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The Lockheed Martin F-22 Raptor

v2.4.0 / 01 jun 13 / greg goebel / public domain

* The current first-line fighter aircraft of the US military, such as the F-15 and F-16, are excellent and formidable aircraft, but they were designed decades ago. Although the end of the Cold War has reduced the need for new weapons, as current aircraft near the end of their useful lives the US military would like to replace them with aircraft featuring the latest technology. To this end, the US Air Force (USAF) has developed an advanced air superiority fighter, the Lockheed Martin "F-22A Raptor", which is intended to be the equal or superior of any threat aircraft now on the horizon. This document provides a history and description of the F-22A.

Lockheed Martin F-22A


[1] ORIGINS: THE ATF
[2] YF-23A VERSUS YF-22A
[3] F-22 IN DEVELOPMENT
[4] F-22 DETAILS
[5] COMMENTS, SOURCES, & REVISION HISTORY

[1] ORIGINS: THE ATF

* The F-22 Raptor was developed in response to a USAF studies conducted through the 1970s on new fighter concepts. By the early 1980s, following several generations of paper studies conducted by aerospace contractors, the USAF had decided to focus on development of an "Advanced Tactical Fighter (ATF)" and issued a request for proposals for such an aircraft in May 1983.

The ATF was intended to be a next-generation air superiority fighter, designed to stay ahead of advanced Soviet aircraft and missile designs then presumed to be in development. The USAF requirements asked for the tidy integration of a wide range of new technologies in an aircraft that was to be relatively inexpensive to operate and easy to maintain.

New technologies considered included advanced cockpit automation and sensors; built-in test and support equipment; high reliability and low maintenance to ensure combat availability; stealth features; and "vectored thrust", meaning engines with a moving nozzle to permit improved maneuverability and shorter takeoffs. One particularly important requirement was for a "supercruise" engine, capable of flying the aircraft at sustained supersonic speeds over extended range without afterburner. Supercruise would allow rapid movement into a target area to ensure quick combat reaction times; fast exit from the target area as a means of defense; and higher launch velocities for munitions, making the ATF "faster on the draw" and improving the range of the munitions.

From seven contenders, the choice for the company to build the ATF was finally narrowed down to two: Lockheed, partnering with Boeing and General Dynamics; and Northrop, partnering with McDonnell Douglas. Each team was awarded a $691 million USD contract on 31 October 1986, initiating a 50-month "demonstration and validation (dem/val)" phase.

During dem/val, the two companies were to build two prototypes each. Lockheed designated their aircraft the "YF-22A", while Northrop designated theirs the "YF-23A". The two examples for each prototype were to have different engine fits, one powered by a pair of Pratt & Whitney (P&W) F119 engines, and the other by a pair of General Electric (GE) F120 engines. Both the P&W and GE engine types were specifically designed for the competition in a parallel "Joint Advanced Fighter Engine (JAFE)" effort.

The USAF wanted to buy a total of 750 ATFs. The US Navy also considered the type as the "Naval ATF (NATF)", with "swing wings", and at one time estimated they would need 550 such aircraft, but soon changed their minds on the NATF. The Navy was committed to the development of the advanced F/A-18E/F Hornet fighter, and feared that involvement with the F-22 would be a diversion of effort that could lead to political confusion, putting the F/A-18E/F program at risk.

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[2] YF-23A VERSUS YF-22A

* The Northrop contender for the ATF contract, the "YF-23A", was officially rolled out first, on 22 June 1990, and made its initial flight on 27 August 1990. The aircraft was informally named the "Black Widow II", in memory of Northrop's P-61 Black Widow night fighter of World War II.

Northrop YF-23A Black Widow II

The YF-23A was unorthodox in appearance. The YF-23A was obviously a "stealth" design, with a diamond-shaped wing, a wide and flattened vee tail, engine exhausts hidden from view from below, a sawtooth rear fuselage across the tail and exhausts, and blended contours. The engine air intakes were underneath the wings, with the two engines buried well back from the inlets to keep them from reflecting radar signals. Air-to-air missiles (AAMs), such as the new AIM-9X Sidewinder and AIM-120 Advanced Medium-Range Air-to-Air Missile (AMRAAM), were to be carried in internal weapons bays, not externally. Such a design was clearly meant to give enemy radars very little to catch onto.

The YF-23A was 20.6 meters (67 feet 5 inches) long, had a 13.3 meter (43 foot 7 inches) wingspan, and a height of 4.27 meters (14 feet). The aircraft had a top speed of at least Mach 2.0 and supersonic cruise at about Mach 1.5. The YF-23A featured a "Vehicle Management System (VMS)" to keep it in the air. The VMS handled the YF-23A's flight control surfaces, including all-moving tailplanes and flaps on both the leading and trailing edges of the wings. The VMS could also monitor the aircraft's hydraulic systems, detecting and isolating damage to keep the fighter airborne.

Northrop YF-23A Black Widow II

* The Lockheed design, the "YF-22A", was rolled out on 29 August 1990, and first flew on 29 September. The aircraft was given the informal name of "Lightning II", after the famous Lockheed P-38 Lightning of World War II, but the name didn't stick.

The YF-22A had a more conventional configuration than the YF-23A, similar in broad plan to the current F-15 fighter: high-set cockpit, air intakes behind either side of the cockpit and extending to engines on either side of the fuselage, and twin tailfins. The YF-22A was less stealthy than the YF-23A, though more stealthy than the F-15. The YF-22A design was more optimized for maneuverability, with such features as thrust-vectoring engine exhausts that swiveled in the vertical plane.

Lockheed YF-22A

* The YF-23A met USAF requirements for survivability, supersonic cruise, stealth, and ease of maintenance. However, the YF-22A was more maneuverable than the YF-23A, and won the competition in April 1991. Another factor was that the YF-22A was also seen as more adaptable to the Navy's NATF, though as it turned out the Navy abandoned NATF a few months later.

The engine selected for the winning YF-22A was the P&W F119, which was judged a lower-risk path. The contract specified that Lockheed provide seven single-seat F-22As, two tandem-seat dual-control F-22Bs, and two nonflying test examples. First flight of a true F-22 was scheduled for 1996, with operational introduction in 2003.

The second YF-22A prototype, powered by the P&W F119, quickly followed the first into the air. Although the first prototype was powered by two GE F120s, it was soon modified to take the P&W F119. Flight tests of the two YF-22A prototypes were augmented by avionics tests using a Boeing 757 configured as a flying laboratory. The 757 eventually acquired small sensor wings above the cockpit, a pointy nose with an AN/APG-77 radar, and small chines along the nose, giving it such cluttered lines that it was nicknamed the "Catfish".

The flight tests went well until 1991, when one of the prototypes suffered a landing accident and was badly burned. The other prototype had been relegated to ground tests by that time, and neither of the two initial prototypes ever flew again.

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[3] F-22 IN DEVELOPMENT

* While the YF-22A won the competition, giving the green light for the "engineering and manufacturing development (EMD)" phase of the program, the program did have obstacles to overcome. The main underlying cause of the uncertainty was the end of the Cold War, which greatly reduced the perceived military threat faced by the United States and called into question the need for highly sophisticated and expensive new weapons.

In 1990, US Secretary of Defense Dick Cheney lowered the planned production rate of the F-22 from 72 per year to 48 per year. The program continued to be whittled down, with the total production reduced from 750 to 648 in 1991, followed by a cut to a total of 442 in 1994. At this point, Lockheed began to feel the pinch between development costs and expected revenues. One Lockheed official, the late Ben Rich of the Lockheed Skunk Works, commented: "The sad truth is that our stockholders would have done better financially if they had invested ... in CDs."

Although the ATF had been originally intended as an air superiority weapon, in 1994 a modest secondary attack role was added to help protect the program. Despite such protective measures, the two-seat F-22B was canceled in 1997, and the total buy of F-22s was further reduced to 339.

The program still continued more or less on track. The first true F-22 prototype, more imaginatively designated the "Raptor", was rolled out at the Lockheed Martin plant at Marietta, Georgia, on 9 April 1997. There were numerous problems with the prototype, including software bugs and fuel leaks, and first flight was delayed to 7 September 1997. The second prototype first flew on 29 June 1998.

However, the pressures on the Raptor didn't go away. In the summer of 1999, faced with rising costs for maintaining military readiness and the burden of extensive military operations in the Balkans, Iraq, and elsewhere, the US House of Representatives moved to defer funding for the F-22. That led to a nasty political squabble, with one House appropriations committee staffer commenting: "The Air Force sent 25 guys up here to brief us on the need for the F-22 program, and they didn't impress us one damn bit." The Air Force managed to prevail in the debate, providing convincing arguments for their need for an "Air Dominance Fighter", as the F-22 was described.

On 15 August 2001, "low-rate initial production (LRIP)" of ten F-22s and 20 F119 engines was finally authorized, no doubt much to the relief of the program's backers. By late 2003, production standard machines were in evaluation. Operational introduction, with the USAF 27th Fighter Squadron, finally took place in 2005 -- not a bad delay considering the ups and downs of the program.

Lockheed Martin F-22 Raptor

By the summer of 2008, 122 F-22s had been delivered. By that time, the perception was increasingly that the Raptor wasn't exactly the right tool for the "dirty little wars" of the 21st century. It had been designed to counter fourth-generation Soviet air superiority fighters that never materialized, and though the Air Force wanted some insurance against the day when such a threat did appear, given the demands of existing struggles against insurgents and terrorists who had no air power at all, there was only so much insurance that made sense. In early 2009, the decision was made to end production after delivery of 187 machines, with the last Raptor rolled out in late 2011.

As for foreign sales, Congress has forbidden export of the aircraft. A few countries, for example Japan, have been interested in obtaining the F-22, but there's no visible prospect of it happening. Not too surprisingly, the Japanese, and a number of other nations, have been evaluating their own aircraft designs that clearly owe much to F-22 ancestry.

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[4] F-22 DETAILS

* The F-22 is more formally the "F-22A", but since there's never been and never will be another F-22 production variant, it's usually just referred to as the "F-22". For a time, from 2002, it was designated the "F/A-22", the "A" standing for "Attack", as a means of emphasizing the aircraft's attack capabilities, but when it was finally introduced to service that subterfuge was dropped -- likely because it was unpersuasive and possibly even counterproductive for a machine being promoted for its air superiority capabilities.

Performance estimates give the F-22 a speed of Mach 1.5 in non-afterburning supercruise mode, and a speed of Mach 2.0 or above with afterburner. Flight tests demonstrate that the F-22 combines good handling characteristics with very high maneuverability. Pilots have described the F-22 as very pleasant to fly, combining the agility of an F-16 with the docile handling of the F-15, and the power of the new design made it, as one pilot put it, "a kick-ass rocket ship".

   LOCKHEED MARTIN F-22 RAPTOR:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                13.56 meters        44 feet 6 inches
   wing area               78.04 sq_meters     840 sq_feet   
   length                  18.92 meters        62 feet 1 inch
   height                  5.05 meters         16 feet 7 inch

   empty weight            19,493 kilograms    42,974 pounds
   MTO weight              36,288 kilograms    80,000 pounds

   max speed at altitude   2,130 KPH           1,325 MPH / 1,150 KT
   supercruise speed       1,810 KPH           1,125 MPH / 980 KT
   service ceiling         15,000 meters       50,000 feet
   combat radius           700 kilometers      430 MI / 375 NMI
   ferry range             3,330 kilometers    2,070 MI / 1,800 NMI
   _____________________   _________________   _______________________

The F-22 has major similarities to the YF-22, but there are clear differences. The F-22's cockpit was moved forward and the air intakes moved back. The wings were clipped off and the rear control surfaces rearranged. The two tailfins were shorter, and the tailplanes were larger and reshaped. The main landing gear retracted sideways on the F-22 instead of forward.

YF-22A versus F-22

The F-22 is constructed of titanium alloys (39% by weight); composites (24%); aircraft aluminum alloy (16%); and thermoplastics (1%). Advanced titanium welding techniques and composite fabrication are used in the aircraft's construction. "Radar absorbent material (RAM)" is used in critical locations to reduce the aircraft's radar signature, and the aircraft's contours are also intended to make it less conspicuous to radar. Apertures, such as weapons bay and landing gear doors, have zigzag edges to break up radar returns. An overall coating reduces the aircraft's infrared signature as well. While older stealth aircraft require substantial maintenance, careful handling, and protection from weather to keep them stealthy, the F-22 does not require extraordinary efforts to maintain its stealth characteristics.

The F-22's twin Pratt & Whitney F119-PW-100 engines can provide supersonic cruise without afterburner. It has a high power-to-weight ratio (PWR) of 1.4:1, and can deliver 156 kN (15,900 kgp / 35,000 lbf) afterburning thrust. The F119 has a minimized parts count and has been designed for maintainability. Important components, harnesses, and plumbing were placed on the bottom of the engine to improve ground crew access, and all components can be removed or replaced with one of six standard tools. The digital engine control modules are redundant, with two controllers per engine and two computers per controller, to improve reliability.

F119-PW-100 engine

The F119 engine includes thrust vectoring exhaust nozzles that can traverse 20 degrees up and down to improve the Raptor's maneuverability in low-speed combat. The nozzles are automatically directed by the F-22's flight control system. The exhaust does not emit visible smoke under proper operating conditions and provides a low infrared signature. Engine starting, as well as ground power, is provided by an auxiliary power unit (APU).

The F-22 features eight internal fuel tanks, and there is a boom-refueling socket in the middle of the back. The internal fuel tanks are normally flooded with nitrogen to reduce the danger of fire from fuel fumes. The nitrogen is derived from the atmosphere by an on-board nitrogen generation system. The F-22 also includes a fire-fighting capability, consisting of infrared and ultraviolet sensors linked to a fire extinguishing system.

* The pilot has an excellent view through the frameless canopy, which is designed to reduce radar reflections. A slightly modified version of the proven Boeing ACES II ejection seat, used on the F-15 and F-16, is used on the Raptor. The F-22 features an "On-Board Oxygen Generation System (OBOGS)", eliminating the need to stock oxygen bottles.

The cockpit control layout features six high-intensity color liquid crystal panel displays, plus a wide-angle holographic "heads-up display (HUD)". The displays are functionally partitioned as follows:

The cockpit features "hands on throttle and stick (HOTAS)" controls that allow the pilot to execute command functions without letting go of the flight controls. Although the USAF's initial ideas for the ATF had envisioned "direct voice input (DVI)" controls, DVI was finally judged too technically risky and abandoned.

* The F-22 includes a single General Electric M61A2 Vulcan 20 millimeter Gatling-type cannon in the right wing root. The Vulcan is a thoroughly proven weapon that's basically been in service since the late 1950s. Ammunition store is 480 rounds, with a linkless feed system. The cannon was not fitted in the YF-22 prototypes. The Raptor also has three weapons bays, including a main weapons bay on the bottom of the fuselage and a small weapons bay on the side of each air intake.

The main weapons bay can accommodate six AMRAAMs, or two AMRAAMs and bombs. The AMRAAMs are the AIM-120C "compressed carriage" variant, designed with short flight surfaces for fit into the F-22's weapons bay. An AMRAAM is thrown away from the aircraft by a "Vertical Ejector Launcher (VEL)" before ignition. Typical internal bombloads include:

Each side weapons bay can accommodate a single AIM-9X Sidewinder missile, capable of "off boresight" attacks as directed by the pilot's Joint Helmet Mounted Cueing System (JHMCS). The doors pop open and the Sidewinder is deployed out into the airstream at an angle to give its seeker a good field of view. The Raptor can also be fitted with a total of four underwing stores pylons for fuel or munitions, though this sacrifices the aircraft's stealth characteristics. The pylons are used for ferry tanks or for strikes after air superiority has been obtained.

* The heart of the F-22's electronics capabilities is the "AN/APG-77" radar system, though it is so much more than a radar that some prefer to call it a "multifunction RF system" instead. With the AN/APG-77, the F-22 is able to detect an enemy aircraft's radar from distances of up to 460 kilometers (250 nautical miles). It can acquire an enemy aircraft at distances of up to 220 kilometers (125 nautical miles), while its "low probability of intercept" radar signals make it very difficult to detect, leaving the "stealthy" F-22 will remain invisible to the enemy's radar. In many cases, the enemy will be hit with little warning.

The AN/APG-77 is built around an "Active Electronically Scanned Array (AESA)", which consists of an array of about 1,500 transmitters-receiver (T/R) modules that are linked together by high-speed processors. The AESA can obtain electronics intelligence; jam enemy electronic systems (the Raptor does not carry any other RF jamming system); provide surveillance; and perform secure voice and datalink communications, in principle all at the same time. The AESA can simultaneously emit several tight beams to perform different functions. Although the Air Force considered auxiliary side-mounted arrays for the AN/APG-77, they were abandoned due to cost, and the AESA is limited to a field of view 120 degrees across in the forward direction. Other antennas provide missile and radar warning behind the aircraft.

When operating as a radar, the AN/APG-77 transmits waveforms that change from burst to burst, and are sent at random frequencies. Such a changing signal is very difficult for an enemy to detect and analyze. If adversaries do manage to detect the signal, they must then try to get a radar lock on the F-22 so it can be attacked. The F-22's stealthiness makes this tricky in the first place, but to make matters more troublesome, the AESA also analyses the enemy's radar and sends out a jamming burst to disrupt the lock. The AESA then goes on to other tasks until the enemy radar begins its lock cycle again.

Between dealing with active threats, the AESA collects information on the "electronic order of battle (EOB)" in the operational area, locating electronic "emitter" systems, classifying them, and alerting the pilot to possible threats or high-priority targets.

The AN/APG-77 was a pioneer in operational development of the AESA. Later development of the concept for the F-35 Joint Strike Fighter has led to cheaper and more powerful AESA systems, and production F-22s feature a much improved AN/APG-77(V)1 system based on this improved technology. The production AESA system also includes a "synthetic aperture radar (SAR)" mode to provide all-weather ground imaging, a very useful capability in the strike role.

* Other F-22 electronic and defensive subsystems include:

Other kit that the Air Force has remained silent about include missile warning gear and active infrared defensive countermeasures. Of course, the Raptor has standard communications gear and identification friend or foe (IFF) systems. The F-22's avionics system also has a "non-cooperative target recognition (NCTR)" capability that obtains a "signature" of a target and compares it to a library of possibilities. The details of NCTR are secret.

The F-22's avionics were designed to allow a single crewman to perform missions traditionally reserved for two-seat aircraft. Almost all electronics gear on board is integrated by two "Common Integrated Processors (CIPs)". The CIPs are based on commercial off-the-shelf electronics and have evolved through a number of configurations as more computing power has become available; the original CIPs would have been put to shame by any modern low-cost personal computer. The CIPs handle almost all the F-22's electronics functions, in particular assessing and prioritizing threats to display to the pilot. The CIPs provide a degree of self-test and reconfigurability that can keep the F-22 flying even with battle damage.

The entire F-22 is thoroughly wired for self-test. Almost every subsystem can check itself for faults and report its operational status. Ground crews can monitor the health of the aircraft through a laptop computer, configured as a "Portable Maintenance Aide (PMA)". The PMA can list faults and perform diagnoses, as well as check the level of consumables such as fuel and oil. Overall maintenance demands for the F-22 are estimated to be half or less that for an F-15, and the Raptor's estimated three-hour mean time between maintenance is three times that of the F-15.

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[5] COMMENTS, SOURCES, & REVISION HISTORY

* The USAF has been conducting a series of investigations towards a next-generation bomber bomber to replace the B-1 and B-2 currently flying. At one time, there was consideration of a near-term "interim solution", with Lockheed Martin proposing a derivative of the F-22, the "FB-22", in response.

In refinement, the FB-22 concept used same fuselage of the F-22 mated to a new wing with about three times the area. The wing would be "wet", providing fuel storage that would triple the FB-22's unrefueled range compared to the F-22. The cannon would be deleted. The main weapons bays would be fitted with bulged doors to permit carriage of more or larger munitions, and the FB-22 could carry two to four stealthy underwing pods, raising the total load of SDBs from 8 to 35. It would also be able to carry heavier munitions and two AMRAAMs for self-defense.

FB-22 concept

FB-22 avionics would be leveraged off F-22 avionics, with some enhancements as necessary or useful, and and would be fitted with improved F119 engines with more power and better fuel economy -- though without thrust-vectoring nozzles. The FB-22 would be capable of supersonic performance, but not supersonic cruise. The Air Force was after a two-seat configuration, which has already been designed for the canceled F-22B. The FB-22 was an interesting idea, but it went nowhere, the USAF focusing on a next-generation flying wing, along the lines of a better and cheaper B-2.

* The political controversy behind the F-22 has had some amusing aspects. At one time, program backers cited estimates that had been devised that gave the "kill ratio" between the F-22 and the MiG-21 as about a thousand to one in the F-22's favor. Even senior USAF brass responded, in essence, to ask them what they had been smoking. It brought up the old joke that fighter complexity and cost was increasing so rapidly that eventually the Air Force would only be able to buy one fighter -- but it would be able to destroy the entire Red Air Force by itself.

I finally saw an F-22 in flight in 2008 at an airshow. It put on a performance that as astounding -- it would do things that wouldn't have been controlled flight in almost any other aircraft, such as going into a climb, halting at the top of the climb, and then sliding back down along its flightpath.

* Sources include:

* Revision history:

   v1.0   / 01 sep 99 
   v2.0   / 01 may 00 / Merged F-22 & JSF documents, added AESA details.
   v2.1   / 01 dec 00 / Added info on first flight of JSF candidates.
   v2.2.0 / 01 jan 02 / Broke out JSF materials, minor update.
   v2.2.1 / 01 jan 04 / Minor update and reorganization.
   v2.3.0 / 01 mar 05 / FB-22 comments.
   v2.3.1 / 01 feb 07 / Review & polish.
   v2.3.2 / 01 feb 09 / Review & polish.
   v2.3.3 / 01 aug 09 / Minor update, changed "F/A-22" to "F-22A".
   v2.3.4 / 01 jul 11 / Review & polish.
   v2.4.0 / 01 jun 13 / General streamlining.
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