A Sample Feature From Aviation News

Raptor – fighter supreme

David Willis reviews the US Air Force’s troubled new fighter as production numbers diminish and the first aircraft is officially handed over to the service for its initial operational squadron.

Above: It began as an Air Dominance Fighter, but the Lockheed Martin/Boeing F/A-22 looks increasingly like being a future fighter-bomber with the USAF. (Photo, LM).

The Lockheed Martin F/A-22 Raptor will revolutionise the way the US Air Force undertakes operations when it finally enters widespread operational service. Several times during the decade and a half the aircraft has been in development the programme has faced cancellation, but it has survived, although fewer will be built than the 750 once envisaged. The role the aircraft is expected to undertake in service has also radically altered.

Studies which would lead to the Raptor began in 1979 looking at new concepts for both air-to-air and air-to-ground combat aircraft under the Advanced Tactical Fighter (ATF) programme. ATF studies were handicapped by a lack of funds, so it was not until May 1981 that a request for information was issued to nine companies, of which seven presented diverse initial responses. Areas of interest for further study involved low-observables (stealth) and supercruise technologies, as well as the pros and cons of low-cost and heavy, large fighters.

Stealth was in its infancy in the 1970s, as the computing power needed to calculate the best shapes to reduce the radar cross section of an aircraft was not widely available. Both Lockheed and Northrop were working on the Experimental Survivable Testbed (XST) programme that would produce the Lockheed Have Blue aircraft, the predecessor of the F-117A Nighthawk. While stealth had obvious advantages for a combat aircraft, the state of the art in the 1970s could not produce an aircraft for use as an air-to-air fighter – it would lack manoeuvrability because of the unique requirements placed on the external shape.

Supercruise (supersonic-cruise) is the ability to fly above Mach 1 without using the afterburner. These use fuel quickly, reducing the range of the aircraft. An aircraft that could supercruise would have the ability to get where it was needed faster than one without it, and thus have a greater combat persistency. As of the late 1970s, no aircraft could supercruise.

Above: Northrop’s highly classified work on stealth was a major factor in the competing, and subsequently unsuccessful, YF-23A which was considered more innovative than the Lockheed Martin design. (Photo, Northrop Grumman).

A new fighter

The ATF programme settled on investigating air-to-air fighter technologies in 1982. This decision was made because the USAF had by then launched a programme for a new long-range strike aircraft to replace the General Dynamics

F-111. It pitted the F-15 Strike Eagle and the cranked-wing General Dynamics

F-16XL against each other, the less-radical Strike Eagle being chosen to meet the requirement. In October 1982 the US Air Force began to crystallise its ATF requirement around a fighter able to supercruise, possessing a range of 600 – 800nm (1110 – 1480km), the ability to take-off from a 2,000ft (610m) runway and easier to maintain than the F-15. As the Air Force personnel in charge of the ATF programme were given glimpses of the stealth technology, it became desirable to incorporate it into the mix. Around 750 ATFs were required from the mid-1990s as F-15 fighter replacements.

Between September 1983 and early-1984 Boeing, General Dynamics, Grumman, Lockheed, McDonnell Douglas, Northrop and Rockwell undertook Concept Definition Investigations (CDI) of potential ATF configurations. This was followed in October 1985 by the launch of a demonstration and validation (Dem/Val) phase. The companies investigated fighter designs in the 50,000lb (27,000kg) class, with a range of about 700nm (1,300km), the ability to supercruise between Mach 1.4 and 1.5 and manoeuvre at supersonic speeds. The designs would also need to exhibit a very low radar cross section from the frontal quadrant. What emphasis the designs placed on each part of the requirement was left for the companies to decide.

While it had initially been planned to down-select an ATF design based on the Dem/Val data, this was altered in May 1986 to extend the phase to include the construction of prototypes. Lockheed and Northrop had scored highly in the initial Dem/Val and their designs were chosen as the basis of the prototypes to be constructed. Two of each would be built. As the USAF would not fund the whole cost of producing prototypes, industry would have to spend its own money. Lockheed teamed with Boeing and General Dynamics in July 1986 to develop their Configuration 092. Northrop teamed with McDonnell Douglas. The Northrop N-14 was to be built as the YF-23A.

Above: The F-22 cockpit in the most advanced of any US fighter. The three main displays are left to right, defence, situation and attack, while the lower centre one is stores management. Like the F-16, the Raptor has a sidestick controller. (Photo, LM).

Improved powerplants

Parallel to the ATF effort, General Electric and Pratt & Whitney had been working on future fighter powerplants under the Joint Advanced Fighter Engine (JAFE) programme. JAFE sought a unaugmented Mach 1.5 plus powerplant in the 35,000lb thrust class power rating at sea level, capable of incorporating two-dimensional thrust vectoring exhaust nozzles. General Electric’s design was the GE37, a variable-cycle turbojet/turbofan with a dual-spool, vaneless, counter-rotating turbine. Development of the GE37 started in 1983, the design gaining the military designation YF120-GE-100. Pratt & Whitney’s PW5000 was a more conservative design, becoming the YF119-PW-100. Both designs incorporated fewer parts than existing fighter engines and promised to be more reliable and less maintenance intensive. For the ATF Dem/Val the competing engines would power one of each team’s two prototypes.

Above: Trials with the two flying prototypes of the F-22 were undertaken at Edwards AFB, Calif, and included in-flight refuelling from a KC-135. Flying chase is an Edwards-based F-16B.

From 092 to 1132

Configuration 092 underwent major changes to produce the YF-22A. These changes were in part to incorporate the experience of the Boeing and General Dynamics designs submitted for the ‘paper’ Dem/Val exercise, and to make sure the design would actually fly, as the 092 as originally submitted would have been uncontrollable in pitch. Design of the new configuration, 1132, started on July 13, 1987. Four days later initial tests of the YF-22’s avionics system commenced on the Avionics Flying Laboratory (AFL), the Boeing-owned prototype Boeing 757. By October, the new configuration was nearing finalisation. The easing of the runway requirement from 2,000ft (610m) to 3,000ft (915m) in December allowed the thrust reservers that would have been required to be dropped from the design, increasing the efficiency at which the aircraft could supercruise.

The frantic redesign efforts were conducted behind closed doors. The use of low-observable technology and other advanced features cloaked the ATF programme in a level of security that was unusual for a US fighter. This situation was eased somewhat on November 10, 1988, when the Lockheed F-117A was revealed. Twelve days later the Northrop B-2A was rolled out. Stealth had come out of the shadows.

On October 6, 1989, the Defense Acquisition Board approved an extension of the Dem/Val stage by six months, thus delaying Full Scale Development (FSD) by the same amount. The Air Force had been working on the requests for proposals for the FSD contracts since August of that year. Dem/Val would now end in mid-1991. Final assembly of the first YF-22A began at Lockheed’s Palmdale, Calif, Site 10 facility in January 1990, followed by the second prototype the next month. The first two flight-rated Pratt & Whitney YF119s were delivered to Lockheed on June 8 and 17. Roll-out of the first YF-22A (powered by General Electric YF120s) painted with the civil registration N22YF and christened the Lightning II, took place at Palmdale on August 28, 1990.

The Lockheed ATF chief test pilot David Ferguson made the first flight on September 29, 1990, taking off from Palmdale and landing at Edwards AFB, Calif. Major Mark D Shackelford became the first Air Force pilot to fly the aircraft on October 25, when he took the aircraft beyond the sound barrier for the first time. (He would later briefly head the F/A-22 System Programe Office.) The YF119-powered second prototype (N22YX) flew four days later, with Lockheed’s Tom Morgenfeld at the controls. For the Dem/Val phase N22YF flew 43 sorties (52.8hr) and N22YX 31 (38.8hr).

The rival

Northrop and McDonnell Douglas had beaten the Lockheed team into the air, their YF-23A flying on August 27 piloted by Northrop’s ATF chief test pilot, Paul Metz. The YF-23A was seen as the most innovative and technologically sophisticated of the two ATF designs. It met the needs of the ATF requirement but that it lost was probably due more to factors outside the control of those associated with it than anything to do with not meeting the needs for an ATF.

The Lockheed team were keen to use the YF-22A demonstrators not only to show the USAF that it could meet all the requirements laid down in the Dem/Val requirements, but also to go beyond it. These included launching an unguided AIM-9 from the second aircraft on November 28, 1990, an AIM-120 on December 20 and extremely high-alpha tests of up to 60°. The YF-23A never fired a missile, while angle-of-attack tests were limited to those stipulated in the requirements. Lockheed also played on its ability to manage a production ATF programme successfully. However, given the difficulties experienced during the subsequent development programme, the Air Force probably wishes it had been more sceptical of such predictions.

Below: The mid-fuselage of the first F-22 being prepared for shipment from Fort Worth, Texas, to Marietta, GA. (Photo, LM).

Selection announcement

In January 1991 the F-22 programme offices began to relocate from Burbank to Marietta, Ga. The team had submitted its FSD proposal to the USAF on the last day of 1990 and the Secretary of the Air Force, Dr Donald Rice, declared the YF119-PW-100-powered YF-22 the ATF winner on April 23. On August 2 a $9.55bn Engineering and Manufacturing Development (EMD, the new term for FSD) contract was awarded for 11 F-22s (including two two-seaters), a static test airframe and one fatigue test airframe. Pratt & Whitney were awarded a $1.375bn contract to develop the F119 and produce 33 F119-PW-100s for the EMD programme.

The day before the F-22 was selected, Rice had announced that the number of ATFs to be acquired was to be cut from 750 to 648. In addition to the Air Force examples, the US Navy was notionally interested in a development of the ATF as the Navy Advanced Tactical Fighter (NATF), a Grumman F-14 Tomcat replacement. The NATF (‘F-22C’) would use the body of the F-22 with a variable geometry wing, a beefed up undercarriage and arrestor hook, a redesigned canopy and cockpit and stabilators. In reality, the Navy was already investing in the F-14D Super Tomcat and all NATF work was terminated in the early 1990s.

The YF-22As had been placed in storage following the Dem/Val phase, but on October 30, 1991, the second example returned to the air for trials associated with the production aircraft. These were brought to a halt on April 25, 1992, when the aircraft experienced a series of pitch oscillations about 40ft (12m) above the Edwards AFB runway. With its undercarriage retracted, the aircraft hit the runway and slid about 800ft (244m), before catching fire. The first YF-22A was used as an engineering mockup after starring in an exhibition of stealth weapons at Andrews AFB, Md, in June 1991.

For the rest of this article please see the January 2005 issue.