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54-550: The Rolls-Royce RB.109 Tyne is a twin-shaft turboprop engine developed in the mid to late 1950s by Rolls-Royce Limited to a requirement for the Vickers Vanguard airliner. It was first test flown during 1956 in the nose of a modified Avro Lincoln . Following company naming convention for gas turbine engines this turboprop design was named after the River Tyne . Designed in 1954 by a team under Lionel Haworth and intended as

108-407: A propelling nozzle and produces all the thrust. The compressor absorbs all 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

162-406: A constant-speed propeller increase their pitch as aircraft speed increases. Another benefit of this type of propeller is that it can also be used to generate reverse thrust to reduce stopping distance on the runway. Additionally, in the event of an engine failure, the propeller can be feathered , thus minimizing the drag of the non-functioning propeller. While the power turbine may be integral with

216-406: A ducted fan. High bypass designs are the dominant type for commercial passenger aircraft and both civilian and military jet transports. Business jets use medium BPR engines. Combat aircraft use engines with low bypass ratios to compromise between fuel economy and the requirements of combat: high power-to-weight ratios , supersonic performance, and the ability to use afterburners . If all

270-421: 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 the sole requirement for bypass is to provide cooling air. This sets

324-416: A large amount of air by a small degree than a small amount of air by a large degree, a low disc loading (thrust per unit disc area) increases the aircraft's energy efficiency , and this reduces the fuel use. Propellers work well until the flight speed of the aircraft is high enough that the airflow past the blade tips reaches the speed of sound. Beyond that speed, the proportion of the power that drives

378-565: A more powerful alternative to the Dart , the RB.109 Tyne was initially designed for a power of 2,500 shp but when first run in April 1955 the engine far exceeded expectations and was soon being type-tested at 4,220 shp. The Tyne was developed primarily for the four-engined Vickers Vanguard airliner, the prototype first flying on 20 January 1959 equipped with four Tyne Mk.506 of 4,985 e.s.h.p. Production deliveries of

432-529: A test-bed not intended for production. It first flew on 20 September 1945. From their experience with the Trent, Rolls-Royce developed the Rolls-Royce Clyde , the first turboprop engine to receive a type certificate for military and civil use, and the Dart , which became one of the most reliable turboprop engines ever built. Dart production continued for more than fifty years. The Dart-powered Vickers Viscount

486-429: Is a turbine engine that drives an aircraft propeller . A turboprop consists of an intake , reduction gearbox , compressor , combustor , turbine , and a propelling nozzle . Air enters the intake and is compressed by the compressor. Fuel is then added to the compressed air in the combustor, where the fuel-air mixture then combusts . The hot combustion gases expand through the turbine stages, generating power at

540-424: Is also quoted for lift fan installations where the fan airflow is remote from the engine and doesn't physically touch the engine core. Bypass provides a lower fuel consumption for the same thrust, measured as thrust specific fuel consumption (grams/second fuel per unit of thrust in kN using SI units ). Lower fuel consumption that comes with high bypass ratios applies to turboprops , using a propeller rather than

594-482: Is normally a constant-speed (variable pitch) propeller type similar to that used with larger aircraft reciprocating engines , except that the propeller-control requirements are very different. Due to the turbine engine's slow response to power inputs, particularly at low speeds, the propeller has a greater range of selected travel in order to make rapid thrust changes, notably for taxi, reverse, and other ground operations. The propeller has 2 modes, Alpha and Beta. Alpha

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648-494: Is sacrificed in favor of shaft power, which is obtained by extracting additional power (beyond that necessary to drive the compressor) from turbine expansion. Owing to the additional expansion in the turbine system, the residual energy in the exhaust jet is low. Consequently, the exhaust jet produces about 10% of the total thrust. A higher proportion of the thrust comes from the propeller at low speeds and less at higher speeds. Turboprops have bypass ratios of 50–100, although

702-404: Is the mode for all flight operations including takeoff. Beta, a mode typically consisting of zero to negative thrust, is used for all ground operations aside from takeoff. The Beta mode is further broken down into 2 additional modes, Beta for taxi and Beta plus power. Beta for taxi as the name implies is used for taxi operations and consists of all pitch ranges from the lowest alpha range pitch, all

756-616: The P-3 Orion , and the C-130 Hercules military transport aircraft. The first turbine-powered, shaft-driven helicopter was the Kaman K-225 , a development of Charles Kaman 's K-125 synchropter , which used a Boeing T50 turboshaft engine to power it on 11 December 1951. December 1963 saw the first delivery of Pratt & Whitney Canada's PT6 turboprop engine for the then Beechcraft 87, soon to become Beechcraft King Air . 1964 saw

810-830: The Piper Meridian , Socata TBM , Pilatus PC-12 , Piaggio P.180 Avanti , Beechcraft King Air and Super King Air . In April 2017, there were 14,311 business turboprops in the worldwide fleet. Between 2012 and 2016, the ATSB observed 417 events with turboprop aircraft, 83 per year, over 1.4 million flight hours: 2.2 per 10,000 hours. Three were "high risk" involving engine malfunction and unplanned landing in single‑engine Cessna 208 Caravans , four "medium risk" and 96% "low risk". Two occurrences resulted in minor injuries due to engine malfunction and terrain collision in agricultural aircraft and five accidents involved aerial work: four in agriculture and one in an air ambulance . Jane's All

864-590: The Tupolev Tu-114 can reach 470 kn (870 km/h; 540 mph). Large military aircraft , like the Tupolev Tu-95 , and civil aircraft , such as the Lockheed L-188 Electra , were also turboprop powered. The Airbus A400M is powered by four Europrop TP400 engines, which are the second most powerful turboprop engines ever produced, after the 11 MW (15,000 hp) Kuznetsov NK-12 . In 2017,

918-442: The compression ratio of the system by adding to the compressor stage to increase overall system efficiency increases temperatures at the turbine face. Nevertheless, high-bypass engines have a high propulsive efficiency because even slightly increasing the velocity of a very large volume and consequently mass of air produces a very large change in momentum and thrust: thrust is the engine's mass flow (the amount of air flowing through

972-620: The Conway varied between 0.3 and 0.6 depending on the variant The growth of bypass ratios during the 1960s gave jetliners fuel efficiency that could compete with that of piston-powered planes. Today (2015), most jet engines have some bypass. Modern engines in slower aircraft, such as airliners, have bypass ratios up to 12:1; in higher-speed aircraft, such as fighters , bypass ratios are much lower, around 1.5; and craft designed for speeds up to Mach 2 and somewhat above have bypass ratios below 0.5. Turboprops have bypass ratios of 50-100, although

1026-519: The Soviet Union had the technology to create the airframe for a jet-powered strategic bomber comparable to Boeing's B-52 Stratofortress , they instead produced the Tupolev Tu-95 Bear, powered with four Kuznetsov NK-12 turboprops, mated to eight contra-rotating propellers (two per nacelle) with supersonic tip speeds to achieve maximum cruise speeds in excess of 575 mph, faster than many of

1080-637: The World's Aircraft . 2005–2006. Bypass ratio Turbofan engines are usually described in terms of BPR, which together with engine pressure ratio , turbine inlet temperature and fan pressure ratio are important design parameters. In addition, BPR 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

1134-447: The aircraft performance required. The first jet aircraft were subsonic and the poor suitability of the propelling nozzle for these speeds due to high fuel consumption was understood, and bypass proposed, as early as 1936 (U.K. Patent 471,368). The underlying principle behind bypass is trading exhaust velocity for extra mass flow which still gives the required thrust but uses less fuel. Turbojet inventor Frank Whittle called it "gearing down

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1188-570: The aircraft, i.e. SFC, a common gas generator has to be used, i.e. no change in Brayton cycle parameters or component efficiencies. Bennett shows in this case a relatively slow rise in losses transferring power to the bypass at the same time as a fast drop in exhaust losses with a significant improvement in SFC. In reality increases in BPR over time come along with rises in gas generator efficiency masking, to some extent,

1242-417: The compressor intake is at the aft of the engine, and the exhaust is situated forward, reducing the distance between the turbine and the propeller. Unlike the small-diameter fans used in turbofan engines, the propeller has a large diameter that lets it accelerate a large volume of air. This permits a lower airstream velocity for a given amount of thrust. Since it is more efficient at low speeds to accelerate

1296-459: The control system. The turboprop system consists of 3 propeller governors , a governor, and overspeed governor, and a fuel-topping governor. The governor works in much the same way a reciprocating engine propeller governor works, though a turboprop governor may incorporate beta control valve or beta lift rod for beta operation and is typically located in the 12 o'clock position. There are also other governors that are included in addition depending on

1350-402: The early 1950s, was an early example of a bypass engine. The configuration was similar to a 2-spool turbojet but to make it into a bypass engine it was equipped with an oversized low pressure compressor: the flow through the inner portion of the compressor blades went into the core while the outer portion of the blades blew air around the core to provide the rest of the thrust. The bypass ratio for

1404-515: The engine were made from mid-1959 onwards to power the 43 Vanguards delivered to British European Airways and Trans-Canada Airlines . The engine was further developed with greater power and used in the later twin-engined Dassault- Breguet Atlantique long-range reconnaissance aircraft; also in the Canadair CL-44 and Transall C-160 transport aircraft. A single stage HP turbine drives the nine-stage HP compressor. A three-stage LP turbine drives

1458-415: The engine) multiplied by the difference between the inlet and exhaust velocities in—a linear relationship—but the kinetic energy of the exhaust is the mass flow multiplied by one-half the square of the difference in velocities. A low disc loading (thrust per disc area) increases the aircraft's energy efficiency , and this reduces the fuel use. The Rolls–Royce Conway turbofan engine, developed in

1512-493: The first jet aircraft and comparable to jet cruising speeds for most missions. The Bear would serve as their most successful long-range combat and surveillance aircraft and symbol of Soviet power projection through to the end of the 20th century. The USA used turboprop engines with contra-rotating propellers, such as the Allison T40 , on some experimental aircraft during the 1950s. The T40-powered Convair R3Y Tradewind flying-boat

1566-546: The first deliveries of the Garrett AiResearch TPE331 , (now owned by Honeywell Aerospace ) on the Mitsubishi MU-2 , making it the fastest turboprop aircraft for that year. In contrast to turbofans , turboprops are most efficient at flight speeds below 725 km/h (450 mph; 390 knots) because the jet velocity of the propeller (and exhaust) is relatively low. Modern turboprop airliners operate at nearly

1620-443: The flow". Power is transferred from the gas generator to an extra mass of air, i.e. a larger diameter propelling jet, moving more slowly. The bypass spreads the available mechanical power across more air to reduce the velocity of the jet. 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, the same helicopter weight can be supported by

1674-558: The gas generator section, many turboprops today feature a free power turbine on a separate coaxial shaft. This enables the propeller to rotate freely, independent of compressor speed. Alan Arnold Griffith had published a paper on compressor design in 1926. Subsequent work at the Royal Aircraft Establishment investigated axial compressor-based designs that would drive a propeller. From 1929, Frank Whittle began work on centrifugal compressor-based designs that would use all

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1728-422: The gas power from a gas turbine is converted to kinetic energy in a propelling nozzle, the aircraft is best suited to high supersonic speeds. If it is all transferred to a separate large 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

1782-455: The gas power produced by the engine for jet thrust. The world's first turboprop was designed by the Hungarian mechanical engineer György Jendrassik . Jendrassik published a turboprop idea in 1928, and on 12 March 1929 he patented his invention. In 1938, he built a small-scale (100 Hp; 74.6 kW) experimental gas turbine. The larger Jendrassik Cs-1 , with a predicted output of 1,000 bhp,

1836-451: The gas turbine's gas power, using extra machinery, to a bypass stream leaving less for 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

1890-454: The improved propulsive efficiency. The turboprop at its best flight speed gives significant fuel savings over a turbojet even though an extra turbine, a gearbox and a propeller were added to the turbojet's low-loss propelling nozzle. The turbofan has additional losses from its extra turbines, fan, bypass duct and extra propelling nozzle compared to the turbojet's single nozzle. To see the influence of increasing BPR alone on overall efficiency in

1944-443: The influence of BPR. Only the limitations of weight and materials (e.g., the strengths and melting points of materials in the turbine) reduce the efficiency at which a turbofan gas turbine converts this thermal energy into mechanical energy, for while the exhaust gases may still have available energy to be extracted, each additional stator and turbine disk retrieves progressively less mechanical energy per unit of weight, and increasing

1998-480: 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 . In a zero-bypass (turbojet) engine the high temperature and high pressure exhaust gas is accelerated by expansion through

2052-406: The model, such as an overspeed and fuel topping governor on a Pratt & Whitney Canada PT6 , and an under-speed governor on a Honeywell TPE331 . The turboprop is also distinguished from other kinds of turbine engine in that the fuel control unit is connected to the governor to help dictate power. To make the engine more compact, reverse airflow can be used. On a reverse-flow turboprop engine,

2106-657: The most widespread turboprop airliners in service were the ATR 42 / 72 (950 aircraft), Bombardier Q400 (506), De Havilland Canada Dash 8 -100/200/300 (374), Beechcraft 1900 (328), de Havilland Canada DHC-6 Twin Otter (270), Saab 340 (225). Less widespread and older airliners include the BAe Jetstream 31 , Embraer EMB 120 Brasilia , Fairchild Swearingen Metroliner , Dornier 328 , Saab 2000 , Xian MA60 , MA600 and MA700 , Fokker 27 and 50 . Turboprop business aircraft include

2160-416: The pilot not being able to see out of the rear of the aircraft for backing and the amount of debris reverse stirs up, manufacturers will often limit the speeds beta plus power may be used and restrict its use on unimproved runways. Feathering of these propellers is performed by the propeller control lever. The constant-speed propeller is distinguished from the reciprocating engine constant-speed propeller by

2214-403: The point of exhaust. Some of the power generated by the turbine is used to drive the compressor and electric generator . The gases are then exhausted from the turbine. In contrast to a turbojet or turbofan , the engine's exhaust gases do not provide enough power to create significant thrust, since almost all of the engine's power is used to drive the propeller. Exhaust thrust in a turboprop

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2268-494: The propeller that is converted to propeller thrust falls dramatically. For this reason turboprop engines are not commonly used on aircraft that fly faster than 0.6–0.7 Mach , with some exceptions such as the Tupolev Tu-95 . However, propfan engines, which are very similar to turboprop engines, can cruise at flight speeds approaching 0.75 Mach. To maintain propeller efficiency across a wide range of airspeeds, turboprops use constant-speed (variable-pitch) propellers. The blades of

2322-477: The propeller. This allows for propeller strike or similar damage to occur without damaging the gas generator and allowing for only the power section (turbine and gearbox) to be removed and replaced in such an event, and also allows for less stress on the start during engine ground starts. Whereas a fixed shaft has the gearbox and gas generator connected, such as on the Honeywell TPE331 . The propeller itself

2376-399: The propulsion airflow is less clearly defined for propellers than for fans. The propeller is coupled to the turbine through a reduction gear that converts the high RPM /low torque output to low RPM/high torque. This can be of two primary designs, free-turbine and fixed. A free-turbine turboshaft found on the Pratt & Whitney Canada PT6 , where the gas generator is not connected to

2430-546: The retirement of the 4 Batch 3 Type 22 frigates (2011) and the last remaining Type 42 Destroyer (2013). They were also used in numerous other European ships such as the Tromp and Kortenaer-class frigates. A Rolls-Royce Tyne is on public display at the Royal Air Force Museum Cosford . Data from Jane's All the World's Aircraft 1962-63. Comparable engines Related lists Turboprop A turboprop

2484-585: The same speed as small regional jet airliners but burn two-thirds of the fuel per passenger. Compared to piston engines, their greater power-to-weight ratio (which allows for shorter takeoffs) and reliability can offset their higher initial cost, maintenance and fuel consumption. As jet fuel can be easier to obtain than avgas in remote areas, turboprop-powered aircraft like the Cessna Caravan and Quest Kodiak are used as bush airplanes . Turboprop engines are generally used on small subsonic aircraft, but

2538-523: The six-stage LP compressor and, through a reduction gearbox, the propeller. The combustor is cannular . The Mark 515 Tyne had a nominal takeoff power output of 5,730 hp (4,273 kW) equivalent power, flat rated to ISA+16.8C. An agreement was signed in 1963 between Hispano-Suiza and Rolls-Royce for the licence production of the Tyne for the Breguet Atlantic and Transall C-160 . Each company that

2592-410: The way down to zero pitch, producing very little to zero-thrust and is typically accessed by moving the power lever to a beta for taxi range. Beta plus power is a reverse range and produces negative thrust, often used for landing on short runways where the aircraft would need to rapidly slow down, as well as backing operations and is accessed by moving the power lever below the beta for taxi range. Due to

2646-504: Was destroyed in a bombing raid. In 1941, the engine was abandoned due to war, and the factory converted to conventional engine production. The first mention of turboprop engines in the general public press was in the February 1944 issue of the British aviation publication Flight , which included a detailed cutaway drawing of what a possible future turboprop engine could look like. The drawing

2700-686: Was operated by the U.S. Navy for a short time. The first American turboprop engine was the General Electric XT31 , first used in the experimental Consolidated Vultee XP-81 . The XP-81 first flew in December 1945, the first aircraft to use a combination of turboprop and turbojet power. The technology of Allison's earlier T38 design evolved into the Allison T56 , used to power the Lockheed Electra airliner, its military maritime patrol derivative

2754-677: Was part of the agreement built parts for itself and the partners, Rolls-Royce (United Kingdom) 20%, Hispano-Suiza (France) 44%, MAN (Germany) 28% and FN (Belgium) 8%. The final assembly was undertaken by both MAN and Hispano-Suiza. The first production batch was for 80 engines and 40 spares for the Atlantic. The marine version, the Rolls-Royce Tyne RM1A, RM1C and RM3C remained in service as the cruise gas turbines in Royal Navy Type 21 frigates, Type 42 destroyers and Type 22 frigates until

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2808-629: Was produced and tested at the Ganz Works in Budapest between 1937 and 1941. It was of axial-flow design with 15 compressor and 7 turbine stages, annular combustion chamber. First run in 1940, combustion problems limited its output to 400 bhp. Two Jendrassik Cs-1s were the engines for the world's first turboprop aircraft – the Varga RMI-1 X/H . This was a Hungarian fighter-bomber of WWII which had one model completed, but before its first flight it

2862-593: Was the first turboprop aircraft of any kind to go into production and sold in large numbers. It was also the first four-engined turboprop. Its first flight was on 16 July 1948. The world's first single engined turboprop aircraft was the Armstrong Siddeley Mamba -powered Boulton Paul Balliol , which first flew on 24 March 1948. The Soviet Union built on German World War II turboprop preliminary design work by Junkers Motorenwerke, while BMW, Heinkel-Hirth and Daimler-Benz also worked on projected designs. While

2916-481: Was very close to what the future Rolls-Royce Trent would look like. The first British turboprop engine was the Rolls-Royce RB.50 Trent , a converted Derwent II fitted with reduction gear and a Rotol 7 ft 11 in (2.41 m) five-bladed propeller. Two Trents were fitted to Gloster Meteor EE227 — the sole "Trent-Meteor" — which thus became the world's first turboprop-powered aircraft to fly, albeit as

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