(Image: An A-10 Thunderbolt II, F-86 Sabre, P-38 Lightning and P-51 Mustang fly in formation during an air show at Langley Air Force Base, Virginia. The formation displays two generations of U.S. Air Force fighter aircraft, and an attack aircraft (the A-10).)

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. Many fighters have secondary ground-attack capabilities, and some are dual-roled as fighter-bombers; the term "fighter" is also sometimes used colloquially for dedicated ground-attack aircraft. 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 defense budgets for modern militaries.

Terminology

The word "fighter" did not become the official English term for such aircraft until after World War I. In Great Britain's Royal Flying Corps – later 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 "istrebitel", meaning "exterminator".

Although the term "fighter" technically refers to aircraft specifically designed to shoot down other aircraft, such designs are often also useful as multirole fighter-bombers and sometimes lighter, fighter-sized tactical ground-attack aircraft. For example, in WWII the US Navy would later favor fighters over dedicated dive bombers, and the P-47 Thunderbolt would be favored for ground attack. The controversial F-111 would be employed largely only as a strike bomber as the fighter variant was abandoned. Bombers generally refer to long-range strategic or theater bombing roles. This blurring follows the use of fighters from their earliest days for "attack" or "strike" operations against enemy troops, field positions, vehicles, and facilities by means of strafing or dropping of bombs or incendiaries.

Some of the most expensive fighters such as the F-14 Tomcat and F-15 Eagle were employed as all-weather interceptors as well as air superiority combat aircraft, only developing air-to-ground roles late in their careers. Multirole fighter-bombers such as the F/A-18 Hornet are often less expensive and tasked (and in this case, given an F/A designation) with ground attack as part of a "high-low mix", or in the case of the Super Hornet, replacing a range of specialized aircraft types.

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 or machine guns. By the end of the war, turbojet engines were already beginning to replace piston engines as the means of propulsion, and increasingly sophisticated refinements to armament were already appearing.

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 Sukhoi Su-37 (NATO reporting name 'Flanker') or Boeing F-15 Eagle), with a cannon as backup armament (typically between 20 and 30 mm in caliber); however, they can also often employ air-to-surface missiles, as well as guided and unguided bombs.

Piston engine fighters

World War I

(Image: 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 realized 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 airplane 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 reconnoiter 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 improvized 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 airplane in a manner that enabled the gun to fire outside the arc of the propeller.

(Image: 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 airplanes. However, this limited the area of coverage chiefly to the rear hemisphere, and the inability to effectively coordinate the pilot's maneuvering with the gunner's aiming, which reduced the accuracy and efficacy of the gunnery. This option was chiefly employed as a defensive measure on two seater reconnaissance aircraft from 1915 on. The alternative configuration mounted a gun on the upper wing to 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 maneuver his aircraft 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 did have some advantages, and was to remain in service from 1915 (Nieuport 11) until 1918 (Royal Aircraft Factory S.E.5). The British Foster mounting was specifically designed for this kind of application.

(Image: 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 synchronization 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 December 1914, French aviator Roland Garros asked Saulnier to install his synchronization gear on Garros' Morane-Saulnier Type L. 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 synchronize the gunfire with a spinning propeller. Because of this, the propeller blades were armored, 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 airplane – along with its synchronization gear and propeller – was captured by the Germans.

However, the synchronization 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 airplane, with a mediocre performance and poor flight characteristics. The first victory for the Eindecker came on 1 July 1915, when Leutnant Kurt 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 five Fokker M.5K/MG production prototype examples of the Eindecker, was armed with a synchronized, air-cooled aviation version of the Parabellum MG14 machine gun, which did not require armored propellers. In some respects, this was the first "true" fighter victory of military aviation history.
Captured Fokker E.III Eindecker 210/16 in flight at Upavon, Wiltshire in 1916

(Image: Captured Fokker E.III Eindecker 210/16 in flight at Upavon, Wiltshire in 1916)

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, designed by Robert Thelen, 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 synchronize 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.

As collective combat experience grew, the more successful pilots such as Oswald Boelcke, Max Immelmann, and Edward Mannock developed innovative new tactical formations and maneuvers to enhance their air units' combat effectiveness and accelerate the learning – and increase the expected lifespan – of newer pilots reaching the front lines.

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.

Notable aircraft of the WWI period

Vickers F.B.5 1915 United Kingdom
Fokker Eindecker 1915 German Empire
Nieuport 11 1915 France
Airco DH-2 1915 United Kingdom
Albatros D.III 1916 German Empire
Nieuport 17 1916 France
Fokker Dr.I 1917 German Empire
SPAD S.XIII 1917 France
Nieuport 28 1917 France
Sopwith Camel 1917 United Kingdom
Royal Aircraft Factory S.E.5 1917 United Kingdom
Fokker D.VII 1918 German Empire
Sopwith Snipe 1918 United Kingdom

Interwar period (1919-1938)

(Image: Replica of the Fokker Dr.I, the "Red Baron's" triplane, at the ILA 2006 air show)

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.

(Image: An early monoplane fighter: the Boeing P-26 Peashooter which first flew in 1932)

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 caliber (12.7 mm) machine guns and 20 mm cannons were deemed "overkill." Considering that many aircraft were constructed similarly to WWI designs (albeit with aluminum 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 (130 kW) in the 1918 Fokker D.VII to 900 hp (670 kW) 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.

(Image: Messerschmitt Bf 110 Zerstörer "heavy fighter")

Some air forces experimented 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 the Soviet Union's 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 World War II, 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.

The Spanish Civil War also provided an opportunity for updating fighter tactics. One of the chief innovations to result from the aerial warfare experience this conflict provided was the development of the "finger-four" formation by the German pilot Werner Mölders. Each fighter squadron (German: Staffel) was divided into several flights (Schwärme) of four aircraft. Each Schwarm was divided into two Rotten which was a pair of aircraft. Each Rotte was composed of a leader and a wingman. This flexible formation allowed the pilots to maintain greater situational awareness, and the two Rotten could split up at any time and attack on their own. The finger-four would become widely adopted as the fundamental tactical formation over the course of World War II.

Notable aircraft of the interwar period

Biplanes
Czechoslovakia - Avia B-534
Italy - Fiat CR.42
Japan - Kawasaki Ki-10 'Perry'
Sweden - Svenska Aero Jaktfalken
United Kingdom - Bristol Bulldog
United Kingdom - Gloster Gladiator
United Kingdom - Hawker Fury
United States - Boeing F4B-4

Monoplanes
Japan - Mitsubishi A5M 'Claude'
Netherlands - Fokker D.XXI
Poland - PZL P.11
Soviet Union - Polikarpov I-16
United Kingdom - Hawker Hurricane
United States - Boeing P-26 Peashooter
United States - F2A Brewster Buffalo
Flag of YugoslaviaYugoslavia - Ikarus IK-2

World War II

(Image: The Mitsubishi A6M Zero typified the highly maneuverable, but lightly armed and armored, fighter design)

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 achieve air superiority over Britain made a German invasion unfeasible. German Field Marshal 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."

During the 1930s, two different streams of thought about air-to-air combat began to emerge, resulting in two different approaches to monoplane fighter development. In Japan and Italy especially, there continued to be a strong belief that lightly armed, highly maneuverable single-seat fighters would still play a primary role in air-to-air combat. Aircraft such as the Nakajima Ki-27, Nakajima Ki-43 and the Mitsubishi A6M Zero in Japan, and the Fiat G.50 and Macchi C.200 in Italy epitomized a generation of monoplanes designed to this concept.

(Image: This Supermarine Spitfire XVI was typical of World War II fighters optimized for high level speeds and good climb rates)

The other stream of thought, which emerged primarily in Britain, Germany, the Soviet Union, and the United States was the belief that the high speeds of modern combat aircraft and the g-forces imposed by aerial combat meant that dogfighting in the classic WWI sense would be impossible. Fighters such as the Messerschmitt Bf 109, the Supermarine Spitfire, the Yakovlev Yak-1 and the Curtiss P-40 Warhawk were all designed for high level speeds and a good rate of climb. Good maneuverability was desirable, but it was not the primary objective.

The 1939 Soviet-Japanese Battle of Khalkhyn Gol and the initial German invasion of Poland that same year were too brief to provide much feedback to the participants for further evolution of their respective fighter doctrines. During the Winter War, the greatly outnumbered Finnish Air Force, which had adopted the German finger-four formation, bloodied the noses of Russia's Red Air Force, which relied on the less effective tactic of a three-aircraft delta formation.

European theater (Western Front)

The Battle of France, however, gave the Germans ample opportunity to prove they had mastered the lessons learned from their experiences in the Spanish Civil War. The Luftwaffe, with more combat-experience pilots and the battle-tested Messerschmitt Bf 109 fighter operating in the flexible finger-four formation, proved superior to its British and French contemporaries relying on the close, three-fighter "vic" (or "V") and other formations, despite their flying fighters with comparable maneuver performance.

The Battle of Britain was the first major military campaign to be fought entirely by air forces, and it offered further lessons for both sides. Foremost was the value of radar for detecting and tracking enemy aircraft formations, which allowed quick concentration of fighters to intercept them farther from their targets. As a defensive measure, this ground-controlled interception (GCI) approach allowed the Royal Air Force (RAF) to carefully marshal its limited fighter force for maximum effectiveness. At times, the RAF's Fighter Command achieved interception rates greater than 80%.

In the summer of 1940, then Flight Lieutenant Adolph Malan introduced a variation of the German formation that he called the "fours in line astern", which spread into more general use throughout Fighter Command. In 1941, Squadron Leader Douglas Bader adopted the "finger-four" formation itself, giving it its English-language name.

The Battle of Britain also revealed inadequacies of extant tactical fighters when used for long-range strategic attacks. The twin-engined heavy fighter concept was revealed as a failed concept as the Luftwaffe's heavily armed but poorly maneuverable Messerschmitt Bf 110s proved highly vulnerable to nimble Hurricanes and Spitfires; the Bf 110s were subsequently relegated to night fighter and fighter-bomber roles for which they proved better-suited. Furthermore, the Luftwaffe's Bf 109s, operating near the limits of their range, lacked endurance for prolonged dogfighting over Britain. When bomber losses induced Reichsmarschall Hermann Göring to assign most fighters to close-in escort duties, forcing them to fly and maneuver at reduced speeds, German fighter effectiveness fell and losses rose.

(Image: Long-range escort fighters like this P-51D Mustang provided crucial protection for Allied strategic bombers)

The Allies themselves, however, would not learn this latter lesson until they sustained heavy bomber losses of their own during daylight raids against Germany. Despite the early assertions be strategic bombing advocates that "the bomber will always get through", even heavily armed U.S. Army Air Force (USAAF) bombers like the Boeing B-17 Flying Fortress and Consolidated B-24 Liberator suffered such high losses to German fighters (such as the Focke-Wulf Fw 190 "bomber destroyer") and anti-aircraft artillery (AAA) that – following the second raid on Schweinfurt in August 1943 – the U.S. Eighth Air Force was forced to suspend unescorted bombing missions into Germany until longer-range fighters became available for escort. These would appear in the form of Lockheed P-38 Lightnings, Republic P-47 Thunderbolts and North American P-51 Mustangs. The use of drop tanks also became common, which further 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 to range over Germany and Japan by 1944.

As the war progressed, the growing numbers of these advanced, long-range fighters flown by pilots with increasing experience eventually overwhelmed their German opposition, despite the Luftwaffe's introduction of technological innovations like jet- and rocket-powered interceptors. The steady attrition of experienced pilots forced the Germans to more frequently dip into their training pool to make up numbers when casualties surged. While new Allied airmen in Europe were well-trained, new Luftwaffe pilots were seldom able to get effective training – particularly by the summer of 1944, when Allied fighters often loitered around their airfields. Luftwaffe training flights were additionally hampered by the increasingly acute fuel shortages that began in April 1944.

European theater (Eastern Front)

(Image: Soviet Air Force MiG-3s in winter camouflage. The slogan on the nearest aircraft reads "Za Rodinu" – "For the Motherland".)

On the Eastern Front, the strategic surprise of Operation Barbarossa demonstrated that Soviet air defense preparations were woefully inadequate, and the Great Purge rendered any lessons learned by the Red Air Force command from previous experience in Spain and Finland virtually useless. During the first few months of the invasion, Axis air forces were able to destroy large numbers of Red Air Force aircraft on the ground and in one-sided dogfights. However, by the winter of 1941–1942, the Red Air Force was able to put together a cohesive air defense 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. These facilities produced more 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, so Soviet pilot losses continued to be disproportionate until a growing number of survivors were matched to more effective machines.

Beginning in 1942, significant numbers of British, and later U.S., fighter aircraft were also supplied to aid the Soviet war effort, with the Bell P-39 Airacobra proving particularly effective in the lower-altitude combat typical of the Eastern Front. Also from that time, the Eastern Front became the largest arena of fighter aircraft use in the world; fighters were used in all of the roles typical of the period, including close air support, interdiction, escort and interception roles. Some aircraft were armed with weapons as large as 45 mm cannon (particularly for attacking enemy armored vehicles), and the Germans began installing additional smaller cannon in under-wing pods to assist with ground-attack missions.

Pacific theatre

(Image: Grumman F4F-3 Wildcat on patrol in early 1942)

In the Pacific Theater, the experienced Japanese used their latest Mitsubishi A6M "Zero" to clear the skies of all opposition. Allied air forces – often flying obsolete aircraft, as the Japanese were not deemed as dangerous as the Germans – were caught off-guard and driven back until the Japanese became overextended. While the Japanese entered the war with a cadre of superbly trained airmen, they were never able to adequately replace their losses with pilots of the same quality, while the British Commonwealth Air Training Plan and U.S. schools produced thousands of competent airmen. Japanese fighter planes were also optimized for agility and range, and in time Allied airmen developed tactics that made better use of the superior armament and protection in their Grumman F4F Wildcats and Curtiss P-40s. From mid-1942, newer Allied fighter models were faster and better-armed than the Japanese fighters, and improved tactics such as the Thach weave helped counter the more agile Zeros and Nakajima Ki-43 'Oscars'. Japanese industry was not up to the task of mass-producing fighter designs equal to the latest Western models, and Japanese fighters had been largely driven from the skies by mid-1944.

Technological innovations

Piston-engine power increased considerably during the war. The Curtiss P-36 Hawk had a 900 hp (670 kW) radial engine but was soon redesigned as the P-40 Warhawk with a 1100 hp (820 kW) in-line engine. By 1943, the latest P-40N had a 1300 hp (970 kW) Allison engine. At war's end, the German Focke-Wulf Ta 152 interceptor could achieve 2050 hp (1530 kW) with an MW-50 (methanol-water injection) supercharger and the American P-51H Mustang fitted with the Packard V-1650-9 could achieve 2218 hp (1650 kW) under war emergency power. The Spitfire Mk I of 1939 was powered by a 1030 hp (770 kW) Merlin II; its 1945 successor, the Spitfire F.Mk 21, was equipped with the 2035 hp (1520 kW) Griffon 61. Likewise, the radial engines favored for many fighters also grew from 1,100 hp (820 kW) to as much as 2090 hp (770 kW) during the same timeframe.

The first turbojet-powered fighter 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. (Rocket-powered interceptors – most notable the Messerschmitt Me 163 – appeared at the same time, but proved less effective.) 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; such turbulence occasionally resulted in a jet breaking up in flight due to the heavy load placed on an aircraft near the so-called "sound barrier". Dive brakes were added to jet fighters late in World War II to minimize these problems and restore control to pilots.
Focke-Wulf Fw 190D-9 fighter-bomber

(Image: Focke-Wulf Fw 190D-9 fighter-bomber)

More powerful armament became a priority early in the war, once it became apparent that newer stressed-skin monoplane fighters could not be easily shot down with rifle-caliber machine guns. The Germans' experiences in the Spanish Civil War led them to put 20 mm cannons on their fighters. The British soon followed suit, putting cannons in the wings of their Hurricanes and Spitfires. The Americans, lacking a native cannon design, instead chose to place multiple .50 caliber (12.7 mm) machine guns on their fighters. Armaments continued to increase over the course of the war, with the German Me 262 jet having four 30 mm cannons in the nose. Cannons 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.

(Image: German Bf 110G-4 night fighter at the RAF Museum in London)

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 extremely capable in this role – though the designer Kurt Tank had designed it as a pure interceptor. While carrying air-to-surface ordnance such as bombs or rockets beneath the aircraft's wing, its maneuverability is decreased because of lessened lift and increased drag, but once the ordnance is delivered (or jettisoned), the aircraft is again a fully capable fighter aircraft. By their flexible nature, fighter-bombers offer the command staff the freedom to assign a particular air group to air superiority or ground-attack missions, as need requires.

Rapid technology advances in radar, which had been invented shortly prior to World War II, would permit their being fitted to some fighters, such as the Messerschmitt Bf 110, Bristol Beaufighter, de Havilland Mosquito, Grumman 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 RAF Bomber Command. The British, who developed the first radar-equipped night fighters in 1940–1941, lost their technical lead to the Luftwaffe. Since the radar of the era was fairly primitive and difficult to use properly, larger two- or three-seat aircraft with dedicated radar operators were commonly adapted to this role.

Notable World War II piston-engine fighters

Australia
CAC Boomerang

France
Bloch MB.150
Dewoitine D.520
Morane-Saulnier M.S.406

Finland
VL Myrsky

Italy
(Image: C.200 in the markings of 372° Sq. Regia Aeronautica)

Macchi C.200
Macchi C.202
Macchi C.205
Fiat G.55
Fiat G.50
Reggiane Re 2000
Reggiane Re 2001
Reggiane Re 2005

Japan
Kawanishi N1K-J

(Image: A Nakajima Ki-43 III-Ko "Oscar" sets off from a Japanese airfield on a kamikaze mission in the Okinawa area on 12 April 1945 as high school girls wave farewell)

Nakajima Ki-27
Nakajima Ki-43
Nakajima Ki-44
Nakajima Ki-84
Kawasaki Ki-61
Kawasaki Ki-100
Mitsubishi A6M Zero
Mitsubishi J2M

Flag of Germany Nazi Germany

(Image: Messerschmitt Bf 109G-2/Trop 'Black 6')

Messerschmitt Bf 109
Messerschmitt Bf 110
Messerschmitt Me 210
Dornier Do 335 Pfeil
Focke-Wulf Fw 190
Heinkel He 100
Heinkel He 112
Junkers Ju 88C/R

Poland
PZL P.24
Flag of Romania Romania
IAR-80
Sweden
Saab 21
FFVS J 22

Yakovlev Yak-9, the most numerous Soviet fighter of WWII

Soviet Union

(Image: Yakovlev Yak-9, the most numerous Soviet fighter of WWII)

Yakovlev Yak-1
Yakovlev Yak-3
Yakovlev Yak-7
Yakovlev Yak-9 'Frank'
Lavochkin LaGG-3
Lavochkin La-5
Lavochkin La-7 'Fin'
Mikoyan-Gurevich MiG-3

United Kingdom

(Image: Hurricane Mk IIc of the Battle of Britain Memorial Flight)

Supermarine Spitfire
Supermarine Spiteful
Hawker Hurricane
Hawker Typhoon
Hawker Tempest
De Havilland Mosquito
Boulton Paul Defiant
Hawker Sea Fury

United States

(Image: A Republic P-47N Thunderbolt in flight. The plane shown is an XP-47N prototype (as seen in its tail))

Grumman F4F Wildcat
Vought F4U Corsair
Grumman F6F Hellcat
Curtiss P-36 Hawk
Lockheed P-38 Lightning
Bell P-39 Airacobra
Curtiss P-40 Warhawk
Republic P-47 Thunderbolt
North American P-51 Mustang
Northrop P-61 Black Widow
Bell P-63 Kingcobra
North American P-64
Vultee P-66 Vanguard
Douglas P-70A Havoc

Flag of Yugoslavia Yugoslavia
Rogozarski IK-3

Post-World War II period

Several prototype fighter programs begun early in 1945 continued on after the war and led to advanced piston-engine fighters that entered production and operational service in 1946. A typical example is the Lavochkin La-9 'Fritz', which was an evolution of the successful wartime Lavochkin La-7 'Fin'. Working through a series of prototypes, the La-120, La-126 and La-130, the Lavochkin design bureau sought to replace the La-7's wooden airframe with a metal one, as well as fit a laminar-flow wing to improve maneuver performance, and increased armament. The La-9 entered service in August 1946 and was produced until 1948; it also served as the basis for the development of a long-range escort fighter, the La-11 'Fang', of which nearly 1200 were produced 1947–1951. Over the course of the Korean War, however, it became obvious that the day of the piston-engined fighter was coming to a close and that the future would lie with the jet fighter.

This period also witnessed experimentation with jet-assisted piston engine aircraft. La-9 derivatives included examples fitted with two underwing auxiliary pulsejet engines (the La-9RD) and a similarly mounted pair of auxiliary ramjet engines (the La-138); however, neither of these entered service. One which did enter service – with the U.S. Navy in March 1945 – was the Ryan FR-1 Fireball; production was halted with the war's end on VJ-Day, with only 66 having been delivered, and the type was withdrawn from service in 1947. The USAAF had ordered its first 13 mixed turboprop-turbojet-powered pre-production prototypes of the Consolidated Vultee XP-81 Silver Bullet fighter, but this program was also canceled by VJ Day, with 80% of the engineering work completed.

Notable post-World War II piston-engine and piston-jet-powered fighters

Czechoslovakia
Avia S-199

(Image: Lavochkin La-9 'Fritz')

Lavochkin La-9 'Fritz'

Soviet Union
Lavochkin La-9 'Fritz'
Lavochkin La-11 'Fang'

Flag of Spain Spain
Hispano Aviación HA-1112

United States
Ryan FR-1 Fireball

Yugoslavia
Ikarus S-49

Rocket-powered fighters

(Image: The Messerschmitt Me 163 was the fastest aircraft of WWII and the only mass-produced rocket-powered fighter)

The first rocket-powered aircraft was the Lippisch Ente, which made a successful maiden flight in March 1928. The only pure rocket aircraft ever to be mass-produced was the Messerschmitt Me 163 in 1944, one of several German World War II projects aimed at developing rocket-powered aircraft. 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.

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 jet designs employing both rocket and jet engines to cover the performance gap that existed in existing 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 ensure 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 planned to be developed into production when economics forced curtailment of most British aircraft programs in the late 1950s. Furthermore, rapid advancements in jet engine technology had rendered mixed-power aircraft designs like Saunders-Roe's SR.53 (and its SR.177 maritime variant) obsolete. The American XF-91 Thunderceptor (which was the first U.S. fighter to exceed Mach 1 in level flight) met a similar fate for the same reason, and no hybrid rocket-and-jet-engine fighter design has ever been placed into service. The only operational implementation of mixed propulsion was Rocket-Assisted Take Off (RATO), a system rarely used in fighters.

Jet-powered fighters

It has become common in the aviation community to classify jet fighters by "generations" for historical purposes. There are no formal, official definitions of these generations; rather, they are a sort of consensus that captures recognizable "stages" in the development of fighter design approaches, performance capabilities, and technological evolution. In essence, they capture a general design philosophy based upon the perceived demands the future aerial warfare environment would pose military aviation strategists as well as the state of the art technologically.

The timeframes associated with each generation are inexact and are only indicative of the period during which their design philosophies and technology employment enjoyed a prevailing influence on fighter design and development. These timeframes also encompass the peak period of service entry for such aircraft, but it should be recognized that it is not unusual for continuing introduction and production of one generation's aircraft as combat "lessons learned" and continuing technological innovation and improvements are already germinating a new design philosophy and prototypes for a successor generation. While new capabilities introduced for an advanced generation can often be retrofitted to older aircraft, doing so does not promote them to the new generation inasmuch as aircraft into which they have been "designed in" are best optimized to benefit from them.

First generation subsonic jet fighters (mid-1940s to mid-1950s)

The first generation of jet fighters comprises the initial, subsonic jet fighter designs introduced late in World War II and in the early post-war period. They differed little from their piston-engined counterparts in appearance, and many employed unswept wings. Initially, guns remained the principal armament. The main impetus for the development of turbojet-powered was to obtain a decisive advantage in maximum speed. Top speeds for fighters rose steadily throughout WWII as more powerful piston engines were developed, and had begun approaching the transonic flight regime where the efficiency of piston-driven propellers drops off considerably.

(Image: Messerschmitt Me 262A at the National Museum of the United States Air Force)

The first jets were developed during World War II and saw combat in its final year. Messerschmitt developed the first operational jet fighter, the Me 262. It was considerably faster than contemporary 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, pilot losses, and technical difficulties with the engines kept the number of sorties low. Nevertheless, the Me 262 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 available piston-engined fighters. By the end of the war almost all work on piston-powered fighters had ended. A few designs combining piston and jet engines for propulsion – 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 their 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 air forces of the major powers (though the types retained were the best of the WWII designs). Innovations including 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 Lockheed P-80 Shooting Star (soon re-designated F-80) was less elegant than the swept-wing Me 262, but had a cruise speed (660 km/h [410 mph]) 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 Mikoyan-Gurevich MiG-15 fighters which were the first to introduce swept wings in combat, an innovation first proposed by German research which allowed flying much closer to the speed of sound than straight-winged designs such as the F-80. Their top speed of 1,075 km/h (668 mph) proved quite a shock to the American F-80 pilots who encountered them over Korea, along with their armanent of two 23 mm cannons and a single 37 mm cannon compared to machine guns. Nevertheless, in the first jet-versus-jet dogfight in history, which occurred during the Korean War on 8 November 1950, an F-80 (as the P-80 had been redesignated) intercepted two North Korean MiG-15s near the Yalu River and shot them down.

(Image: A de Havilland Sea Vampire Mk.10 taking off from the Royal Navy aircraft carrier HMS Ocean on 3 December 1945, the occasion of the first take-off and landing of a jet airplane from an aircraft carrier)

The Americans responded by rushing their own swept-wing F-86 squadrons to battle against the MiGs which had similar trans-sonic performance. The two aircraft had different strengths, but were similar enough that the superior technology such as a radar ranging gunsight and skills and of the veteran United States Air Force pilots allowed them to prevail.

The world's navies also transitioned to jets during this period, despite the need for catapult-launching of the new aircraft. Grumman's F9F Panther was adopted by the U.S. Navy as their primary jet fighter in the Korean War period, and it was one of the first jet fighters to employ an afterburner. The de Havilland Vampire was the Royal Navy's first jet fighter. Radar was used on specialized night fighters such as the F3D Skyknight which also downed MiGs over Korea, and later fitted to the F2H Banshee and swept wing F7U Cutlass and F3H Demon as all-weather / night fighers. Early versions of Infra-red (IR) air-to-air missiles (AAMs) such as the AIM-9 Sidewinder and radar guided missiles such as the AIM-7 Sparrow which would be developed into the 21st century were first introduced on swept wing subsonic Demon and Cutlass naval fighters.

Notable first generation jet fighter aircraft

Canada
Avro CF-100 Canuck

France

(Image: MD450 Ouragan in the markings of India's No. 47 "Black Archers" Squadron)

Dassault Ouragan
Dassault Mystère
Dassault Mystère IV

Nazi Germany

(Image: Captured Heinkel He 162 undergoing post-war trials in the U.S.)

Messerschmitt Me 262
Heinkel He 162

People's Republic of China
Shenyang J-5 'Fresco'

Sweden
Saab 21R
Saab 29 Tunnan

Soviet Union

(Image: A MiG-15 in Polish markings)

Mikoyan-Gurevich MiG-9 'Fargo'
Mikoyan-Gurevich MiG-15 'Fagot'
Mikoyan-Gurevich MiG-17 'Fresco'
Lavochkin La-15 'Fantail'
Yakovlev Yak-15/17 'Feather'
Yakovlev Yak-23 'Flora'
Yakovlev Yak-25 'Flashlight'

United Kingdom

(Image: RAF Gloster Meteor)

de Havilland Vampire
de Havilland Venom
Gloster Meteor
Hawker Sea Hawko Supermarine Attacker

United States
Bell P-59 Airacomet
Lockheed P-80 Shooting Star
Republic F-84 Thunderjet
Republic F-84F Thunderstreak

(Image: F-86 Sabres of the Pakistan Air Force)

North American F-86 Sabre
Northrop F-89 Scorpion
Lockheed F-94 Starfire
North American FJ-1 Fury
North American FJ-2/3/4 Fury
McDonnell F2H Banshee
McDonnell F3H Demon

(Image: F9F Panther and AJ-2 Savage conducting in-flight refueling trials in 1953)

Douglas F3D Skyknight
Douglas F4D Skyray
Vought F7U Cutlass
Grumman F9F Panther

Second generation jet fighters (mid-1950s to early 1960s)

(Image: North American F-100 Super Sabre day fighter)

The development of second-generation fighters was shaped by significant technological breakthroughs, lessons learned from the aerial battles of the Korean War, and a growing focus on conducting operations in a nuclear warfare environment. Technological advances in aerodynamics, propulsion and aerospace building materials (primarily aluminium alloys) permitted designers to experiment with a variety of aeronautical innovations, such as swept wings, delta wings, and area-ruled fuselages. Widespread use of afterburning turbojet engines made these the first production aircraft to break the sound barrier, and the ability to sustain supersonic speeds in level flight became a common capability amongst fighters of this generation.

(Image: The Mirage IIIO and DO (top) were licence-built variants of the Mirage IIIE and D produced by Government Aircraft Factories (GAF) for the Royal Australian Air Force)

Fighter designs also took advantage of new electronics technologies that made effective radars small enough to be carried aboard smaller aircraft. Onboard radars permitted detection of enemy aircraft beyond visual range, thereby improving the handoff of targets by longer-ranged ground-based warning and tracking radars. Similarly, advances in guided missile development allowed air-to-air missiles to begin supplementing the gun as the primary offensive weapon for the first time in fighter history. During this period, passive-homing infrared-guided (IR) missiles became commonplace, but early IR missile sensors had poor sensitivity and a very narrow field of view (typically no more than 30°), which limited their effective use to only close-range, tail-chase engagements. Radar-guided (RF) missiles were introduced as well, but early examples proved unreliable. These semi-active radar homing (SARH) missiles could track and intercept an enemy aircraft "painted" by one's own aircraft's onboard radar. Medium- and long-range RF air-to-air missiles promised to open up a new dimension of "beyond-visual-range" (BVR) combat, and much effort was placed in further development of this technology.

(Image: Republic F-105 Thunderchief fighter-bomber)

The prospect of a potential third world war featuring large mechanized armies and nuclear weapon strikes led to a degree of specialization along two design approaches: interceptors (like the English Electric Lightning and Mikoyan-Gurevich MiG-21F) and fighter-bombers (such as the Republic F-105 Thunderchief and the Sukhoi Su-7). Dogfighting, per se, was de-emphasized in both cases. The interceptor was an outgrowth of the vision that guided missiles would completely replace guns and combat would take place at beyond visual ranges. As a result, interceptors were designed with a large missile payload and a powerful radar, sacrificing agility in favor of high speed, altitude ceiling and rate of climb. With a primary air defense role, emphasis was placed on the ability to intercept strategic bombers flying at high altitudes. Specialized point-defense interceptors often had limited range and little, if any, ground-attack capabilities. Fighter-bombers could swing between air superiority and ground-attack roles, and were often designed for a high-speed, low-altitude dash to deliver their ordnance. Television- and IR-guided air-to-surface missiles were introduced to augment traditional gravity bombs, and some were also equipped to deliver a nuclear bomb.

Notable second generation jet fighter aircraft

France
Dassault Étendard IV
Dassault Super Mystère
Dassault Mirage III/5
India
HAL HF-24 Marut
Israel
IAI Nesher
Italy
Fiat G.91
People's Republic of China
Shenyang J-6 'Farmer'

(Image: Saab 32 Lansen fighter-bomber)

Chengdu J-7 'Fishbed'
Sweden
Saab 32 Lansen
Saab 35 Draken
Soviet Union

(Image: Early-model Mikoyan-Gurevich MiG-21F-13 'Fishbed-B' day fighter of the Vietnam People's Air Force captured by the Americans)

Mikoyan-Gurevich MiG-19 'Farmer'
Mikoyan-Gurevich MiG-21F 'Fishbed'
Sukhoi Su-7 'Fitter-A'
Sukhoi Su-9/11 'Fishpot'
United Kingdom
De Havilland Sea Vixen
English Electric Lightning
Gloster Javelin

(Image: Hawker Hunter fighter-bomber)

Hawker Hunter
Supermarine Scimitar
Supermarine Swift
United States
Chance-Vought F-8 Crusader
Grumman F-9 Cougar
Grumman F-11 Tiger
North American F-100 Super Sabre
McDonnell F-101 Voodoo
Convair F-102 Delta Dagger

(Image: English Electric Lightning)

Lockheed F-104 Starfighter
Republic F-105 Thunderchief
Convair F-106 Delta Dart

Third generation jet fighters (early 1960s to circa 1970)

(Image: McDonnell Douglas F-4E Phantom II making a practice bombing run)

The third generation witnessed continued maturation of second-generation innovations, but it is most marked by renewed emphases on maneuverability and traditional ground-attack capabilities. Over the course of the 1960s, increasing combat experience with guided missiles demonstrated that combat could and would devolve into close-in dogfights. Analog avionics began to be introduced, replacing older "steam-gauge" cockpit instrumentation. Popular enhancements to improve the aerodynamic performance of third-generation fighters included flight control surfaces such as canards, powered slats, and blown flaps. A number of technologies would be tried for Vertical/Short Takeoff and Landing, but thrust vectoring would be successful on the Harrier jump jet.

(Image: Mikoyan-Gurevich MiG-25 'Foxbat' interceptor)

Growth in air combat capability focused on the introduction of improved air-to-air missiles, radar systems, and other avionics. While guns remained standard equipment, air-to-air missiles became the primary weapons for air superiority fighters, which employed more sophisticated radars and medium-range RF AAMs to achieve greater "stand-off" ranges, however, kill probabilities proved unexpectedly low for RF missiles due to poor reliability and improved electronic countermeasures (ECM) for spoofing radar seekers. Infrared-homing AAMs saw their fields of view expand to 45°, which strengthened their tactical usability. Nevertheless, the low dogfight loss-exchange ratios experienced by American fighters in the skies over Vietnam led the U.S. Navy to establish its famous "TOPGUN" fighter weapons school, which provided a graduate-level curriculum to train fleet fighter pilots in advanced Air Combat Maneuvering (ACM) and Dissimilar Air Combat Training (DACT) tactics and techniques.

This era also saw a significant expansion in ground-attack capabilities, principally in guided missiles, and witnessed the introduction of the first truly effective avionics for enhanced ground attack, including terrain-avoidance systems. Air-to-surface missiles (ASM) equipped with electro-optical (E-O) contrast seekers – such as the initial model of the widely used AGM-65 Maverick – became standard weapons, and laser-guided bombs (LGBs) became widespread an effort to improve precision-attack capabilities. Guidance for such precision-guided munitions (PGM) was provided by externally mounted targeting pods, which were introduced in the mid-1960s.

(Image: IAI Kfir of the Colombian Air Force)

It also led to the development of new automatic-fire weapons, primarily chain-guns that use an electric engine to drive the mechanism of a cannon; this allowed a single multi-barrel weapon (such as the 20 mm Vulcan) to be carried and provided greater rates of fire and accuracy. Powerplant reliability increased and jet engines became "smokeless" to make it harder to visually sight aircraft at long distances.

Dedicated ground-attack aircraft (like the Grumman A-6 Intruder, SEPECAT Jaguar and LTV A-7 Corsair II) offered longer range, more sophisticated night attack systems or lower cost than supersonic fighters. With variable-geometry wings, the supersonic F-111 introduced the Pratt & Whitney TF30, the first turbofan equipped with afterburner. The ambitious project sought to create a versatile common fighter for many roles and services. It would serve well as an all-weather bomber, but lacked the performance to defeat other fighters.

(Image: Dassault Mirage F1)

The McDonnell F-4 Phantom was designed around radar and missles as all-weather interceptor, but emerged as a versatile strike bomber nimble enough to prevail in air combat, adopted by the U.S. Navy, Air Force and Marine Corps. Despite numerous shortcomings that would be not be fully addressed until newer fighters, the Phantom claimed 280 aerial kills, more than any other U.S. fighter over Vietnam. With range and payload capabilities that rivaled that of WWII bombers such as B-24 Liberator, the Phantom would became a highly successful multirole aircraft.

Notable third generation jet fighter aircraft

France
Dassault Mirage F1
Iran
HESA Azarakhsh
HESA Saeqeh
Israel
IAI Kfir
Japan
Mitsubishi F-1
People's Republic of China
Shenyang J-8I/IIB&D 'Finback'
Xian JH-7 'Flounder'
South Africa
Atlas Cheetah
Sweden
Saab 37 Viggen
Soviet Union
Mikoyan-Gurevich MiG-21MF/bis 'Fishbed'
Mikoyan-Gurevich MiG-23 'Flogger'
Mikoyan-Gurevich MiG-25 'Foxbat'
Sukhoi Su-15 'Flagon'
Sukhoi Su-17 'Fitter'
Tupolev Tu-28 'Fiddler'
United States
McDonnell Douglas F-4 Phantom II
Northrop F-5 Freedom Fighter / Tiger II

Fourth generation jet fighters (circa 1970 to mid-1990s)

(Image: Mikoyan MiG-31 'Foxhound')

Fourth-generation fighters continued the trend towards multirole configurations, and 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 that were capable of performing "fast transients" – quick changes in speed, altitude, and direction – as opposed to relying chiefly on high speed alone.

(Image: Grumman F-14 Tomcat)

E-M characteristics were first applied to the 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 General Dynamics' (now Lockheed Martin's) F-16 Fighting Falcon.

The F-16's maneuverability was further enhanced by its being intentionally designed to be slightly aerodynamically unstable.

(Image: Sukhoi Su-27 'Flanker')

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 system integration techniques. Analog avionics, required to enable FBW operations, became a fundamental requirement and 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 were 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.

(Image: Dassault Mirage 2000)

Other innovative technologies introduced in fourth-generation fighters include 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 of which have become essential equipment. Composite materials in the form of bonded aluminum honeycomb structural elements and graphite epoxy laminate skins began to be incorporated into flight control surfaces and airframe 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.

(Image: Mikoyan MiG-29 'Fulcrum' and F-16 Fighting Falcon)

Another significant revolution came in the form of a stronger reliance on ease of maintenance, which led to standardisation 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 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.

Aerodynamic innovations included variable-camber wings and exploitation of the vortex lift effect to achieve higher angles of attack through the addition of leading-edge extension devices such as strakes.

(Image: Panavia Tornado ADV)

Unlike interceptors of the previous eras, most fourth-generation air-superiority fighters were designed to be agile dogfighters, (although though the Mikoyan MiG-31 and Panavia Tornado ADV are notable exceptions). The continually rising cost of fighters, however, continued to emphasize the value of multirole fighters. The need for both types of fighters led to the concept of the "high/low mix" which envisioned a high-capability – and high-cost – core of dedicated air-superiority fighters (like the F-15 and Sukhoi Su-27) supplemented by a much larger contingent of lower-cost multirole fighters (such as the F-16 and Mikoyan MiG-29).

Most fourth-generation fighter-bombers, such as the Boeing F/A-18 Hornet and Dassault Mirage 2000, are true multirole warplanes, designed as such from the start. This was facilitated by multimode avionics which could switch seamlessly between air and ground modes. The earlier approaches of adding on strike capabilities or designing separate models specialized for different roles generally became passé (with the Panavia Tornado being an exception in this regard). Dedicated attack roles were generally assigned either to interdiction strike aircraft such as the Sukhoi Su-24 and Boeing F-15E Strike Eagle or to armored "tank-plinking" close air support (CAS) specialists like the Fairchild-Republic A-10 Thunderbolt II and Sukhoi Su-25.

(Image: AIDC F-CK-1 Ching-kuo)

Perhaps the most novel technology to be introduced for combat aircraft was "stealth", which involves the use of special "low-observable" (L-O) materials and design techniques to reduce the susceptibility of an aircraft to detection by the enemy's sensor systems, particularly radars. The first stealth aircraft to be introduced were the Lockheed F-117 Nighthawk attack aircraft (introduced in 1983) and the Northrop Grumman B-2 Spirit bomber (which first flew in 1989). Although no stealthy fighters per se appeared amongst the fourth generation, some radar-absorbent coatings and other L-O treatments developed for these programs are reported to have been subsequently applied to fourth-generation fighters.

Notable fourth generation jet fighter aircraft

(Image: McDonnell Douglas F-15 Eagle)

France
Dassault Mirage 2000/2000N/2000D
People's Republic of China
Xian JH-7A 'Flounder'
Shenyang J-11A 'Flanker'
People's Republic of China / Pakistan
JF-17 Thunder
Republic of China
AIDC F-CK-1 Ching-kuo
Soviet Union
Mikoyan MiG-29 'Fulcrum'
Mikoyan MiG-31 'Foxhound'
Sukhoi Su-27 'Flanker'
Sukhoi Su-33 'Flanker D'
United Kingdom / Germany / Italy
Panavia Tornado ADV
United States
Grumman F-14 Tomcat
McDonnell Douglas / Boeing F-15 Eagle
General Dynamics / Lockheed Martin F-16 Fighting Falcon
McDonnell Douglas F/A-18 Hornet

4.5th generation jet fighters (1990s to the present)

(Image: Eurofighter Typhoon)

The end of the Cold War in 1989 led many governments to significantly decrease military spending as a "peace dividend". Air force inventories were cut, and research and development programs intended to produce what was then anticipated to be "fifth-generation" fighters took serious hits; many programs were cancelled during the first half of the 1990s, and those which survived were "stretched out". While the practice of slowing the pace of development reduces annual investment expenses, it comes at the penalty of increased overall program and unit costs over the long-term. In this instance, however, it also permitted designers to leverage the tremendous achievements being made in the fields of computers, avionics and other flight electronics, which had become possible largely due to the advances made in microchip and semiconductor technologies in the 1980s and 1990s. This opportunity enabled designers to develop fourth-generation designs – or redesigns – with significantly enhanced capabilities. These improved designs have become known as "Generation 4.5" fighters, recognizing their intermediate nature between the 4th and 5th generations, and their contribution in furthering development of individual fifth-generation technologies.

(Image: Chengdu J-10)

The primary characteristics of this sub-generation are the extensive application of advanced digital avionics and aerospace materials, modest signature reduction (primarily RF "stealth"), and highly integrated systems and weapons. These fighters have been designed to operate in a "network-centric" battlefield environment and are principally multirole aircraft. Key weapons technologies introduced include beyond-visual-range (BVR) AAMs; Global Positioning System (GPS)-guided weapons, solid-state phased-array radars; helmet-mounted sights; and improved secure, jamming-resistant datalinks. Thrust vectoring to further improve transient maneuvering capabilities have also been adopted by many 4.5th generation fighters, and uprated powerplants have enabled some designs to achieve a degree of "supercruise" ability. Stealth characteristics are focused primarily on frontal-aspect radar cross section (RCS) signature-reduction techniques including radar-absorbent materials (RAM), L-O coatings and limited shaping techniques.

(Image: India's Sukhoi Su-30MKI 'Flanker')

These "half-generation" designs have been based on existing airframes, modified existing airframes or on new airframes following similar design theory as previous iterations; however, these modifications have introduced the structural use of composite materials to reduce weight, greater fuel fractions to increase range, and signature reduction treatments to achieve lower RCS compared to their predecessors. Prime examples include the Boeing F/A-18E/F Super Hornet evolution of the 1970s F/A-18 Hornet design and the Mikoyan MiG-29M/35. These aircraft are now being retrofitted with Active Electronically Scanned Array (AESA) radars, which are also being developed for the Eurofighter Typhoon, Dassault Rafale, and Saab JAS 39 Gripen NG, among others. 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 4.5th generation designs, only the Super Hornet, Strike Eagle, and the Rafale have seen combat action.

4.5th generation fighters were first entered into service in the 1990s, and they are still being produced and evolved. It is quite possible that they may continue in production alongside fifth-generation fighters due to the expense of developing the advanced level of stealth technology needed to achieve aircraft designs featuring very low observables (VLO), which is currently one of the defining features of fifth-generation fighters.

Notable 4.5th generation jet fighters

France
Dassault Rafale
Japan / United States
Mitsubishi F-2
People's Republic of China
Chengdu J-10
Shenyang J-11B 'Flanker'
Russia
Mikoyan MiG-29M 'Fulcrum E'
Mikoyan MiG-35 'Fulcrum F'
Sukhoi Su-30M 'Flanker ?'
Sukhoi Su-32/34 'Fullback'
Sukhoi Su-35 'Flanker E'
Russia / India
Su-30MKI 'Flanker H'
Russia / People's Republic of China
Su-30MKK/MK2 'Flanker G'
Sweden
Saab 39 Gripen
United Kingdom / Germany / Italy / Spain
Eurofighter Typhoon
United States
McDonnell Douglas / Boeing F-15E Strike Eagle and derivatives
Lockheed Martin F-16E/F Block 60
Boeing F/A-18E/F Super Hornet

Fifth generation jet fighters (2005 to the present)

The fifth generation was ushered in by the Lockheed Martin/Boeing F-22 Raptor in late 2005. Currently the cutting edge of fighter design, fifth-generation fighters are characterized by being designed from the start to operate in a network-centric combat environment, and to feature extremely low, all-aspect, multi-spectral signatures employing advanced materials and shaping techniques. They have multifunction AESA radars with high-bandwidth, low-probability of intercept (LPI) data transmission capabilities. IRST sensors are incorporated for air-to-air combat as well as for air-to-ground weapons delivery. These sensors, along with advanced avionics, glass cockpits, helmet-mounted sights, and improved secure, jamming-resistant LPI datalinks are highly integrated to provide multi-platform, multi-sensor data fusion for vastly improved situational awareness while easing the pilot's workload. Avionics suites rely on extensive use of very high-speed integrated circuit (VHSIC) technology, common modules, and high-speed data buses. Overall, the integration of all these elements is claimed to provide fifth-generation fighters with a "first-look, first-shot, first-kill capability".

The AESA radar offers unique capabilities for fighters (and it is also quickly becoming a sine qua non for Generation 4.5 aircraft designs, as well as being retrofitted onto some fourth-generation aircraft). In addition to its inherent high resistance to ECM and LPI features, it enables the fighter to function as a sort of "mini-AWACS," providing high-gain electronic support measures (ESM) and electronic warfare (EW) jamming functions.

Other technologies common to this latest generation of fighters includes integrated electronic warfare system (INEWS) technology, integrated communications, navigation, and identification (CNI) avionics technology, centralized "vehicle health monitoring" systems for ease of maintenance, fiber optics data transmission, and stealth technology.

Maneuver performance remains important and is enhanced by thrust-vectoring, which also helps reduce takeoff and landing distances. Supercruise may or may not be featured; it permits flight at supersonic speeds without the use of the afterburner – a device that significantly increases IR signature when used in full military power.

A key attribute of fifth-generation fighters is very-low-observables stealth. Great care has been taken in intentionally designing its layout and internal structure to minimize RCS over a broad bandwidth of detection and tracking radar frequencies; furthermore, to maintain its VLO signature during combat operations, primary weapons are carried in internal weapon bays that are only briefly opened to permit weapon launch. Furthermore, stealth technology has advanced to the point where it can be employed without a tradeoff with compromised aerodynamics performance. In contrast to previous stealth efforts, significant attention has also been paid to reducing IR signatures. Detailed information on these signature-reduction techniques are classified and thus unavailable, but in general include special shaping approaches, thermoset and thermoplastic materials, extensive structural use of advanced composites, conformal sensors, heat-resistant coatings, low-observable wire meshes to cover intake and cooling vents, and coating internal and external metal areas with radar-absorbent materials and paint (RAM/RAP).

The expense of developing such sophisticated aircraft is as high as their capabilities. The U.S. Air Force had originally planned to acquire 650 F-22s, but it now appears that only about 200 will be built. As a result, its unit flyaway cost (FAC) is reported to be around $140 million. To spread the development costs – and production base – more broadly, the Joint Strike Fighter (JSF) program enrolls eight other countries as cost- and risk-sharing partners. Altogether, the nine partner nations anticipate procuring over 3000 Lockheed Martin F-35 Lightning II fighters at an anticipated average FAC of $80-85 million. The F-35, however, is designed to be a family of three aircraft, a conventional take-off and landing (CTOL) fighter, a short take-off and vertical landing (STOVL) fighter, and a carrier-capable fighter, each of which has a different unit price. Other countries have initiated fifth-generation fighter development projects, with Russia's Sukhoi PAK-FA anticipated to enter service circa 2012–2015. In October 2007, Russia and India signed an agreement for joint participation in a Fifth-Generation Fighter Aircraft Program (FGFA), which will give India responsibility for development of a two-seat model of the PAK-FA. China is reported to be pursuing multiple fifth-generation projects under the western code name; J-XX, and both Japan and South Korea have proposed indigenous programs.

Source: WikiPedia