The Lightweight Fighter (LWF) program was a United States Air Force technology evaluation program initiated in the late 1960s by a group of officers and defense analysts known as the "Fighter Mafia". It was spurred by then-Major John Boyd's 'energy-maneuverability' (E-M) theory, which indicated that excessive weight would have severely debilitating consequences on the maneuverability of an aircraft. Boyd's design called for a light-weight fighter with a high thrust-to-weight ratio, high maneuverability, and a gross weight of less than 20,000lb (9,100kg), half that of its counterpart, the McDonnell Douglas F-15 Eagle.[1] It resulted in the development of the General Dynamics YF-16 and Northrop YF-17. Late in the program, in 1974, with the promise of European sales, the Air Force changed the program name to Air Combat Fighter (ACF), and committed to purchasing 650 models of the YF-16, adopted as the F-16 Fighting Falcon. The U.S. Navy adopted a modified version of the YF-17 as the McDonnell Douglas F/A-18 Hornet.
Project Forecast, a 1963 Air Force study, attempted to identify future weapons trends and "certain high-priority areas for research and development (R&D), recommendations based on the greatest potential payoff for the future."[2] The report strongly suggested that future air combat would be carried out primarily by long-range missile fire. Future "fighters" would be designed primarily for long range, high speed, and equipped with extremely large radar systems in order to detect and engage opposing fighters at beyond visual range (BVR). This made them much more like interceptors than classic fighter designs, and led to increasingly heavier and more technologically sophisticated designs – and thus costlier.
The US Navy had long ago come to similar conclusions, and had been designing a series of aircraft dedicated to this role. Notable among these was the well named Douglas F6D Missileer, a long endurance but slow and unmaneuverable design equipped with very powerful missiles and radar for fleet defense. The US Air Force had similar designs, but these had been dedicated to the interceptor role, where the large size of its targets allowed reasonable radar performance. As radar equipment improved, in particular the introduction of Doppler radar systems, fighters gained similar range performance against smaller targets. By the early 1960s, even before the release of Forecast, both the Air Force and Navy expected to use the General Dynamics F-111 Aardvark (then still in development as the TFX) and McDonnell Douglas F-4 Phantom II for their long- and medium-range needs. The perception of a declining need for close-in "dogfighting" capabilities resulted in the original decision to not install internal cannons in the Phantom.[1][3]
Combat experience and E-M theory
However, real-world experience in the Vietnam War revealed some shortcomings in American fighter capabilities, as early generation Soviet jet fighters proved to be more of a challenge than expected for U.S. designs. Although U.S. pilots had achieved favorable kill-to-loss ratios, combat had revealed that air-to-air missiles (AAM) of this era were significantly less reliable than anticipated. Furthermore, the rules of engagement in Vietnam precluded long-range missile attacks in most instances, as visual identification was normally required. Under these conditions, combat invariably closed to short ranges where maneuverability and short-range air-to-air weapons became critical, even for dedicated interceptors like the Convair F-102 Delta Dagger.[3][4]
Based on his experiences in the Korean War and as a fighter tactics instructor, in the early 1960s Colonel John Boyd and mathematician Thomas Christie developed the Energy-Maneuverability (E-M) theory of the value of aircraft specific energy maintenance as an advantage in fighter combat. Maneuverability was the means of getting “inside” an adversary’s decision-making cycle, a process Boyd called the "OODA" loop (from "Observation-Orientation-Decision-Action"). This approach emphasized an aircraft design capable of “fast transients” – quick changes in speed, altitude, and direction. A fighter that is superior in its ability to gain or lose energy while out-turning an opponent can initiate and control any engagement opportunity; a fast transient capability allows the pilot to stay inside a hard-turning opponent when on the offensive or to force an overshoot of an opponent when on the defensive.
These parameters called for a small, lightweight aircraft – which would minimize drag and increase the thrust-to-weight ratio – but a larger, higher-lift wing to minimize wing loading – which tends to reduce top speed while increasing payload, and can lower range (which can be compensated for by increased fuel in the larger wing).[5][6]
The need for new air superiority fighters led the USAF to initiate two concept development studies in 1965: the Fighter Experimental (F-X) project originally envisioned a 60,000-pound (27,200kg) class twin-engine design with a variable-geometry wing. This would be a very expensive aircraft, too expensive to consider equipping the entire Air Force with it as its standard aircraft. For this reason a less-expensive Advanced Day Fighter (ADF) was also considered, a lightweight design in the 25,000lb (11,300kg) class which would out-perform the MiG-21 by 25%.[7]
Boyd used his E-M theory to argue that the F-X design was far too heavy, and this led to new requirements for a smaller F-X in the 40,000-pound (18,100kg) class.[8] However, the appearance of the Mach-3-capable MiG-25 in July 1967 led to serious concerns within the Defense Department that the Soviets had developed a super fighter capable of outrunning anything the US fielded, while its huge wing would make it highly maneuverable. In response, the ADF effort was essentially ignored in favour of an all-out effort to develop a superior F-X, which would emerge as the F-15 Eagle.[9]
Boyd was unimpressed with the resulting weight growth in the F-15, and the shelving of the ADF. In the late 1960s he gathered a group of like-minded innovators that became known as the "Lightweight Fighter Mafia". In 1969, this "Fighter Mafia" was able to secure funds for a "Study to Validate the Integration of Advanced Energy-Maneuverability Theory with Trade-Off Analysis". General Dynamics received $49,000 and Northrop $100,000 study contracts to design concepts that embodied Boyd's E-M theory – a small, low-drag, low-weight, pure fighter with no bomb racks; their work would lead to the YF-16 and YF-17, respectively.[10][11]
Although the Air Force’s F-X proponents remained hostile to the concept because they perceived it as a threat to the F-15 program, the ADP concept (revamped and renamed as the "F-XX") gained civilian political support under the reform-minded Deputy Secretary of Defense David Packard, who favored the idea of competitive prototyping. As a result, in May 1971 the Air Force Prototype Study Group was established, with Boyd a key member. Two of its six proposals would be funded, one being the Lightweight Fighter (LWF). The Request for Proposals (RFP) was issued 6 January 1972, and called for a 20,000lb (9,100kg) class fighter with a good turn rate, acceleration and range, and optimized for combat at speeds of Mach 0.6–1.6 and altitudes of 30,000–40,000ft (9,150–12,200m). This was the region in which the USAF expected most future air combat to occur, based on studies of the Vietnam, Six-Day, and Indo-Pakistani wars. The anticipated average flyaway cost of a production version was $3million.[12][13]
Five manufacturers – Boeing, General Dynamics, Lockheed, Northrop, and Vought – submitted proposals. The Vought V-1100 and the Lockheed CL-1200-2 Lancer were eliminated in March 1972. Though the Boeing Model 908-909 was initially most favored, it was quite similar in technology and appearance to the cheaper General Dynamics Model 401-16B. Since one of the goals of the program was to validate emerging technologies, Secretary of the Air Force Robert Seamans chose to select the General Dynamics and Northrop entries.
The first YF-16 had its official maiden flight on 2 February 1974. The second YF-16 prototype first flew on 9May1974. This was followed by the first flights of the Northrop’s YF-17 prototypes, which were achieved on 9June and 21August1974, respectively. The fly-off commenced in 1974 as both prototypes were delivered. The YF-16s would complete 330 sorties during the flyoff, accumulating a total of 417 flight hours; the YF-17s would accomplish 268 sorties.[14]
Air Combat Fighter competition
Three factors would converge to turn the LWF into a serious acquisition program. First, four North Atlantic Treaty Organization (NATO) members – Belgium, Denmark, the Netherlands, and Norway – were looking to replace their F-104G fighter-bomber variants of the Lockheed F-104 Starfighter interceptor; furthermore, they were seeking an aircraft that their own aerospace industries could manufacture under license, as they had the F-104G. In early 1974, they reached an agreement with the U.S. that if the USAF placed orders for the aircraft winning the LWF flyoff, they would consider ordering it as well.
Secondly, while the USAF was not particularly interested in a complementary air superiority fighter competing with F-X, it did need to begin replacing its F-4 and Republic F-105 Thunderchief fighter-bombers. In April 1974, U.S. Secretary of DefenseJames R. Schlesinger announced that the LWF program would be redirected to a multirole fighter design in the new Air Combat Fighter (ACF) competition. ACF would not be a pure fighter, but more of a fighter-bomber, which essentially ended opposition from the F-X group.
Finally, the U.S. Congress was seeking to achieve greater commonality in fighter procurements by the Air Force and Navy. In August 1974, Congress redirected funds for the Navy’s VFAX program to a new Navy Air Combat Fighter (NACF) program that would essentially be a navalized variant of ACF. These requirements meshed relatively well, but the timing of the procurement was driven by the timeframe needs of the four allies, who had formed a "Multinational Fighter Program Group" (MFPG) and were pressing for a U.S. decision by December 1974. The U.S. Air Force had planned to announce the ACF winner in May 1975, but the decision was advanced to the beginning of the year, and accelerated testing.[15][16][17][18]
ACF also raised the stakes for GD and Northrop because it brought in further competitors intent on securing the lucrative order that was touted at the time as "the arms deal of the century". These included the Dassault-BreguetMirage F1 E (E for Europe) powered by a Snecma M53 engine and utilizing a fly-by-wire system similar to the one used in Dassault Mirage 2000 series.[N 1] Only two prototypes were built for the ACF program,[19] the Anglo-French SEPECAT Jaguar, and a proposed derivative of the Saab 37 Viggen named the Saab 37E Eurofighter (not to be confused with the later and unrelated Eurofighter Typhoon). Northrop also offered their earlier design, the P-530 Cobra, which looked very similar to its YF-17. The Jaguar and Cobra were dropped by the MFPG early on, leaving two European and the two U.S. LWF designs as candidates.
On 11 September 1974, the U.S. Air Force confirmed firm plans to place an order for of the winning ACF design sufficient to equip five tactical fighter wings. The flight test program revealed that the YF-16 had superior acceleration, climb rates, endurance, and (except around Mach 0.7) turn rates. Another advantage was the fact that the YF-16 – unlike the YF-17 – employed the Pratt & Whitney F100 turbofan engine, which was the same powerplant used by the F-15; such commonality would lower the unit costs of the engines for both programs.[18][20] On 13 January 1975, Secretary of the Air ForceJohn L. McLucas announced that the YF-16 had been selected as the winner of the ACF competition.[21] The chief reasons given by the Secretary for the decision were the YF-16's lower operating costs; greater range; and maneuver performance that was "significantly better" than that of the YF-17, especially at near-supersonic and supersonic speeds.
The General Dynamics F-16 Fighting Falcon is an American single-engine supersonic multirole fighter aircraft originally developed by General Dynamics for the United States Air Force (USAF). Designed as an air superiority day fighter, it evolved into a successful all-weather multirole aircraft. Over 4,600 aircraft have been built since production was approved in 1976. Although no longer being purchased by the U.S. Air Force, improved versions are being built for export customers. In 1993, General Dynamics sold its aircraft manufacturing business to the Lockheed Corporation, which in turn became part of Lockheed Martin after a 1995 merger with Martin Marietta.
John Richard Boyd was a United States Air Force fighter pilot and Pentagon consultant during the second half of the 20th century. His theories have been highly influential in military, business, and litigation strategies and planning.
The McDonnell XF-85 Goblin is an American prototype fighter aircraft conceived during World War II by McDonnell Aircraft. It was intended to deploy from the bomb bay of the giant Convair B-36 bomber as a parasite fighter. The XF-85's intended role was to defend bombers from hostile interceptor aircraft, a need demonstrated during World War II. McDonnell built two prototypes before the Air Force (USAAF) terminated the program.
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The Northrop YF-17 is a prototype lightweight fighter aircraft designed by Northrop aviation for the United States Air Force's Lightweight Fighter (LWF) technology evaluation program. The LWF was initiated because many in the fighter community believed that aircraft like the F-15 Eagle were too large and expensive for many combat roles. The YF-17 was the culmination of a long line of Northrop designs, beginning with the N-102 Fang in 1956, continuing through the F-5 family.
A light fighter or lightweight fighter is a fighter aircraft towards the low end of the practical range of weight, cost, and complexity over which fighters are fielded. The light or lightweight fighter retains carefully selected competitive features, in order to provide cost-effective design and performance.
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The Advanced Tactical Fighter (ATF) was a demonstration and validation program undertaken by the United States Air Force to develop a next-generation air superiority fighter to counter emerging worldwide threats, including Soviet Sukhoi Su-27 and Mikoyan MiG-29 fighters under development in the 1980s. Lockheed and Northrop were selected in 1986 to develop the YF-22 and the YF-23 technology demonstrator aircraft. These aircraft were evaluated in 1991 and the Lockheed YF-22 was selected and later developed into the F-22 Raptor.
The Pratt & Whitney F119, company designation PW5000, is an afterburning turbofan engine developed by Pratt & Whitney for the Advanced Tactical Fighter (ATF) program, which resulted in the Lockheed Martin F-22 Raptor. The engine delivers thrust in the 35,000 lbf (156 kN) class and was designed for sustained supersonic flight without afterburners, or supercruise. Delivering almost 22% more thrust with 40% fewer parts than its F100 predecessor, the F119 allows the F-22 to achieve supercruise speeds of up to Mach 1.8. The F119's nozzles incorporate thrust vectoring that enable them to direct the engine thrust ±20° in the pitch axis to give the F-22 enhanced maneuverability.
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The Lockheed/Boeing/General Dynamics YF-22 is an American single-seat, twin-engine fighter aircraft technology demonstrator designed for the United States Air Force (USAF). The design was a finalist in the USAF's Advanced Tactical Fighter competition, and two prototypes were built for the demonstration/validation phase of the competition. The YF-22 won the contest against the Northrop YF-23, and entered production as the Lockheed Martin F-22 Raptor. The YF-22 has a similar aerodynamic layout and configuration as the F-22, but with differences in the position and design of the cockpit, tail fins and wings, and in internal structural layout.
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The Fighter Mafia was a controversial group of U.S. Air Force officers and civilian defense analysts who, in the 1960s and 1970s, advocated for fighter design criteria in opposition to those of the design boards of the time. Their assertions included:
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The General Dynamics–Grumman F-111B is a long-range carrier-based interceptor aircraft planned as a follow-on to the F-4 Phantom II for the United States Navy (USN).
The Vought/General Dynamics Model 1600 series was a fighter aircraft proposal designed for the United States Navy's Navy Air Combat Fighter (NACF) program. The Model 1600 was a carrier-based derivative of the General Dynamics F-16 Fighting Falcon, but lost to the Northrop/McDonnell Douglas F/A-18 Hornet.
The Boeing Model 908-909 was a prototype single-engine supersonic multirole fighter aircraft originally developed for the United States Air Force (USAF) Lightweight Fighter program, a program that later developed into the Air Combat Fighter (ACF) program. It was initially the favored design but lost at the conclusion of the competition to the General Dynamics 401, later the YF-16.
References
Notes
↑ The F-1 E should not be confused with the Dassault Mirage F1E version in service in the French Air Force at the end of the 20th century.
↑ Higham, Robin and Carol Williams. Flying Combat Aircraft of USAAF-USAF (Vol. 2). Manhattan, Kansas: Sunflower University Press, 1978. ISBN0-8138-0375-6.
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