Friday, July 19, 2013

Lockheed Martin F-22 Raptor

Lockheed Martin F-22 Raptor


The Lockheed Martin/Boeing F-22 Raptor is a single-seat, twin-engine fifth-generation supermaneuverable fighter aircraft that uses stealth technology. It was designed primarily as an air superiority fighter, but has additional capabilities that include ground attack, electronic warfare, and signals intelligence roles.[5] Lockheed Martin Aeronautics is the prime contractor and is responsible for the majority of the airframe, weapon systems and final assembly of the F-22. Program partner Boeing Defense, Space & Security provides the wings, aft fuselage, avionics integration, and training systems.
The aircraft was variously designated F-22 and F/A-22 during the years prior to formally entering USAF service in December 2005 as the F-22A. Despite a protracted and costly development period, the United States Air Force considers the F-22 a critical component of U.S. tactical air power, and claims that the aircraft is unmatched by any known or projected fighter.[6] Lockheed Martin claims that the Raptor's combination of stealth, speed, agility, precision and situational awareness, combined with air-to-air and air-to-ground combat capabilities, makes it the best overall fighter in the world today.[7] Air Chief Marshal Angus Houston, former Chief of the Australian Defence Force, said in 2004 that the "F-22 will be the most outstanding fighter plane ever built."[8]
The high cost of the aircraft, a lack of clear air-to-air combat missions because of delays in the Russian and Chinese fifth-generation fighter programs, a U.S. ban on Raptor exports, and the ongoing development of the planned cheaper and more versatile F-35 resulted in calls to end F-22 production.[N 1] In April 2009, the U.S. Department of Defense proposed to cease placing new orders, subject to Congressional approval, for a final procurement tally of 187 operational aircraft.[10] The National Defense Authorization Act for Fiscal Year 2010 lacked funding for further F-22 production. The final F-22 rolled off the assembly line on 13 December 2011 during a ceremony at Dobbins Air Reserve Base.[11]
Starting in 2010, the F-22 was plagued by problems with its pilot oxygen systems which contributed to one crash and death of a pilot. In 2011 the fleet was grounded for four months before resuming flight operations, but reports of oxygen systems issues have continued.[12] In July 2012, the Air Force announced that the hypoxia-like symptoms experienced were caused by a faulty valve in the pilots' pressure vest; the valve was replaced and changes to the filtration system were also made.


Origins

Main articles: Advanced Tactical Fighter and Lockheed YF-22
An F-22 during takeoff, at Elmendorf AFB, Anchorage, Alaska
In 1981 the U.S. Air Force developed a requirement for an Advanced Tactical Fighter (ATF) as a new air superiority fighter to replace the F-15 Eagle and F-16 Fighting Falcon. This was influenced by the emerging worldwide threats, including development and proliferation of Soviet Su-27 "Flanker"- and MiG-29 "Fulcrum"-class fighter aircraft. It would take advantage of the new technologies in fighter design on the horizon including composite materials, lightweight alloys, advanced flight-control systems, more powerful propulsion systems, and stealth technology. A request for proposals (RFP) was issued in July 1986 and two contractor teams, Lockheed/Boeing/General Dynamics and Northrop/McDonnell Douglas, were selected on 31 October 1986 to undertake a 50-month demonstration phase, culminating in the flight test of two prototypes, the YF-22 and the YF-23.[13][14][15]
Each design team produced two prototypes featuring one of two engine options, one featuring thrust vectoring. The Pratt & Whitney F119 turbofan with vectored thrust permits a tighter turning radius, a valuable capability in dogfights. The ATF's increasing weight and cost drove out some features during development. A dedicated infra-red search and track (IRST) system was downgraded from multi-color to single color and then deleted, the side-looking radars were deleted and the ejection seat requirement was downgraded from a fresh design to the existing McDonnell Douglas ACES II.[16]
On 23 April 1991, the YF-22 was then announced by Secretary of the U.S. Air Force Donald Rice as the winner of the ATF competition.[17] The YF-23 design was more stealthy and faster, but the YF-22 was more agile.[18] The aviation press speculated that the YF-22 was also more adaptable to the Navy's Navalized Advanced Tactical Fighter (NATF), but the U.S. Navy abandoned NATF by 1992.[19] In 1991, the air force planned to buy 650 aircraft.[20]

Production and procurement

F-22 being painted. Workers wearing white apparel standing on the aircraft's top applying a gray and black coat over the F-22. Temporary construction equipment surround its leading edges and nose sections.
The first operational F-22 Raptor is painted at the Lockheed Martin assembly plant at Marietta, Georgia
The production F-22 model was unveiled on 9 April 1997 at Lockheed Georgia Co., Marietta, Georgia. It first flew on 7 September 1997. The first production F-22 was delivered to Nellis Air Force Base, Nevada, on 7 January 2003.[21] In 2006 the Raptor's development team, composed of Lockheed Martin and over 1,000 other companies, plus the United States Air Force, won the Collier Trophy, American aviation's most prestigious award.[22] In 2006, the USAF sought to acquire 381 F-22s, to be divided among seven active duty combat squadrons and three integrated Air Force Reserve Command and Air National Guard squadrons.[23]
Several design changes were made from the YF-22 for production. The swept-back angle on the wing's leading edge was decreased from 48° to 42°, while the vertical stabilizer area was decreased by 20%. To improve pilot visibility, the canopy was moved forward 7 inches (178 mm), and the engine intakes were moved rearward 14 inches (356 mm). The shape of the wing and stabilator trailing edges was refined to improve aerodynamics, strength, and stealth characteristics.[24][25] Also, the vertical stabilizer was shifted rearward.[26]
During the development process the aircraft continued to gain weight at the cost of range and aerodynamic performance, even as capabilities were deleted or delayed in the name of affordability.[27]
F-22 production was split up over many subcontractors across 46 states, in a strategy to increase Congressional support for the program.[28][29] However the production split, along with the implementation of several new technologies were likely responsible for increased costs and delays.[30] Many capabilities were deferred to post-service upgrades, reducing the initial cost but increasing total project cost.[31] Each aircraft required "1,000 subcontractors and suppliers and 95,000 workers" to build.[32] The F-22 was in production for 15 years, at a rate of roughly two per month.[33]
Two F-22s overflying snow-capped mountains.
Two F-22s during flight testing, the upper one being the first EMD F-22, "Raptor 01"
The United States Air Force originally planned to order 750 ATFs at a cost of $26.2 billion,[34] with production beginning in 1994; however, the 1990 Major Aircraft Review led by Defense Secretary Dick Cheney altered the plan to 648 aircraft beginning in 1996. The goal changed again in 1994, when it became 438 aircraft entering service in 2003 or 2004, but a 1997 Department of Defense report put the purchase at 339.[34] In 2003, the Air Force said that the existing congressional cost cap limited the purchase to 277. In December 2004, the Department of Defense reduced procurement funding so only 183 aircraft could be bought.[35] The Pentagon stated the reduction to 183 fighters would save $15 billion but raise the cost of each aircraft; this was implemented in the form of a multi-year procurement plan, which allowed for further orders later. The total cost of the program by 2006 was $62 billion.[23]
In April 2006, the cost of the F-22 was assessed by the Government Accountability Office to be $361 million per aircraft. By April 2006, $28 billion had been invested in F-22 development and testing; while the Unit Procurement Cost was estimated at $177.6 million in 2006, based on a production run of 181 aircraft.[36][37] It was estimated by the end of production, $34 billion will have been spent on procurement, resulting in a total program cost of $62 billion, around $339 million per aircraft. The incremental cost for an additional F-22 was estimated at about $138 million.[23][38] In March 2012, the GAO increased the estimated cost to $412 million per aircraft.[39][40]
Two F-22 Raptors line up for refueling during their first official deployment, October 2005
On 31 July 2007, Lockheed Martin received a multi-year contract for 60 F-22s worth a total of $7.3 billion.[41][42] The contract brought the number of F-22s on order to 183 and extended production through 2011.[41] If production were restarted the cost for another 75 aircraft was estimated in 2009 to be an extra $70 million per unit.



Upgrades

On 5 January 2001, Raptor 4005 flew with the Block 3.0 software, which was the first combat-capable avionics version.[100] In June 2009, Increment 3.1 was tested at Edwards Air Force Base. This provided a basic ground-attack capability through synthetic-aperture radar mapping, electronic attack and the GBU-39 Small Diameter Bomb. The Increment 3.1 Modification Team with the 412th Test Wing received the Chief of Staff Team Excellence Award for upgrading 149 Raptors.[101][102] The fleet upgrade should start at the end of 2011.[103] An additional $808 million will be spent in 2013 to implement the 3.1 upgrade.[104] The first upgraded aircraft were delivered in early 2012.[105]
F-22 Raptor, Andrews Air Force Base
Increment 3.2 was to add an improved SDB capability, an automatic ground collision avoidance system for low level operations (no longer planned) and enable use of the AIM-9X Sidewinder and AIM-120D AMRAAM missiles. However, a helmet mounted cueing system has been deferred by technical issues.[106][107] Increment 3.2 was expected to be fielded in FY15,[108] possibly including the Multifunction Advanced Data Link (MADL).[109][110] In July 2009, the USAF announced the modification of three business jets with the interim Battlefield Airborne Communications Node (BACN) to allow communication between F-22s and other platforms until MADL is installed.[111] In March 2010, the USAF accelerated software portions of the Increment 3.2 upgrades to be completed in FY 2013, other upgrades will be completed later.[112] Upgrading the first 183 aircraft to the 3.2 upgrade is estimated to cost $8 billion.[113] In May 2009, Gen. Norton A. Schwartz and Air Force Secretary Michael B. Donley gave testimony to Congress that this would be paid for through the early retirement of legacy fighters.[114] A total of 249 fourth-generation fighters were retired during Fiscal Year 2010.[115] On 16 September 2009, Gates said "Our commitment to this aircraft is underscored by the 6 and-a half billion dollars... to upgrade the existing F-22 fleet to be fully mission-capable."[116]
The USAF opened the Raptor enhancement, development and integration (REDI) contract to other bidders in January 2011 with a total budget of $16 billion.[117] On 18 November 2011, the upgrade contract with Lockheed Martin was increased by $1.4 billion to a maximum value of $7.4 billion. This increment opens the way for further upgrades in 2012.[118][119][120] The $11.7 billion allocated for the planned upgrades to the 3.2B level (of which $5.5 billion has been spent) includes almost $2 billion for structural repairs and reliability issues, but does not include related infrastructure costs. One of the goals of the reliability costs is to raise the fleet availability rate from its current level of 55.5% to 70.6% by 2015. The 3.2C level upgrades will be bid out as a separate project.[121]
Lockheed Martin has proposed upgrades to add capabilities from the newer F-35.[122] Elements such as MADL are delayed until the F-35 program is completed to reduce risk.[123] One upgrade from the F-35 is new high-durability stealth coatings to lower maintenance.[124] The Ada software language was blamed for slow progress and increased costs on the program, leading to a reorganization in 2011.[125] Increment 3.2A in 2014 focuses on electronic warfare, communications and identification. Increment 3.2B in 2017 will support the AIM-9X and AIM-120D missiles. Increment 3.2C in 2019 may migrate some avionics to an open platform, allowing features to be added by various companies.[126] Lockheed Martin is working on upgrading the AN/AAR-56 Missile Launch Detector (MLD) to provide situational awareness and defensive Infrared Search and Track similar to the F-35's SAIRST.[127]
The current upgrade schedule is:
  • Increment 3.1 now entering service adds capabilities for SDB, SAR, and electronic attack.
  • Update 4 in 2012 will add a rudimentary capability for the AIM-120D.
  • Increment 3.2A will be fielded in 2014 with Link 16 and electronic warfare improvements. (The Link 16 receive capability has been moved up to 2013.)[128]
  • Also by May 30, 2015 an automatic backup oxygen supply will be installed on all aircraft.[129][130]
  • Update 5 in 2015 will add an initial capability for the AIM-9X.
  • In 2016 the fleet will be upgraded to 36 Block 20 training aircraft and 149 Block 30/35 operational aircraft.
  • Increment 3.2B in 2018 will add full capability for the air to air missiles, and "significantly improved ground threat geolocation". This schedule has slipped seven years because of "requirements and funding instability".[131] Because of this delay the upgrade will be applied to fielded aircraft that have already consumed a significant fraction of their useful airframe lifespan.[132][133]
  • Increment 3.2C was renamed 3.3 and while it is still being defined,[134] it will include air traffic control updates.[135]
Features not currently planned for addition or upgrades include:
  • The previously planned side-mounted AESA radar arrays
  • Infrared search and track (IRST)
  • Helmet-mounted sight
  • Powered air to surface missiles, the GBU-53 Small Diameter Bomb II, or other systems capable of engaging moving ground targets[136]
Because of these limitations, the Raptor will be unable to use the off-boresite and lock-on after launch features of its missiles.[137]
The Raptor were designed with a lifespan of 30 years and 8000 flight hours, but to achieve this goal required a $100 million "structures retrofit program".[138] Investigations are being made for upgrades to extend their useful lives further.[139][140] The F-22 is expected to eventually be replaced by the fighter from the Next Generation Air Dominance program.[141]
While no definitive, single cause has been found for the frequent oxygen deprivation issues that have killed at least one pilot, the F-22 will be upgraded with a 10 pound backup oxygen system, software upgrades and oxygen sensors to allow the pilots to operate normally in spite of the problem.[142] Due to frequent stand downs during the investigation, the F-22 fleet averaged less than eight flight hours per month over 2011.[143] In early 2013 the faulty flight vest valves will be replaced in the field, lifting the altitude restrictions, and once a backup oxygen system is installed the distance restrictions will be lifted, allowing F-22s to resume their air sovereignty missions over Alaska.[144]
In February 2013 Lockheed's upgrade contract was modified to include the 3.2B features. This brought the total upgrade cost for the fleet to $6.9 billion (including work already done) and the upgrade work is expected to be completed by 2023. The 3.2C features were moved to a 3.3 upgrade to be decided later.[145]
The USAF was to evaluate the Visionix Scorpion helmet-mounted cueing system (HMCS) for use on the F-22 in order to enable the use of high off-boresight missile launches,[146] however this was canceled when the US House failed to find the needed revenues to offset sequestration.[147]

Characteristics

Rear view of jet aircraft in-flight at dawn/dusk above mountains. Its engines are in full afterburner, evident through the presence of shock diamonds.
F-22 Raptor flying with its F119-PW-100 engines on full afterburner
The F-22 Raptor is a fifth generation fighter that is considered a fourth-generation stealth aircraft by the USAF.[148] Its dual afterburning Pratt & Whitney F119-PW-100 turbofans incorporate pitch axis thrust vectoring, with a range of ±20 degrees. The maximum thrust is classified, though most sources place it at about 35,000 lbf (156 kN) per engine.[149] Maximum speed, without external weapons, is estimated to be Mach 1.82 in supercruise mode,[150] as demonstrated by General John P. Jumper, former U.S. Air Force Chief of Staff, when his Raptor exceeded Mach 1.7 without afterburners on 13 January 2005.[151] With afterburners, it is "greater than Mach 2.0" (greater than 1,317 mph, 2,120 km/h). Former Lockheed chief test pilot Paul Metz stated that the Raptor has a fixed inlet, as opposed to variable intake ramps, and that the F-22 has a greater climb rate than the F-15, despite the F-15's higher thrust-to-weight ratio of 1.2:1 (the F-22 has a ratio closer to 1:1).[152] The U.S. Air Force claims that the Raptor cannot be matched by any known or projected fighter types,[6] and Lockheed Martin claims: "the F-22 is the only aircraft that blends supercruise speed, super-agility, stealth and sensor fusion into a single air dominance platform."[153]
F-22 Raptor flight demonstration video
The ability of airframes to withstand both stress and heat is a major design factor, thus the F-22 makes use of various materials. The use of internal weapons bays allows the aircraft to maintain a comparatively higher performance while carrying a heavy payload over many other aircraft due to a lack of drag from external stores. It is one of only a few aircraft that can supercruise or sustain supersonic flight without the use of afterburners, which consume vastly more fuel. The F-22 can intercept time-critical or rapidly moving targets that a subsonic aircraft would not have the speed to follow and an afterburner-dependent aircraft would lack fuel to reach.[154]
The F-22 is highly maneuverable, at both supersonic and subsonic speeds. It is extremely departure-resistant,[155] enabling it to remain controllable at extreme pilot inputs. The Raptor's thrust vectoring nozzles allow the aircraft to turn tightly, and perform extremely high alpha (angle of attack) maneuvers such as the Herbst maneuver (or J-turn), Pugachev's Cobra,[152] and the Kulbit.[152] The F-22 is also capable of maintaining a constant angle of attack of over 60°, yet still having some control of roll.[152][156] During June 2006 exercises in Alaska, F-22 pilots demonstrated that cruise altitude has a significant effect on combat performance, and routinely attributed their altitude advantage as a major factor in achieving an unblemished kill ratio against other U.S. fighters and 4th/4.5th generation fighters.[157]
The F-22 has a unique combination of speed, altitude, agility, sensor fusion and stealth that all work together to increase its effectiveness. Altitude plus advanced active and passive electronic warfare systems allow the F-22 to spot targets for its own weapons at considerable ranges. Altitude plus speed increases the reach of the F-22's own weapons. Altitude naturally increases the range from ground based defenses, which increases the effectiveness of stealth, and when combined with speed reduces the time defensive systems have to react to the F-22's attacks.[158][159][160][161]

Avionics

The F-22's avionics include BAE Systems E&IS radar warning receiver (RWR) AN/ALR-94,[162] AN/AAR 56 Infra-Red and Ultra-Violet MAWS (Missile Approach Warning System) and the Northrop Grumman AN/APG-77 Active Electronically Scanned Array (AESA) radar. The AN/ALR-94 is a passive receiver system to detect radar signals; composed of more than 30 antennas blended into the wings and fuselage that provide all around coverage. It was described by Tom Burbage, former F-22 program head at Lockheed Martin, as "the most technically complex piece of equipment on the aircraft." It has a greater range (250+ nmi) than the radar, allowing the F-22 to limit its own radar emissions to maximise stealth. As a target approaches, the receiver can cue the AN/APG-77 radar to track the target with a narrow beam, which can be as focused down to 2° by 2° in azimuth and elevation.[163]
Two personnel in white apparel handing a radar
The AN/APG-77 AESA radar
The AN/APG-77 radar, designed for air superiority and strike operations, features a low-observable, active-aperture, electronically-scanned array that can track multiple targets in any weather. The AN/APG-77 changes frequencies more than 1,000 times per second to lower interception probability. Additionally, radar emissions can be focused in an electronic-attack capability to overload enemy sensors.[164][165]
The radar's information is processed by two Raytheon Common Integrated Processor (CIP)s. Each CIP can process 10.5 billion instructions per second and has 300 megabytes of memory. Information can be gathered from the radar and other onboard and offboard systems, filtered by the CIP, and offered in easy-to-digest ways on several cockpit displays, enabling the pilot to remain on top of complicated situations. The F-22's avionics software has some 1.7 million lines of code, the majority involving processing data from the radar.[166] The radar has an estimated range of 125–150 miles, though planned upgrades will allow a range of 250 miles (400 km) or more in narrow beams.[157] In 2007, tests by Northrop Grumman, Lockheed Martin, and L-3 Communications enabled the AESA system of a Raptor to act like a WiFi access point, able to transmit data at 548 megabits per second and receive at gigabit speed; this is far faster than the Link 16 system used by U.S. and allied aircraft, which transfers data at just over 1 Mbit/s.[167]
The F-22 has a threat detection and identification capability comparative with the RC-135 Rivet Joint.[157] The F-22's stealth allows it to safely operate far closer to the battlefield, compensating for the reduced capability.[157] The F-22 is capable of functioning as a "mini-AWACS", however the radar is less powerful than dedicated platforms such as the E-3 Sentry.[152] The F-22 allows its pilot to designate targets for cooperating F-15s and F-16s, and determine whether two friendly aircraft are targeting the same aircraft.[152][157] This radar system can sometimes identify targets "many times quicker than the AWACS".[157] The radar is capable of high-bandwidth data transmission; conventional radio "chatter" can be reduced via these alternative means.[157] The IEEE-1394B data bus developed for the F-22 was derived from the commercial IEEE-1394 "FireWire" bus system.[168] Sensor fusion combines data from all onboard and offboard sensors into a common view to prevent the pilot from being overwhelmed.[169]
In a critical article former Navy Secretary John Lehman wrote "[a]t least [the F-22s] are safe from cyberattack. No one in China knows how to program the '83 vintage IBM software that runs them."[170] Former Secretary of the USAF Michael Wynne blamed the use of the DoD's Ada as a reason for cost overruns and schedule slippages on many major military projects, including the F-22 Raptor.[171] The F-22 uses the INTEGRITY-178B operating system from Green Hills Software, which is also used on the F-35, several commercial airliners and the Orion Crew Exploration Vehicle.[172] However cyberattacks on Lockheed Martin's subcontractors have raised doubts about the security of the F-22's systems and its usefulness in combat as a result.[173]
Herbert J. Carlisle has said that the F-22 can datalink with the Tomahawk (missile).[174]

Cockpit

Cockpit of the F-22, showing instruments, head up display and throttle top (lower left)
The F-22 features a glass cockpit with no analog flight instruments.[175] The primary flight controls are a force-sensitive side-stick controller and a pair of throttles. The monochrome head-up display offers a wide field of view and serves as a primary flight instrument for the pilot; information is also displayed upon six color liquid crystal display (LCD) panels.[175] The canopy's dimensions are approximately 140 inches long, 45 inches wide, and 27 inches tall (355 cm x 115 cm x 69 cm) and weighs 360 pounds.[176] In August 2006, the Air Force Packaging Technology Engineering Facility (AFPTEF) was tasked with the design of a new shipping and storage container for the fragile F-22 Canopy.[177]
The Raptor has integrated radio functionality for communicating on standard frequencies, the signal processing systems are virtualised rather than a separated hardware module.[178] Radio functions are inactive during the strictest emissions control protocols (EMCON level) to maintain stealth; at lower EMCON levels the pilot may use the radio at will.[citation needed] There has been several media reports on the F-22's inability to communicate with other aircraft and funding cuts on integrating the new datalinking standard, MADL.[179][180] Voice communication is possible, but not data transfer yet.[181] However, the Joint Tactical Radio System (JTRS), the software-defined radio project, was cancelled in October 2011 (before delivery to the F-22).[182]
The integrated control panel (ICP) is a keypad system for entering communications, navigation, and autopilot data. Two 3 in × 4 in (7.6 cm × 10 cm) up-front displays located around the ICP are used to display integrated caution advisory/warning data, communications, navigation and identification (CNI) data[183] and also serve as the stand-by flight instrumentation group and fuel quantity indicator.[184] The stand-by flight group displays an artificial horizon, for basic instrument meteorological conditions. The 8 in × 8 in (20 cm × 20 cm) primary multi-function display (PMFD) is located under the ICP, and is used for navigation and situation assessment.[184] Three 6.25 in × 6.25 in (15.9 cm × 15.9 cm) secondary multi-function displays are located around the PMFD for tactical information and stores management.
The ejection seat is a version of the ACES II (Advanced Concept Ejection Seat) commonly used in USAF aircraft, with a center-mounted ejection control. The F-22 has a complex life support system. Components include the on-board oxygen generation system (OBOGS), protective pilot garments, and a breathing regulator/anti-g valve controlling flow and pressure to the pilot's mask and garments. The protective garments are designed to protect against chemical/biological hazards and cold-water immersion, to counter g-forces and low pressure at high altitudes, and to provide thermal relief. It was developed under the Advanced Technology Anti-G Suit (ATAGS) project. Suspicions regarding the performance of the OBOGS and life support equipment have been raised by several crashes.
The USAF initially wanted the aircraft to use direct voice input (DVI) controls. This was finally judged too technically risky and was abandoned.

Armament

Jet fighter flying above a streaking missile, which had moments earlier been released by the former.
An F-22 fires an AIM-120 AMRAAM
The Raptor has three internal weapons bays: a large bay on the bottom of the fuselage, and two smaller bays on the sides of the fuselage, aft of the engine intakes.[189] It can carry six compressed-carriage medium range missiles[190] in the center bay and one short range missile in each of the two side bays. Four of the medium range missiles can be replaced with two bomb racks that can each carry one medium-size bomb or four small diameter bombs.[159] Carrying missiles and bombs internally maintains its stealth capability and maintains lower drag resulting in higher top speeds and longer combat ranges. Launching missiles requires opening the weapons bay doors for less than a second, while the missiles are pushed clear of the airframe by hydraulic arms. This reduces the Raptor's chance of detection by enemy radar systems due to launched ordnance and also allows the F-22 to launch long range missiles while maintaining supercruise.[191] The F-22 can also carry air-to-surface weapons such as bombs with Joint Direct Attack Munition (JDAM) guidance and the Small-Diameter Bomb, but cannot self-designate for laser-guided weapons.[192] Air-to-surface ordnance is limited to 2,000 lb (compared to 17,000 lb of F/A-18).[193] The Raptor has an M61A2 Vulcan 20 mm cannon in the right wing root. The M61A2 carries 480 rounds; enough ammunition for approximately five seconds of sustained fire. The opening for the cannon's firing barrel is covered by a door when not in use to maximise stealth.[194] The F-22 has been able to close to gun range in training dogfights while avoiding detection.[152] The cannon fire is tracked by the aircraft's radar and displayed on the pilot's head up display.
For stealth, the F-22 carries weapons in internal bays. The doors for the center bay and smaller side bays are open showing the six LAU-142/A AMRAAM Vertical Ejection Launchers (AVEL).
The Raptor's very high sustained cruise speed and operational altitude add significantly to the effective range of both air-to-air and air-to-surface munitions. This gives it a 40% greater employment range for air to air missiles than the F-35.[196] The USAF plans to procure the AIM-120D AMRAAM, reported to have a 50% increase in range compared to the AIM-120C. While specific figures remain classified, it is expected that JDAMs employed by F-22s will have twice or more the effective range of munitions dropped by legacy platforms.[197] In testing, a Raptor dropped a 1,000 lb (450 kg) unpowered, free-fall JDAM from 50,000 feet (15,000 m), while cruising at Mach 1.5, striking a moving target 24 miles (39 km) away.[198] This reach advantage of the F-22 has been cited by Robert Gottliebsen as sufficient reason for Australia to reject the F-35 in favor of a F-22 that has been updated with F-35 systems.[199]
While the F-22 typically carries its weapons internally, the wings include four hardpoints, each rated to handle 5,000 lb (2,300 kg). Each hardpoint has a pylon that can carry a detachable 600 gallon fuel tank or a launcher holding two air-air missiles. However, the use of external stores has a detrimental effect on the F-22's stealth, maneuverability and speed. The two inner hardpoints are "plumbed" for external fuel tanks; the hardpoints can be jettisoned in flight so the fighter can maximise its stealth after exhausting external stores.[200] A stealth ordnance pod and pylon is being developed to carry additional weapons internally.[201]

Stealth

The stealth of the F-22 is due to a combination of factors, including the overall shape of the aircraft, the use of radar absorbent material (RAM), and attention to detail such as hinges and pilot helmets that could provide a radar return.[202] However, reduced radar cross section is one of five facets of presence reduction addressed in the designing of the F-22. The F-22 was designed to disguise its infrared emissions, reducing the threat of infrared homing ("heat seeking") surface-to-air or air-to-air missiles, including its flat thrust vectoring nozzles.[203] The aircraft was designed to be less visible to the naked eye; radio, heat and noise emissions are equally controlled.[202]
F-22 with external weapons pylons.
The F-22 reportedly relies less on maintenance-intensive radar absorbent coatings than previous stealth designs like the F-117. These materials are susceptible to adverse weather conditions.[204] Unlike the B-2, which requires climate-controlled hangars, the F-22 can undergo repairs on the flight line or in a normal hangar.[204] The F-22 features a Signature Assessment System which delivers warnings when the radar signature is degraded and has necessitated repair.[204] The exact radar cross section (RCS) remains classified; however, in 2009 Lockheed Martin released information indicating it to have a RCS (from certain angles) of −40 dBsm – the equivalent radar reflection of a "steel marble".[205] Effectively maintaining the stealth features can decrease the F-22's mission capable rate to 62–70%.[N 2]
The effectiveness of the stealth characteristics is difficult to gauge. The RCS value is a restrictive measurement of the aircraft's frontal or side area from the perspective of a static radar. When an aircraft maneuvers it exposes a completely different set of angles and surface area, potentially increasing visibility. Furthermore, stealth contouring and radar absorbent materials are chiefly effective against high-frequency radars, usually found on other aircraft. Low-frequency radars, employed by weather radars and ground warning stations, are alleged to be less affected by stealth technologies and are thus more capable as detection platforms.[207][208] Rebecca Grant states that while faint or fleeting radar contacts make defenders aware that a stealth aircraft is present, interception cannot be reliably vectored to attack the aircraft.[209]
The F-22 also includes measures designed to minimize its detection by infrared, including special paint and active cooling of leading edges to deal with the heat buildup encountered during supercruise flight












Variants

  • YF-22A – pre-production version used for ATF testing and evaluation. Two were built.
  • F-22A – single-seat production version. Was designated "F/A-22A" in early 2000s.
  • F-22B – planned two-seat variant, but was dropped in 1996 to save development costs.[261]
  • Naval F-22 variant – a carrier-borne variant of the F-22 with swing-wings for the U.S. Navy's Navy Advanced Tactical Fighter (NATF) program to replace the F-14 Tomcat. Program was canceled in 1993.[261] Former SoAF Donald Rice has called the possibility of the naval variant the deciding factor for his choice of the YF-22 over the YF-2
  • General characteristics
  • Crew: 1
  • Length: 62 ft 1 in (18.90 m)
  • Wingspan: 44 ft 6 in (13.56 m)
  • Height: 16 ft 8 in (5.08 m)
  • Wing area: 840 ft² (78.04 m²)
  • Airfoil: NACA 64A?05.92 root, NACA 64A?04.29 tip
  • Empty weight: 43,340 lb (19,700 kg[6][312])
  • Loaded weight: 64,460 lb (29,300 kg[N 5])
  • Max. takeoff weight: 83,500 lb (38,000 kg)
  • Powerplant: 2 × Pratt & Whitney F119-PW-100 Pitch Thrust vectoring turbofans
  • Fuel capacity: 18,000 lb (8,200 kg) internally,[6][312] or 26,000 lb (11,900 kg) with two external fuel tanks.[6][312] About 3,050 gal or 20,333 lb JP-8 (without additions) internally.[316]
Performance
USAF poster overview of key features and armament
Armament
Avionics
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 From Wikipedia, the free encyclopedia






 

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