LOOK AT FIGHTER evolution in 25-year steps, and the technological advance which can occur in a quarter-century is obvious. The 1915 Fokker DVII, 1940 North American P-51 and 1965 McDonnell Douglas F-4 were each the dominant fighters of their age, and illustrate the advances that have been achieved. Another 25 years - and a technological leap equally as great, its developers argue - separate the roll-out of the Lockheed Martin/Boeing F-22 from the first flight of the McDonnell Douglas F-15.

Externally, the gap may not seem as great as that between the P-51 and the F-4, but the F-22 is designed to fight on the information battlefield of the 21st century, says programme general-manager Tom Burbage, who likens the F-15 to a "morse-code transmitter on the Internet". The F-22 is designed to exploit information while denying information to the enemy, through its sensors and stealth, he explains.

The F-22 represents an advance over the F-15 in "traditional" areas of design, with its combination of stealth, speed and manoeuvrability, but heralds a revolutionary change in "non-traditional" areas, argues Burbage. The F-22 has twice the flight envelope of the F-15, he says, but more important is its computing power - 10.5 billion operations/s throughput and 300 megabytes memory, with 200% growth capacity.

That computing power is used to provide the F-22 pilot with a fused, easy to read, picture of the information available from onboard sensors and offboard sources, and to handle all housekeeping tasks. "The pilot manages the mission, not the sensors," says Burbage. The design aim is to enable every F-22 pilot to be a fighter ace, by unlocking "human potential" and combining it with stealth, speed and manoeuvrability to guarantee "-overwhelming lethality against air-to-air targets and high survivability against surface-to-air threats", he says.

Burbage says that the F-22 presented unique design challenges, requiring the combination of stealth with agility and low observability with situational awareness. Apertures which enable the F-22's sensors to look out while preventing threat sensors from looking in are "-the most advanced technology on the aircraft", he says.

Aerodynamically, the F-22 is "-more than just an F-15 replacement", argues Burbage. Low drag and high power allow "supercruise" - sustained high-supersonic speed without afterburner - which reduces infra-red signature and extends range. "Speed and stealth compress the timeline of threat reaction," he says. The F-22's "unbounded manoeuvrability" will include the ability to fly at 60í angle-of-attack and 80kt (150km/h) and still roll the aircraft - although the pilot should rarely get into a dogfight, he says.

"If the F-22 gets into a 9g turning fight, then we've done something wrong," says Burbage, for the operational concept is "-first look, first shot, first kill" - the ability to detect, identify and engage targets while still beyond range of their sensors and weapons. Targets will be identified passively by their emissions, or by information arriving via datalink from other F-22s or surveillance aircraft. Radar will be used sparingly and covertly. Data will be fused, targets prioritised and a "shoot list" displayed.

"The pilot does not care which sensor is providing what data,"Burbage says. The concept is to "maximise information and minimise data", he adds. The pilot will move a cursor down the shoot list and launch AIM-120 advanced medium-range air-to-air missiles (AMRAAM) - the F-22's primary armament - from the underfuselage weapons bays towards their targets, hopefully without ever coming under attack.


Design environment

Burbage's counterpart at the US Air Force's F-22 programme office, Brig Gen Michael Mushala, highlights the role which computing power has played in the design of the F-22. "The most sophisticated design environment available is used throughout the programme," resulting in significant savings, he says. Using the CATIA design system and COMOK modelling tool across the F-22 team, including subcontractors, has ensured that parts produced at different sites "-fit exactly together", he says.

Final assembly has gone "very smoothly", Mushala says. Major assemblies have been mated within hours: "They go 'click', and everything checks out," he adds.

Mushala also praises the integrated environment used for design of the F-22's software. "Contractors have common operating hardware, use the same operating-system software and are connected electronically," he says. "TRW, for example, can develop software, test it on real flight hardware, and deliver it electronically to Boeing, where it is loaded on to identical hardware, with the same operating system, and checked out in the avionics-integration laboratory," Mushala explains. "There have been very few integration problems," he says.

Burbage says that the avionics architecture will enable component obsolescence to be overcome by inserting new technology over the life of the F-22. Plug-in modules will enable the aircraft to be upgraded regularly to take advantage of rapidly advancing electronics technology. "The challenge is that we will have to change parts; the opportunity is that we can change parts, and achieve savings and increase reliability," agrees Mushala, adding: "I really want to replace [obsolete] parts, so that I can take advantage of technology insertion."



Mushala also highlights the "very aggressive" engine programme. Some 40% of ground testing of the Pratt & Whitney F119 has been at simulated altitude and speed at the Air Force's Arnold Engineering Development Center, "...which is almost like flight test," he says. Walt Bylciw, senior vice-president F119 programmes at P&W, says that engines have been tested "...to a level of sophistication and understanding far beyond anything we have done before."

Heavily instrumented engines were tested early in development to gain an "excellent signature" of the F119's operation, Bylciw says. This has enabled P&W to tackle the root causes of problems encountered during development. Computational fluid-dynamics has been used extensively in design of the F119, and in the identification and solution of those problems, he says.

Bylciw emphasises the "tight co-ordination" between P&W, Lockheed Martin/Boeing and the Air Force that has resulted from the integrated product-development environment created for the programme. The F-22's ultimate user, USAir Force Air Combat Command, has been included on the design teams, Mushala points out. The aircraft that has resulted from this process is "...a high-quality product that will meet user expectations," he maintains.

"The F-22 is meeting or exceeding all key performance parameters and we have a solid foundation from which to take the aircraft forward into production," Mushala says. There are no significant technical challenges ahead, he believes. "The first challenge is to design and build the aircraft, then it is how to make it cheaper and more reliable," he says, acknowledging that cost remains the key issue.

The programme was restructured early in 1997 to extend development and reduce production costs. Changes to the development timescale are mainly to reduce schedule risk in avionics flight-testing, but result in a slowing down of production over the first five years. At the same time, the team has agreed to invest in cost-reduction initiatives intended to offset cost growth and inflation over the planned 438-aircraft production programme.

"Our overall goal is to do better the zero growth," says Mushala. Burbage says that the intention is to reduce the average unit cost by "several million dollars". The plan is to demonstrate the producibility improvements over the first five years of low-rate production, so as to qualify for multi-year procurement - an approach which won dramatic cost reductions on the McDonnell Douglas C-17 programme.



F-22 engineering and manufacturing development is now scheduled to be completed in March 2003, at an estimated cost of $18.7 billion. Initial operating capability is still planned for November 1994. Production of the planned 438 aircraft for the US Air Force is projected to cost $48 billion, with the average F-22 flyaway unit cost over the life of the programme estimated at almost $72 million in 1996 prices.

Burbage believes that the controversy surrounding the F-22's cost has overshadowed the engineering achievement that the aircraft represents. "The team has advanced the state of the art through this programme, and should be recognised for its contribution to the US science and technology base," he says. Mushala agrees: "The overall capability of the US aerospace industry has increased with this programme."

Source: Flight International