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92-515: The Rolls-Royce Trent XWB is a high-bypass turbofan produced by Rolls-Royce Holdings . In July 2006, the Trent XWB was selected to power exclusively the Airbus A350 . The first engine was run on 14 June 2010, it first flew on an A380 testbed on 18 February 2012, it was certified in early 2013, and it first flew on an A350 on 14 June 2013. It had its first in-flight shutdown on 11 September 2018 as

184-490: A gas turbine engine unexpectedly stops producing power due to a malfunction other than fuel exhaustion . It often applies for aircraft , but other turbine engines can also fail, such as ground-based turbines used in power plants or combined diesel and gas vessels and vehicles. Turbine engines in use on today's turbine-powered aircraft are very reliable . Engines operate efficiently with regularly scheduled inspections and maintenance. These units can have lives ranging in

276-422: A Trent XWB powered Cathay Pacific A350-1000 suffered an in-flight engine fire, following which the aircraft was able to land safely. The airline conducted an inspection of all 48 of its A350s, finding several with a defect similar to the incident aircraft, said to be a damaged flexible fuel line. The European Union Aviation Safety Agency announced that it would require a one-time inspection of Trent XWB engines as

368-465: A combination of these two portions working together. Engines that use more jet thrust relative to fan thrust are known as low-bypass turbofans ; conversely those that have considerably more fan thrust than jet thrust are known as high-bypass . Most commercial aviation jet engines in use are of the high-bypass type, and most modern fighter engines are low-bypass. Afterburners are used on low-bypass turbofan engines with bypass and core mixing before

460-693: A competitor to the Boeing 787 Dreamliner , then in October 2005 launched the A350 , at the time an improved A330 . Rolls-Royce initially offered a conventional bleed air engine variant of the Trent 1000 with a throttle-push to 75,000 lbf (330 kN) static thrust, the Trent 1700. In 2006, after a review of the Airbus A350, Rolls-Royce reached an agreement to supply all versions of

552-482: A contained and uncontained engine failure derives from regulatory requirements for design, testing, and certification of aircraft engines under Part 33 of the U.S. Federal Aviation Regulations , which has always required turbine aircraft engines to be designed to contain damage resulting from rotor blade failure. Under Part 33, engine manufacturers are required to perform blade off tests to ensure containment of shrapnel if blade separation occurs. Blade fragments exiting

644-412: A continuing risk to the flight. Once the aircraft lands, fire department personnel assist with inspecting the aircraft to ensure it is safe before it taxis to its parking position. Turboprop -powered aircraft and turboshaft -powered helicopters are also powered by turbine engines and are subject to engine failures for many similar reasons as jet-powered aircraft. In the case of an engine failure in

736-434: A corresponding increase in pressure and temperature in the exhaust duct which in turn cause a higher gas speed from the propelling nozzle (and higher KE and wasted fuel). Although the engine would use less fuel to produce a pound of thrust, more fuel is wasted in the faster propelling jet. In other words, the independence of thermal and propulsive efficiencies, as exists with the piston engine/propeller combination which preceded

828-437: A crosswind over the engine's inlet, ice accumulation around the engine inlet, ingestion of foreign material, or an internal component failure such as a broken blade . While this situation can be alarming, the engine may recover with no damage. Other events that can happen with jet engines, such as a fuel control fault, can result in excess fuel in the engine's combustor . This additional fuel can result in flames extending from

920-427: A direct hazard to an airplane and its crew and passengers because high-energy disk fragments can penetrate the cabin or fuel tanks, damage flight control surfaces, or sever flammable fluid or hydraulic lines. Engine cases are not designed to contain failed turbine disks. Instead, the risk of uncontained disk failure is mitigated by designating disks as safety-critical parts, defined as the parts of an engine whose failure

1012-419: A discordant nature known as "buzz saw" noise. All modern turbofan engines have acoustic liners in the nacelle to damp their noise. They extend as much as possible to cover the largest surface area. The acoustic performance of the engine can be experimentally evaluated by means of ground tests or in dedicated experimental test rigs. In the aerospace industry, chevrons are the "saw-tooth" patterns on

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1104-400: A dispatch reliability of 99.4%. By February 2018, it has completed 1.3 million flight hours with a 99.9% dispatch reliability. It took two years to reach one million flying hours and nine months for the second million by July 2018, as 500 were delivered; at that time, it had a 99.9% dispatch reliability and had had no in-flight shutdown . As the fleet accumulated 2.2 million flight hours and

1196-410: A fixed total applied fuel:air ratio, the total fuel flow for a given fan airflow will be the same, regardless of the dry specific thrust of the engine. However, a high specific thrust turbofan will, by definition, have a higher nozzle pressure ratio, resulting in a higher afterburning net thrust and, therefore, a lower afterburning specific fuel consumption (SFC). However, high specific thrust engines have

1288-408: A helicopter, it is often possible for the pilot to enter autorotation , using the unpowered rotor to slow the aircraft's descent and provide a measure of control, usually allowing for a safe emergency landing even without engine power. Most in-flight shutdowns are harmless and likely to go unnoticed by passengers. For example, it may be prudent for the flight crew to shut down an engine and perform

1380-426: A high dry SFC. The situation is reversed for a medium specific thrust afterburning turbofan: i.e., poor afterburning SFC/good dry SFC. The former engine is suitable for a combat aircraft which must remain in afterburning combat for a fairly long period, but has to fight only fairly close to the airfield (e.g. cross border skirmishes). The latter engine is better for an aircraft that has to fly some distance, or loiter for

1472-416: A higher nozzle pressure ratio than the turbojet, but with a lower exhaust temperature to retain net thrust. Since the temperature rise across the whole engine (intake to nozzle) would be lower, the (dry power) fuel flow would also be reduced, resulting in a better specific fuel consumption (SFC). Some low-bypass ratio military turbofans (e.g. F404 , JT8D ) have variable inlet guide vanes to direct air onto

1564-572: A long time, before going into combat. However, the pilot can afford to stay in afterburning only for a short period, before aircraft fuel reserves become dangerously low. The first production afterburning turbofan engine was the Pratt & Whitney TF30 , which initially powered the F-111 Aardvark and F-14 Tomcat . Low-bypass military turbofans include the Pratt & Whitney F119 , the Eurojet EJ200 ,

1656-461: A precautionary landing in the event of a low oil pressure or high oil temperature warning in the cockpit. However, passengers in a jet powered aircraft may become quite alarmed by other engine events such as a compressor surge — a malfunction that is typified by loud bangs and even flames from the engine's inlet and tailpipe. A compressor surge is a disruption of the airflow through a gas turbine jet engine that can be caused by engine deterioration,

1748-432: A precautionary landing is usually performed with airport fire and rescue equipment positioned near the runway. The prompt landing is a precaution against the risk that another engine will fail later in the flight or that the engine failure that has already occurred may have caused or been caused by other as-yet unknown damage or malfunction of aircraft systems (such as fire or damage to aircraft flight controls) that may pose

1840-403: A pure-jet of the same thrust, and jet noise is no longer the predominant source. Turbofan engine noise propagates both upstream via the inlet and downstream via the primary nozzle and the by-pass duct. Other noise sources are the fan, compressor and turbine. Modern commercial aircraft employ high-bypass-ratio (HBPR) engines with separate flow, non-mixing, short-duct exhaust systems. Their noise

1932-524: A result of the incident. The Trent XWB is an axial flow , high bypass turbofan keeping the characteristic coaxial three-shaft architecture of the Rolls-Royce Trent . The 3.00 m (118 in) fan is driven by a 6-stage turbine , an 8-stage IP compressor is powered by a 2-stage turbine and a 6-stage HP compressor is turned by a single stage turbine, rotating in the opposite direction of the two others. The annular combustor has 20 fuel spray nozzles and

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2024-591: A set of rules known as ETOPS (Extended Twin-engine Operational Performance Standards) is used to ensure a twin turbine engine powered aircraft is able to safely arrive at a diversionary airport after an engine failure or shutdown, as well as to minimize the risk of a failure. ETOPS includes maintenance requirements, such as frequent and meticulously logged inspections and operation requirements such as flight crew training and ETOPS-specific procedures. Engine failures may be classified as either as "contained" or "uncontained". The very specific technical distinction between

2116-513: A shop visit. The higher-thrust XWB-97 for the A350-1000 remains a loss-maker, and could stay that way as extending time-on-wing is more profitable. In 2023 Dubai Airshow , the president of the Emirates , Tim Clark , said the A350-1000's engine, Trent XWB-97, would offer only a quarter of the time between maintenance visits compared to their needs. Citigroup analysts claim these comments form part of

2208-550: A static thrust of 4,320 lb (1,960 kg), and had a bypass ratio of 6:1. The General Electric TF39 became the first production model, designed to power the Lockheed C-5 Galaxy military transport aircraft. The civil General Electric CF6 engine used a derived design. Other high-bypass turbofans are the Pratt & Whitney JT9D , the three-shaft Rolls-Royce RB211 and the CFM International CFM56 ; also

2300-547: A stronger fan casing and takes advantage of technologies developed through the European Environmentally Friendly Engine (EFE) research programme. Its core operating temperature capability will be increased. On 18 June 2007, Rolls-Royce announced that it had signed a contract with Qatar Airways worth US$ 5.6 billion at list prices, to power 80 Airbus A350 XWBs : US$ 35 million each. A large contract with Emirates to power 70 aircraft with Trent XWBs

2392-473: A turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. A bypass ratio of 6, for example, means that 6 times more air passes through the bypass duct than the amount that passes through the combustion chamber. Turbofan engines are usually described in terms of BPR, which together with overall pressure ratio, turbine inlet temperature and fan pressure ratio are important design parameters. In addition BPR

2484-421: A turbojet engine uses all of the engine's output to produce thrust in the form of a hot high-velocity exhaust gas jet, a turbofan's cool low-velocity bypass air yields between 30% and 70% of the total thrust produced by a turbofan system. The thrust ( F N ) generated by a turbofan depends on the effective exhaust velocity of the total exhaust, as with any jet engine, but because two exhaust jets are present

2576-496: A turbojet even though an extra turbine, a gearbox and a propeller are added to the turbojet's low-loss propelling nozzle. The turbofan has additional losses from its greater number of compressor stages/blades, fan and bypass duct. Froude, or propulsive, efficiency can be defined as: η f = 2 1 + V j V a {\displaystyle \eta _{f}={\frac {2}{1+{\frac {V_{j}}{V_{a}}}}}} where: While

2668-704: A turbojet which accelerates a smaller amount more quickly, which is a less efficient way to generate the same thrust (see the efficiency section below). The ratio of the mass-flow of air bypassing the engine core compared to the mass-flow of air passing through the core is referred to as the bypass ratio . Engines with more jet thrust relative to fan thrust are known as low-bypass turbofans , those that have considerably more fan thrust than jet thrust are known as high-bypass . Most commercial aviation jet engines in use are high-bypass, and most modern fighter engines are low-bypass. Afterburners are used on low-bypass turbofans on combat aircraft. The bypass ratio (BPR) of

2760-507: Is best suited to high supersonic speeds. If it is all transferred to a separate big mass of air with low kinetic energy, the aircraft is best suited to zero speed (hovering). For speeds in between, the gas power is shared between a separate airstream and the gas turbine's own nozzle flow in a proportion which gives the aircraft performance required. The trade off between mass flow and velocity is also seen with propellers and helicopter rotors by comparing disc loading and power loading. For example,

2852-410: Is considerable potential for reducing fuel consumption for the same core cycle by increasing BPR.This is achieved because of the reduction in pounds of thrust per lb/sec of airflow (specific thrust) and the resultant reduction in lost kinetic energy in the jets (increase in propulsive efficiency). If all the gas power from a gas turbine is converted to kinetic energy in a propelling nozzle, the aircraft

Rolls-Royce Trent XWB - Misplaced Pages Continue

2944-417: Is designed around ensuring that an engine failure will not endanger the flight. This is done by planning the takeoff around three critical V speeds , V1, VR and V2. V1 is the critical engine failure recognition speed, the speed at which a takeoff can be continued with an engine failure, and the speed at which stopping distance is no longer guaranteed in the event of a rejected takeoff . VR is the speed at which

3036-430: Is due to the speed, temperature, and pressure of the exhaust jet, especially during high-thrust conditions, such as those required for takeoff. The primary source of jet noise is the turbulent mixing of shear layers in the engine's exhaust. These shear layers contain instabilities that lead to highly turbulent vortices that generate the pressure fluctuations responsible for sound. To reduce the noise associated with jet flow,

3128-430: Is one per 20,704 flight hours, lowering to one per 163,934 flight hours in 2013–2014. The General Electric GE90 has an in-flight shutdown rate (IFSD) of one per million engine flight-hours. The Pratt & Whitney Canada PT6 is known for its reliability with an in-flight shutdown rate of one per 333,333 hours from 1963 to 2016, lowering to one per 651,126 hours over 12 months in 2016. Following an engine shutdown,

3220-413: Is quoted for turboprop and unducted fan installations because their high propulsive efficiency gives them the overall efficiency characteristics of very high bypass turbofans. This allows them to be shown together with turbofans on plots which show trends of reducing specific fuel consumption (SFC) with increasing BPR. BPR can also be quoted for lift fan installations where the fan airflow is remote from

3312-420: Is sufficient core power to drive the fan. A smaller core flow/higher bypass ratio cycle can be achieved by raising the inlet temperature of the high-pressure (HP) turbine rotor. To illustrate one aspect of how a turbofan differs from a turbojet, comparisons can be made at the same airflow (to keep a common intake for example) and the same net thrust (i.e. same specific thrust). A bypass flow can be added only if

3404-411: Is very fuel intensive. Consequently, afterburning can be used only for short portions of a mission. Unlike in the main engine, where stoichiometric temperatures in the combustor have to be reduced before they reach the turbine, an afterburner at maximum fuelling is designed to produce stoichiometric temperatures at entry to the nozzle, about 2,100 K (3,800 °R; 3,300 °F; 1,800 °C). At

3496-472: The Bristol Olympus , and Pratt & Whitney JT3C engines, increased the overall pressure ratio and thus the thermodynamic efficiency of engines. They also had poor propulsive efficiency, because pure turbojets have a high specific thrust/high velocity exhaust, which is better suited to supersonic flight. The original low-bypass turbofan engines were designed to improve propulsive efficiency by reducing

3588-677: The General Electric F110 , the Klimov RD-33 , and the Saturn AL-31 , all of which feature a mixed exhaust, afterburner and variable area propelling nozzle. To further improve fuel economy and reduce noise, almost all jet airliners and most military transport aircraft (e.g., the C-17 ) are powered by low-specific-thrust/high-bypass-ratio turbofans. These engines evolved from the high-specific-thrust/low-bypass-ratio turbofans used in such aircraft in

3680-421: The 1960s. Modern combat aircraft tend to use low-bypass ratio turbofans, and some military transport aircraft use turboprops . Low specific thrust is achieved by replacing the multi-stage fan with a single-stage unit. Unlike some military engines, modern civil turbofans lack stationary inlet guide vanes in front of the fan rotor. The fan is scaled to achieve the desired net thrust. The core (or gas generator) of

3772-529: The Trent XWB had successfully made its maiden flight aboard Airbus’ dedicated Airbus A380 flying test bed. By October, the first engine was expected to enter service in 2014. Certification for the early engine variants was achieved in early 2013. The first flight of the Trent XWB powering the Airbus A350 XWB took place on 14 June 2013. On 15 May 2014 Rolls-Royce delivered the first production 84,000 lbf (370 kN) thrust Trent XWB engines intended for

Rolls-Royce Trent XWB - Misplaced Pages Continue

3864-464: The aerospace industry has sought to disrupt shear layer turbulence and reduce the overall noise produced. Fan noise may come from the interaction of the fan-blade wakes with the pressure field of the downstream fan-exit stator vanes. It may be minimized by adequate axial spacing between blade trailing edge and stator entrance. At high engine speeds, as at takeoff, shock waves from the supersonic fan tips, because of their unequal nature, produce noise of

3956-422: The afterburner, raising the temperature of exhaust gases by a significant degree, resulting in a higher exhaust velocity/engine specific thrust. The variable geometry nozzle must open to a larger throat area to accommodate the extra volume and increased flow rate when the afterburner is lit. Afterburning is often designed to give a significant thrust boost for take off, transonic acceleration and combat maneuvers, but

4048-409: The afterburner. Modern turbofans have either a large single-stage fan or a smaller fan with several stages. An early configuration combined a low-pressure turbine and fan in a single rear-mounted unit. The turbofan was invented to improve the fuel consumption of the turbojet. It achieves this by pushing more air, thus increasing the mass and lowering the speed of the propelling jet compared to that of

4140-691: The aircraft with a brand-new Trent XWB variant with 75,000 to 95,000 lbf (330 to 420 kN) of thrust. Before the December 2008 design freeze, Airbus established that the A350's empty weight was 2.2t greater than the 133.5t target. Due to this, the MTOW was increased by 3t in order to maintain the payload and range capability. As a further result, Rolls-Royce announced that the nominal engine thrusts were increased slightly, each variant receiving an additional 1,000 lbf (4 kN) thrust. A350 programme chief Didier Evrard

4232-482: The airline's "commercial negotiation" tactics involving prices or guarantees. They claim the higher thrust 97-XWB would be expected to run at higher temperatures with faster wear, particularly in hot and sandy climates, noting Qatar Airways operates the Trent XWB-97 without major issues. Rolls-Royce was later reported to be working with Emirates to improve durability in "hot and sandy conditions" On September 2, 2024,

4324-424: The airline's existing 66 Trent engines, resulting in a total of nearly 210, the airline has become the largest operator of Trent XWB engines. Related development Comparable engines Related lists High-bypass turbofan The ratio of the mass-flow of air bypassing the engine core to the mass-flow of air passing through the core is referred to as the bypass ratio . The engine produces thrust through

4416-471: The average stage loading and to maintain LP turbine efficiency. Reducing core flow also increases bypass ratio. Bypass ratios greater than 5:1 are increasingly common; the Pratt & Whitney PW1000G , which entered commercial service in 2016, attains 12.5:1. Further improvements in core thermal efficiency can be achieved by raising the overall pressure ratio of the core. Improvements in blade aerodynamics can reduce

4508-445: The engine and doesn't flow past the engine core. Considering a constant core (i.e. fixed pressure ratio and turbine inlet temperature), core and bypass jet velocities equal and a particular flight condition (i.e. Mach number and altitude) the fuel consumption per lb of thrust (sfc) decreases with increase in BPR. At the same time gross and net thrusts increase, but by different amounts. There

4600-466: The engine is controlled by a dual-channel FADEC . The Trent XWB features a 2-stage IP turbine rather than a single stage from previous Trent engines . The 97,000 lbf (430 kN) engine version for the A350-1000 maintains the same 3.0 m fan size and a 5% larger core , the additional thrust will require the fan to run 6% faster which will require strengthening to withstand the increased fan-blade forces produced. It has thicker titanium fan blades and

4692-501: The engine itself, such as damage to portions of the turbine or oil leaks, as well as damage outside the engine such as fuel pump problems or fuel contamination. A turbine engine failure can also be caused by entirely external factors, such as volcanic ash , bird strikes or weather conditions like precipitation or icing . Weather risks such as these can sometimes be countered through the usage of supplementary ignition or anti-icing systems. A turbine-powered aircraft's takeoff procedure

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4784-427: The engine must generate enough power to drive the fan at its rated mass flow and pressure ratio. Improvements in turbine cooling/material technology allow for a higher (HP) turbine rotor inlet temperature, which allows a smaller (and lighter) core, potentially improving the core thermal efficiency. Reducing the core mass flow tends to increase the load on the LP turbine, so this unit may require additional stages to reduce

4876-443: The engine's exhaust pipe. As alarming as this would appear, at no time is the engine itself actually on fire. Also, the failure of certain components in the engine may result in a release of oil into bleed air that can cause an odor or oily mist in the cabin. This is known as a fume event . The dangers of fume events are the subject of debate in both aviation and medicine . Engine failures can be caused by mechanical problems in

4968-516: The exhaust velocity to a value closer to that of the aircraft. The Rolls-Royce Conway , the world's first production turbofan, had a bypass ratio of 0.3, similar to the modern General Electric F404 fighter engine. Civilian turbofan engines of the 1960s, such as the Pratt & Whitney JT8D and the Rolls-Royce Spey , had bypass ratios closer to 1 and were similar to their military equivalents. The first Soviet airliner powered by turbofan engines

5060-426: The failure event starts, secondary events of a random nature may occur whose course and ultimate conclusion cannot be precisely predicted. Some of the structural interactions that have been observed to affect containment are the deformation and/or deflection of blades, cases, rotor, frame, inlet, casing rub strips, and the containment structure. Uncontained turbine engine disk failures within an aircraft engine present

5152-494: The fan nozzle. The amount of energy transferred depends on how much pressure rise the fan is designed to produce (fan pressure ratio). The best energy exchange (lowest fuel consumption) between the two flows, and how the jet velocities compare, depends on how efficiently the transfer takes place which depends on the losses in the fan-turbine and fan. The fan flow has lower exhaust velocity, giving much more thrust per unit energy (lower specific thrust ). Both airstreams contribute to

5244-560: The first Airbus A350 XWB to enter service with Qatar Airways . Final assembly of these production engines had started in February 2014. On 15 July 2014 Rolls-Royce announced the first run of the Trent XWB-97 powerplant with 97,000 lbf (430 kN) thrust for the Airbus A350-1000. On 26 July 2017, Airbus delivered the 100th A350, on track for 10 per month by 2018 end, and over the first 30 months most engine removals have been to stagger

5336-450: The first fan rotor stage. This improves the fan surge margin (see compressor map ). Since the 1970s, most jet fighter engines have been low/medium bypass turbofans with a mixed exhaust, afterburner and variable area exit nozzle. An afterburner is a combustor located downstream of the turbine blades and directly upstream of the nozzle, which burns fuel from afterburner-specific fuel injectors. When lit, large volumes of fuel are burnt in

5428-405: The fleet accumulated 2.2 million flight hours. It keeps the characteristic three-shaft layout of the Rolls-Royce Trent , with a 3.00 m (118 in) fan, an IP and HP spool. The 84,200–97,000 lbf (375–431 kN) engine has a 9.6:1 bypass ratio and a 50:1 pressure ratio . It is the most powerful member of the Trent family. By 2004 Airbus had been facing pressure from customers to develop

5520-496: The fuel used to move the aircraft forwards. A turbofan harvests that wasted velocity and uses it to power a ducted fan that blows air in bypass channels around the rest of the turbine. This reduces the speed of the propelling jet while pushing more air, and thus more mass. The other penalty is that combustion is less efficient at lower speeds. Any action to reduce the fuel consumption of the engine by increasing its pressure ratio or turbine temperature to achieve better combustion causes

5612-429: The gross thrust of the engine. The additional air for the bypass stream increases the ram drag in the air intake stream-tube, but there is still a significant increase in net thrust. The overall effective exhaust velocity of the two exhaust jets can be made closer to a normal subsonic aircraft's flight speed and gets closer to the ideal Froude efficiency . A turbofan accelerates a larger mass of air more slowly, compared to

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5704-474: The hot nozzle to convert to kinetic energy. Turbofans represent an intermediate stage between turbojets , which derive all their thrust from exhaust gases, and turbo-props which derive minimal thrust from exhaust gases (typically 10% or less). Extracting shaft power and transferring it to a bypass stream introduces extra losses which are more than made up by the improved propulsive efficiency. The turboprop at its best flight speed gives significant fuel savings over

5796-530: The inlet may also cause airframe parts such as the inlet duct and other parts of the engine nacelle to depart the aircraft due to deformation from the fan blade fragment's residual kinetic energy. The containment of failed rotating parts is a complex process which involves high energy, high speed interactions of numerous locally and remotely located engine components (e.g., failed blade, other blades, containment structure, adjacent cases, bearings, bearing supports, shafts, vanes, and externally mounted components). Once

5888-401: The inlet or exhaust can still pose a hazard to the aircraft, and this should be considered by the aircraft designers. A nominally contained engine failure can still result in engine parts departing the aircraft as long as the engine parts exit via the existing openings in the engine inlet or outlet, and do not create new openings in the engine case containment. Fan blade fragments departing via

5980-568: The leading engine has operated 3,500 cycles, an Iberia A350-900 delivered at the end of July diverted to Boston after an inflight shutdown at 41,000 ft on the September 11, 2018 flight from New York to Madrid, apparently due to slight secondary damage on variable stator vanes . In 2019, the unit losses on the XWB-84 were reduced by over 20%, as Rolls-Royce expects break-even by the end of 2020, while fleet-leading engines had flown over 22,000h without

6072-417: The mechanical power produced by the turbine. In a bypass design, extra turbines drive a ducted fan that accelerates air rearward from the front of the engine. In a high-bypass design, the ducted fan and nozzle produce most of the thrust. Turbofans are closely related to turboprops in principle because both transfer some of the gas turbine's gas power, using extra machinery, to a bypass stream leaving less for

6164-417: The nose is lifted off the runway, a process known as rotation. V2 is the single-engine safety speed, the single engine climb speed. The use of these speeds ensure that either sufficient thrust to continue the takeoff, or sufficient stopping distance to reject it will be available at all times. In order to allow twin-engined aircraft to fly longer routes that are over an hour from a suitable diversion airport,

6256-474: The number of extra compressor stages required, and variable geometry stators enable high-pressure-ratio compressors to work surge-free at all throttle settings. The first (experimental) high-bypass turbofan engine was the AVCO-Lycoming PLF1A-2, a Honeywell T55 turboshaft-derived engine that was first run in February 1962. The PLF1A-2 had a 40 in diameter (100 cm) geared fan stage, produced

6348-538: The on-wing life of a particular aircraft or to collect in-service data; nine in ten of the Trent XWBs have a long-term service agreements with Rolls, which has designated seven shops as MRO providers: its Derby facility, its joint ventures with HAECO , SIAEC , N3 Engine Overhaul Services  [ de ] and independents Delta TechOps , Mubadala and Air France Industries -KLM. It passed 1 million flight hours in October 2017 without any in-flight disruptions and with

6440-467: The required thrust still maintained by increasing the mass accelerated. A turbofan does this by transferring energy available inside the engine, from the gas generator, to a ducted fan which produces a second, additional mass of accelerated air. The transfer of energy from the core to bypass air results in lower pressure and temperature gas entering the core nozzle (lower exhaust velocity), and fan-produced higher pressure and temperature bypass-air entering

6532-399: The same helicopter weight can be supported by a high power engine and small diameter rotor or, for less fuel, a lower power engine and bigger rotor with lower velocity through the rotor. Bypass usually refers to transferring gas power from a gas turbine to a bypass stream of air to reduce fuel consumption and jet noise. Alternatively, there may be a requirement for an afterburning engine where

6624-527: The smaller TF34 . More recent large high-bypass turbofans include the Pratt & Whitney PW4000 , the three-shaft Rolls-Royce Trent , the General Electric GE90 / GEnx and the GP7000 , produced jointly by GE and P&W. The Pratt & Whitney JT9D engine was the first high bypass ratio jet engine to power a wide-body airliner. Turbine engine failure A turbine engine failure occurs when

6716-502: The sole requirement for bypass is to provide cooling air. This sets the lower limit for BPR and these engines have been called "leaky" or continuous bleed turbojets (General Electric YJ-101 BPR 0.25) and low BPR turbojets (Pratt & Whitney PW1120). Low BPR (0.2) has also been used to provide surge margin as well as afterburner cooling for the Pratt & Whitney J58 . Propeller engines are most efficient for low speeds, turbojet engines for high speeds, and turbofan engines between

6808-454: The speed of the propelling jet has to be reduced because there is a price to be paid in producing the thrust. The energy required to accelerate the gas inside the engine (increase in kinetic energy) is expended in two ways, by producing a change in momentum ( i.e. a force), and a wake which is an unavoidable consequence of producing thrust by an airbreathing engine (or propeller). The wake velocity, and fuel burned to produce it, can be reduced and

6900-520: The technology and materials available at the time. The first turbofan engine, which was only run on a test bed, was the German Daimler-Benz DB 670 , designated the 109-007 by the German RLM ( Ministry of Aviation ), with a first run date of 27 May 1943, after the testing of the turbomachinery using an electric motor, which had been undertaken on 1 April 1943. Development of the engine

6992-443: The tens of thousands of hours of operation. However, engine malfunctions or failures occasionally occur that require an engine to be shut down in flight. Since multi-engine airplanes are designed to fly with one engine inoperative and flight crews are trained to fly with one engine inoperative, the in-flight shutdown of an engine typically does not constitute a serious safety of flight issue. The Federal Aviation Administration (FAA)

7084-497: The thrust equation can be expanded as: F N = m ˙ e v h e − m ˙ o v o + B P R ( m ˙ c ) v f {\displaystyle F_{N}={\dot {m}}_{e}v_{he}-{\dot {m}}_{o}v_{o}+BPR\,({\dot {m}}_{c})v_{f}} where: The cold duct and core duct's nozzle systems are relatively complex due to

7176-606: The trailing edges of some jet engine nozzles that are used for noise reduction . The shaped edges smooth the mixing of hot air from the engine core and cooler air flowing through the engine fan, which reduces noise-creating turbulence. Chevrons were developed by GE under a NASA contract. Some notable examples of such designs are Boeing 787 and Boeing 747-8  – on the Rolls-Royce Trent 1000 and General Electric GEnx engines. Early turbojet engines were not very fuel-efficient because their overall pressure ratio and turbine inlet temperature were severely limited by

7268-428: The turbine inlet temperature is not too high to compensate for the smaller core flow. Future improvements in turbine cooling/material technology can allow higher turbine inlet temperature, which is necessary because of increased cooling air temperature, resulting from an overall pressure ratio increase. The resulting turbofan, with reasonable efficiencies and duct loss for the added components, would probably operate at

7360-425: The turbojet uses the gas from its thermodynamic cycle as its propelling jet, for aircraft speeds below 500 mph there are two penalties to this design which are addressed by the turbofan. Firstly, energy is wasted as the propelling jet is going much faster rearwards than the aircraft is going forwards, leaving a very fast wake. This wake contains kinetic energy that reflects the fuel used to produce it, rather than

7452-445: The turbojet, is lost. In contrast, Roth considers regaining this independence the single most important feature of the turbofan which allows specific thrust to be chosen independently of the gas generator cycle. The working substance of the thermodynamic cycle is the only mass accelerated to produce thrust in a turbojet which is a serious limitation (high fuel consumption) for aircraft speeds below supersonic. For subsonic flight speeds

7544-453: The turbojet. This is done mechanically by adding a ducted fan rather than using viscous forces. A vacuum ejector is used in conjunction with the fan as first envisaged by inventor Frank Whittle . Whittle envisioned flight speeds of 500 mph in his March 1936 UK patent 471,368 "Improvements relating to the propulsion of aircraft", in which he describes the principles behind the turbofan, although not called as such at that time. While

7636-476: The two flows may combine within the ducts, and share a common nozzle, which can be fitted with afterburner. Most of the air flow through a high-bypass turbofan is lower-velocity bypass flow: even when combined with the much-higher-velocity engine exhaust, the average exhaust velocity is considerably lower than in a pure turbojet. Turbojet engine noise is predominately jet noise from the high exhaust velocity. Therefore, turbofan engines are significantly quieter than

7728-418: The two. Turbofans are the most efficient engines in the range of speeds from about 500 to 1,000 km/h (270 to 540 kn; 310 to 620 mph), the speed at which most commercial aircraft operate. In a turbojet (zero-bypass) engine, the high temperature and high pressure exhaust gas is accelerated when it undergoes expansion through a propelling nozzle and produces all the thrust. The compressor absorbs

7820-510: The use of two separate exhaust flows. In high bypass engines, the fan is situated in a short duct near the front of the engine and typically has a convergent cold nozzle, with the tail of the duct forming a low pressure ratio nozzle that under normal conditions will choke creating supersonic flow patterns around the core . The core nozzle is more conventional, but generates less of the thrust, and depending on design choices, such as noise considerations, may conceivably not choke. In low bypass engines

7912-676: The world, with an experience base of over 10 million service hours. The CF700 turbofan engine was also used to train Moon-bound astronauts in Project Apollo as the powerplant for the Lunar Landing Research Vehicle . A high-specific-thrust/low-bypass-ratio turbofan normally has a multi-stage fan behind inlet guide vanes, developing a relatively high pressure ratio and, thus, yielding a high (mixed or cold) exhaust velocity. The core airflow needs to be large enough to ensure there

8004-599: Was abandoned with its problems unsolved, as the war situation worsened for Germany. Later in 1943, the British ground tested the Metrovick F.3 turbofan, which used the Metrovick F.2 turbojet as a gas generator with the exhaust discharging into a close-coupled aft-fan module comprising a contra-rotating LP turbine system driving two co-axial contra-rotating fans. Improved materials, and the introduction of twin compressors, such as in

8096-788: Was announced on 11 November 2007, but never filled. The announced contract concerned 50 A350-900 and 20 A350-1000 aircraft, with a further 50 option rights. Due to be delivered from 2014, the Emirates order was potentially worth up to $ 8.4 billion at list prices, including options. However, on 11 June 2014, Airbus announced that Emirates Airline had decided to cancel its order of 70 A350 XWB aircraft. More than 1,500 engines had been sold by July 2015 to 40 customers. Rolls-Royce offered its maintenance programme to Vietnam Airlines for £340 million for 14 airplanes, or £12.1 million per engine. On 15 December 2023, Rolls-Royce announced that Turkish Airlines had ordered 100 XWB-84 and 40 XWB-97 engines. In addition to

8188-629: Was derived from the General Electric J85/CJ610 turbojet 2,850 lbf (12,700 N) to power the larger Rockwell Sabreliner 75/80 model aircraft, as well as the Dassault Falcon 20 , with about a 50% increase in thrust to 4,200 lbf (19,000 N). The CF700 was the first small turbofan to be certified by the Federal Aviation Administration (FAA). There were at one time over 400 CF700 aircraft in operation around

8280-415: Was quoted as saying that the change had a "very marginal" impact on fuel consumption. This was then revised again in 2011, and the engines for the largest A350 have been uprated to 97,000 lbf (430 kN) to meet new performance requirements, and better compete with the Boeing 777-300ER . The first engine test on a static test-bed was made on 14 June 2010. On 18 February 2012, Airbus announced that

8372-574: Was quoted as stating turbine engines have a failure rate of one per 375,000 flight hours, compared to of one every 3,200 flight hours for aircraft piston engines. Due to "gross under-reporting" of general aviation piston engines in-flight shutdowns (IFSD), the FAA has no reliable data and assessed the rate "between 1 per 1,000 and 1 per 10,000 flight hours". Continental Motors reports the FAA states general aviation engines experience one failures or IFSD every 10,000 flight hours, and states its Centurion engines

8464-568: Was the Tupolev Tu-124 introduced in 1962. It used the Soloviev D-20 . 164 aircraft were produced between 1960 and 1965 for Aeroflot and other Eastern Bloc airlines, with some operating until the early 1990s. The first General Electric turbofan was the aft-fan CJ805-23 , based on the CJ805-3 turbojet. It was followed by the aft-fan General Electric CF700 engine, with a 2.0 bypass ratio. This

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