The Lockheed Martin F-22 Raptor

v2.2.0 / 01 jan 02 / 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-22 Raptor", which is intended to be the equal or superior of any threat aircraft now on the horizon. This document outlines the development of the F-22.

[2] YF-23A VERSUS YF-22A
[4] F-22 DETAILS


* 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 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 an engine 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 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 contenders: 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)", and at one time estimated they would need 550 such aircraft, but presently 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.


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

* The Northrop contender for the ATF contract, the "YF-23A", was formally 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.

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 advanced AIM-9X Sidewinder and the 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 lock onto.

The YF-23A was 20.6 meters (67.4 feet) long, had a 13.3 meter (43.6 foot) 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.

* 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 general 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 vertical tailplanes.

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, featuring design elements such as thrust-vectoring engine exhausts that swiveled in the vertical plane.

* 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 quickly 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 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.



* Although 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 cancelled in 1997, and the total buy of F-22s was further reduced to 339.

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 of the F-22. This 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 the F-22 was finally authorized, no doubt much to the relief of the program's backers. The initial production aircraft are now being built, and operational introduction is expected in 2005.


[4] F-22 DETAILS

* 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 problems and fuel leaks, and first flight was delayed to 7 September 1997. The second prototype first flew on 29 June 1998. By late 2001, there were eight F-22s flying.

Test pilots describe the F-22 as very pleasant, combining the agility of an F-16 with the docile handling of the F-16, and the power of the new design makes it, as one pilot put it, "a kick-ass rocket ship".

The F-22 is 18.9 meters (62 feet) long, with a wingspan of 13.6 meters (44.5 feet) and a height of 5.2 meters (17 feet). While the USAF is quiet about many of the Raptor's specifications, it is estimated to have an empty weight of about 15 tonnes (16.5 tons) and a fully loaded weight of about 27 tonnes (30 tons).

The YF-22A and the F-22 are similar but have clear differences. The F-22's cockpit has been moved forward and the air intakes moved back. The wings are clipped off and the rear control surfaces rearranged. The two vertical tailplanes are shorter, and the horizontal tailplanes are larger and reshaped. The main landing gear now retracts sideways instead of forward.

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. Service ceiling is thought to be over 15 kilometers (50,000 feet) and the maximum range is believed to be over 3,000 kilometers (1,860 miles). Flight tests demonstrate that the F-22 combines good handling characteristics with very high maneuverability.

* The F-22 includes a single M61A2 20 millimeter Gatling-type cannon, though the gun was not fitted in the YF-22 prototypes. The Raptor 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 a pair of bombs, the bombs envisioned as being either 450 kilogram (1,000 pound) "Joint Direct Attack Munition (JDAM)" GPS-guided bombs or "Wind Corrected Munitions Dispenser (WCMD)" inertially-guided cluster bombs.

Each side weapons bay can accommodate a single AIM-9X Sidewinder missile, capable of "off boresight" attacks as directed by the pilot's helmet mounted sight. The Raptor can also be fitted with a total of four underwing stores pylons for fuel or external stores, though this sacrifices the aircraft's stealth characteristics, and is intended mainly for carriage of ferry tanks.

"Small diameter bombs (SDBs)", previously known as "small smart bombs", have been under development that would allow the F-22, with its modest attack load without external stores, to take on more than two targets on a single strike sortie. In fact, some cynics have suggested that the main rationale behind development of the SDB is simply to help justify the F-22's existence. This may be so, but a small and effective smart munition would clearly be valuable in itself, greatly extending the strike effectiveness of any attack aircraft.

* The heart of the F-22's electronics capabilities is the "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 APG-77, the F-22 will be able to detect an enemy aircraft's radar from distances of up to 460 kilometers (250 nautical miles). It will be able to acquire an enemy aircraft with radar at distances of up to 220 kilometers (125 nautical miles), while its "low probability of intercept" radar signal will be very difficult to detect and the "stealthy" F-22 will remain invisible to the enemy's radar.

Once AIM-120 Extended Range Air To Air Missiles (ERAAM) are available, the F-22 will be able to destroy that enemy at a range of 185 kilometers (100 nautical miles). In many cases, the enemy will be hit without warning.

The APG-77 is built around an "Active Electronically Scanned Array (AESA)", which consists of an array of about 2,000 transmitters-receiver (T/R) modules that are linked together by high-speed processors. The AESA can obtain electronics intelligence; jam enemy electronic systems; provide surveillance; and perform secure voice and datalink communications, all that the same time. The AESA can simultaneously emit several tight beams to perform different functions. "Anything that can be done with X-band RF can be done with that antenna," one program official commented.

Although the Air Force considered auxiliary side-mounted arrays for the 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 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 the enemy does manage to detect the signal, he or she 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.

The APG-77 is not intended to give the F-22 a "standoff jamming" capability, such as that provided by electronic warfare aircraft like the Grumman EA-6B Prowler, blinding enemy radars over wide areas on a continuous basis. The APG-77's mission is mainly to allow the F-22 to fight effectively while remaining difficult to detect. A standoff jamming platform, in contrast, can't help but advertise its presence.

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

Other F-22 electronic and defensive subsystems include:

The F-22's avionics were designed to allow a single crewman to perform missions traditionally reserved for two-seat aircraft. The secure datalink system is particularly important, allowing combat integration between multiple F-22s or other types of NATO fighter and attack aircraft, between F-22s and an Airborne Warning & Control System (AWACS) aircraft, or one-way data downloads from reconnaissance platforms.

Almost all electronics gear on board is integrated by two "Common Integrated Processors (CIP)", built by Hughes. The CIPs are breadbox-sized, and accommodate 66 plug-in modules. Both of the CIPs have 19 slots still open, and there is space in the aircraft for a third CIP, allowing still more room for future expansion.

The CIPs handle almost all the F-22's electronics functions. The CIPs provide a degree of self-test and reconfigurability that can keep the F-22 flying even with battle damage. Each CIP operates at 10.5 billion instructions per second and has 300 megabytes of memory. The Raptor is run by 2.5 million lines of software, with about 90% of it written in the Department of Defense's Ada language. Ada was not used for all the software because some functions required optimizations, and so waivers were granted.

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.

The F-22 includes a fire-fighting capability, consisting of infrared and ultraviolet sensors linked to a Halon 1301 fire extinguishing system. While Halon is an ozone-attacking Freon, designers are searching for "green" alternatives, and the fire extinguishing system was designed to allow the storage of alternative agents with up to 2.5 times the volume of Halon.

The aircraft's eight 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 is constructed mainly from composites (24% by weight) and titanium alloys (42% by weight). Advanced composite fabrication and titanium welding techniques 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 intended to make it less conspicuous to radar. While older stealth aircraft require substantial maintenance, careful handling, and protection from weather to keep them stealthy, the F-22 will not require extraordinary efforts to maintain its stealth characteristics.

The cockpit control layout is based on high-intensity color liquid crystal panel displays, plus a wide-angle holographic "heads-up display (HUD)". 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 risky and abandoned.

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 Pratt & Whitney F119-PW-100 engine is another a very advanced piece of technology. Its ability to provide supersonic cruise without afterburner provides the F-22 with one of its most important capabilities. It has a high power-to-weight ratio (PWR), and can deliver 15,900 kilograms (35,000 pounds) afterburning thrust.

The F119 engine 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.

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.



* The political controversy behind the F-22 has had some amusing aspects. At one time, F-22 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.

* An earlier release of this document featured materials on what would become the F-35 Joint Strike Fighter (JSF). At the time, the JSF program was still in a nebulous state and couldn't really support a stand-alone document.

With the selection of Lockheed Martin as the prime JSF contractor in late 2001, details of the JSF program began to solidify rapidly, and so with the v2.2.0 release of this document, I split the materials on the JSF and created a stand-alone document with them.

* Sources include:

* Revision history:

   v1.0   / 01 sep 99 / gvg
   v2.0   / 01 may 00 / gvg / Merged F-22 & JSF documents, added AESA details.
   v2.1   / 01 dec 00 / gvg / Added info on first flight of JSF candidates.
   v2.2.0 / 01 jan 02 / gvg / Broke out JSF materials, minor update.