A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets by dropping bombs. Fighters are comparatively small, fast, and maneuverable. Fighter aircraft are the primary means by which armed forces gain air superiority over their opponents above a particular battle space. Since at least World War II, achieving and maintaining air superiority has been a key component of victory in most modern warfare, particularly conventional warfare between regular armies (as opposed to guerrilla warfare), and the acquisition, training and maintenance of a fighter fleet represent a very substantial proportion of defence budgets for modern militaries.
Terminology
The word "fighter" did not become the official English term for such aircraft until after the First World War. In Great Britain’s Royal Flying Corps – which would later become the Royal Air Force – these aircraft continued to be called "scouts" into the early 1920s. The U.S. Army called their fighters "pursuit" aircraft (reflected by their designation in the "P" series) from 1916 until the late 1940s. In the French and German languages the term used (and still in use) literally means "hunter". This has been followed in most other languages, an exception being Russian, in which the fighter is called "истребитель" (pronounced "istrebitel") which word used is literally "exterminator".
Although the term "fighter" technically refers to aircraft specifically designed to shoot down other aircraft, colloquial usage often extends to include multirole fighter-bombers and sometimes lighter, fighter-sized tactical ground-attack aircraft (as opposed to bombers, which serve mainly in strategic bombing roles). In recent decades, only the highest-capability fighters have been optimized as air superiority combat aircraft (with limited air-to-ground capabilities), with most other aircraft being designed as multirole fighter-bombers (a term that is slowly being replaced by simply "fighters"). The combination of air-superiority fighters and multirole fighters is often referred to as the “high-low mix”.
Introduction
Fighters were developed in response to the fledgling use of aircraft and dirigibles in World War I for reconnaissance and ground-attack roles. Early fighters were very small and lightly armed by later standards, and were mostly biplanes. As aerial warfare became increasingly important, so did control of the airspace. By World War II, fighters were predominantly all-metal monoplanes with wing-mounted batteries of cannons cannons or machine guns. By the end of the war, turbojets were already beginning to replace piston engines as the means of propulsion, and missiles to augment or replace guns and simple gravity bombs.
Modern jet fighters are predominantly powered by one or two turbofan engines, and are equipped with a radar as the primary method of target acquisition. Armament consists primarily of air-to-air missiles (from as few as two on some lightweight day fighters to as many as eight or twelve on air superiority fighters like the Su-37 Flanker or F-15 Eagle), with a cannon as backup armament (typically between 20 and 30 mm in calibre); however, they can also often employ air-to-surface missiles, as well as guided and unguided bombs.
Piston engine fighters
World War I
Vickers F.B.5 Gunbus
The word “fighter” was first used to describe a two-seater aircraft with sufficient lift to carry a machine gun and its operator as well as the pilot. The first such “fighters” belonged to the “gunbus” series of experimental gun carriers of the British Vickers company which culminated in the Vickers F.B.5 Gunbus of 1914. The main drawback of this type of aircraft was its lack of speed. It was quickly realised that an aircraft intended to destroy its kind in the air needed at least to be fast enough to catch its quarry.
Fortunately, another type of military aircraft already existed, which was to form the basis for an effective "fighter" in the modern sense of the word. It was based on the small fast aircraft developed before the war for such air races as the Gordon Bennett Cup and Schneider Trophy. The military scout aeroplane was not initially expected to be able to carry serious armament, but rather to rely on its speed to be able to reach the location it was required to “scout” or reconnoitre and then return quickly to report – while at the same time making itself a difficult target for anti-aircraft artillery or enemy gun-carrying aircraft. British “scout” aircraft in this sense included the Sopwith Tabloid and Bristol Scout; French equivalents included the light, fast Morane-Saulnier N.
In practice, soon after the actual commencement of the war, the pilots of small scout aircraft began to arm themselves with pistols, carbines, grenades, and an assortment of improvised weapons with which to attack enemy aircraft. It was inevitable that sooner or later means of effectively arming “scouts” would be devised. One method was to build a “pusher” scout such as the Airco DH.2, with the propeller mounted behind the pilot. The main drawback was that the high drag of a pusher type's tail structure meant that it was bound to be slower than an otherwise similar “tractor” aircraft. The other initial approach was to mount the machine gun armament on a tractor-type aeroplane in a manner that enabled the gun to fire outside the arc of the propeller.
Airco DH.2 "pusher" scout
Only two configuration options were practical initially for tractor aircraft. One involved having a second crew member added behind the pilot to aim and fire a swivel-mounted machine gun at enemy aeroplanes. However, this limited the area of coverage chiefly to the rear hemisphere, and the inability to effectively coordinate the pilot’s manoeuvring with the gunner’s aiming, which reduced the accuracy and efficacy of the gunnery. This option was chiefly employed as a defensive measure on scouts later on during the war as true fighters became increasingly effective. The alternative configuration mounted the guns on the upper wing where they could fire over the propeller arc. While more effective for offensive combat, since the pilot could move and aim the guns as a unit, this placement made determining the proper aim point more difficult. Furthermore, this location made it nearly impossible for a pilot to manoeuvre his aeroplane and have access to the gun’s breech – a very important consideration, given the tendency of early machine guns to jam – hence this was a stopgap solution at best. Nevertheless, a machine gun firing over the propeller arc was to remain in service from 1915 (Nieuport 11) until 1918 (Royal Aircraft Factory S.E.5 with its purpose-built Foster mounting).
A captured Morane-Saulnier Type L with German insignia
The need to arm a tractor scout with a forward-firing gun whose bullets actually passed through the propeller arc was evident even before the outbreak of war, and its approach motivated inventors in both France and Germany to devise a practical synchronisation gear that could time the firing of the individual rounds to when the propeller wasn't in the way. Franz Schneider, a Swiss engineer, had patented such a device in Germany in 1913, but his original work was not followed up. French aircraft designer Raymond Saulnier patented a practical device in April 1914, but trials were unsuccessful because of the propensity of the machine gun employed to hang fire due to unreliable ammunition. In Dec. 1914, French aviator Roland Garros asked Saulnier to install his synchronisation gear on Garros’ Morane-Saulnier Type L scout. Unfortunately the gas-operated Hotchkiss machine gun had a firing cycle which caused the bullet to leave the weapon too late to effectively and consistently synchronise the gunfire with a spinning propeller. Due to this problem, the propeller blades were armoured, and Garros’ mechanic, Jules Hue, fitted metal wedges to the blades to protect the pilot from ricochets. Garros’ modified monoplane was first flown in March 1915 and he began combat operations soon thereafter. Firing 8 mm (.323 in) solid copper bullets, Garros scored three victories in three weeks before he was himself shot down on 18 April and his aeroplane – along with its synchronisation gear and propeller – was captured by the Germans.
However, the synchronisation gear (called the Zentralsteuerung in German) devised by the engineers of Anthony Fokker's firm was the first gear to attract official sponsorship, and this would make the pioneering Fokker Eindecker monoplane a feared name over the Western Front, despite its being an adaptation of an obsolete pre-war French Morane-Saulnier racing aeroplane, with a mediocre performance and poor flight characteristics. The first victory for the Eindecker came on 1 July 1915, when LeutnantKurt Wintgens, flying with the Fliegerabteilung 6 unit on the Western Front, forced down a Morane-Saulnier Type L two-seat "parasol" monoplane of Luneville. Wintgens' aircraft, one of the Fokker M.5K/MG production prototypes of the Eindecker, was armed with a synchronised, air-cooled aviation version of the Parabellum MG14 machine gun, which did not require armoured propellors. In some respects, this was the first "true" fighter victory of military aviation history.
The success of the Eindecker kicked off a competitive cycle of improvement among the combatants, building ever more capable single-seat fighters. The Albatros D.I of late 1916 set the classic pattern followed by almost all such aircraft for about twenty years. Like the D.I, they were biplanes (only very occasionally occasionally monoplanes or triplanes). The strong box structure of the biplane wing allowed for a rigid wing that afforded accurate lateral control, which was essential for fighter-type maneuvers. They had a single crew member, who flew the aircraft and also operated its armament. They were armed with two Maxim-type machine guns – which had proven much easier to synchronise than other types – firing through the propeller arc. The gun breeches were typically right in front of the pilot’s face. This had obvious implications in case of accidents, but enabled jams (to which Maxim-type machine guns always remained liable) to be cleared in flight and made aiming much easier.
The use of metal in fighter aircraft was pioneered in World War I by Germany, as Anthony Fokker used chrome-molybdenum steel tubing (a close chemical cousin to stainless steel) for the fuselage structure of all his fighter designs, and the innovative German engineer Hugo Junkers developed two all-metal, single-seat fighter monoplane designs with cantilever wings: the strictly experimental Junkers J 2 private-venture aircraft, made with steel, and some forty examples of the Junkers D.I, made with corrugated duralumin, all based on his pioneering Junkers J 1 all-metal airframe technology demonstration aircraft of late 1915.
Allied and, until 1918, German pilots of World War I were not equipped with parachutes, so most cases of an aircraft catching fire, or structurally breaking up in flight were fatal. Parachutes were well-developed by 1918, and were adopted by the German flying services during the course of that year (the famous "Red Baron" was wearing one when he was killed), but the allied command continued to oppose their use, on various grounds.[1]
Fighter development slowed between the wars, with the most significant change coming late in the period, when the classic WWI type machines started to give way to metal monocoque or semi-monocoque monoplanes, with cantilever wing structures. Given limited defense budgets, air forces tended to be conservative in their aircraft purchases, and biplanes remained popular with pilots because of their agility. Designs such as the Gloster Gladiator, Fiat CR.42, and Polikarpov I-15 were common even in the late 1930s, and many were still in service as late as 1942. Up until the mid-1930s, the vast majority of fighter aircraft remained fabric-covered biplanes.
Fighter armament eventually began to be mounted inside the wings, outside the arc of the propeller, though most designs retained two synchronized machine-guns above the engine (which were considered more accurate). Rifle-caliber guns were the norm, with .50 calibre (12.7 mm) machine guns and 20 mm cannons were deemed "overkill." Considering that many aircraft were constructed similarly to WWI designs (albeit with aluminium frames), it was not considered unreasonable to use WWI-style armament to counter them. There was insufficient aerial combat during most of the period to disprove this notion.
The rotary engine, popular during WWI, quickly disappeared, replaced chiefly by the stationary radial engine. Aircraft engines increased in power several-fold over the period, going from a typical 180 hp in the 1918 Fokker D.VII to 900 hp in the 1938 Curtiss P-36. The debate between the sleek in-line engines versus the more reliable radial models continued, with naval air forces preferring the radial engines, and land-based forces often choosing in-line units. Radial designs did not require a separate (and vulnerable) cooling system, but had increased drag. In-line engines often had a better power-to-weight ratio, but there were radial engines that kept working even after having suffered significant battle damage.
Some air forces dabbled with "heavy fighters" (called "destroyers" by the Germans). These were larger, usually two-engined aircraft, sometimes adaptations of light or medium bomber types. Such designs typically had greater internal fuel capacity (thus longer range) and heavier armament than their single-engine counterparts. In combat, they proved ungainly and vulnerable to more nimble single-engine fighters.
The primary driver of fighter innovation, right up to the period of rapid rearmament in the late thirties, were not military budgets, but civilian aircraft races. Aircraft designed for these races pioneered innovations like streamlining and more powerful engines that would find their way into the fighters of World War II.
At the very end of the inter-war period came the Spanish Civil War. This was just the opportunity the German Luftwaffe, Italian Regia Aeronautica, and Soviet Red Air Force needed to test their latest aircraft designs. Each party sent several aircraft to back their side in the conflict. In the dogfights over Spain, the latest Messerschmitt fighters (Bf 109) did well, as did the Soviet Polikarpov I-16. The German design, however, had considerable room for development and the lessons learned in Spain led to greatly improved models in World War II. The Russians, whose side lost in the conflict, nonetheless determined that their planes were sufficient for their immediate needs. I-16s were later slaughtered en masse by these improved German models in the Second World War, although they remained the most common Soviet front-line fighter until well into 1942. For their part, the Italians were satisfied with the performance of their Fiat CR.42 biplanes, and being short on funds, continued with this design even though it was obsolescent.
Aerial combat formed an important part of World War II military doctrine. The ability of aircraft to locate, harass, and interdict ground forces was an instrumental part of the German combined-arms doctrine, and their inability to seize air superiority over Britain made a German invasion unfeasible. Erwin Rommel noted the effect of airpower: "Anyone who has to fight, even with the most modern weapons, against an enemy in complete command of the air, fights like a savage against modern European troops, under the same handicaps and with the same chances of success."
The pre-war Soviet-Japanese battle of Khalkhyn Gol, and the 1939's initial German invasion of Poland were too brief to provide much feedback to the participants. The Battle of France gave the Germans ample opportunity to encounter British and French aircraft in combat, which overall went very well for the Luftwaffe's Messerschmitt Bf 109. The Soviets got their noses bloodied by the outnumbered Finnish Air Force in the Winter War, with poor doctrine and training hampering the large Soviet formations.[citation needed]
The Battle of Britain pitted a very capable Royal Air Force against the veteran Luftwaffe pilots, some of whom had combat experience in Spain. The result was a victory for the British, with lessons learned on both sides. British fighters tore apart the lightly-armed German bombers (especially the Stuka dive-bombers), while the Bf 110 was finally revealed as a failed concept and relegated to night fighter and fighter-bomber roles.
Operation Barbarossa showed that strategic surprise made Soviet preparations woefully inadequate, and Red Air Force command had rendered any lessons learned from previous experience in Spain and Finland virtually useless. The Axis were able to destroy large numbers of the Red Air Force aircraft on the ground, and in one-sided dogfights in the first few months. However, by winter 1941 the Red Air Force was able to put together a cohesive air defence of Moscow, successfully interdict attacks on Leningrad and begin production of new aircraft types in the relocated semi-built factories in the Urals, Siberia, Central Asia and the Caucasus to replace the aging designs with advanced monoplane fighters, such as the Yak-1, Yak-3, LaGG-3, and MiG-3, to wrest air superiority from the Luftwaffe. However, Soviet aircrew training was hasty in comparison to that provided to the Luftwaffe, and Soviet pilots died in droves until a growing number of survivors were matched to more effective machines. From 1942 significant numbers of British, and later US, fighter aircraft were also sent to aid the Soviet war effort, with the P-39 proving particularly effective in the lower altitude combat typical of the Eastern Front. From 1942 the Eastern Front became the largest area of fighter aircraft use in the World, used in all the roles typical of the period, including close air support, interdiction, escort and interception roles. Some aircraft were armed with weapons as large as 45mm cannon, and the Germans began installing additional smaller cannon in under-wing pods to assist with ground-attack missions.
Eventually, the Allies developed advanced piston-engined fighters such as the P-47, P-51 and improved Spitfires that simply overwhelmed their German opposition. Despite having jets and even a rocket-powered interceptor Me 163, the Germans were swamped by superior numbers. Additionally, the Germans often dipped into their training pool to make up numbers when casualties surged, and the Luftwaffe was additionally hampered by acute fuel shortages from April of 1944 onwards. While Allied airmen in Europe were well trained, new Luftwaffe pilots were seldom able to get effectively trained -- particularly by the summer of 1944 when Allied fighters often loitered around their airfields.
In the Pacific Theater, the experienced Japanese used their latest A6M Zero to clear the skies of all opposition. Caught off-guard, the Allied air forces (often flying obsolete aircraft, as the Japanese were not deemed as dangerous as the Germans) were driven back until the Japanese became overextended. Additionally, the Japanese went to war with a cadre of superbly trained airmen, but these were never replaced by pilots of the same quality while the British Commonwealth Air Training Plan and US schools produced thousands of competent airmen. Japanese fighter planes were also optimised for agility and range, and it took time for Allied airmen to realize tactics that made better use of the superior armanent and protection in their Wildcats and P-40s. By 1943, newer Allied fighter models were faster and better-armed than the Japanese fighters, and improved tactics (see Thach Weave) helped counter the nimble Zero. Japanese industry was not up to the task of creating fighter designs equal to the latest Western models, and they were largely driven from the skies by mid-1944.
Piston-engine power increased considerably during the war. The Curtiss P-36 "Hawk" had a 900 HP radial engine but was soon redesigned as the P-40 "Warhawk" with an 1100 HP in-line engine. By 1943, the latest P-40N had a 1300 HP Allison engine. At war's end, the Ta 152 German interceptor could achieve over 2000 HP with MW-50 (methanol-water injection) and American P-51s had a similar amount of power.
The first jet-powered designs became operational in 1944, and clearly outperformed their piston-engined counterparts. New designs such as the Messerschmitt Me 262 and Gloster Meteor demonstrated the effectiveness of the new propulsion system. Many of these fighters could do over 660 km/h in level flight, and were fast enough in a dive that they started encountering the transonic buffeting experienced near the speed of sound, occasionally breaking up in flight due to the heavy load placed on an aircraft near the so-called "sound barrier". Dive brakes were developed late in World War II to minimise these problems and restore control to pilots.
Armament became a priority once it became apparent that newer stressed-skin monoplane fighters could not be easily shot down with rifle-caliber machine guns. The Germans, with experience from the Spanish Civil War put 20 mm cannons on their fighters. The British soon followed suit, putting cannons in the wings of Hawker Hurricanes and Supermarine Spitfires. The Americans, lacking a native cannon design, instead chose to place multiple .50 caliber (12.7mm) MGs on their fighters. Armaments continued to increase, with the German Me 262 jet having four 30 mm cannons in the nose. Cannon fired explosive shells, and could blast a hole in an enemy aircraft rather than relying on kinetic energy from a solid bullet striking a critical subsystem (fuel line, hydraulics, control cable, pilot, etc.). A debate existed over the merits of high rate-of-fire machine guns versus slower-firing, but more devastating, cannon.
As the war progressed, use of drop tanks became common. This made the heavy twin-engine fighter designs redundant, as single-engine fighters could now cover a similar distance. Extra fuel was carried in lightweight aluminum tanks below the aircraft, and the tanks were discarded when empty. Such innovations allowed American fighters cover to range over Germany and Japan by 1944.
Focke-Wulf Fw 190
With the increasing need for close air support on the battlefield, fighters were increasingly fitted with bomb racks and used as fighter-bombers. Some designs, such as the German Fw 190, proved extraordinarily capable in this role -- though the designer Kurt Tank had designed it as a pure interceptor. Because an aircraft's lift is derived from the upper surface of the wing, the lower surface can easily be festooned with a variety of rockets, bombs, and other ordnance. This increases drag, and thus the performance of the fighter is lessened, but once the ordnance is delivered or jettisoned, the aircraft is again a fully capable fighter aircraft. Command staff had the freedom to designate a particular air group as air superiority or ground-attack as need occasioned in many cases.
Radar, invented shortly prior to World War II, was fitted to some fighters, such as the Messerschmitt Bf 110, Beaufighter, de Havilland Mosquito, F6F Hellcat and Northrop P-61 Black Widow to enable them to locate targets at night. The Germans developed several night fighter types as they were under constant night bombardment by British Bomber Command. The British, who developed the first radar-equipped night fighters in 1940/41, lost their technical lead to the Luftwaffe. Since the radar of the era was fairly primitive and difficult to use properly, larger 2-3 seat aircraft with dedicated radar operators were commonly adapted to this role.
The first rocket-powered aircraft was the Lippisch Ente, flown in 1928[2]. The only pure rocket aircraft ever to be mass-produced was the Messerschmitt Me 163 in 1944, one of several GermanWorld War II attempts at rocket-powered aircraft.[3] Later variants of the Me 262 (C-1a and C-2b) were also fitted with rocket powerplants, while earlier models were fitted with rocket boosters, but were not mass produced with these modifications.[4]
The USSR experimented with a rocket-powered interceptor in the years immediately following World War II, the Mikoyan-Gurevich I-270. Only two were built.
In the 1950s the British developed mixed power designs to cover the performance gap that existed in current turbojet designs. The rocket was the main engine for delivering the speed and height required for high speed interception of high level bombers and the turbojet gave increased fuel economy in other parts of flight, most notably to make sure the aircraft was able to make a powered landing rather than risking an unpredictable gliding return. The Saunders-Roe SR.53 was a successful design and was due to be developed into production when economics forced curtailment of most British aircraft programmes in the late 1950s (both SR.53 and SR.177 aircraft used a mixture of rocket and jet engines).
The American XF-91 Thunderceptor was a similar project, but the advancement of the turbojet engine output made a return to mixed power unnecessary and no hybrid rocket and jet engine fighter design has ever been placed into service. The only operational implementation of mixed propulsion was in Rocket-Assisted Take Off, a system rarely used in fighters.
For historical purposes, jet fighters are sometimes classified by "generation". The generation terminology is not without anomalies and ambiguities, and the particular "generation" classification used in this article is by no means the only way it could have been organised.
The first generation represents the first attempts at using turbojets for propulsion, providing greatly increased speed (the efficiency of piston-driven propellers drops off considerably at transsonic speeds). Many of these early jets resembled their piston-driven counterparts in several ways. Many were straight-winged aircraft armed primarily with heavy machine-guns; radar was not yet in common usage except on specialized night fighters.
The first jets were developed during World War II and saw combat in its last year. Messerschmitt developed the first operational jet fighter, the Me 262. It was considerably faster than piston-driven aircraft, and in the hands of a competent pilot, was quite difficult for Allied pilots to defeat. The design was never deployed in numbers sufficient to stop the Allied air campaign, and a combination of fuel shortages and technical difficulties with the engines kept the number of sorties low. Nevertheless the plane indicated the obsolescence of piston-driven aircraft. Spurred by reports of the German jets, Britain's Gloster Meteor entered production soon after and the two entered service around the same time in 1944. Meteors were commonly used to intercept the V-1 "buzz bomb", as they were faster than piston-engined contemporaries. By the end of the war almost all work on piston powered fighters had ended. Mixed-propulsion designs such as the Ryan FR Fireball saw brief use, but by the end of the 1940s virtually all new combat aircraft were jet-powered.
Despite the advantages, the early jet fighters were far from perfect, particularly in the opening years of the generation. Their operational lifespans could be measured primarily in hours; the engines themselves were fragile and bulky, and power could be adjusted only slowly. Many squadrons of piston-engined fighters were retained until the early-to-mid 1950s, even in the US and Soviet Air Forces (though the types retained were the best of the WW2 designs -- such as the F-4U Corsair). Innovations such as swept wings, ejector seats, and all-moving tailplanes were introduced in this period.
The Americans were one of the first to begin using jet fighters post-war. The P-80 (soon re-designated F-80) was less elegant than the swept-wing Messerschimitt, but had a cruise speed (410 mph / 660 km) as high as the combat maximum of many piston-engined fighters. The British designed several new jets, including the iconic de Havilland Vampire which was sold to the air forces of many nations. Ironically, the British transferred the technology of the Rolls-Royce Nene jet engine technology to the Soviets, who soon put it to use in their advanced MiG-15 fighters. These proved quite a shock to the American F-80 pilots who encountered them over Korea. Where the American jets were armed with a "traditional" load of six .50 cal (12.7mm) heavy machine-guns, the MiGs used two 23mm cannons and a single 37mm cannon (good against bombers). A few hits from the MiG could knock an American fighter out of the sky.
The response to this was to rush F-86 squadrons to battle against the MiGs. While carrying the same armament as the F-80, the F-86 was a true swept-wing transonic fighter, as was the MiG-15. The two aircraft had different strengths, but were similar enough that only the superior skills of the veteran United States Air Force pilots allowed them to prevail.
The world's navies also went for jets during this period, despite the need for catapult-launching of the new aircraft. The F9F Panther was adopted by the US Navy as their primary jet fighter in the Korean War period. The Vampire was commonly used in this role for the Royal Navy.
The second generation describes the integration of many new technologies to greatly improve the fighting capability of the jet fighter. The introduction of guided missiles such as the AIM-9 Sidewinder and AIM-7 Sparrow moved combat to beyond visual range (though it often devolved into dogfights in visual range), necessitating the standardization of radar to acquire targets. Designers experimented with a variety of aeronautical innovations, such as the swept wing, delta wing, variable-geometry wings, and area ruled fuselages. With the aid of swept wing, these were the first production aircraft to break the sound barrier.
The primary specializations of this era were the fighter-bomber (such as the F-105 and the Sukhoi Su-7), and the interceptor (English Electric Lightning and F-104 Starfighter). The interceptor was an outgrowth of the vision that guided missiles would completely replace guns and combat would take place at beyond visual range. As a result, interceptors were designed with a large missile payload and a powerful radar, sacrificing agility in favor of speed and rate of climb.
The third generation is marked by maturity in the innovations introduced in the first generation. As this aeronautical development approached maturity, growth in combat capability grew via the introduction of improved missiles, radar, and other avionics. Most significantly, as a result of combat experience with guided missiles, designers deduced that combat could and would degenerate into close dogfights. New automatic-fire weapons, primarily chain-guns that use an electric engine to drive the mechanism of a cannon -- allowed a single multi-barrel weapon (such as the 20mm Vulcan) to be carried -- with greater rate-of-fire and accuracy. Third generation designs also put a new emphasis on maneuverability for many aircraft.
These innovations, while greatly improving the capabilities of fighters (the F-4 could carry a payload greater than the B-24 Liberator, a World War II heavy bomber), also came at a considerable increase at cost. Whereas militaries had previously specialized fighters for specific roles, such as night fighter, heavy fighter and strike fighter, in order to counter the growing cost of fighters, militaries began to consolidate missions. The McDonnell F-4 Phantom II was designed as a pure interceptor for the United States Navy, but became a highly successful multi-role aircraft for the Air Force, Navy and Marine Corps as well as many other nations. It is the only combat aircraft to be simultaneously flown by the Navy, Air Force and Marines.
In reaction to the continually rising cost of fighters and the demonstrated success of the F-4 Phantom II, multirole fighters became popular during this period, and even aircraft designed for a specific role (as the F-4 had) acquired multi-role capability. Fighters such as the MiG-23 and Panavia Tornado have versions specially suited for various roles, while true multirole warplanes include the F/A-18 Hornet and Dassault Mirage 2000. This was facilitated by avionics which could switch seamlessly between air and ground modes. As development costs increased, economics further pushed the development for multirole aircraft.
Unlike interceptors of the previous era, most modern air-superiority fighters have been designed to be agile dog-fighters, though the MiG-31 and Panavia Tornado ADV are notable exceptions. Fly-by-wire controls and relaxed stability are common among modern fighters. Aircraft here make up most of the "fourth generations" of fighter jets. The other significant revolution came with standardization of parts and a stronger reliance on ease of maintenance -- some early jet fighters might require 50 man hours of work by a ground crew for every hour in the air; later models substantially reduced this to allow faster 'turn-around' times and more sorties in a day. Some modern military aircraft only require 10 man-hours of work per hour of flight time, and others are even more efficient.
This half-generation has been coined to describe an interim period of aircraft design marked by a relative stagnation of aerodynamic technologies compared to third and fourth generation advances, but with tremendous achievements made in the field of avionics and other flight electronics. This was largely due to advances made in microchip and semiconductor technology in the 1980s and 1990s. This combination led designers to produce "upgraded" fourth-generation designs, with airframes either based on existing airframes or on similar design theory as previous iterations, but implementing the avionics and radar advances developed in the interim as well as some of the lessons learned in fourth-generation stealth designs, which would later be fully envisaged in fifth-generation fighters. A prime example of this generation is the F/A-18E/F Super Hornet, based on the 1970s F/A-18 Hornet design. While the external profile remains largely the same, the Super Hornet features improved avionics in the form of a glass cockpit (which is still 90% common to the original), a solid-state AESA fixed-array radar, new engines, the structural use of composite materials to reduce weight, and a slightly modified shape to minimize its radar signature. Another is the F-15E Strike Eagle, a ground-attack variant of the Cold War-era F-15 Eagle fighter with an strengthened airframe and upgraded engines, glass cockpit displays, and the very latest terrain-following navigation and targeting systems. Of the 4.5 generation designs, only the Super Hornet, Strike Eagle, and the Rafale have seen combat action.
The current cutting edge of fighter design combines previous emphasis on versatility with new developments such as thrust vectoring, short takeoff/landing, composite materials, supercruise, stealth technology, advanced radar and sensors, and integrated avionics designed to reduce the pilot's workload while vastly improving situational awareness. The avionics technologies such as glass cockpits and helmet-mounted display and targeting that were developed during Generation 4.5 have been further advanced and integrated into totally new aircraft designs, which draw on lessons learned from fourth-generation stealth, VTOL and composite aircraft like the F-117, B-2 and AV-8 Harrier.
Of these, only the American F-22 Raptor, put into production in 2004, is operational, and is often regarded as the first of a new generation of fighters, termed the "fifth-generation". Design elements of the F-35 Lightning II (formerly Joint Strike Fighter) currently in pre-production, and the F-22 Raptor have influenced continued development of fourth-generation designs, and the shape of design work for the Russian PAK FA and other countries long-term fighter development projects like the Indian Medium Combat Aircraft, the rumoured Chinese Shenyang J-XX project and South Korean KFX. Later cancelled technology demonstrators of fifth-generation fighter aircraft include the United States YF-23 Black Widow II (which lost the Advanced Tactical Fighter competition to what is now the F-22), Boeing X-32 (which lost the Joint Strike Fighter competition to the X-35) and McDonnell Douglas X-36, and the Soviet UnionProject 1.42, later upgraded by Russia to version 1.44.
United Kingdom
German Empire
France
Soviet Union
United Kingdom
United States
France
People's Republic of China
Pakistan
Taiwan
West Germany / 
Italy
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Japan / 
India
Russia
Sweden
Spain
South Korea
