Lightweight Fighter (LWF)
During the transitional period of the late 1960s, when fighter planes were growing ever heavier and more complex, an ad hoc group of jet pilots in the U.S. Air Force – dubbed the "Fighter Mafia" – sized up the problem and offered a new direction. There were four key individuals in this mafia: Charles ("Chuck") Myers, a former test pilot and Lockheed salesman turned private consultant; Maj (subsequently Col) John R. Boyd, Pierre Sprey of the Systems Analysis Office within DOD; and Col Everest Riccioni. One "outsider" deserves more attention for his part in reasserting the primacy of the air superiority fighter within the Air Force: Maj Gen Arthur C. Agan, the Air Staff's director of plans.
They believed the trend toward multi-role aircraft (nominally called "fighters") weakened their capabilities. For example, the F-105 Thunderchief, a laudable combat plane, was far more a supersonic bomber than it was a dogfighter – and the racy F-106 and powerhouse F-4 initially weren’t even built with a gun for close-quarter combat.
What the Fighter Mafia believed was needed was a return to the air superiority fighters of previous decades – a fighter that could maneuver when needed to bring guns to bear. Any additional features such as the ability to bomb must not diminish the fighter's air superiority capability. These experienced airmen believed that applying the K.I.S.S. ("keep it simple, stupid") principle would enable the pilots to avoid task saturation and concentrate on keeping their eyes on the enemy and their hands on the throttle. The Fighter Mafia envisioned a fighter less constrained by aircraft limitations. This technologically- superior craft would rely on the balance between energy, speed and position to dictate the fight.
The load factor requirements established in 1949 provided three classes of fighter aircraft. These fighter classes were established to provide sufficient strength and rigidity for a primary. This strict tactical definition minimized multi-mission capability.
Class I fighters were known as low altitude, high strength, general purpose types designed to limit load factors of +8.67 and -4.0 at combat weight. Aircraft of this Class were designed for high maneuverability and high speeds at low altitudes. Consequently, they were limited to a relatively short radius of action. This type was suited for close air support work at shorter ranges. These airplanes were not adaptable to high altitude fighting. They could be satisfactorily used at intermediate ranges and altitudes by substitution of fuel tanks for weapons. These aircraft were rugged and well suited for training.
Class II fighters were long range, intermediate altitude types of medium strength. They were used for escort work, interdiction, or air superiority at longer ranges. They were designed to +7.33 and -3.0 at combat weight. They were adequate for limited use at short range and high altitude if fuel load was reduced. They could be used for close air support at lower load factors by the replacement of fuel with weapons.
Class III fighters were high altitude interceptors low load factor (+5.33 to -3.0) capability. This allowed minimum structural weight and maximum high altitude performance. They were adequate for limited use at intermediate altitudes but were inadequate for general air superiority or close air support missions.
The Korean War in the early 1950s was viewed in some circles as an anachronism because gun-firing, dogfighting jets like the F-86 and the Soviet-made MiG-15 prevailed. But it was argued that the advent of reliable homing missiles carried by supersonic interceptors would change the way of aerial warfare forever. To that end, the Air Force fostered the development of dazzling jet fighters that could reach the stratosphere quickly, and unleash guided missiles at an attacker too distant to be seen. They were Mach 2 fighters such as the F-104, F-106 and F-4 Phantom.
After 1953, air superiority, so far as fighter aircraft were concerned,was again limited largely to the defense of the U.S. against enemy bombers. Tactical fighters were designed primarily for nuclear war where penetration was more important than maneuverability, ordnance, load-carrying ability more important than armament, alert status more important that sustained sortie rates. The tactical fighter became less and less an air superiority system, more and more what once was called an attack aircraft.
Between 1954 and 1960, Boyd had revolutionized the teaching of air-to-air tactics at the USAF Fighter Weapons School and Combat Crew Training Squadrons at Nellis AFB. While at Nellis, he wrote his famous Aerial Attack Study. After leaving the Fighter Weapons School in 1960, Boyd moved to the Air Proving Grounds Center at Eglin AFB, Florida, where he, assisted by mathematician Tom Christie, developed the "Energy Maneuverability Theory." This provided concise, quantitative aircraft maneuverability comparisons as a tool for tactics development, and also created a new language for pilots to use in talking with aircraft designers.
Boyd's work provided the tools needed to explain the character of aircraft maneuvering performance that was required to yield a superior air combat fighter. These new three-dimensional fighter maneuvers and the maneuver/countermaneuver logic developed by Boyd are still the basis for the fighter tactics of every modern air force in today's world.
When it came to eyeballs-out-the-cockpit dogfighting – American fighters of the 1960s couldn’t compare with gunfighters designed specifically for air-to-air combat. That lesson was driven home above Vietnam in the 1960s, when the F-4 Phantom II – the most versatile of the Air Force stable – was outmaneuvered by smaller, more nimble North Vietnamese MiG-17s and -21s designed a generation earlier. During the Vietnam Era, US fighter aircraft had limited maneuvering capabilities at transonic speeds. Air Force and Navy Phantom pilots were required to adhere to the "rules of engagement," which demanded that they visually identify and confirm their target as an enemy aircraft. This ruled out the firing of missiles from long distances.
When they flew close enough to see the MiGs, they found themselves in the classic dogfighter's game. The maneuverable Soviet-designed jets had the edge. In addition, the missiles fired by the American flyers were better suited to downing big, slow bombers rather than small evasive fighters. To be sure, American fighter pilots responded with initiative and found ways to leverage the capabilities of the powerful twin-engine F-4 in vertical flight. Yet the necessity for close-in combat merely pointed out the limitations of American fighters of that era.
Two technological developments – high-thrust afterburning turbofan engines and computerized fly-by-wire control systems – offered real possibilities for the development of this new-era dogfighter. The result was an aircraft with transonic maneuver capability.
Early in 1966, the "Preliminary Concept for FX" was released by TAC. It was oriented to the air-to-air problem, but invited additional multipurpose capabilities for night and poor weather air-to-ground capability. Soon thereafter, the Navy (in the process of escaping from the TFX/F-111B commonality trap) created an operational requirement for the VFX (initially called the VFAX), a deep-strike, all-weather interceptor, dual-purpose aircraft. At that point OSD (DDR&E) suggested that the Air Force and Navy combine their requirements to yield a new common "fighter."
By late 1967 both the Air Force and the Navy wanted to develop a new fighter to replace the F-4. They believed it was needed to counter the latest Soviet fighters. At that time the services recommended that DOD plan to proceed with "Contract Definition" in FY 69 leading to an Initial Operational Capability in 1975. The FY69 cost of this proposal was estimated at about $104 million. At that time properly defined and substantiated joint-Service plan for F-X/VFAX had not yet been developed. Several important issues had not been resolved, including the extent to which the two Service versions can be common, the size of the crew, and the extent to which all-weather air-to-ground electronics should be included. Initial spending focused on an extensive experimental effort in avionics and propulsion to help resolve these issues and to reduce program risks, permitting start of full-scale development in FY 70.
Following the disastrous attempt to achieve interservice aircraft commonality with the F-111, the Navy issued a request for proposals (RFP) for a new VFX fighter in July 1968. Competitors included Grumman, General Dynamics, Ling-Temco-Vought, McDonnell Douglas, and North American Rockwell. On January 14, 1969, the Navy announced the award of the contract for the VFX fighter, now designated F-14, to Grumman.
The F-15 System Program Office (SPO) at Wright-Patterson AFB featured a banner that read "Not a pound for air-to ground!" This ultimately proved as farfetched as ignoring the air-to-air mission. Virtually all air superiority fighter aircraft, with the exception of a few specialized interceptors, virtually all air superiority fighter aircraft since the First World War have dropped bombs or attacked ground targets. While air superiority fighters have succeeded as bomb droppers, there are no cases of taking a dedicated ground attack aircraft and making it into a successful fighter.
In 1968, fearful that the F-15 would turn out to be another big fast unmaneuverable sled, members of the Fighter Mafia began arguing for a highly agile, single-engine, and less-than-Mach 2 "austere" fighter, the so-called F-XX. The F-XX germinated in late summer of 1971 in the so-called Lightweight Fighter Program.
In January 1972, the Lightweight Fighter Program solicited design specifications from several American manufacturers. Participants were told to tailor their specifications toward the goal of developing a true air superiority lightweight fighter. Three proposals that looked especially promising were submitted by Boeing, Northrop and General Dynamics. Ultimately, the Air Force funded the construction of two prototypes each from Northrop and General Dynamics (now Lockheed Martin).
The LWF program received a boost from the redirection of defense acquisition in June 1970, when Richard M. Nixon's "Blue Ribbon Defense Panel" recommended ending so-called total package procurement and returning to competitive prototyping, something that had been abandoned since the late 1950s. Fly-before-buy was a return to earlier procurement philosophies. Aircraft purchased before first flight frequently were attended with subsequent delays and hurdles. As a result, General Dynamics and Northrop were asked to build prototypes, which could be evaluated with no promise of a follow-on production contract. These were to be strictly technology demonstrators. The two contractors were given creative freedom to build their own vision of a lightweight air superiority fighter, with only a limited number of specified performance goals.
Originally, no direct competition was scheduled. Both companies were given broad performance requirements to determine the feasibility of developing a small, light and lowcost fighter. Each was also responsible for evaluating advanced technologies and design concepts, determining the aircraft capabilities and establishing its possible operational utility.
With the guidelines drawn, Northrop produced the twin-engine YF-17, using breakthrough aerodynamic technologies and two high-thrust engines. General Dynamics countered with the compact YF-16, built around a single F100 engine. The YF-16 was a small airframe densely packed with all the necessary equipment and stowage. There was no room to weight it down with mission-complicating gear.
In the 1960s, the MIL-A-8860 series specifications had established a limit loads factor of 7.33g for fighters with the asymmetric limit load factor being 80% of the symmetric value. During the Lightweight Fighter program in the mid-1970s, it was found that the design symmetric load factor could be increased from 7.33g to 9g with very little weight penalty. However, the design asymmetric load factor remained at 80% of 7.33g (5.86g). As the program matured, trade studies were conducted to investigate the impact of increasing the design asymmetric load factor to 80% of 9g (7.2g). Results indicated that the weight penalty for increasing the asymmetric limit was substantially greater than that for the increased symmetric limit.
The fast pace of the lightweight fighter prototype development quickly revealed problems in early-generation high-thrust engine designs, used in conventional fighter planes. Lightweight "hot rod" fighters make punishing demands on their engines: frequent and extreme changes in throttle settings tax engine response. Sluing through the air at high angles of attack means that engines have to labor to convert air and fuel into reliable thrust. The engines for the lightweight fighter prototypes had to perform superbly in maneuvers and flight conditions that conventional fighters simply could not reach.
Each firm was free to establish their own timetable. The General Dynamics aircraft rolled out in December 1973 and made its first flight Feb. 2, 1974 at Edwards Air Force Base, Calif. The first Northrop aircraft rolled out in April 1974 and made its first flight in June 1974. When the Lightweight Fighter program was completed early in 1975, both the YF-16 and the YF-17 showed great promise. The two prototypes performed so well, in fact, that both were selected for military service.
The Lightweight Fighter Program stands as a shining example of the art of aircraft development. By giving developers creative freedom in the design and evaluation process, more innovations were tried and verified in short order than would have been the case with other acquisition methods.
Air Combat Fighter (ACF)
In April 1974, the LWF Program changed from a technology demonstration program to a competition for an Air Force Air Combat Fighter (ACF). This marked a shift from the original intention to use the two airplanes strictly as technology demonstrators. The flight-test programs for the YF-16 and YF-17 were rushed through in a few months instead of the planned 2 years.
On 13 January 1975, the Air Force announced that the YF-16's performance had made it the winner of its Air Combat Fighter (ACF) competition. General Dynamics' YF-16 had generally shown superior performance over its rival from Northrop. At the same time, the shark-like fighter was judged to have production costs lower than expected, both for initial procurement and over the life cycle of the plane. At the same time, the YF-16 had proved the usefulness not only of fly-by-wire flight controls, but also such innovations as reclined seat backs and transparent head-up display (HUD) panels to facilitate high-G maneuvering, and the use of high profile, one-piece canopies to give pilots greater visibility. Thus, the Air Force had its lightweight fighter, the F-16.
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