History 

Although everyone hopes it will never happen, if there were military conflict between the two superpowers, the Soviet side would outnumber the Americans both on the ground and in the air. To win a conventional war, as demonstrated in the final stages of World War II against Germany and Japan, and in Korea at the beginning of the 1950s, the Americans would need air superiority. As today's fighting forces have to operate in almost every conceivable situation, this air superiority would have to apply to night-time flying and to every possible type of weather. In the Western world, there is only one aircraft type that is superior to the best of the Soviet Union's military aircraft, even when outnumbered by the other side. This is the McDonnell Douglas F-15 Eagle.

It is an essential part of USAF doctrine that the first and highest priority of tactical air forces is to achieve air superiority, denying the opposing force the effective use of air space, while simultaneously accomplishing their own missions. In Korea, air superiority was evidenced by a kill ratio of better than 10:1 in favour of the North American F-86s lost in the air. A crucial factor in this success was that the F-86 had bases reasonably close to the combat area: Suwon was only 270 miles (430 km) from where MiGs patrolled and Kimpo was even closer. At one stage (January 1951) the F-86s were forced to withdraw Johnson AFB in Japan, which took them out of reach of the Korean action.

Jet fighters were thus not true replacements for the long-range piston-engined fighters of World War II, such as the North American P-51 Mustang, Republic P-47 Thunderbolt and Lockheed P-38 Lightning. This point was driven home in the 1960s, when the USAF attempted to win control of the air over North Vietnam. Some degree of control was eventually won, but at times the monthly kill ratio favored the enemy's Mikoyan-Gurevich MiG-17s and MiG-21s, and the USAF prevailed only by the extensive use of inflight refuelling for its fighters.

It appears to be common practice after a war for air forces to decide that aerial dogfights are a thing of the past. Fighter speeds progress, and the air staffs judge that close combat is no longer possible: the opposing aircraft will be moving too fast to see one another or manouver to maintain contact, and (in any case) the pilots will be subjected to crushing g-loads. Whether for these or other reasons, the idea of an air superiority fighter was largely abandoned by the USAF after Korea. The service took little interest in the Lockheed F-104 Starfighter, funding instead nuclear strike aircraft such as the Republic F-105 and General Dynamics F-111, and all-weather interceptors such as the Convair F-102 and F-106.

The commitment to USAF aircraft to the Vietnam war in 1962 thus found the service with only a handful of F-104Cs in the air-superiority category. This was initially of no great consequence, since it was a counter-insurgency war with no opposing aircraft, but when bombing missions were scheduled against North Vietnam late in 1964, the gap in the inventory gave rise to serious problems.

Following unsuccessful trials with various types of fighter (including the F-102 and F-104) in the air-superiority role, the USAF was forced to adopt the US Navy's McDonnell F-4 Phantom all-weather interceptor. This was first (F-4D) fitted with an external gunpod (the F-4's missile armament having limited value in a dogfight, especially in terms of g-capability and combat persistence), and later was given a nose cannon and leading-edge manouvering flaps. The resulting F-4E entered service in October 1967, and proved invaluable both for MiGCAP (MiG combat air patrol) duties and as a bomb-carrier.

However, the radius of action needed in Vietnam was far greater than that required in Korea, and the problem was compounded by the new fighter generation's fuel-guzzling afterburning engines. Missions to Hanoi and Haipong had to be flown from remote, secure bases in South Vietnam and Thailand, over a radius of 400 miles (640 km) or more. Although the Phantom was designed for relatively long range and endurance, the only way that adequate combat time could be achieved at such distances was by inflight refuelling, which was generally used both into and out of the target.

Lavish use of aerial tankers (Boeing KC-135s) allowed the F-4E to protect USAF strike aircraft and go hunting for MiGs, but it was blindingly clear that in a "hotter" scenario the tankers would not enjoy such a permissive operating environment, and that many more of them would be needed to support the strategic bombers, rather than tactical fighters. What was required was a new class of fighter that could beat anything the Russians put in the air, yet would have sufficient range and combat persistence significantly to reduce demands on tanker support.

In 1965 the USAF requested funding for feasibility studies of a new air-superiority fighter, designated F-X, and in due course an RFP (Request For Propoposals) was issued in September 1968. The finalists in the competition were Fairchild-Republic, North American Rockwell, and the McDonnell Aircraft (McAir) division of the McDonnell Douglas Corporation (MDC). In December 1969 McAir was selected to proceed with the development of the F-15 under the direction of Air Force Systems Command, with formal authorization in January 1970. This was the first completely new fighter developed specifically for the USAF since the F-101 Voodoo, also a McAir product, which first flew on 29 September 1954.

The initial contract covered the manufacture of 20 pre-series aircraft: 18 single-seat F-15As and two TF-15A (later redesignated F-15B) tandem-seat trainers. The F-X requirement had called for a single-seat, twin-engined aircraft to perform the fighter sweep, escort and CAP missions. Preliminary details suggested that the F-15 would be twice as good as the F-4E in rate of climb and acceleration.

To achieve this breakethrough in performance, the F-15 was given a relatively low wing loading and a thrust/weight in excess of unity, the first time so much power had been installed in a non-V/STOL fighter. In broad terms, it would have a clean weight of 40,000 lb (18144 kg), and a total thrust of 50,000 lb (22680 kg). In terms of level flight speed, this thrust would give a sea-level capability of about Mach 1.2, a sustained level speed of Mach 2.2 at altitude and a dash speed in excess of Mach 2.5.

The installation of so much thrust was possible by virtue of a new generation of engines, with a thrust/weight ratio of around 8:1, giving so light a powerplant weight that there was still plenty of scope for internal fuel. The engine chosen was the Pratt & Whitney F100 afterburning turbofan, selected in February 1970. A few months later the Hughes APG-63 radar was chosen, giving an all-aspect, look-down, shoot-down capability in combination with AIM-7F Sparrow and AIM-9L Sidewinder missiles.

The F-15 was also to have had Philco-Ford GAU-7A 25-mm Gatling gun with caseless ammunition. In this concept the projectile is bonded to a solid block of propellant, to eliminate the weight of the normal case and the time needed to extract it after firing.

Unfortunately, development problems with the gun and its revolutionary ammunition led to its cancellation, and the F-15 reverted to the well-proven General-Electric M61 Vulcan gun that arms most American fighters.

The first F-15A was formally rolled out in June 1972, and had its maiden flight on 27 July, being followed by the first two-seater on 7 July 1973. Funding for the first 30 production aircraft was released late in 1973, and for a further 77 aircraft (to complete the first wing) a year later. The first of 729 production F-15s then planned (one in seven being a two-seater) left the ground on 25 November 1974. Initial operational capability was declared on July 1975, following delivery of the 24th aircraft. The first wing was fully equipped by the end of 1976.

Having got the F-15 into service, this may be a convenient point to describe the aircraft that McAir had produced. In several respects the F-15 bears a strong family resemblance to the preceding F-4, despite being a completely new design. The highly tapered, moderately swept wing is broadly in line with F-4 practice, although it is set high on the fuselage and avoids the need for the steep outboard dihedral of its predecessor. A better clue to the F-15's ancestry comes from the semi-recessed Sparrow missiles and the way the jetpipes are cut short, with the tail mounted well aft. In the case of the F-4, there is a single fin mounted on what is effectively a vestigial fuselage or tail boom. For the F-15, the use of Vigilante-style intakes necessitated the use of twin vertical tails to avoid the destabilizing airflow from the flat upper surface of the cowlings, so the aircraft has been given twin tail-booms on either side of the afterburners, with half the vertical tail and half the tailplane mounted on each.

One of the most important considerations in the design of the F-15 was operation at high angles of attack (AOA). This led to the choice of horizontal-ramp two-dimensional intakes, rather than the vertical ramps used on the F-4. A feature unique to the F-15 is that the intakes are hinged about the lower lip, and rotated downwards as AOA increases, which minimizes spillage, drag and its adverse effect on the vertical tails. Another important consideration was all-round view: the F-15 provided the best rear view of any fighter since the F-86, with the pilot seated high in a bubble canopy. Combat effectiveness also benfits from the use of an advanced head-up display (HUD) and the fact that most of the control functions needed in combat can be carried out without the pilot removing his hands from the control column and throttles. This HOTAS (hands-on-throttle-and-stick) system has controls for radar and missiles, gun, air-brake, microphone button and weapons release.

The F-15 airframe is relatively conventional in construction, but the rear fuselage is largely built of titanium, which makes up 26.5 per cent of structure weight. Graphite composites are used in the airbrake and the tail surfaces, but represent only 1.0 per cent of the structure. Dash speeds of more than Mach 2.5 are permitted, as are indicated airspeeds of 936 mph (1506 km/h), and load factors of +9g and -3g. The aircraft has been flown to an AOA of +120° and -60° . In air-superiority configuration, the F-15 takes off in 900 ft (275 m) and lands in 2,500 ft (760 m).

Perhaps the most dramatic demonstration of the aircraft's performance was the USAF "Strike Eagle" project of early 1975 in which an F-15 set new record times to eight altitudes, beating figures previously set by the F-4 for the lower five and the Soviet Union's E-266 (MiG-25 "Foxbat") for the upper three heights. The new times were: 27.57 sec to 9,845 ft (3000 m), 39.33 sec to 19,685 ft (6000 m), 48.86 sec to 29,530 ft (9000 m), 59.38 sec to 39,370 ft (12000 m), 77.04 sec to 49,215 ft (15000 m), 122.94 sec to 65,615 ft (20000 m), 161.02 sec to 82,020 ft (25000 m) and 207.8 sec to 98,425 ft (30000 m).

The F-15 thus made its mark even before the first unit was fully equipped. In 1986 the USAF had nine F-15 squadrons in the continental USA, four in Europe, and three in the Pacific. Aside from the 57th Tactical Training Wing (tail code WA) at Nellis AFB, Nevada and the 58th TTW at Luke AFB, Arizona (code LA), the F-15 equipped the 1st Tactical Fighter Wing (code FF) at Langley AFB, Virginia, the 36th TFW (code BT) at Bitburg AB in Germany, the 49th TFW (code HO) at Holloman AFB, New Mexico, the 33rd TFW (code ED) at Eglin AFB, Florida, the 32nd Tactical Fighter Squadron (code CR) at Camp New Amsterdam in the Netherlands, and the 18th TFW at Kadena AB, Okinawa (code ZZ).

The F-15A and F-15B have also been sold to Israel under the "Peace Fox" program, which involved 51 aircraft, of which deliveries began in 1976. The F-15s are flown by No. 133 Sqn, apparently as escorts to strike and reconnaissance aircraft. They have been involved in several dogfights with Syrian MiG-21s and MiG-23s over Lebanon (with very statisfactory results), and escorted the F-16s making the strike against Iraq's Osirak nuclear powerplant on 7 June 1981, covering a radius of 600 miles (960 km).

On 26 February 1979 the first of the new F-15Cs took to the air, and deliveries began in the middle of 1980. This second single-seat model has its internal fuel increased from 11,635 lb (5278 kg) to 13,455 lb (6103 kg) under the PEP-2000 program. The F-15C also has provisions for FAST (Fuel And Sensor Tactical) packs on each side of the fuselage, each giving an additional 5,000 lb (2268 kg) of fuel. With FAST packs in place and three 600-US gal (2271-litre) tanks on pylons, the F-15C's gross weight is increased to 66,700 lb (30255 kg). This gives an endurance of over five hours, and an unrefuelled ferry range of 3,080 miles (4957 km). The F-15C and the corresponding F-15D two-seater also have a programmable radar signal processor, giving a fourfold increase in computer capacity, and the ability to continue tracking one target while searching for others at the same time.

The Japanese Air Self-Defence Force (JASDF) acquired 88 F-15s to replace four squadrons of F-104Js and operate alongside six squadrons of F-4EJs, the latter apparently being tasked with the less difficult targets. Deliveries began in July 1980. This "Peace Eagle" program includes 12 F-15DJ two-seaters, which, like the first two F-15J single-seaters, will be built at St. Louis by McAir. The remaining 86 F-15Js will be constructed by Mitsubishi Heavy Industries. The first F-15J, which is identical to the F-15C aside from some avionics changes, was handed over in July 1981, and the first operational squadron was activated at Nyutabaru AB in late 1982 or early 1983.

The third export customer for the F-15 is Saudi Arabia, which took 62 F-15Cs and 15 F-15Ds delivered between early 1982 and late 1984, with two further F-15Cs as attrition reserves. These aircraft replaced three BAe (BAC) Lightning squadrons based at Dharan, Taif and Khamis Mushayt. Their primary role is be air defence, but the Royal Saudi air force has also requested FAST packs, inflight refuelling provisions, multiple ejection racks (MERs), glide bombs and cluster bomb units (CBUs).

At the Farnborough Air Show in 1980 McAir displayed a modified F-15 termed Strike Eagle, a two-seater with FAST packs, provisions for up to 12,000 lb (5443 kg) of external stores, and with its Hughes APG-63 modified to function as a synthetic aperture radar (SAR), giving extremely high resolution against ground targets, without loss of the normal air-to-air modes. It has been reported that with this modification the radar can distinguish between two points less than 10 ft (3 m) apart, from a range of 11 miles (18.5 km).

Deriving from the Strike Eagle demonstrations, the USAF is now to buy approximately 400 F-15E two-seaters for the all-weather ground-attack role. It is not known whether or not this new variant will have SAR, but it is expected to have some avionics changes, provisions for new types of weapon, and possibly a forward-looking infa-red (FLIR) sensor.

Other possible uses for the F-15 in the future are photo reconaissance (with the RF-15 being used as a replacement for the FR-4E), and "Wild Weasel", or defence suppression using non-heat-sensitive AGM-88A high-speed rockets (HARM) built by Texas Instruments. The F-15 is also currently being tested as a launch platform for Anti-Satellite Rockets (ASAT).

"World's Greatest Aircraft" Ó Copyright Marshall Cavedish Books 1986, 1988 by Marshall Cavedish

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