A schematic diagram showing the operation of a turboprop engine.

The P&W PT6, one of the most popular turboprop engines. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout

A turboprop engine is a type of gas turbine engine used in aircraft. A gas turbine, also called a combustion turbine, is a rotary Engine that extracts energy from a flow of Combustion gas Most of a turboprop engine's power is used to drive a propeller, and the propellers used are very similar to the propellers used in piston or reciprocating engine-driven aircraft (with the exception that turboprops usually use a constant velocity propeller). A propeller is essentially a type of fan which transmits power by converting Rotational motion into Thrust for propulsion of a vehicle such as an A piston is a component of Reciprocating engines Pumps and Gas compressors It is located in a cylinder and is made gas-tight by Piston A reciprocating engine, also often known as a piston engine, is a Heat engine that uses one or more reciprocating Pistons to convert

A turboprop engine is similar to a turbojet but has additional stages in the turbine to recover more power from the engine to turn the propeller. TurboJET (噴射飛航 is the brand name for the operations of the Hong Kong -based Shun Tak-China Travel Ship Management Limited (信德中旅船務管理有限公司 A turbine is a rotary Engine that extracts Energy from a Fluid flow Turboprop engines are generally used on small or slow subsonic aircraft, but some aircraft outfitted with turboprops have cruising speeds in excess of 500 kt (926 km/h, 575 mph).

In its simplest form, a turboprop consists of an intake, compressor, combustor, turbine and a propelling nozzle. A combustor is a component or area of a Gas turbine, Ramjet or Pulsejet A turbine is a rotary Engine that extracts Energy from a Fluid flow Air propulsion is the act of moving an object through the air A nozzle is a mechanical device or Orifice designed to control the characteristics of a Fluid flow as it exits (or enters an enclosed chamber or Pipe. Air is drawn into the intake and compressed by the compressor. Fuel is then added to the compressed air in the combustor. The hot combustion gases expand through the turbine. Part of the power generated by the turbine is used to drive the compressor. The rest goes through the reduction gearing to the propeller. Further expansion of the gases occurs in the propelling nozzle, where the gases exhaust to atmospheric pressure. The propelling nozzle provides a relatively small proportion of the thrust generated by a turboprop; the remainder comes from the conversion of shaft power to thrust in the propeller.

Turboprops are very efficient at modest flight speeds (below 450 mph) because the jet velocity of the propeller (and exhaust) is relatively low. Due to the high price of turboprop engines, they are mostly used where high-performance short-takeoff and landing (STOL) capability and efficiency at modest flight speeds are required. STOL is an Initialism for short take-off and landing, a term used to describe Aircraft with very short Runway requirements In a civilian aviation context, the most common application of turboprop engines is in small commuter aircraft.

Technological aspects

Polish turboprop, single engine, two seat trainer PZL-130 Orlik TC-I of Orlik Aerobatic Team

In a turboprop, much of the jet thrust is sacrificed in favor of shaftpower, which is obtained by extracting additional power (to that necessary to drive the compressor) from the turbine expansion process. Poland (Polska officially the Republic of Poland A trainer is an Aircraft used to develop piloting navigational or war-fighting skills in flight crew PZL 130 Orlik ( Spotted Eagle) is a Polish Turboprop, single engine two seat trainer. Orlik Aerobatic Team ( Zespół Akrobacyjny "ORLIK") is an Aerobatic demonstration team of the Polish Air Forces While the power turbine may be integral with 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. Owing to the additional expansion in the turbine system, the residual energy in the exhaust jet is fairly low. Consequently, the exhaust jet produces (typically) less than 10% of the total thrust, including that from the propeller.

Because the propeller is much larger in diameter than the power turbine, the tip speed of the propeller can become supersonic. To prevent this, a speed reduction gearbox is inserted between the power turbine and propeller shafts. The gearbox is part of the engine, whereas in a turboshaft the (helicopter) rotor reduction gearbox is remote from the engine. A turboshaft engine is a form of Gas turbine which is optimized to produce Shaft power, rather than Jet thrust. History Since 400 AD Chinese children have played with bamboo flying toys.

Residual thrust on a turboshaft is avoided by further expansion in the turbine system and/or truncating and turning the exhaust through 180 degrees, to produce two opposing jets. Apart from the above, there is very little difference between a turboprop and a turboshaft.

While most modern turbojet and turbofan engines use axial-flow compressors, turboprop engines, because of their small size, usually contain at least one stage of centrifugal compression. TurboJET (噴射飛航 is the brand name for the operations of the Hong Kong -based Shun Tak-China Travel Ship Management Limited (信德中旅船務管理有限公司 A turbofan is a type of Jet engine, similar to a Turbojet. It essentially consists of a Ducted fan with a smaller diameter turbojet engine Axial compressors are rotating aerofoil based compressors in which the working fluid principally flows parallel to the axis of rotation Centrifugal compressor, (sometimes referred to as radial compressors) are a special class of radial-flow work-absorbing Turbomachinery that includes pumps NOTE: it is difficult to manufacture robust blading for the rear stages of small axial-flow compressors.

Propellers lose efficiency as aircraft speed increases, so turboprops are normally not used on high-speed aircraft. However, propfan engines, which are very similar to turboprop engines, can cruise at flight speeds approaching Mach 0. An unducted fan or propfan is a modified Turbofan engine with the fan placed outside of the Engine nacelle on the same axis as the compressor Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid 75. To increase the efficiency of the propellers, a mechanism can be used to alter the pitch, thus adjusting the pitch to the airspeed. The variable pitch propeller, also called controllable pitch propeller, can also be used to generate negative thrust while decelerating on the runway. A controllable pitch propeller (CPP or variable pitch propeller is a special type of Propeller with blades that can be rotated around their long axis to change their After an engine outage, the pitch can be adjusted to a vaning pitch (called feathering), thus minimizing the drag of the non-functioning propeller.

Common passenger airliners with turboprop engines include the Dash 8, ATR42, ATR72, BAe Jetstream 31, The Fairchild-Swearighan Metroliner and Saab 340 and 2000.

History

A Rolls-Royce RB. 50 Trent on a test rig at Hucknall, in March 1945

The world's first turboprop was the Jendrassik Cs-1 designed by the Hungarian mechanical engineer György Jendrassik. The Jendrassik Cs-1 was the world's first working Turboprop engine Hungary (Magyarország 'mɔɟɔrorsaːg) officially in English the Republic of Hungary ( Magyar Köztársaság, literally Magyar (Hungarian Republic György Jendrassik (1898-1954 was born in Budapest, Hungary. Jendrassik completed his education at Budapest's József Technical University then at the University It was produced and tested in the Ganz factory in Budapest between 1939 and 1942. It was planned to fit to the Varga RMI-1 X/H twin-engined reconnaissance bomber designed by László Varga in 1940, but the program was cancelled. Jendrassik had also designed a small-scale 75 kW turboprop in 1937.

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 five-bladed propeller. For the present day company see Rolls-Royce plc. For other uses see Rolls-Royce (disambiguation. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Dowty Rotol is the final incarnation of three major British aviation supply firms Dowty Equipment, Rotol Airscrews and British Messier, which A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit Inches redirects here To see the Les Savy Fav album see Inches. Two Trents were fitted to Gloster Meteor EE227 — the sole "Trent-Meteor" — which became the first relatively reliable turboprop powered aircraft. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout A serial number is a unique Number assigned for Identification which varies from its Successor or Predecessor by a fixed discrete Integer From their experience with the Trent, Rolls-Royce developed the Dart, which became one of the most reliable turboprop engines ever built. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Dart production continued for more than fifty years.

While the Soviet Union had the technology to create a jet-powered strategic bomber comparable to Boeing's B-52 Stratofortress, they instead produced the Tu-95 "Bear", which uses 8 contra-rotating propellers (two per nacelle) with supersonic tip speeds to achieve maximum cruise speeds in excess of 575 mph, faster than many of the first jet aircraft and comparable to jet cruising speeds for most missions. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout The Bear would serve as their most successful long-range combat and surveillance aircraft and symbol of Soviet power projection throughout the end of the 20th century. The USA would incorporate contra-rotating turboprop engines, such as the ill-fated Allison T40, into a series of experimental aircraft during the 1950s, but none would be adopted into service. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout

The first American turboprop was the General-Electric T31. America skipped over turboprop airliners in favor of the Boeing 707, but the technology of the Lockheed Electra would be used in both the long-lived P-3 Orion as well as the classic C-130 Hercules, one of the most successful military aircraft ever in terms of length of production. The Lockheed L-188 Electra is an American Turboprop airliner built by Lockheed. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout One of the most popular turboprop engines is the Pratt & Whitney Canada PT6 engine. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout

See also

• Gas turbine
• Jet engine
• Jet engine performance
• Jet aircraft
• Jetboat
• Propfan
• Ramjet
• Supercharger
• Turbocharger
• Turbofan
• Turbojet
• Turboshaft
• Wikibooks: Jet propulsion