repair.

At the time of the crash, Morgenfeld had been carrying out a planned go-around, and he had just switched on his afterburners and had retracted his undercarriage at less than 50 feet off the runway with thrust vectoring active. At a speed of 175 knots, the aircraft began an uncommanded pitchup followed by a severe stick-forward command from the pilot. The aircraft then entered a series of pitch oscillations, with rapid tail and thrust nozzle fluctuations, exacerbated by control surface actuators hitting rate limiters causing commands to get out of synchronization with their execution.

An investigation later showed that Morgenfeld had ignored a test-card that required that the vectoring nozzles to be locked into position in just such a configuration that he had found himself at the time of the crash. However, most engineers had also ignored this instruction since they thought it to be unnecessary. At the time of the accident, the aircraft had made some 760 flights and had logged 100.4 hours in the air.

After this accident, no further flight testing of the prototypes was carried out, and the program moved into the EMD phase. The other YF-22 (N22YF) was later stripped of its engines and was used for ground testing. N22YF is now on display at the USAF Museum in Dayton, Ohio.

By early 1992, the definitive shape of the EMD F-22 had been finalized. There were some important changes. The length was reduced to 62 feet 6 inches, the wing span was increased to 44 feet 6 inches, and the wing sweep angle was decreased to 42 degrees. Other edges that had to be aligned with the wing sweep angle for low RCS were also changed to 42 degrees. The wing shape was modified to incorporate a clipped section between the ailerons and the tip. The thickness of the root was decreased and the camber and twist were modified. The engine inlets were moved aft by 1 foot 5 3/4 inches. The entire cockpit was moved further forward, with subsequent changes to the nose and radome profile, giving the forward fuselage a blunter shape. The tail surfaces were modified, with the fin/rudder being decreased in area and the horizontal tail being increased in area. The tail planform was modified to a diamond shape, and the aircraft height was reduced to 16 feet 5 inches.

The production F-22A will carry a single General Electric M61A2 20-mm cannon above and aft of the starboard engine intake. This is an improved, lighter version of the standard M61A1 cannon that has been carried by US fighters since the 1950s. Production F-22s will also have a ground-attack capability, and will be provided with two sets of hardpoints underneath each wing, although the carriage of external stores will severely degrade the low-observable characteristics of the aircraft. The aircraft will be able to carry a pair of Joint Direct Attack Munitions (JDAM) in the under-fuselage weapons bay and two Tri-Service Stand-Off Attack Missiles (TSSAMs) underneath the wing for deep strike missions. The JDAM is a 1000-lb smart bomb that dispenses infrared/acoustic-guided submunitions. The early versions of the JDAM will be directed by a GPS guidance system, but this will perhaps be replaced with an image seeker in a later version. The Air Force may even want to equip the F-22 with HARM missiles for anti-radiation missions.

Initial Operational Capability (IOC) has slipped steadily over the years. The decision to build prototypes meant that the Dem/Val program had to be extended for a longer time than expected. Metal for the first EMD aircraft was first cut in December of 1993. By that time, the number of pre-production aircraft on order had been cut to nine. The first three EMD F-22s were be used primarily for airframe tests, and the fourth will be used for avionics tests. The seventh and ninth aircraft were to be two-seat F-22Bs, whereas the eighth was to carry out low-observability tests. The nine EMD F-22A and B aircraft were to be followed by four Pre-Production Verification (PPV) aircraft.

Exactly how many production F-22s will be built is still uncertain, since the deployment plans for the F-22 are continuously in flux because of funding cuts and budgetary uncertainties. The initial 1985 RFP had indicated a requirement for 760 aircraft, but budget cuts and force realignments have steadily reduced the total numbers expected to be built. In 1993, the Pentagon cut the planned F-22 fleet from 648 to 442, and then cut it again to 339 in mid 1997. In July of 1996, the USAF deferred the development of the F-22B two-seater and cut the two F-22Bs from the test program, leaving only seven EMD prototypes.

The first of seven F-22A EMD prototypes (91-4001, c/n 4001, named Spirit of America) was unveiled to the public at the Lockheed Martin plant at Marietta, Georgia on April 9, 1997. It was announced that the name Raptor has been chosen for the aircraft. Raptor 01 (as the plane was labeled) was equipped with a pair of vectoring exhaust Pratt & Whitney F119-PW-100 engines, rated at 35,000 lb.s.t. each with afterburning. It flew for the first time on September 7, 1997. The plane was delivered to Edwards AFB aboard a C-5 transport on February 5, 1998. It was reflown for the first time at Edwards AFB on May 17, 1998.

The second EMD F-22A prototype (91-4002, c/n 4002) was rolled off the production line at Marietta, Georgia on February 10, 1998. It flew for the first time on June 29, 1998, and flew cross-country to Edwards AFB on August 26, 1998 to join 91-4001 in the test program. By the end of 1998, the first two F-22s had been able to reach a speed of Mach 1.4 without afterburning.

The third F-22A (91-4003, c/n 4003) was rolled of the production line in Georgia on May 22, 1999. Technically, this was actually the fourth F-22A off the production line, since the third F-22A (3999) serves as a static test vehicle. 91-4003 flew for the first time on March 6, 2000. The plane was the first of the Block 2 F-22s, which is the first Raptor to have an internal structure that is fully representative of the production version. It also had full-envelope flight capability. The fourth Raptor (91-4004) was to be the first F-22 with fully-integrated avionics

A Boeing 757-200 (c/n 22212, registration N757A) was converted as an avionics laboratory to test the radar and other electronics systems. The aircraft was fitted with an F-22 forward fuselage as well as a sensor wing on top of the fuselage just aft of the flight deck. The 757 testbed flew for the first time on March 11, 1999.

Anxiety over the rising costs of the F-22--along with the general opinion that the threat that it was designed to counter no longer existed and that no current or conceivable future threat justifies the expense--led to a move in Congress to remove six F-22 aircraft from the Air Force FY 2000 budget. In July of 1999, the House of Representatives voted to cut the six F-22s that had been planned for FY 2000 out of the budget and to re-allocate the money to more F-15Es, F-16CJs and C-130Js. However, the Senate readily approved the six FY2000 fighters, and a compromise was reached in conference in which the six F-22As requested would be procured as Production Representative Test Vehicle II (PRTV II) aircraft and not as Low Rate Initial Production (LRIP) aircraft. The procurement of ten LRIP aircraft in FY2001 were to be conditional on the test program attaining successful flight testing of the avionics software as well as a verification of its stealth capabilities. The contract for the six F-22 Production Representative Test Vehicle II aircraft was awarded to Lockheed Martin on December 30, 1999. The first PRTV II aircraft were be delivered by March 2002.

On August 25, 1999, the Raptor achieved flight in excess of 60 degrees angle of attack. Raptor 01 demonstrated its supercruise capability on July 21, 1999 by sustaining Mach 1.5 without afterburner.

On August 15, 2001, the Pentagon's Defense Acquisition Board approved LRIP for the F-22A, but reduced the total order from 339 to 295. Construction began on the first operational aircraft (01-4018) and it was announced that the first 13 Raptors in Lot 2 would enter service with the 325th Wing at Tyndall AFB beginning in 2003. It was announced that some Raptors would go the the 57th Fighter Wing at Nellis AFB for operational development work. The first operational wing would be the 1st FW, based at Langley AFB, VA.

The final flight test aircraft (91-4009) under the Engineering and Manufacturing Development (EMD) phase contract, was delivered to the USAF on Apr 15, 2002. It was dedicated to the evaluation of the ease of maintenance and repair for the Raptor. After these tests were completed, the plane was delivered to Edwards AFB to join the other six F-22s already there.

On April 25, 2002, the latest Block 3.1 avionics software package was flight tested on 91-4006 at Edwards AFB. This software provides more than 90 percent of that required for full functionality in production Raptors.

Alarmed at the high cost of the F-22A program , some people in Congress insisted on an air-to-ground role for the Raptor, and work was initiated in determining if the two internal weapons bay could accommodate air-to-ground weapons such as the GBU-32 JDAM, as well as 1000-pound bombs. In order to keep Congress happy, on September 17, 2002, General John Jumper, the Air Force Chief of Staff, announced that the Raptor was going to be redesignated F/A-22 to indicate the support of a dual-role mission. At that time, the USAF had the goal of acquiring 339 Raptors, although up to 762 Raptors could ultimately be required.

At the same time, Air Force Secretary James Roche announced that the 1st Fighter Wing at Langley AFB would develop a limited air-to-ground mission in addition to its primary air-to-air role. The basic problem is that if the air-to ground mission requires stealth, the Raptor will not be able to carry air-to-missiles in the weapons bay, nor will it be able to carry anything on underwing pylons, thus entirely losing its air-to-air capability. However, if stealth is not required, the aircraft can be equipped with four underwing stations that can carry bombs, missiles, or 600 gallon fuel tanks. Each station can carry up to 5000 pounds of weapons or fuel.

Raptor number 10 (99-4010), the first Production Representative Test Vehicle, was formally accepted by the USAF on October 23, 2002. It was assigned to Edwards AFB to serve with the Air Force Operaational test and Evaluation Center to support the Dedicated Initial Operational Test and Evaluation phase.

On November 5, 2002, Lockheed Martin was awarded a contract for Low Rate Initial Production Lot 3, comprising 16 aircraft.

Raptor number 11 (99-4011), the last Dedicated Initial Operational Test and Evaluation aircraft, made its first flight on September 16, 2002 and was formally accepted by the USAF on November 26, 2002. On November 22, aircraft 4007 succeeded in launching an unarmed AIM-9M missile. Also accomplished in 2002 was the interception of an aerial target by an AIM-120 launched from a supercruising F/A-22.

The first F/A-22A Raptor (00-4012) was delivered to Nellis AFB, Nevada on January 14, 2003. A further seven Raptors will are scheduled to join 00-4012 with the 422nd Test and Evaluation Squadron by the end of 2004, with nine more due to join the 57th Wing at Nellis AFB between 2008 and 2009. The Block 4 F-22A is scheduled for introduction into service in 2005. It may turn out that F-22 serves with the USAF for forty years, perhaps not being replaced by some later type until the year 2045.

There ia a proposal for an enlarged derivative of the Raptor, the FB-22. It is intended as a pure bomber and is proposed as a replacement for the B-52, B-1B, and B-2. It will have the same stealth characteristics as the Raptor, but will be able to carry up to 30 small-diameter bombs at supersonic speeds at ranges as high as 2000 miles without the need for midair refuelling. This project is at the preliminary concept stage, and time will tell if it ever evolves into anything practical.

Serials of Lockheed Martin F/A-22 Raptor

91-4001/4009		Lockheed F-22A Raptor
				EMD aircraft
99-006/007		Lockheed Martin F-22A Raptor
				PRTV aircraft.  Serials cancelled and replaced
				with 99-4010/4011.
99-4010/4011		Lockheed Martin F-22A Raptor
				c/n 4010/4011.  PRTV aircraft
99-4012/4017		Lockheed Martin F-22A Raptor
				c/n 4012/4017.  IP aircraft
99-4018/4025		Lockheed Martin F-22A Raptor
				c/n 4018/4025.  Reserved for future use
Ten Raptors are included in the FY2001 budget

Specification of Lockheed YF-22A

Engines: Two Pratt & Whitney YF119-PW-100 or two General Electric YF120-GE-100 afterburning turbofans, each rated at 35,000 lb.s.t.. Performance (estimated): Maximum speed at military power Mach 1.6 (1059 mph). Maximum speed Mach 2.2 (1450 mph) at maximum power with afterburning at altitude. Maximum speed Mach 1.2 (915 mph) at sea level. Maximum sustained cruising speed above 36,000 feet Mach 1.4-1.5 (925-990 mph). Service ceiling 65,000 feet. 3500 feet takeoff length. 750-800 nautical mile unrefuelled combat radius. Weights: 33,000 pounds empty, 58,000 pounds normal takeoff. 62,000 pounds combat takeoff weight. Dimensions: Wingspan 43 feet 0 inches, length 64 feet 2 inches, height 17 feet 8 7/8 inches, wing area 830 square feet. Four AIM-9 Sidewinder missiles are carried in internal bays in the sides of the engine intake ducts. Four AIM-120 AMRAAM missiles are carried in internal bays underneath the air intakes.

Sources:


  1. Lockheed F-22: Stealth with Agility, Bill Sweetman, World Airpower Journal, Volume 6, Summer 1991.

  2. From ATF to Lightning II: A Bolt in Anger. Design Options and the YF-23A, David Baker, Air International, December 1994.

  3. From ATF to Lightning II: A Bolt in Anger. Lockheed's YF-22A, David Baker, Air International, January 1995.

  4. Lockheed Martin F-22 Raptor, Bill Sweetman, World AirPower Journal, Vol 38, Fall 1999.

  5. Air Intel, Tom Kaminski, Combat Aircraft, Oct-Nov 1999.

  6. Airscene Headlines, Air International, April 2003.

  7. Classics Compared: F-86 Sabre and F/A-22 Raptor, Robert F. Dorr, Air International, February 2003.

  8. Airscene Headlines, Air International January 2003.

  9. Airscene Headlines, Air International November 2002

  10. Airscene Headlines, Air International October 2002.

  11. Airscene Headlines, Air International June 2002.