A jet aircraft (or simply jet ) is an aircraft (nearly always a fixed-wing aircraft ) propelled by one or more jet engines .
94-476: A four-engined jet , sometimes called a quadjet , is a jet aircraft powered by four engines . The presence of four engines offers increased power and redundancy, allowing such aircraft to be used as airliners , freighters , and military aircraft . Many of the first purpose-built jet airliners had four engines, among which stands the De Havilland Comet , the world's first commercial jetliner. In
188-454: A T-tail configuration. The larger widebody Lockheed TriStar and DC-10/MD-11 mount an engine underneath each wing. Preliminary studies were done on the TriStar to reuse the fuselage and wing for a twinjet design though these never materialized due to Lockheed's lack of funds. Additionally in the late-1990s Boeing, which had taken over McDonnell Douglas, considered removing the tail engine from
282-458: A flying wing , the wing is the main structural component). This reduces the heat signature of the engines by concealing the fans and minimizing the exhaust signature. The Hawker Siddeley Trident 3B not only has two engines in rear fuselage external nacelles , but also has other two engines mounted vertically in the tail. The aircraft was initially designed as trijet , but the Trident 3B added
376-560: A combination still unmatched by twinjets at the time, making this the most commercially successful 747 variant. Airbus, after ending collaboration talks with McDonnell Douglas who went on to produce the MD-11 long-range trijet, instead launched the A340 quadjet in 1993 as a long-range derivative of the A330 twinjet as their initial variants shared the same fuselage and wing. Between the 1970 and
470-525: A compromise between fuel efficiency and redundancy. In 1969, Boeing launched the 747 . Nicknamed the "Jumbo Jet", it was the first wide-body airliner , able to carry significantly more passengers than any other aircraft. Its capacity and performance were unmatched, even after the launch of wide-body trijet competition in the form of the McDonnell Douglas DC-10 and Lockheed L-1011 TriStar . Within its own category in commercial aviation,
564-436: A fourth engine as additional power was required by the stretched fuselage, increased wing chord and raised gross weight. A major advantage of having four engines is the redundancy offered, leading to increased safety. A single engine failure is much less significant as the three remaining engines can usually provide sufficient power to comfortably reach a diversion airport or continue the journey, depending on factors such as
658-606: A high cost-to-passenger-mile ratio. On the other hand, the large four-engined types were less suited for frequent short-haul services, which demanded multiple take-offs and landings daily, costing more fuel while also typically carrying fewer passengers per flight. This prompted the development of large trijets and twinjets . Due to limitations in engine technology, twinjets of this era were small and had relatively short range. The FAA's 60-Minute Rule also prevented them from flying farther than 60 minutes away from diversion airports due to their lower engine redundancy. Trijets represented
752-429: A higher risk of the engines ingesting foreign objects as they have a lower ground clearance, and a larger yawing moment during an engine failure . The supersonic airliner Concorde had its engines mounted in rectangular pods conformal to the underside of the wing, without any pylons. The omission of pylons reduces drag and eliminates the risk of them being overstressed. The four podded engines can also be attached to
846-522: A highly flammable fabric surface. During the 1920s and 1930s a number of approaches were tried. A variety of motorjet , turboprop , pulsejet and rocket powered aircraft were designed. Rocket-engine research was being carried out in Germany and the first aircraft to fly under rocket power was the Lippisch Ente , in 1928. The Ente had previously been flown as a glider. The next year, in 1929,
940-569: A jet fighter on 26 July 1944, the day before the British Gloster Meteor entered operational service. The Me 262 had first flown on April 18, 1941, but mass production did not start until early 1944, with the first squadrons operational that year, too late for any effect on the outcome of the World War II . While only around 15 Meteors were operational during WW2, up to 1,400 Me 262 were produced, with 300 entering combat. Only
1034-516: A jet-powered aircraft in 1910, the Coandă-1910 . However, to support this claim, he had to make substantial alterations to the drawings which he used to support his subsequently debunked claims. In fact the ducted-fan engine backfired, setting the aircraft on fire before any flights were ever made, and it lacked nearly all of the features necessary for a jet engine - including a lack of fuel injection, and any concern about hot jet efflux being directed at
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#17327870911321128-509: A lower exhaust speed than turbojets, and are mostly used for high sonic, transonic, and low supersonic speeds. High bypass turbofans are relatively efficient, and are used by subsonic aircraft such as airliners. Jet aircraft fly considerably differently than propeller aircraft . One difference is that jet engines respond relatively slowly. This complicates takeoff and landing maneuvers. In particular, during takeoff, propeller aircraft engines blow air over their wings and that gives more lift and
1222-412: A need for high-capacity aircraft. Conversely, the point-to-point model transports passengers directly from origin to destination, spreading them out across different routes and requiring fewer seats on the servicing aircraft. Especially with the recent appearance of low-cost carriers which operate many point-to-point flights, it is more difficult to fill the seats of the largest airliners. For this reason,
1316-526: A new trijet called the MD-XX, which were lengthened versions of the MD-11 . The MD-XX Long Range aircraft would have been capable of traveling distances up to 8,320 nautical miles (15,410 km) and had a wingspan of 65 metres (213 ft). The project was canceled in 1996, one year before McDonnell Douglas was acquired by Boeing. Boeing ended production of the MD-11 after filling remaining customer orders since
1410-672: A new wing design and entered serial production from 1984 as the Tu-154M . With the exceptions of the Dassault Falcon 7X , Falcon 8x , and Falcon 900 business jets, no manufacturer currently produces three-engine airliners. Modern engines have extremely low failure rates and can generate much higher shaft power and thrust than early types. This makes twinjets more suitable than they were before for long-haul trans-oceanic operations, resulting in eased ETOPS restrictions; modern wide-body twin-engine jets usually have an ETOPS 180 or (in
1504-564: A new, twin-tail trijet design, whose tail engine appears to use a "straight" layout similar to the MD-11, but it is unknown if and when this will be developed or produced. However, the proposed Boeing X-48 blended wing body design, Lockheed's N+2 design study, and Aerion AS2 supersonic business jet were also supposed to have three engines. The AS2 programme was cancelled in May 2021 when Aerion Corporation shut down. Boom Technology 's planned Overture supersonic transport (SST) airliner
1598-413: A shorter takeoff. These differences caught out some early BOAC Comet pilots. In aircraft overall propulsive efficiency η {\displaystyle \eta } is the efficiency, in percent, with which the energy contained in a vehicle's propellant is converted into useful energy, to replace losses due to air drag , gravity, and acceleration. It can also be stated as the proportion of
1692-422: A speed that is the same as, or nearly the same as, the vehicle velocity. The exact formula for air-breathing engines as given in the literature, is where c is the exhaust speed, and v is the speed of the aircraft. For a long range jet operating in the stratosphere , the speed of sound is constant, hence flying at fixed angle of attack and constant Mach number causes the aircraft to climb, without changing
1786-657: A trijet aircraft) and Boeing worked on new widebody twinjet designs that would become the A330 and 777, respectively. The MD-11's long-range advantage was brief as it soon was threatened by the A330's four-engine derivative, the A340 , and the 777. The only other notable trijet development during the 1980s was in the Soviet Union , where the Tupolev Tu-154 was re-engined with the Soloviev D-30 engine as well as
1880-500: A version of the Whittle engine built by General Electric . The Meteor was the first production jet, with the first orders for production examples being made on 8 August 1941, the prototype first flying on 5 March 1943 and the first production aircraft flying on 12 January 1944, while the first orders for production Me 262 aircraft were not issued until 25 May 1943, and the first production Me 262 did not fly until 28 March 1944 despite
1974-684: Is known as the Breguet range equation after the French aviation pioneer Louis Charles Breguet . Trijet A trijet is a jet aircraft powered by three jet engines . In general, passenger airline trijets are considered to be second-generation jet airliners , due to their innovative engine locations, in addition to the advancement of turbofan technology. Trijets are more efficient than quadjets , but not as efficient as twinjets , which replaced trijets as larger and more reliable turbofan engines became available. The Dassault Falcon 7X /8X and
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#17327870911322068-416: Is often less important than for scheduled-route operating airlines, trijets may still be of interest due to their immunity from ETOPS and the ability to take off from shorter runways and therefore have access to more airports. As a result, a sizeable number of trijets, such as the newly built Dassault Falcons , are in use by private operators and corporate flight departments. Airbus filed a patent in 2008 for
2162-658: Is the X-15 at Mach 6.85. The Space Shuttle , while far faster than the X-43 or X-15, was not regarded as an aircraft during ascent as it was carried ballistically by rocket thrust, rather than the air. During re-entry it was classed (like a glider) as an unpowered aircraft. The first flight was in 1981. The Bell 533 (1964), Lockheed XH-51 (1965), and Sikorsky S-69 (1977-1981) are examples of compound helicopter designs where jet exhaust added to forward thrust. The Hiller YH-32 Hornet and Fairey Ultra-light Helicopter were among
2256-427: Is the cycle efficiency and η p {\displaystyle \eta _{p}} is the propulsive efficiency. The cycle efficiency, in percent, is the proportion of energy that can be derived from the energy source that is converted to mechanical energy by the engine . For jet aircraft the propulsive efficiency (essentially energy efficiency ) is highest when the engine emits an exhaust jet at
2350-570: Is therefore an important consideration. Jet aircraft are usually designed using the Whitcomb area rule , which says that the total area of cross-section of the aircraft at any point along the aircraft from the nose must be approximately the same as that of a Sears-Haack body . A shape with that property minimises the production of shockwaves which would waste energy. There are several types of engine which operate by expelling hot gas: The different types are used for different purposes. Rockets are
2444-553: The 707 and a year later, Douglas rolled out its DC-8 , both types also with four engines. Both were very successful and the 707 in particular is credited with advancing the Jet Age. The large airliners flourished during this period, frequently operating on both domestic and international routes. By the 1960s it became apparent that having four engines reduced fuel efficiency. This was not an issue for long-haul routes which carried 300 or more passengers for 8 to 12 hours, allowing for
2538-612: The 727 , Tu-154 , DC-10, and MD-11, have found second careers as cargo aircraft, as well as in limited charter, governmental, and military service. However, because of the average age of trijets and the COVID-19 pandemic , most non-private operators have chosen to retire quadjets and trijets and replace them with more efficient and cost-saving twinjets. Today, the only widely used trijet is the MD-11, mostly operated by UPS Airlines and FedEx Express in cargo service. For smaller private and corporate operators, where maximum fuel efficiency
2632-459: The 777 's General Electric GE90 . During the 1980s, McDonnell Douglas was the only Western manufacturer to continue development of the trijet design with an update to the DC-10 , the MD-11 , which initially held a range and payload advantage over its closest medium wide-body competitors which were twinjets, the in-production Boeing 767 and upcoming Airbus A330 . McDonnell Douglas had planned
2726-472: The 777-300ER pushed the passenger capacity to just under 400, approaching the 747 and superseding the A340 , while being more efficient and incurring lower engine maintenance costs. Airbus, not seeing much success with updated A340-500/600 variants powered by the Rolls-Royce Trent 500 , went for the all-new A350XWB to compete against the 777 and upcoming 787 Dreamliner . By the early 2000s,
2820-530: The Airbus A340 , Airbus A380 , and Boeing 747 . Many military airlifters also feature this design, including the Antonov An-124 , Boeing C-17 Globemaster , and Lockheed C-5 Galaxy . In this location, the engines can act as a relieving load and reduce the structural weight of the wing by 15%. They are also in a more accessible location for maintenance or replacement. However, disadvantages include
2914-745: The Airbus A350 and Boeing 787 , as opposed to a spoke-hub model which favours massive aircraft such as the A380. The largest operator of the A380, Emirates , profits from its fleet because its primary hub is situated at Dubai International Airport , where many long-haul routes have their stopovers. This makes it easier for Emirates to fill the seats of its A380s. After Emirates reduced its last order in February 2019, Airbus announced that A380 production would end in 2021. As engine power continued to grow and capacity demands decreased, twinjet aircraft such as
Four-engined jet aircraft - Misplaced Pages Continue
3008-655: The Boeing 707 to enter service in 1958 and thus to dominate the market for civilian airliners. The underslung engines were found to be advantageous in the event of a propellant leak, and so the 707 looked rather different from the Comet: the 707 has a shape that is effectively the same as that of contemporary aircraft, with marked commonality still evident today for example with the 737 (fuselage) and A340 (single deck, swept wing, four below-wing engines). Turbofan aircraft with far greater fuel efficiency began entering service in
3102-412: The Boeing 787 twinjet. With jet fuel a large part of total costs, this makes quadjets less attractive to airlines and many are shifting their attention towards more efficient aircraft types. Four engines also incur higher maintenance costs, as each one needs to undergo regular inspections and servicing. Approximately half of the airliner maintenance costs are derived from routine engine maintenance, so
3196-464: The Boeing 787 Dreamliner and Airbus A350 XWB ate into the markets that traditionally demanded four engines. In response to the A380, Boeing introduced the 747-8 in 2011 as a successor to the 747-400. The 747-8I passenger variant has only received 50 orders as of 2018, while the 747-8F freighter variant has been more successful with over 100 orders. As of 2018 the 747-8F is unmatched in range and payload, making it an option for cargo carriers. After
3290-399: The Dassault Falcon 7X . The S-duct has low drag, and since the third engine is mounted closer to the centerline, the aircraft will normally be easy to handle in the event of an engine failure. However, S-duct designs are more complex and costlier, particularly for an airliner. Furthermore, the central engine bay would require structural changes in the event of a major re-engining (remodeling of
3384-573: The Dassault Falcon 900 are the only trijets still in production. One consideration with trijets is positioning the central engine. This is usually accomplished by placing the engine along the centerline, but still poses difficulties. The most common configuration is having the central engine located in the rear fuselage and supplied with air by an S-shaped duct ; this is used on the Hawker Siddeley Trident , Boeing 727 , Tupolev Tu-154 , Lockheed L-1011 TriStar , and, more recently,
3478-597: The General Electric CF6 , and the additional power from the third engine gave the DC-10/MD-11 advantages in longer range and/or heavier payload over the A300/A310/A330 twinjet. Since the 1990s, with further advancements in high-bypass turbofan technology, large twinjets have been equipped with purpose-designed engines such as the Boeing 777 's General Electric GE90 , allowing twinjets to perform
3572-473: The Hawker Siddeley Trident (1962) and the Boeing 727 (1963). Both were compromises to meet airline requirements; in the case of the Trident, it was to meet BEA's changing needs, while the 727 had to be acceptable for three different airlines. Although collaboration between the manufacturers was considered, it did not come about. Early American twinjet designs were limited by the FAA 's 60-minute rule , whereby
3666-805: The Nakajima J9Y Kikka , a modified, and slightly smaller version of the Me 262 that had folding wings. By the end of 1945, the US had introduced their first jet fighter, the Lockheed P-80 Shooting Star into service and the UK its second fighter design, the de Havilland Vampire . The US introduced the North American B-45 Tornado , their first jet bomber, into service in 1948. It was capable of carrying nuclear weapons, but
3760-570: The Opel RAK.1 became the first purpose-built rocket aircraft to fly. The turbojet was invented in the 1930s, independently by Frank Whittle and later Hans von Ohain . The first turbojet aircraft to fly was the Heinkel He 178 , on August 27, 1939 in Rostock (Germany), powered by von Ohain's design. This was largely a proof of concept, as the problem of " creep " (metal fatigue caused by
3854-586: The low-bypass turbofans and turbojets of the time were much weaker compared to modern high-bypass turbofans . The Pratt & Whitney JT3D from 1958 had a thrust output of 76 kilonewtons (17,000 lbf ), while modern engines like the General Electric GE90 can produce over 440 kilonewtons (100,000 lbf) of thrust, making this advantage less significant nowadays as larger airliners no longer necessarily need four engines. The largest four-engined jet airliners are distinguished with having
Four-engined jet aircraft - Misplaced Pages Continue
3948-488: The speed of sound . Jet aircraft generally cruise most efficiently at about Mach 0.8 (981 km/h (610 mph)) and at altitudes around 10,000–15,000 m (33,000–49,000 ft) or more. The idea of the jet engine was not new, but the technical problems involved did not begin to be solved until the 1930s. Frank Whittle , an English inventor and RAF officer, began development of a viable jet engine in 1928, and Hans von Ohain in Germany began work independently in
4042-462: The supersonic airliner Concorde began service in 1976. Its four Rolls-Royce/Snecma Olympus 593 turbojets allowed it to cruise at twice the speed of sound. At the time of inception it was regarded as the future of air transportation. However, in large part due to high operating costs and noise issues, Concorde never achieved the predicted level of success. When the BAe 146 was introduced in 1983, it
4136-499: The wide-body fleets of these airlines are dominated by lower capacity, long range twinjets such as the A330 and 787 . Prior to the Jet Age , airliners were powered by piston engines . Engine failures were relatively common, so providing redundancy with four engines was important for long range flights. This need extended into the beginning of the Jet Age, and combined with the limited thrust available from early jet engines , it
4230-548: The 1950s and 1960s, and became the most commonly used type of jet. The Tu-144 supersonic transport was the fastest commercial jet aircraft at Mach 2.35 (2,503 km/h (1,555 mph)). It went into service in 1975, but was withdrawn from commercial service shortly afterwards. The Mach 2 Concorde entered service in 1976 and flew for 27 years. The fastest military jet aircraft was the SR-71 Blackbird at Mach 3.35 (3,661 km/h (2,275 mph)). Most people use
4324-453: The 1990s, twinjets, trijets, and quadjets shared engines of similar output, such as when the DC-10, MD-11, Boeing 767, and Airbus A300, A310, and A330, and Boeing 747 all had variants powered by the widespread General Electric CF6 , so at the time additional engines were needed for larger capacities and longer range. The major advantages of three and four engines became much less significant when
4418-530: The 727, as its central engine bay would require an extremely expensive redesign to accommodate quieter high-bypass turbofans, and it was soon supplanted by Airbus with their A320 and Boeing with their 737 and 757 . Further advancements in high-bypass turbofan technology and subsequent relaxation in airline safety rules made the trijet and even the quadjet nearly obsolete for passenger services, as their range and payload could be covered more efficiently with large twinjets powered with purpose-designed engines such as
4512-525: The A300 and 767 twinjets. Thus trijet designs such as the DC-10 and L-1011 TriStar represented the best compromise with medium- to long-range and medium size that US airlines sought for their domestic and transatlantic routes. As a result of these trijet wide-bodies, as well as the popularity of the Boeing 727, in their heyday of the 1980s trijets made up a majority of all such US jet airliners. From 1985 to 2003
4606-641: The Airbus A380 ended production, the Boeing 747-8 also stopped production with the last delivery taking place on January 31 2023, meaning no double-deck passenger jets were any longer in production. Boeing attributed the retirement of their 747 fleets to the effect of the COVID-19 pandemic. Jet aircraft Whereas the engines in propeller-powered aircraft generally achieve their maximum efficiency at much lower speeds and altitudes, jet engines achieve maximum efficiency at speeds close to or even well above
4700-509: The ETOPS 330 standard), where the most direct route for some flights is over Antarctica . Since 2000, both narrow-body and wide-body trijet production has ceased for almost all commercial aircraft, being replaced by twinjets . As of 2016, the Falcon 7X, 8X, and 900 business jets, all of which use S-ducts , are the only trijets in production. Trijets that are no longer in production, such as
4794-424: The MD-11 to make it a twinjet but instead cancelled MD-11 production altogether. Trijets are more efficient and cheaper than four-engine aircraft, as the engines are the most expensive part of the plane and having more engines consumes more fuel, particularly if quadjets and trijets share engines of similar power. For widebody aircraft this makes the trijet configuration more suited to a mid-size airliner compared to
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#17327870911324888-418: The MD-11 would have competed with the 767 and 777. A study to remove the MD-11's tail-mounted engine (which would have made it a twinjet) never came to fruition as it would have been very expensive, and the MD-11 had very little in common in terms of design or type rating with other Boeing airliners. In contrast to McDonnell Douglas sticking with their existing trijet configuration, Airbus (which never produced
4982-528: The Me 262 program having started earlier than that of the Meteor, as Projekt 1065, with initial plans drawn up by Waldemar Voigt's design team in April 1939. The Messerschmitt Me 262 was the first operational jet fighter , manufactured by Germany during World War II and entering service on 19 April 1944 with Erprobungskommando 262 at Lechfeld just south of Augsburg. An Me 262 scored the first combat victory for
5076-458: The S-duct. Also, as the engine is located much higher up than the wing-mounted engines, engine failure will produce a greater pitching moment, making it more difficult to control. The placement of the remaining two engines varies. Most smaller aircraft, such as the Hawker Siddeley Trident and the Boeing 727 , as well as the intermediate-sized Tupolev Tu-154 , have two side-mount engine pylons in
5170-460: The additional expense in maintaining four engines is significant. The ability of a very large aircraft to carry a large number of passengers can be a drawback when the seats are not filled. This is an emerging trend, particularly because the airline industry has been transitioning from a spoke-hub model to a point-to-point model. In the spoke-hub model, passengers are moved from smaller outlying points and concentrated at large hubs. This introduces
5264-419: The aircraft structure. The de Havilland Comet incorporated four turbojets buried inside its wing roots , the most common location for buried engines. This design reduces both drag and the risk of ingesting foreign objects, but increases the difficulty of maintenance and complicates the wing structure. The Northrop Grumman B-2 Spirit stealth strategic bomber has all four turbofans buried within its wing (as
5358-512: The case of the Boeing 777 and 787 ) ETOPS 330 rating, and even ETOPS 370 for the Airbus A350 . As such, having more than two engines is no longer considered necessary, except for very large or heavy aircraft such as the Boeing 747 , Airbus A380 (over 400 seats in a mixed-class configuration), Antonov An-124 , and An-225 , or for flights through the Southern Hemisphere, primarily to and from Australia (which has not yet adopted
5452-399: The decades following their introduction, their use has gradually declined due to a variety of factors, including the approval of twin-engine jets to fly farther from diversion airports as reliability increased, and an increased emphasis on fuel efficiency . The engines of a 4-engined aircraft are most commonly found in pods hanging from pylons underneath the wings. This can be observed in
5546-492: The early 1930s. In August 1939 the turbojet powered Heinkel He 178 , the world's first jet aircraft, made its first flight. A wide range of different types of jet aircraft exist, both for civilian and military purposes. After the first instance of powered flight, a large number of jet engine designs were suggested. René Lorin , Morize, Harris proposed systems for creating a jet efflux. After other jet engines had been run, Romanian inventor Henri Coandă claimed to have built
5640-415: The engine). For example, the 727's central bay was only wide enough to fit a low-bypass turbofan and not the newer high-bypass turbofans which were quieter and more powerful. Boeing decided that a redesign was too expensive and ended its production instead of pursuing further development. The Lockheed Tristar's tail section was too short to fit an existing two-spool engine as it was designed only to accommodate
5734-435: The failure of one engine, the power to weight ratio drops to 1 to 4.7 ( 747-400 ), 1 to 5.5 ( MD-11 ), and 1 to 6.6 ( 767-300ER ). The Boeing 747-400 experiences the least degradation in performance, making it safer during an engine failure. Fitting an aircraft with four engines also increases power, enabling more passengers, heavier payloads, and increased performance. This was especially important for early jet airliners, as
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#17327870911325828-458: The first commercial jet service, from London to Johannesburg , in 1952 with the de Havilland Comet jetliner . This highly innovative aircraft travelled far faster and higher than propeller aircraft, was much quieter, smoother, and had stylish blended wings containing hidden jet engines. However, due to a design defect, and use of aluminium alloys, the aircraft suffered catastrophic metal fatigue which led to several crashes, which gave time for
5922-429: The flight path of twin-engine jetliners was restricted to within 60 minutes' flying time from a suitable airport, in case of engine failure. In 1964, this rule was lifted for trijet designs, as they had a greater safety margin. For second-generation jet airliners, with the innovations of the high-bypass turbofan for greater efficiency and reduced noise, and the wide-body (twin-aisle) for greater passenger/cargo capacity,
6016-433: The four engines will still be functioning, constituting a 25% reduction in thrust, compared to 33% for trijets and 50% for twinjets . This can be observed in the following example involving the Boeing 747-400 quadjet, McDonnell Douglas MD-11 trijet, and Boeing 767-300ER twinjet. With all engines operative at maximum takeoff weight , all three aircraft have the power to weight ratios of approximately 1 to 3.4. Following
6110-416: The ground with one engine inoperative, approval can be granted to perform two-engine ferry flights. Prior to the introduction of ETOPS , only trijets and quadjets were able to perform long international flights over areas without any diversion airports. However, this advantage has largely disappeared in recent years as ETOPS-certified twin-engined aircraft are able to do so as well. Another major advantage of
6204-495: The high temperatures within the engine) had not been solved, and the engine quickly burned out. Von Ohain's design, an axial-flow engine, as opposed to Whittle's centrifugal flow engine, was eventually adopted by most manufacturers by the 1950s. The first flight of a jet-propelled aircraft to come to public attention was the Italian Caproni Campini N.1 motorjet prototype which flew on August 27, 1940. It
6298-541: The highest passenger capacities—the Airbus A380 can carry up to 853 passengers in a single class layout. This allows them to satisfy demand on extremely busy routes, and when filled with passengers to distribute the cost, they can be very profitable. Four smaller engines consume more fuel than two larger ones, driving up operational costs. Specifically, the Boeing 747 quadjet consumes 2.5 litres (0.66 US gallons) more fuel per kilogram (2.2 pounds) of payload compared to
6392-476: The many helicopters where the rotors were driven by tip jets . Jet-powered wingsuits exist – powered by model aircraft jet engines – but of short duration and needing to be launched at height. Because of the way they work, the typical exhaust speed of jet engines is transonic or faster, therefore most jet aircraft need to fly at high speeds, either supersonic or speeds just below the speed of sound (" transonic ") so as to achieve efficient flight. Aerodynamics
6486-576: The mechanical energy actually used to propel the aircraft. It is always less than 100% because of kinetic energy loss to the exhaust, and less-than-ideal efficiency of the propulsive mechanism, whether a propeller , a jet exhaust, or a fan. In addition, propulsive efficiency is greatly dependent on air density and airspeed. Mathematically, it is represented as η = η c η p {\displaystyle \eta =\eta _{c}\eta _{p}} where η c {\displaystyle \eta _{c}}
6580-512: The new three-spool Rolls-Royce RB211 engine, and delays in the RB211's development, in turn, pushed back the TriStar's entry into service which affected sales. The McDonnell Douglas DC-10 and related MD-11 use an alternative "straight-through" central engine layout, which allows for easier installation, modification, and access. It also has the additional benefit of being much easier to re-engine. However, this sacrifices aerodynamics compared to
6674-518: The number of such planes in service had sunk from 1488 to 602. The number of twinjets, on the other hand, had more than quadrupled in the same period. Both Lockheed and McDonnell Douglas were financially weakened competing in the widebody market, which led to Lockheed ending production of the L-1011 in 1984 after producing only half the units needed to break even, while a number of fatal DC-10 crashes also slowed its sales. In 1984 Boeing ended production of
6768-399: The oldest type, and are mainly used when extremely high speeds are needed, or operation at extremely high altitudes where there is insufficient air to operate a jet engine. Due to the extreme, typically hypersonic , exhaust velocity and the necessity of oxidiser being carried on board, they consume propellant extremely quickly, making them impractical for routine transportation. Turbojets are
6862-576: The only remaining advantage of the largest types was their ability to carry more passengers than the largest twinjets. In the years following the September 11 attacks , the increase in fuel prices and decline in the aviation industry heightened the need to minimise operating costs and expenditures. Production of the 747-400 passenger variant ceased by 2005 and deliveries of the A340 dropped to 11 per year, as they faced competition from more efficient and comparably capable twinjets. The use of four engines
6956-468: The original models of the Airbus A300 twinjet were limited to short- to medium-range distances. During this period, different jet airliners shared engines of similar output, such as when the McDonnell Douglas DC-10 , Airbus A300 , and Boeing 767 were powered by the General Electric CF6 , the additional power from the third engine gave the DC-10 advantages in longer range and/or heavier payload over
7050-539: The plane slightly less stable and more complex to handle during takeoff and landing. (The McDonnell Douglas DC-9 twinjet and its derivatives, whose engines are mounted on pylons near the rear empennage , have similar advantages/disadvantages of the trijet design, such as the wings located further aft and a more rearward center of gravity.) The first trijet design to fly was the Tupolev Tu-73 bomber prototype, first flown in 1947. The first commercial trijets were
7144-455: The quadjet layout for jumbo jets (i.e. the DC-10 versus the quadjet Boeing 747 ). However the difficulty and complexity of mounting the third engine through the tail will somewhat negate the cost/efficiency advantage. Nonetheless, this was worth the trade-off in the 1960s to the 1990s when widebody trijets and twinjets shared engines of similar output, such as when the DC-10, MD-11, Boeing's 767, and Airbus's A300, A310, and A330 were all powered by
7238-557: The rear fuselage , necessitating a T-tail . This reduces cabin noise and frees up more space on the wings for high-lift devices and fuel storage. The airflow over the wings is also undisturbed due to the absence of pylons. However, the rear-mounted engines shift the centre of gravity aft, and are located further from the fuel supply. The Ilyushin Il-62 and Vickers VC10 both have their four engines mounted in this configuration. Jet aircraft can also be designed with engines buried within
7332-562: The rocket-propelled Messerschmitt Me 163 Komet was a faster operational aircraft during the war. Around this time, mid 1944, the United Kingdom's Meteor was being used for defence of the UK against the V-1 flying bomb – the V-1 itself a pulsejet -powered aircraft and direct ancestor of the cruise missile – and then ground-attack operations over Europe in the last months of
7426-419: The runway is an issue. Unlike twinjets, trijets are not required to land immediately at the nearest suitable airport if one engine fails. (This advantage is also shared with quadjets.) This is advantageous if the aircraft is not near one of the operator's maintenance bases, as the pilots may then continue the flight and land at an airport where it is more suitable to perform repairs. Additionally, for trijets on
7520-436: The same tasks as most trijets and even many quadjets but more efficiently. Due to their added thrust, trijets will have slightly improved takeoff performance compared to twinjets if an engine fails. Because takeoff performance for aircraft is usually calculated to include an extra margin to account for a possible engine failure, trijets are better able to take off from hot and high airports or those where terrain clearance near
7614-409: The second oldest type; they have a high, usually supersonic, exhaust speed and low frontal cross-section, and so are best suited to high-speed, usually supersonic, flight. Although once widely used, they are relatively inefficient compared to turboprop and turbofans for subsonic flight. The last major aircraft to use turbojets were Concorde and Tu-144 supersonic transports . Low bypass turbofans have
7708-415: The severity of the malfunction, altitude, fuel load, and weather conditions. With the increased reliability of jet engines, engine failures rates can be as low as 1 in-flight shutdown per 100,000 engine-hours, reducing the significance of this advantage. During a single-engine failure, the amount of power lost with four engines is proportionately lower than three or two engines. This is because three of
7802-484: The term 'jet aircraft' to denote gas turbine based airbreathing jet engines , but rockets and scramjets are both also propelled by jet propulsion. Cruise missiles are single-use unmanned jet aircraft, powered predominantly by ramjets or turbojets or sometimes turbofans, but they will often have a rocket propulsion system for initial propulsion. The fastest airbreathing jet aircraft is the unmanned X-43 scramjet at around Mach 9–10. The fastest manned (rocket) aircraft
7896-433: The trijet design is that the wings can be located further aft on the fuselage, compared to twinjets and quadjets with all wing-mounted engines, allowing main cabin exit and entry doors to be more centrally located for quicker boarding and deplaning, ensuring shorter turnaround times. The rear-mounted engine and wings shift the aircraft's center of gravity rearwards, improving fuel efficiency , although this will also make
7990-424: The trijet design was seen as the optimal configuration for the medium wide-body jet airliner, sitting in terms of size, range, and cost between quadjets (four-engine aircraft) and twinjets, and this led to a flurry of trijet designs. The four-engine Boeing 747 was popular for transoceanic flights due to its long-range and large size, but it was expensive and not all routes were able to fill its seating capacity, while
8084-399: The twin-engined Boeing 777 was introduced in 1995, equipped with the purpose-designed General Electric GE90 engine developed from further advancements in high-bypass turbofan technology. The original 777-200 could seat upwards of 300 passengers, a significant increase upon existing twinjets such as the 767 , which could typically only seat 200-300 passengers. The subsequent development of
8178-578: The value of the local speed of sound. In this case: V = a M {\displaystyle V=aM} where M {\displaystyle M} is the cruise Mach number and a {\displaystyle a} the local speed of sound. The range equation can be shown to be: R = a M c T C L C D l n W 1 W 2 {\displaystyle R={\frac {aM}{c_{T}}}{\frac {C_{L}}{C_{D}}}ln{\frac {W_{1}}{W_{2}}}} which
8272-486: The war. In 1944 Germany introduced the Arado Ar 234 jet reconnaissance and bomber aircraft into service, though chiefly used in the former role, with the Heinkel He 162 Spatz single-jet light fighter appearing at the end of 1944. USSR tested its own Bereznyak-Isayev BI-1 in 1942, but the project was scrapped by leader Joseph Stalin in 1945. The Imperial Japanese Navy also developed jet aircraft in 1945, including
8366-505: Was invigorated in 2005 when Airbus introduced the A380 , currently the world's largest airliner. It was designed for routes with ultra-high demand, typically seating 575 passengers in two full-length decks. However, as of 2018, Airbus has only fulfilled a quarter of its initial projected figure of 1,200 sales over two decades. This can be attributed to a modern trend towards point-to-point travel using smaller but highly efficient twinjets such as
8460-482: Was most practical to design large jet airliners with four engines. The first commercial jet aircraft was the four-engined De Havilland Comet , which first flew in 1949. However, due to a series of fatal metal fatigue accidents between 1953 and 1954, the Comet was grounded. This greatly tarnished its reputation and it was the later airliners that truly benefited from the subsequent improvements. In 1958, Boeing introduced
8554-450: Was no longer necessary and they could no longer compete with the lower fuel consumption and maintenance costs of twinjets with higher-powered engines. All but the largest four-engined types, such as the Boeing 747, became uneconomical and this led to the retirement of the ageing 707 and DC-8 fleets for passenger service. Nonetheless, Boeing rolled out the 747-400 in 1989, which enjoyed high capacities (over 300 passengers) and long range,
8648-717: Was the first jet aircraft recognised by the Fédération Aéronautique Internationale (at the time the German He 178 program was still kept secret). Campini began development of the motorjet in 1932; it differed from a true turbojet in that the turbine was driven by a piston engine, rather than combustion of the turbine gases - which was a much more complex solution. The British experimental Gloster E.28/39 first flew on May 15, 1941, powered by Sir Frank Whittle 's turbojet. The United States Bell XP-59A flew on October 1, 1942, using two examples of
8742-531: Was unusual because it was a four-engined short range regional airliner . Its design ultimately enabled quieter operation and short take off and landing capabilities. In the 1980s, the increased reliability and available power of jet engines enabled twinjets to safely fly on one engine. This prompted the introduction of ETOPS ratings for twinjets, allowing them to circumvent the 60-Minute Rule and fly on transoceanic routes previously serviced by four-engined types. The advantage of redundancy brought by four engines
8836-645: Was used for reconnaissance over Korea. On November 8, 1950, during the Korean War , United States Air Force Lt. Russell J. Brown, flying in an F-80 , intercepted two North Korean MiG-15s near the Yalu River and shot them down in the first jet-to-jet dogfight in history. The UK put the English Electric Canberra into service in 1951 as a light bomber . It was designed to fly higher and faster than any interceptor . BOAC operated
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