Pratt & Whitney Canada PT6
The PT6, manufactured by Pratt & Whitney Canada, is the most popular turboprop aircraft engine in history [1]. It is produced in a wide variety of models, covering the power range between 580 and 920 shp in the original series, and up to 1,940 shp in the "large" line. The PT6 family are particularly well known for their extremely high reliability, with MTBO's on the order of 9000 hours in some models.[1]
Development
Development of the PT6 family started in the late 1950s, apparently as a modern replacement for the
The engine consists of two sections that can be easily separated for maintenance. In the gas-generator section air enters through a grill into the low-pressure three-stage axial compressor, then into a single-stage centrifugal compressor, through the annular reverse-flow combustion chamber, and finally through a single-stage turbine that powers the compressors at about 45,000 rpm. Some power is also taken off of the compressor end of the shaft to power an accessories section, which also loads the engine [citation needed] when idle to keep it from racing out of control. The hot gas from the gas generator section then flows into a separate power section of the engine, containing a single-stage turbine driving the power take-off system at about 30,000 rpm. For turboprop use, this powers a two-stage planetary output reduction gearbox, which turns the propeller at a speed of 1,900 to 2,200 rpm. The exhaust gas then escapes through two side mounted ducts in the power turbine housing, and is directed away from the engine in order to provide about 600 lbf of thrust. The engine is arranged such that the power turbines are mounted inside the combustion chamber, reducing overall length.
In most aircraft installations the PT6 is mounted backwards in the nacelle, so that the intake side of the engine is facing the rear of the aircraft, and the exhaust side can directly drive the propeller. Intake air is usually fed to the engine via an underside mounted duct, and the two exhaust outlets are directed rearward. This arrangement also aids maintenance by allowing the entire propeller section to be easily removed along with the power section, exposing the gas-generator section.
Several other versions of the PT6 have appeared over time. The PT6A large added an additional power turbine stage and a deeper output reduction, producing almost twice the power output, between 1,090 and 1,920 shp. The PT6B is a helicopter turboshaft model, featuring an offset reduction gearbox with a freewheeling clutch and power turbine governor, producing 1,000 hp at 4,500 rpm. The PT6C is a helicopter model, with a single side-mounted exhaust, producing 2,000 hp at 30,000 rpm, which is stepped down in a user-supplied gearbox. The PT6T Twin-Pac consists of two PT6 engines driving a common output reduction gearbox, producing almost 4,000 hp at 6,000 rpm. The ST6 is a version intended for stationary applications, originally developed for the UAC TurboTrain, and now widely used as auxiliary power units on large aircraft, as well as many other roles.[3]
When de Havilland Canada asked for a much larger engine, roughly twice the power of the PT6 Large, P&WC responded with a design initially known as the PT7. During development this was renamed to become the Pratt & Whitney Canada PW100. Unlike the PT6, the PW100 uses a three-spool turbine with the power turbine attached to the rest of the engine, meaning it cannot be completely removed as with the PT6. The PW100 also uses two centrifugal compressors driven by the first two turbine stages, as opposed to the mix of axial and centrifugal compressors in the PT6. This makes the engine somewhat harder to disassemble, but results in a much more compact engine.
Variants
PT6A
The PT6A is a free turbine providing 580 to 1,940 shaft horsepower (433 to 1,447 kW). Aircraft that it powers include:
- AASI Jetcruzer 500 (1 x PT6A-66A)
- Aero Ae 270 Ibis (1 x PT6A-42A)
- Air Tractor AT-503 (1 x PT-6A-45R)
- Air Tractor AT-802 (1 x PT-6A-67)
- AMI DC3
- Ayres Turbo Thrush
- Beechcraft (Raytheon):
- Beechcraft King Air (2 x PT6A-42)
- C-12 Huron (2 x PT6A-42)
- Beechcraft Starship (2 x PT6A-67A)
- Beechcraft 99/C99 (2 x PT6A-27/2 x PT6A-36)
- Beechcraft 1900 (2 x PT6A-65C (1900C), or PT6A-67D (1900D))
- Basler Turbo BT-67 (2 x PT6A-67R)
- CASA C.212 Aviocar series 300P (2 x PT6A-25)
- CATIG/HAIG Y-12
- Cessna Caravan I (1 x PT6A-114)
- Conair S2 Turbo-Firecat
- Croplease
- De Havilland Canada DHC-6 Twin Otter (2 x PT6A-20)
- De Havilland Canada Dash 7 (4 x PT6A-50)
- Dornier Seastar
- EADS Socata
- Embraer
- Bandeirante EMB-110 and EMB-111
- Tucano (1 x PT6A-25C)
- Embraer EMB 110 Bandeirante (2 x PT6A-34)
- Embraer EMB 121 Xingu (2 x PT6A-42)
- Epic Aircraft LT and Dynasty (1 x PT6A-67)
- Fieldmaster
- Firemaster
- Fairchild Dornier Turbo Skyservant
- Frakes
- Greenwich Aircraft DC-3
- Harbin Y-12 (2 x PT6A-27)
- LET L410
- Pacific Aerospace Corporation (PAC)
- Piaggio P.180 Avanti (2 x PT6A-66A)
- Piper Cheyenne, I, IA, II, IIXL, III, IIIA (2 x PT6A-11/28/41/61/135)
- Piper Malibu (1 x PT6A-42A)
- Pilatus PC-6 Turbo Porter (1 x PT6A-27)
- Pilatus PC-7 (1 x PT6A-25C)
- Pilatus PC-9 (1 x PT6A-62)
- Pilatus PC-12 (1 x PT6A-67B)
- Pilatus PC-21 (1 x PT6A-68B)
- PZL M-18/T45 Turbine Dromader (1 x PT6A-45)
- PZL M-28 Skytruck
- PZL-130 Orlik TC-II(1 x PT6A-25P)
- Quest Kodiak (1 x PT6A-34)
- Reims F406 Caravan II
- Scaled Composites Model 133 ATTT (2 x PT6A-135A)
- Shorts 330 (2 x PT6A-45)
- Shorts 360 (2 x PT6A-65R)
- Shorts 360-300 (2 x PT6A-67R)
- Socata TBM-700/850
- T-34C Turbo Mentor (1 x PT6A-25)
- T-44A/C Pegasus (2 x PT6A-34B)
- T-6 Texan II (1 x PT6A-68)
- NAL Saras (Civilian Aircraft)- Pusher Propeller Configuration
- Schweizer AG-Cat Turbine
- Vazar Dash 3 Turbo Otter
- Wheatherly 620 TP
PT6B
The PT6B is 981 horsepower (732 kW) engine designed for helicopters. It powers the Agusta A119 Koala and the Sikorsky S-76B.
PT6C
The PT6C is a 1600 to 2300 horsepower (1190 to 1720 kW) engine for helicopters/tiltrotors. It powers the AgustaWestland AW139 and the PZL-Swidnik Sokol helicopters, and the Bell/Agusta BA609 tiltrotor.
PT6T
The PT6T/T400 (Twin-Pac) is a twinned turboshaft designed for helicopters. It powers the Agusta-Bell 212 and 412, the Bell AH-1J and AH-1T, CH-146 Griffon, and UH-1N Twin Huey, and the Sikorsky S-58T.
ST6
The ST6 is a variant of the PT6 that was originally developed as a powerplant for the UAC TurboTrain locomotives, but later developed as a stationary power generator and auxiliary power unit.
References
- ^ PT6A Model Specifications
- ^ Pratt & Whitney Canada's PT6 Turboprop Marks 40 Years of In-flight Success
- ^ Pratt & Whitney PT6A-42 Turboprop - primary source for the description
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