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120-537: The war was over before it could power airplanes into combat. It powered many of the last generation of large piston-engined aircraft before turbojets , but was supplanted by equivalent (and superior) powered turboprops (such as the Allison T56 ). Its main rival was the twin-row, 18-cylinder, nearly 3,350 cu in (54.9 L) displacement, up to 3,700 hp (2,800 kW) Wright R-3350 Duplex-Cyclone , first run some seven years earlier (May 1937). The R-4360

240-416: A i r + m ˙ f ) V j − m ˙ a i r V {\displaystyle F_{N}=({\dot {m}}_{air}+{\dot {m}}_{f})V_{j}-{\dot {m}}_{air}V} where: If the speed of the jet is equal to sonic velocity the nozzle is said to be " choked ". If the nozzle is choked, the pressure at the nozzle exit plane

360-615: A power-to-weight ratio of 1.11 hp/lb (1.82 kW/kg). Wasp Majors were produced between 1944 and 1955; 18,697 were built. A derivative engine, the Pratt & Whitney R-2180-E Twin Wasp E , was essentially the R-4360 "cut in half". It had two rows of seven cylinders each, and was used on the postwar Saab 90 Scandia airliner. Data from White, 1995 Related development Comparable engines Related lists Turbojet The turbojet

480-565: A by now mediocre performance. The first Eindecker victory came on 1 July 1915, when Leutnant Kurt Wintgens , of Feldflieger Abteilung 6 on the Western Front, downed a Morane-Saulnier Type L. His was one of five Fokker M.5 K/MG prototypes for the Eindecker , and was armed with a synchronized aviation version of the Parabellum MG14 machine gun. The success of the Eindecker kicked off

600-463: A cadre of exceptional pilots. In the United Kingdom, at the behest of Neville Chamberlain (more famous for his 'peace in our time' speech), the entire British aviation industry was retooled, allowing it to change quickly from fabric covered metal framed biplanes to cantilever stressed skin monoplanes in time for the war with Germany, a process that France attempted to emulate, but too late to counter

720-465: A combatant's efforts to gain air superiority hinges on several factors including the skill of its pilots, the tactical soundness of its doctrine for deploying its fighters, and the numbers and performance of those fighters. Many modern fighter aircraft also have secondary capabilities such as ground attack and some types, such as fighter-bombers , are designed from the outset for dual roles. Other fighter designs are highly specialized while still filling

840-435: A competitive cycle of improvement among the combatants, both sides striving to build ever more capable single-seat fighters. The Albatros D.I and Sopwith Pup of 1916 set the classic pattern followed by fighters for about twenty years. Most were biplanes and only rarely monoplanes or triplanes . The strong box structure of the biplane provided a rigid wing that allowed the accurate control essential for dogfighting. They had

960-443: A difficult deflection shot. The first step in finding a real solution was to mount the weapon on the aircraft, but the propeller remained a problem since the best direction to shoot is straight ahead. Numerous solutions were tried. A second crew member behind the pilot could aim and fire a swivel-mounted machine gun at enemy airplanes; however, this limited the area of coverage chiefly to the rear hemisphere, and effective coordination of

1080-552: A form that would replace all others in the 1930s. As collective combat experience grew, the more successful pilots such as Oswald Boelcke , Max Immelmann , and Edward Mannock developed innovative tactical formations and maneuvers to enhance their air units' combat effectiveness. Allied and – before 1918 – German pilots of World War I were not equipped with parachutes , so in-flight fires or structural failures were often fatal. Parachutes were well-developed by 1918 having previously been used by balloonists, and were adopted by

1200-580: A gas turbine to power an aircraft was filed in 1921 by Frenchman Maxime Guillaume . His engine was to be an axial-flow turbojet, but was never constructed, as it would have required considerable advances over the state of the art in compressors. In 1928, British RAF College Cranwell cadet Frank Whittle formally submitted his ideas for a turbojet to his superiors. In October 1929 he developed his ideas further. On 16 January 1930 in England, Whittle submitted his first patent (granted in 1932). The patent showed

1320-645: A great deal of ground-attack work. In World War II, the USAAF and RAF often favored fighters over dedicated light bombers or dive bombers , and types such as the Republic P-47 Thunderbolt and Hawker Hurricane that were no longer competitive as aerial combat fighters were relegated to ground attack. Several aircraft, such as the F-111 and F-117, have received fighter designations though they had no fighter capability due to political or other reasons. The F-111B variant

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1440-542: A landing field, lengthening flights. The increase in reliability that came with the turbojet enabled three- and two-engine designs, and more direct long-distance flights. High-temperature alloys were a reverse salient , a key technology that dragged progress on jet engines. Non-UK jet engines built in the 1930s and 1940s had to be overhauled every 10 or 20 hours due to creep failure and other types of damage to blades. British engines, however, utilised Nimonic alloys which allowed extended use without overhaul, engines such as

1560-431: A number of twin-engine fighters were built; however they were found to be outmatched against single-engine fighters and were relegated to other tasks, such as night fighters equipped with radar sets. By the end of the war, turbojet engines were replacing piston engines as the means of propulsion, further increasing aircraft speed. Since the weight of the turbojet engine was far less than a piston engine, having two engines

1680-534: A part of military nomenclature, a letter is often assigned to various types of aircraft to indicate their use, along with a number to indicate the specific aircraft. The letters used to designate a fighter differ in various countries. In the English-speaking world, "F" is often now used to indicate a fighter (e.g. Lockheed Martin F-35 Lightning II or Supermarine Spitfire F.22 ), though "P" used to be used in

1800-622: A range of specialized aircraft types. Some of the most expensive fighters such as the US Grumman F-14 Tomcat , McDonnell Douglas F-15 Eagle , Lockheed Martin F-22 Raptor and Russian Sukhoi Su-27 were employed as all-weather interceptors as well as air superiority fighter aircraft, while commonly developing air-to-ground roles late in their careers. An interceptor is generally an aircraft intended to target (or intercept) bombers and so often trades maneuverability for climb rate. As

1920-719: A result, during the early months of these campaigns, Axis air forces destroyed large numbers of Red Air Force aircraft on the ground and in one-sided dogfights. In the later stages on the Eastern Front, Soviet training and leadership improved, as did their equipment. By 1942 Soviet designs such as the Yakovlev Yak-9 and Lavochkin La-5 had performance comparable to the German Bf 109 and Focke-Wulf Fw 190 . Also, significant numbers of British, and later U.S., fighter aircraft were supplied to aid

2040-454: A second generation SST engine using the 593 core were done more than three years before Concorde entered service. They evaluated bypass engines with bypass ratios between 0.1 and 1.0 to give improved take-off and cruising performance. Nevertheless, the 593 met all the requirements of the Concorde programme. Estimates made in 1964 for the Concorde design at Mach 2.2 showed the penalty in range for

2160-638: A separate (and vulnerable) radiator, but had increased drag. Inline engines often had a better power-to-weight ratio . Some air forces experimented with " heavy fighters " (called "destroyers" by the Germans). These were larger, usually twin-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 vulnerable to more agile single-engine fighters. The primary driver of fighter innovation, right up to

2280-411: A significant impact on commercial aviation . Aside from giving faster flight speeds turbojets had greater reliability than piston engines, with some models demonstrating dispatch reliability rating in excess of 99.9%. Pre-jet commercial aircraft were designed with as many as four engines in part because of concerns over in-flight failures. Overseas flight paths were plotted to keep planes within an hour of

2400-420: A single operator, who flew the aircraft and also controlled its armament. They were armed with one or two Maxim or Vickers machine guns, which were easier to synchronize than other types, firing through the propeller arc. Gun breeches were in front of the pilot, with obvious implications in case of accidents, but jams could be cleared in flight, while aiming was simplified. The use of metal aircraft structures

2520-405: A small helicopter engine compressor rotates around 50,000 RPM. Turbojets supply bleed air from the compressor to the aircraft for the operation of various sub-systems. Examples include the environmental control system , anti-icing , and fuel tank pressurization. The engine itself needs air at various pressures and flow rates to keep it running. This air comes from the compressor, and without it,

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2640-513: A turbojet application, where the output from the gas turbine is used in a propelling nozzle, raising the turbine temperature increases the jet velocity. At normal subsonic speeds this reduces the propulsive efficiency, giving an overall loss, as reflected by the higher fuel consumption, or SFC. However, for supersonic aircraft this can be beneficial, and is part of the reason why the Concorde employed turbojets. Turbojet systems are complex systems therefore to secure optimal function of such system, there

2760-512: A turbojet engine is always subsonic, regardless of the speed of the aircraft itself. The intake has to supply air to the engine with an acceptably small variation in pressure (known as distortion) and having lost as little energy as possible on the way (known as pressure recovery). The ram pressure rise in the intake is the inlet's contribution to the propulsion system's overall pressure ratio and thermal efficiency . The intake gains prominence at high speeds when it generates more compression than

2880-494: A turbojet is high enough at higher thrust settings to cause the nozzle to choke. If, however, a convergent-divergent de Laval nozzle is fitted, the divergent (increasing flow area) section allows the gases to reach supersonic velocity within the divergent section. Additional thrust is generated by the higher resulting exhaust velocity. Thrust was most commonly increased in turbojets with water/methanol injection or afterburning . Some engines used both methods. Liquid injection

3000-480: A two-stage axial compressor feeding a single-sided centrifugal compressor . Practical axial compressors were made possible by ideas from A.A. Griffith in a seminal paper in 1926 ("An Aerodynamic Theory of Turbine Design"). Whittle later concentrated on the simpler centrifugal compressor only, for a variety of practical reasons. A Whittle engine was the first turbojet to run, the Power Jets WU , on 12 April 1937. It

3120-430: Is a call for the newer models being developed to advance its control systems to implement the newest knowledge from the areas of automation, so increase its safety and effectiveness. Fighter aircraft Fighter aircraft (early on also pursuit aircraft ) are military aircraft designed primarily for air-to-air combat . In military conflict, the role of fighter aircraft is to establish air superiority of

3240-413: Is a component of a turbojet used to divert air into the intake, in front of the accessory drive and to house the starter motor. An intake, or tube, is needed in front of the compressor to help direct the incoming air smoothly into the rotating compressor blades. Older engines had stationary vanes in front of the moving blades. These vanes also helped to direct the air onto the blades. The air flowing into

3360-402: Is a fast, heavily armed and long-range type, able to act as an escort fighter protecting bombers , to carry out offensive sorties of its own as a penetration fighter and maintain standing patrols at significant distance from its home base. Bombers are vulnerable due to their low speed, large size and poor maneuvrability. The escort fighter was developed during World War II to come between

3480-539: Is able to defend itself while conducting attack sorties. The word "fighter" was first used to describe a two-seat aircraft carrying a machine gun (mounted on a pedestal) and its operator as well as the pilot . Although the term was coined in the United Kingdom, the first examples were the French Voisin pushers beginning in 1910, and a Voisin III would be the first to shoot down another aircraft, on 5 October 1914. However at

3600-402: Is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle . The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and a turbine (that drives the compressor). The compressed air from the compressor is heated by burning fuel in the combustion chamber and then allowed to expand through

3720-523: Is greater than atmospheric pressure, and extra terms must be added to the above equation to account for the pressure thrust. The rate of flow of fuel entering the engine is very small compared with the rate of flow of air. If the contribution of fuel to the nozzle gross thrust is ignored, the net thrust is: F N = m ˙ a i r ( V j − V ) {\displaystyle F_{N}={\dot {m}}_{air}(V_{j}-V)} The speed of

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3840-616: Is known as an interceptor . Recognized classes of fighter include: Of these, the Fighter-bomber , reconnaissance fighter and strike fighter classes are dual-role, possessing qualities of the fighter alongside some other battlefield role. Some fighter designs may be developed in variants performing other roles entirely, such as ground attack or unarmed reconnaissance . This may be for political or national security reasons, for advertising purposes, or other reasons. The Sopwith Camel and other "fighting scouts" of World War I performed

3960-568: Is modelled approximately by the Brayton cycle . The efficiency of a gas turbine is increased by raising the overall pressure ratio, requiring higher-temperature compressor materials, and raising the turbine entry temperature, requiring better turbine materials and/or improved vane/blade cooling. It is also increased by reducing the losses as the flow progresses from the intake to the propelling nozzle. These losses are quantified by compressor and turbine efficiencies and ducting pressure losses. When used in

4080-585: Is more commonly by use of a turboshaft engine, a development of the gas turbine engine where an additional turbine is used to drive a rotating output shaft. These are common in helicopters and hovercraft. Turbojets were widely used for early supersonic fighters , up to and including many third generation fighters , with the MiG-25 being the latest turbojet-powered fighter developed. As most fighters spend little time traveling supersonically, fourth-generation fighters (as well as some late third-generation fighters like

4200-540: The Combined Bomber Offensive . Unescorted Consolidated B-24 Liberators and Boeing B-17 Flying Fortress bombers, however, proved unable to fend off German interceptors (primarily Bf 109s and Fw 190s). With the later arrival of long range fighters, particularly the North American P-51 Mustang , American fighters were able to escort far into Germany on daylight raids and by ranging ahead attrited

4320-613: The F-111 and Hawker Siddeley Harrier ) and subsequent designs are powered by the more efficient low-bypass turbofans and use afterburners to raise exhaust speed for bursts of supersonic travel. Turbojets were used on Concorde and the longer-range versions of the Tu-144 which were required to spend a long period travelling supersonically. Turbojets are still common in medium range cruise missiles , due to their high exhaust speed, small frontal area, and relative simplicity. The first patent for using

4440-679: The Gloster Meteor , entered service in 1944, towards the end of World War II , the Me 262 in April and the Gloster Meteor in July. Only about 15 Meteor saw WW2 action but up to 1400 Me 262s were produced, with 300 entering combat, delivering the first ground attacks and air combat victories of jet planes. Air is drawn into the rotating compressor via the intake and is compressed to a higher pressure before entering

4560-571: The Heinkel HeS 3 ), or an axial compressor (as in the Junkers Jumo 004 ) which gave a smaller diameter, although longer, engine. By replacing the propeller used on piston engines with a high speed jet of exhaust, higher aircraft speeds were attainable. One of the last applications for a turbojet engine was Concorde which used the Olympus 593 engine. However, joint studies by Rolls-Royce and Snecma for

4680-572: The Junkers D.I , made with corrugated duralumin , all based on his experience in creating the pioneering Junkers J 1 all-metal airframe technology demonstration aircraft of late 1915. While Fokker would pursue steel tube fuselages with wooden wings until the late 1930s, and Junkers would focus on corrugated sheet metal, Dornier was the first to build a fighter (the Dornier-Zeppelin D.I ) made with pre-stressed sheet aluminum and having cantilevered wings,

4800-515: The North American XB-70 Valkyrie , each feeding three engines with an intake airflow of about 800 pounds per second (360 kg/s). The turbine rotates the compressor at high speed, adding energy to the airflow while squeezing (compressing) it into a smaller space. Compressing the air increases its pressure and temperature. The smaller the compressor, the faster it turns. The (large) GE90-115B fan rotates at about 2,500 RPM, while

4920-502: The RAF and the USAAF against German industry intended to wear down the Luftwaffe. Axis fighter aircraft focused on defending against Allied bombers while Allied fighters' main role was as bomber escorts. The RAF raided German cities at night, and both sides developed radar-equipped night fighters for these battles. The Americans, in contrast, flew daylight bombing raids into Germany delivering

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5040-479: The Rolls-Royce Welland and Rolls-Royce Derwent , and by 1949 the de Havilland Goblin , being type tested for 500 hours without maintenance. It was not until the 1950s that superalloy technology allowed other countries to produce economically practical engines. Early German turbojets had severe limitations on the amount of running they could do due to the lack of suitable high temperature materials for

5160-569: The Sopwith Tabloid and Bristol Scout . The French and the Germans didn't have an equivalent as they used two seaters for reconnaissance, such as the Morane-Saulnier L , but would later modify pre-war racing aircraft into armed single seaters. It was quickly found that these were of little use since the pilot couldn't record what he saw while also flying, while military leaders usually ignored what

5280-760: The Stangensteuerung in German, for "pushrod control system") devised by the engineers of Anthony Fokker 's firm was the first system to enter service. It would usher in what the British called the " Fokker scourge " and a period of air superiority for the German forces, making the 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 poor flight characteristics and

5400-424: The Tu-144 , also used afterburners as does Scaled Composites White Knight , a carrier aircraft for the experimental SpaceShipOne suborbital spacecraft. Reheat was flight-trialled in 1944 on the W.2/700 engines in a Gloster Meteor I . The net thrust F N {\displaystyle F_{N}\;} of a turbojet is given by: F N = ( m ˙

5520-402: The battlespace . Domination of the airspace above a battlefield permits bombers and attack aircraft to engage in tactical and strategic bombing of enemy targets, and helps prevent the enemy from doing the same. The key performance features of a fighter include not only its firepower but also its high speed and maneuverability relative to the target aircraft. The success or failure of

5640-577: The propeller was geared at 0.375:1 so that the tips did not reach inefficient supersonic speeds. The engine was a technological challenge and the first product from Pratt and Whitney's new plant near Kansas City, Missouri . The four-row configuration had severe thermal problems that decreased reliability, with an intensive maintenance regime involving frequent replacement of cylinders required. Large cooling flaps were required, which decreased aerodynamic efficiency, putting extra demands on engine power when cooling needs were greatest. Owing in large part to

5760-643: The British Royal Flying Corps and Royal Air Force referred to them as " scouts " until the early 1920s, while the U.S. Army called them "pursuit" aircraft until the late 1940s (using the designation P, as in Curtiss P-40 Warhawk , Republic P-47 Thunderbolt and Bell P-63 Kingcobra ). The UK changed to calling them fighters in the 1920s , while the US Army did so in the 1940s. A short-range fighter designed to defend against incoming enemy aircraft

5880-621: The British, the Americans, the Spanish (in the Spanish civil war) and the Germans. Given limited budgets, air forces were conservative in aircraft design, and biplanes remained popular with pilots for their agility, and remained in service long after they ceased to be competitive. Designs such as the Gloster Gladiator , Fiat CR.42 Falco , and Polikarpov I-15 were common even in the late 1930s, and many were still in service as late as 1942. Up until

6000-483: The German flying services during the course of that year. The well known and feared Manfred von Richthofen , the "Red Baron", was wearing one when he was killed, but the allied command continued to oppose their use on various grounds. In April 1917, during a brief period of German aerial supremacy a British pilot's average life expectancy was calculated to average 93 flying hours, or about three weeks of active service. More than 50,000 airmen from both sides died during

6120-606: The German invasion. The period of improving the same biplane design over and over was now coming to an end, and the Hawker Hurricane and Supermarine Spitfire started to supplant the Gloster Gladiator and Hawker Fury biplanes but many biplanes remained in front-line service well past the start of World War II. While not a combatant in Spain, they too absorbed many of the lessons in time to use them. The Spanish Civil War also provided an opportunity for updating fighter tactics. One of

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6240-724: The Italians developed several monoplanes such as the Fiat G.50 Freccia , but being short on funds, were forced to continue operating obsolete Fiat CR.42 Falco biplanes. From the early 1930s the Japanese were at war against both the Chinese Nationalists and the Russians in China, and used the experience to improve both training and aircraft, replacing biplanes with modern cantilever monoplanes and creating

6360-932: The Japanese Nakajima Ki-27 , Nakajima Ki-43 and Mitsubishi A6M Zero and the Italian Fiat G.50 Freccia and Macchi MC.200 . In contrast, designers in the United Kingdom, Germany, the Soviet Union, and the United States believed that the increased speed of fighter aircraft would create g -forces unbearable to pilots who attempted maneuvering dogfights typical of the First World War, and their fighters were instead optimized for speed and firepower. In practice, while light, highly maneuverable aircraft did possess some advantages in fighter-versus-fighter combat, those could usually be overcome by sound tactical doctrine, and

6480-605: The Luftwaffe to establish control of the skies over Western Europe. By the time of Operation Overlord in June 1944, the Allies had gained near complete air superiority over the Western Front. This cleared the way both for intensified strategic bombing of German cities and industries, and for the tactical bombing of battlefield targets. With the Luftwaffe largely cleared from the skies, Allied fighters increasingly served as ground attack aircraft. Allied fighters, by gaining air superiority over

6600-637: The Luftwaffe, and while the Luftwaffe maintained a qualitative edge over the Red Air Force for much of the war, the increasing numbers and efficacy of the Soviet Air Force were critical to the Red Army's efforts at turning back and eventually annihilating the Wehrmacht . Meanwhile, air combat on the Western Front had a much different character. Much of this combat focused on the strategic bombing campaigns of

6720-539: The Soviet Polikarpov I-16 . The later German design was earlier in its design cycle, and had more room for development and the lessons learned led to greatly improved models in World War II. The Russians failed to keep up and despite newer models coming into service, I-16s remaining the most common Soviet front-line fighter into 1942 despite being outclassed by the improved Bf 109s in World War II. For their part,

6840-580: The Soviet war effort as part of Lend-Lease , with the Bell P-39 Airacobra proving particularly effective in the lower-altitude combat typical of the Eastern Front. The Soviets were also helped indirectly by the American and British bombing campaigns, which forced the Luftwaffe to shift many of its fighters away from the Eastern Front in defense against these raids. The Soviets increasingly were able to challenge

6960-594: The US for pursuit (e.g. Curtiss P-40 Warhawk ), a translation of the French "C" ( Dewoitine D.520 C.1 ) for Chasseur while in Russia "I" was used for Istrebitel , or exterminator ( Polikarpov I-16 ). As fighter types have proliferated, the air superiority fighter emerged as a specific role at the pinnacle of speed, maneuverability, and air-to-air weapon systems – able to hold its own against all other fighters and establish its dominance in

7080-529: The United States, Russia, India and China. The first step was to find ways to reduce the aircraft's reflectivity to radar waves by burying the engines, eliminating sharp corners and diverting any reflections away from the radar sets of opposing forces. Various materials were found to absorb the energy from radar waves, and were incorporated into special finishes that have since found widespread application. Composite structures have become widespread, including major structural components, and have helped to counterbalance

7200-661: The advantages of fighting above Britain's home territory allowed the RAF to deny Germany air superiority, saving the UK from possible German invasion and dealing the Axis a major defeat early in the Second World War. On the Eastern Front , Soviet fighter forces were overwhelmed during the opening phases of Operation Barbarossa . This was a result of the tactical surprise at the outset of the campaign,

7320-464: The aircraft decreases the efficiency of the engine because it has been compressed, but then does not contribute to producing thrust. Compressor types used in turbojets were typically axial or centrifugal. Early turbojet compressors had low pressure ratios up to about 5:1. Aerodynamic improvements including splitting the compressor into two separately rotating parts, incorporating variable blade angles for entry guide vanes and stators, and bleeding air from

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7440-494: The basis for an effective "fighter" in the modern sense of the word. It was based on small fast aircraft developed before the war for air racing such with the Gordon Bennett Cup and Schneider Trophy . The military scout airplane was not expected to carry serious armament, but rather to rely on speed to "scout" a location, and return quickly to report, making it a flying horse. British scout aircraft, in this sense, included

7560-496: The battlefield. Early fighters were very small and lightly armed by later standards, and most were biplanes built with a wooden frame covered with fabric, and a maximum airspeed of about 100 mph (160 km/h). A successful German biplane, the Albatross, however, was built with a plywood shell, rather than fabric, which created a stronger, faster airplane. As control of the airspace over armies became increasingly important, all of

7680-414: The bombers and enemy attackers as a protective shield. The primary requirement was for long range, with several heavy fighters given the role. However they too proved unwieldy and vulnerable, so as the war progressed techniques such as drop tanks were developed to extend the range of more nimble conventional fighters. The penetration fighter is typically also fitted for the ground-attack role, and so

7800-410: The combustion chamber. Fuel is mixed with the compressed air and burns in the combustor. The combustion products leave the combustor and expand through the turbine where power is extracted to drive the compressor. The turbine exit gases still contain considerable energy that is converted in the propelling nozzle to a high speed jet. The first turbojets, used either a centrifugal compressor (as in

7920-432: The combustor and pass through to the turbine in a continuous flowing process with no pressure build-up. Instead, a small pressure loss occurs in the combustor. The fuel-air mixture can only burn in slow-moving air, so an area of reverse flow is maintained by the fuel nozzles for the approximately stoichiometric burning in the primary zone. Further compressed air is introduced which completes the combustion process and reduces

8040-421: The compressor enabled later turbojets to have overall pressure ratios of 15:1 or more. After leaving the compressor, the air enters the combustion chamber. The burning process in the combustor is significantly different from that in a piston engine . In a piston engine, the burning gases are confined to a small volume, and as the fuel burns, the pressure increases. In a turbojet, the air and fuel mixture burn in

8160-401: The compressor is passed through these to keep the metal temperature within limits. The remaining stages do not need cooling. In the first stage, the turbine is largely an impulse turbine (similar to a pelton wheel ) and rotates because of the impact of the hot gas stream. Later stages are convergent ducts that accelerate the gas. Energy is transferred into the shaft through momentum exchange in

8280-474: The compressor stage. Well-known examples are the Concorde and Lockheed SR-71 Blackbird propulsion systems where the intake and engine contributions to the total compression were 63%/8% at Mach 2 and 54%/17% at Mach 3+. Intakes have ranged from "zero-length" on the Pratt & Whitney TF33 turbofan installation in the Lockheed C-141 Starlifter , to the twin 65 feet (20 m) long, intakes on

8400-601: The defense budgets of modern armed forces. The global combat aircraft market was worth $ 45.75 billion in 2017 and is projected by Frost & Sullivan at $ 47.2 billion in 2026: 35% modernization programs and 65% aircraft purchases, dominated by the Lockheed Martin F-35 with 3,000 deliveries over 20 years. A fighter aircraft is primarily designed for air-to-air combat . A given type may be designed for specific combat conditions, and in some cases for additional roles such as air-to-ground fighting. Historically

8520-656: The design approach of the Italians and Japanese made their fighters ill-suited as interceptors or attack aircraft. During the invasion of Poland and the Battle of France , Luftwaffe fighters—primarily the Messerschmitt Bf 109 —held air superiority, and the Luftwaffe played a major role in German victories in these campaigns. During the Battle of Britain , however, British Hurricanes and Spitfires proved roughly equal to Luftwaffe fighters. Additionally Britain's radar-based Dowding system directing fighters onto German attacks and

8640-516: The early 1960s since both were believed unusable at the speeds being attained, however the Vietnam War showed that guns still had a role to play, and most fighters built since then are fitted with cannon (typically between 20 and 30 mm (0.79 and 1.18 in) in caliber) in addition to missiles. Most modern combat aircraft can carry at least a pair of air-to-air missiles. In the 1970s, turbofans replaced turbojets, improving fuel economy enough that

8760-513: The fighter. Rifle-caliber .30 and .303 in (7.62 and 7.70 mm) calibre guns remained the norm, with larger weapons either being too heavy and cumbersome or deemed unnecessary against such lightly built aircraft. It was not considered unreasonable to use World War I-style armament to counter enemy fighters as there was insufficient air-to-air combat during most of the period to disprove this notion. The rotary engine , popular during World War I, quickly disappeared, its development having reached

8880-406: The guns were subjected). Shooting with this traditional arrangement was also easier because the guns shot directly ahead in the direction of the aircraft's flight, up to the limit of the guns range; unlike wing-mounted guns which to be effective required to be harmonised , that is, preset to shoot at an angle by ground crews so that their bullets would converge on a target area a set distance ahead of

9000-475: The high-temperature materials used in their turbosuperchargers during World War II. Water injection was a common method used to increase thrust, usually during takeoff, in early turbojets that were thrust-limited by their allowable turbine entry temperature. The water increased thrust at the temperature limit, but prevented complete combustion, often leaving a very visible smoke trail. Allowable turbine entry temperatures have increased steadily over time both with

9120-433: The innovations 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

9240-504: The interceptor. The equipment necessary for daytime flight is inadequate when flying at night or in poor visibility. The night fighter was developed during World War I with additional equipment to aid the pilot in flying straight, navigating and finding the target. From modified variants of the Royal Aircraft Factory B.E.2c in 1915, the night fighter has evolved into the highly capable all-weather fighter. The strategic fighter

9360-441: The introduction of superior alloys and coatings, and with the introduction and progressive effectiveness of blade cooling designs. On early engines, the turbine temperature limit had to be monitored, and avoided, by the pilot, typically during starting and at maximum thrust settings. Automatic temperature limiting was introduced to reduce pilot workload and reduce the likelihood of turbine damage due to over-temperature. A nose bullet

9480-401: The jet V j {\displaystyle V_{j}\;} must exceed the true airspeed of the aircraft V {\displaystyle V\;} if there is to be a net forward thrust on the airframe. The speed V j {\displaystyle V_{j}\;} can be calculated thermodynamically based on adiabatic expansion . The operation of a turbojet

9600-400: The jet era. Engine displacement was 4,362.5 cu in (71.5 L), hence the model designation. Initial models developed 3,000 hp (2,200 kW), and later models 3,500 hp (2,600 kW). One model that used two large turbochargers in addition to the supercharger delivered 4,300 horsepower (3,200 kW). Engines weighed 3,482–3,870 lb (1,579–1,755 kg), giving

9720-420: The last piston engine support aircraft could be replaced with jets, making multi-role combat aircraft possible. Honeycomb structures began to replace milled structures, and the first composite components began to appear on components subjected to little stress. With the steady improvements in computers, defensive systems have become increasingly efficient. To counter this, stealth technologies have been pursued by

9840-564: The leadership vacuum within the Soviet military left by the Great Purge , and the general inferiority of Soviet designs at the time, such as the obsolescent Polikarpov I-15 biplane and the I-16 . More modern Soviet designs, including the Mikoyan-Gurevich MiG-3 , LaGG-3 and Yakolev Yak-1 , had not yet arrived in numbers and in any case were still inferior to the Messerschmitt Bf 109 . As

9960-419: The main air superiority role, and these include the interceptor and, historically, the heavy fighter and night fighter . Since World War I, achieving and maintaining air superiority has been considered essential for victory in conventional warfare . Fighters continued to be developed throughout World War I, to deny enemy aircraft and dirigibles the ability to gather information by reconnaissance over

10080-635: The maintenance requirements of the R-4360, all airplanes equipped with it were costly to operate and suffered decreased availability. Its commercial application in the Boeing Stratocruiser was unprofitable without government subsidy. Abandonment of the Stratocruiser was almost immediate when jet aircraft became available, while aircraft with smaller powerplants such as the Lockheed Constellation and Douglas DC-6 remained in service well into

10200-471: The major powers developed fighters to support their military operations. Between the wars, wood was largely replaced in part or whole by metal tubing, and finally aluminum stressed skin structures (monocoque) began to predominate. By World War II , most fighters were all-metal monoplanes armed with batteries of machine guns or cannons and some were capable of speeds approaching 400 mph (640 km/h). Most fighters up to this point had one engine, but

10320-410: The mid-1930s, the majority of fighters in the US, the UK, Italy and Russia 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 directly ahead of the pilot, where they were more accurate (that being the strongest part of the structure, reducing the vibration to which

10440-495: The most modern weapons, against an enemy in complete command of the air, fights like a savage…" Throughout the war, fighters performed their conventional role in establishing air superiority through combat with other fighters and through bomber interception, and also often performed roles such as tactical air support and reconnaissance . Fighter design varied widely among combatants. The Japanese and Italians favored lightly armed and armored but highly maneuverable designs such as

10560-402: The opposite way to energy transfer in the compressor. The power developed by the turbine drives the compressor and accessories, like fuel, oil, and hydraulic pumps that are driven by the accessory gearbox. After the turbine, the gases expand through the exhaust nozzle producing a high velocity jet. In a convergent nozzle, the ducting narrows progressively to a throat. The nozzle pressure ratio on

10680-607: The opposition. Subsequently, radar capabilities grew enormously and are now the primary method of target acquisition . Wings were made thinner and swept back to reduce transonic drag, which required new manufacturing methods to obtain sufficient strength. Skins were no longer sheet metal riveted to a structure, but milled from large slabs of alloy. The sound barrier was broken, and after a few false starts due to required changes in controls, speeds quickly reached Mach 2, past which aircraft cannot maneuver sufficiently to avoid attack. Air-to-air missiles largely replaced guns and rockets in

10800-488: The outbreak of World War I , front-line aircraft were mostly unarmed and used almost exclusively for reconnaissance . On 15 August 1914, Miodrag Tomić encountered an enemy airplane while on a reconnaissance flight over Austria-Hungary which fired at his aircraft with a revolver, so Tomić fired back. It was believed to be the first exchange of fire between aircraft. Within weeks, all Serbian and Austro-Hungarian aircraft were armed. Another type of military aircraft formed

10920-479: The period of rapid re-armament in the late 1930s, were not military budgets, but civilian aircraft racing. Aircraft designed for these races introduced innovations like streamlining and more powerful engines that would find their way into the fighters of World War II. The most significant of these was the Schneider Trophy races, where competition grew so fierce, only national governments could afford to enter. At

11040-433: The period, going from a typical 180 hp (130 kW) in the 900 kg (2,000 lb) Fokker D.VII of 1918 to 900 hp (670 kW) in the 2,500 kg (5,500 lb) Curtiss P-36 of 1936. 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 inlines. Radial designs did not require

11160-452: The pilot's maneuvering with the gunner's aiming was difficult. This option was chiefly employed as a defensive measure on two-seater reconnaissance aircraft from 1915 on. Both the SPAD S.A and the Royal Aircraft Factory B.E.9 added a second crewman ahead of the engine in a pod but this was both hazardous to the second crewman and limited performance. The Sopwith L.R.T.Tr. similarly added a pod on

11280-451: The pilots reported. Attempts were made with handheld weapons such as pistols and rifles and even light machine guns, but these were ineffective and cumbersome. The next advance came with the fixed forward-firing machine gun, so that the pilot pointed the entire aircraft at the target and fired the gun, instead of relying on a second gunner. Roland Garros bolted metal deflector plates to the propeller so that it would not shoot itself out of

11400-410: The point where rotational forces prevented more fuel and air from being delivered to the cylinders, which limited horsepower. They were replaced chiefly by the stationary radial engine though major advances led to inline engines gaining ground with several exceptional engines—including the 1,145 cu in (18,760 cm ) V-12 Curtiss D-12 . Aircraft engines increased in power several-fold over

11520-518: The propeller arc was evident even before the outbreak of war and inventors in both France and Germany devised mechanisms that could time the firing of the individual rounds to avoid hitting the propeller blades. 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

11640-461: The propeller arc. Wing guns were tried but the unreliable weapons available required frequent clearing of jammed rounds and misfires and remained impractical until after the war. Mounting the machine gun over the top wing worked well and was used long after the ideal solution was found. The Nieuport 11 of 1916 used this system with considerable success, however, this placement made aiming and reloading difficult but would continue to be used throughout

11760-454: The propeller blades were fitted with metal wedges to protect them from ricochets . Garros' modified monoplane first flew in March 1915 and he began combat operations soon after. Garros scored three victories in three weeks before he himself was downed on 18 April and his airplane, along with its synchronization gear and propeller was captured by the Germans. Meanwhile, the synchronization gear (called

11880-426: 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 parasol monoplane . Unfortunately the gas-operated Hotchkiss machine gun he was provided had an erratic rate of fire and it was impossible to synchronize it with the propeller. As an interim measure,

12000-532: The skies above the battlefield. The interceptor is a fighter designed specifically to intercept and engage approaching enemy aircraft. There are two general classes of interceptor: relatively lightweight aircraft in the point-defence role, built for fast reaction, high performance and with a short range, and heavier aircraft with more comprehensive avionics and designed to fly at night or in all weathers and to operate over longer ranges . Originating during World War I, by 1929 this class of fighters had become known as

12120-417: The sky and a number of Morane-Saulnier Ns were modified. The technique proved effective, however the deflected bullets were still highly dangerous. Soon after the commencement of the war, pilots armed themselves with pistols, carbines , grenades , and an assortment of improvised weapons. Many of these proved ineffective as the pilot had to fly his airplane while attempting to aim a handheld weapon and make

12240-408: The steady increases in aircraft weight—most modern fighters are larger and heavier than World War II medium bombers. Because of the importance of air superiority, since the early days of aerial combat armed forces have constantly competed to develop technologically superior fighters and to deploy these fighters in greater numbers, and fielding a viable fighter fleet consumes a substantial proportion of

12360-468: The supersonic airliner, in terms of miles per gallon, compared to subsonic airliners at Mach 0.85 (Boeing 707, DC-8) was relatively small. This is because the large increase in drag is largely compensated by an increase in powerplant efficiency (the engine efficiency is increased by the ram pressure rise which adds to the compressor pressure rise, the higher aircraft speed approaches the exhaust jet speed increasing propulsive efficiency). Turbojet engines had

12480-446: The temperature of the combustion products to a level which the turbine can accept. Less than 25% of the air is typically used for combustion, as an overall lean mixture is required to keep within the turbine temperature limits. Hot gases leaving the combustor expand through the turbine. Typical materials for turbines include inconel and Nimonic . The hottest turbine vanes and blades in an engine have internal cooling passages. Air from

12600-535: The thrust from a turbojet engine. It was flown by test pilot Erich Warsitz . The Gloster E.28/39 , (also referred to as the "Gloster Whittle", "Gloster Pioneer", or "Gloster G.40") made the first British jet-engined flight in 1941. It was designed to test the Whittle jet engine in flight, and led to the development of the Gloster Meteor. The first two operational turbojet aircraft, the Messerschmitt Me 262 and then

12720-480: The top wing with no better luck. An alternative 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 made it slower than a similar "tractor" aircraft. A better solution for a single seat scout was to mount the machine gun (rifles and pistols having been dispensed with) to fire forwards but outside

12840-708: The turbine. The turbine exhaust is then expanded in the propelling nozzle where it is accelerated to high speed to provide thrust. Two engineers, Frank Whittle in the United Kingdom and Hans von Ohain in Germany , developed the concept independently into practical engines during the late 1930s. Turbojets have poor efficiency at low vehicle speeds, which limits their usefulness in vehicles other than aircraft. Turbojet engines have been used in isolated cases to power vehicles other than aircraft, typically for attempts on land speed records . Where vehicles are "turbine-powered", this

12960-412: The turbines would overheat, the lubricating oil would leak from the bearing cavities, the rotor thrust bearings would skid or be overloaded, and ice would form on the nose cone. The air from the compressor, called secondary air, is used for turbine cooling, bearing cavity sealing, anti-icing, and ensuring that the rotor axial load on its thrust bearing will not wear it out prematurely. Supplying bleed air to

13080-408: The turbines. British engines such as the Rolls-Royce Welland used better materials giving improved durability. The Welland was type-certified for 80 hours initially, later extended to 150 hours between overhauls, as a result of an extended 500-hour run being achieved in tests. General Electric in the United States was in a good position to enter the jet engine business due to its experience with

13200-460: The two Rotten could split up at any time and attack on their own. The finger-four would be widely adopted as the fundamental tactical formation during World War Two, including by the British and later the Americans. World War II featured fighter combat on a larger scale than any other conflict to date. German Field Marshal Erwin Rommel noted the effect of airpower: "Anyone who has to fight, even with

13320-589: The very end of the inter-war period in Europe came the Spanish Civil War . This was just the opportunity the German Luftwaffe , Italian Regia Aeronautica , and the Soviet Union's Voenno-Vozdushnye Sily needed to test their latest aircraft. Each party sent numerous aircraft types to support their sides in the conflict. In the dogfights over Spain, the latest Messerschmitt Bf 109 fighters did well, as did

13440-473: The war as the weapons used were lighter and had a higher rate of fire than synchronized weapons. The British Foster mounting and several French mountings were specifically designed for this kind of application, fitted with either the Hotchkiss or Lewis Machine gun , which due to their design were unsuitable for synchronizing. The need to arm a tractor scout with a forward-firing gun whose bullets passed through

13560-443: The war. Fighter development stagnated between the wars, especially in the United States and the United Kingdom, where budgets were small. In France, Italy and Russia, where large budgets continued to allow major development, both monoplanes and all metal structures were common. By the end of the 1920s, however, those countries overspent themselves and were overtaken in the 1930s by those powers that hadn't been spending heavily, namely

13680-399: Was a 28- cylinder four-row air-cooled radial engine. Each row of seven air-cooled cylinders possessed a slight angular offset from the previous, forming a semi-helical arrangement to facilitate effective airflow cooling of the cylinder rows behind them, inspiring the engine's "corncob" nickname. A mechanical supercharger geared at 6.374:1 ratio to engine speed provided forced induction, while

13800-424: Was liquid-fuelled. Whittle's team experienced near-panic during the first start attempts when the engine accelerated out of control to a relatively high speed despite the fuel supply being cut off. It was subsequently found that fuel had leaked into the combustion chamber during pre-start motoring checks and accumulated in pools, so the engine would not stop accelerating until all the leaked fuel had burned off. Whittle

13920-420: Was no longer a handicap and one or two were used, depending on requirements. This in turn required the development of ejection seats so the pilot could escape, and G-suits to counter the much greater forces being applied to the pilot during maneuvers. In the 1950s, radar was fitted to day fighters, since due to ever increasing air-to-air weapon ranges, pilots could no longer see far enough ahead to prepare for

14040-472: Was originally intended for a fighter role with the U.S. Navy , but it was canceled. This blurring follows the use of fighters from their earliest days for "attack" or "strike" operations against ground targets by means of strafing or dropping small bombs and incendiaries. Versatile multi role fighter-bombers such as the McDonnell Douglas F/A-18 Hornet are a less expensive option than having

14160-501: Was pioneered before World War I by Breguet but would find its biggest proponent in Anthony Fokker, who used chrome-molybdenum steel tubing for the fuselage structure of all his fighter designs, while 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

14280-629: Was tested on the Power Jets W.1 in 1941 initially using ammonia before changing to water and then water-methanol. A system to trial the technique in the Gloster E.28/39 was devised but never fitted. An afterburner or "reheat jetpipe" is a combustion chamber added to reheat the turbine exhaust gases. The fuel consumption is very high, typically four times that of the main engine. Afterburners are used almost exclusively on supersonic aircraft , most being military aircraft. Two supersonic airliners, Concorde and

14400-479: Was unable to interest the government in his invention, and development continued at a slow pace. In Germany, Hans von Ohain patented a similar engine in 1935. His design, an axial-flow engine, as opposed to Whittle's centrifugal flow engine, was eventually adopted by most manufacturers by the 1950s. On 27 August 1939 the Heinkel He 178 , powered by von Ohain's design, became the world's first aircraft to fly using

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