page_title: Fighter aircraft
section_title: Fourth-generation jet fighters (circa 1970 to mid-1990s)
hierarchical_section_title: Fighter aircraft / Jet-powered fighters / Fourth-generation jet fighters (circa 1970 to mid-1990s)
caption_attribution_description: Čeština: Saab JAS-39 Gripen startuje z letecké základny u Čáslavi. English: Saab JAS-39 Gripen of the Czech Air Force taking off from AFB Čáslav. Français&#160;: Un Saab JAS 39 Gripen de la force aérienne tchèque décolle de la base aérienne de Čáslav, en Tchéquie. Polski: Saab JAS 39 Gripen Czeskich Sił Powietrznych startujący z&#160;bazy w&#160;Czasławiu.
context_page_description: A fighter aircraft, often referred to simply as a fighter, is a military fixed-wing aircraft designed primarily for air-to-air combat against other aircraft. The key performance features of a fighter include not only its firepower but also its high speed and maneuverability relative to the target aircraft.
  The fighter's main tactical purpose is to establish air superiority over the battlefield. The success or failure of a combatant's efforts to gain air superiority hinges on several factors including the skill of its pilots, the tactical soundness of its doctrine for deploying its fighters, and the numbers and performance of those fighters.
  Many fighters have secondary capabilities such as ground attack and some types, such as fighter-bombers, are designed from the outset for dual roles. Other fighter designs are highly specialized while still filling the main air superiority role, these include the interceptor, heavy fighter, and night fighter.
context_section_description: Fourth-generation fighters continued the trend towards multirole configurations, and were equipped with increasingly sophisticated avionics- and weapon-systems. Fighter designs were significantly influenced by the Energy-Maneuverability (E-M) theory developed by Colonel John Boyd and mathematician Thomas Christie, based upon Boyd's combat experience in the Korean War and as a fighter-tactics instructor during the 1960s. E-M theory emphasized the value of aircraft-specific energy maintenance as an advantage in fighter combat. Boyd perceived maneuverability as the primary means of getting "inside" an adversary's decision-making cycle, a process Boyd called the "OODA loop" (for "Observation-Orientation-Decision-Action"). This approach emphasized aircraft designs capable of performing "fast transients" – quick changes in speed, altitude, and direction – as opposed to relying chiefly on high speed alone.
  E-M characteristics were first applied to the McDonnell Douglas F-15 Eagle, but Boyd and his supporters believed these performance parameters called for a small, lightweight aircraft with a larger, higher-lift wing. The small size would minimize drag and increase the thrust-to-weight ratio, while the larger wing would minimize wing loading; while the reduced wing loading tends to lower top speed and can cut range, it increases payload capacity and the range reduction can be compensated for by increased fuel in the larger wing. The efforts of Boyd's "Fighter mafia" would result in the General Dynamics F-16 Fighting Falcon (now Lockheed Martin's).
  The F-16's maneuverability was further enhanced by its slight aerodynamic instability. This technique, called "relaxed static stability" (RSS), was made possible by introduction of the "fly-by-wire" (FBW) flight-control system (FLCS), which in turn was enabled by advances in computers and in system-integration techniques. Analog avionics, required to enable FBW operations, became a fundamental requirement, but began to be replaced by digital flight-control systems in the latter half of the 1980s. Likewise, Full Authority Digital Engine Controls (FADEC) to electronically manage powerplant performance was introduced with the Pratt & Whitney F100 turbofan. The F-16's sole reliance on electronics and wires to relay flight commands, instead of the usual cables and mechanical linkage controls, earned it the sobriquet of "the electric jet". Electronic FLCS and FADEC quickly became essential components of all subsequent fighter designs.
  Other innovative technologies introduced in fourth-generation fighters included pulse-Doppler fire-control radars (providing a "look-down/shoot-down" capability), head-up displays (HUD), "hands on throttle-and-stick" (HOTAS) controls, and multi-function displays (MFD), all essential equipment as of 2019. Aircraft designers began to incorporate composite materials in the form of bonded-aluminum honeycomb structural elements and graphite epoxy laminate skins to reduce weight. Infrared search-and-track (IRST) sensors became widespread for air-to-ground weapons delivery, and appeared for air-to-air combat as well. "All-aspect" IR AAM became standard air superiority weapons, which permitted engagement of enemy aircraft from any angle (although the field of view remained relatively limited). The first long-range active-radar-homing RF AAM entered service with the AIM-54 Phoenix, which solely equipped the Grumman F-14 Tomcat, one of the few variable-sweep-wing fighter designs to enter production. Even with the tremendous advancement of air-to-air missiles in this era, internal guns were standard equipment.
  Another revolution came in the form of a stronger reliance on ease of maintenance, which led to standardization of parts, reductions in the numbers of access panels and lubrication points, and overall parts reduction in more complicated equipment like the engines. Some early jet fighters required 50 man-hours of work by a ground crew for every hour the aircraft was in the air; later models substantially reduced this to allow faster turn-around times and more sortie
caption: Saab JAS-39 Gripen of the Czech Air Force taking off from AFB Čáslav.
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