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Pratt & Whitney Canada PT6 / T74 / T101




Development of the PT6 family started in the late 1950s, as a modern replacement for the Pratt & Whitney Wasp radial engines of that time. It first flew on 30 May 1961, mounted on a Beech 18 aircraft at de Havilland Canada's Downsview, Ontario facility. Full-scale production started in 1963, entering service the next year.
The engine consists of two sections that can be easily separated for maintenance. In the gas-generator section air enters through an inlet screen into the low-pressure axial compressor. This has three stages on small and medium versions of the engine and four stages on large versions. The air then flows into a single-stage centrifugal compressor, through the annular reverse-flow combustion chamber, and finally through a single-stage compressor turbine that powers the compressors at about 45,000 rpm. The hot gas from the gas generator section then flows into a separate power section of the engine, containing a single-stage power 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 up to 600 lbf (2,700 N) of jet 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. This places the power section at the front of the nacelle, where it can drive the propeller directly without the need for a long shaft. 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 power section to be removed along with the propeller, exposing the gas-generator section.
In US military use, they are designated as T74 or T101.
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 (1,430 kW).


The PT6B is a helicopter turboshaft model, featuring an offset reduction gearbox with a freewheeling clutch and power turbine governor, producing 1,000 hp (750 kW) at 4,500 rpm.
The PT6C is a helicopter model, with a single side-mounted exhaust, producing 2,000 hp (1,500 kW) 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 2,000 hp (1,500 kW) 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.
When de Havilland Canada asked for a much larger engine, roughly twice the power of the PT6 Large, Pratt & Whitney Canada responded with a new design initially known as the PT7. During development this was renamed to become the Pratt & Whitney Canada PW100.
By the 40th anniversary of its maiden flight in 2001, over 36,000 PT6As had been delivered, not including the other versions. The engine is used in over 100 different applications.


The PT6A Dash 66D engine in the 850 has four stages of axial compressors plus a final stage of centrifugal compression. The pressure is increased by each stage of the process. When the engine is operating at cruise power, only a small portion of the compressed air must be bled to maintain the 6.2 psi cabin pressure and keep the TBM 850 cabin pumped up. But, the rules require that the cabin pressure must be maintained when the engine power is low. In other words, you must be able to chop the power at the certified ceiling without the cabin altitude climbing. To meet that requirement, the TBM 700 tapped bleed air from a higher pressure section of the compressor than was needed for normal cruise and descent and that used more engine power. The new 850 has two engine-bleed taps to satisfy normal cruise power pressurization and the low power high-altitude condition.


The PT6A-67A is equipped with an epicyclic speed reduction gear box to minimise the propeller noise by optimising the output speed. It also houses a single-stage centrifugal compressor, multistage axial, reverse flow combustor and a single-stage compressor turbine.



The PT6A family is a series of free turbine turboprop engine providing 500 to 1,940 shp (433 to 1,447 kW).


525 equivalent shaft horsepower (eshp) and 500 shaft horsepower (shp)


528 eshp and 500 shp


optimised for agricultural aircraft
715 eshp and 680 shp


579 eshp and 550 shp


580 eshp and 550 shp


580 eshp and 550 shp (-25, -25A)
783 eshp and 750 shp (-25C)


715 eshp and 680 shp


715 eshp and 680 shp


778 eshp and 750 shp


783 eshp and 750 shp


787 eshp and 750 shp


783 eshp and 750 shp


801 eshp and 750 shp


749 eshp and 700 shp


903 eshp and 850 shp


903 eshp and 850 shp


1070 eshp and 1020 shp


1022 eshp and 973 shp


898 eshp and 850 shp


1113 eshp and 1050 shp (-60, -60A)
1081 ehsp and 1020 shp (-60AG)


902 eshp and 850 shp


1218 eshp and 950 shp


747 eshp and 700 shp


1249 eshp and 1173 shp (-65B, -65R)
1298 eshp and 1220 shp (-65AG, -65AR)


905 eshp and 850 shp (-66, -66A, -66D)
1010 eshp and 950 shp (-66B)


1272 eshp and 1200 shp (-67, -67A, -67B, -67P)
1285 eshp and 1214 shp (-67D)
1294 eshp and 1220 shp (-67AF, -67AG, -67R, -67T)
1796 eshp and 1700 shp (-67F)


1324 eshp and 1250 shp


502 eshp and 475 shp


528 eshp and 500 shp


632 eshp and 600 shp (-114)

725 eshp and 675 shp (-114A)


736 eshp and 700 shp


647 eshp and 615 shp


787 eshp and 750 shp


United States military designation for the PT6A-20/27, used in the Beechcraft U-21.


United States military designation for the T101-CP-100 / PT6A-45R, used in the Shorts 330 and Shorts C-23 Sherpa.


550 hp (410.1 kW) turbo-shaft engine for use in helicopters. A later mark of PT6B is rated at 981 hp (731.5 kW).


1600 to 2300 horsepower (1190 to 1720 kW) engine for helicopters and tiltrotors.


Based on the PT6A-114A. The main difference is the deletion of the second stage reduction gearing and output shaft, because the engine is intended for integration with a combining gearbox incorporating power turbine governors and a propeller output shaft.


Twin PT6 power units combining outputs through a gearbox for use in helicopters.


Variant originally developed as a powerplant for the UAC TurboTrain power cars, but later developed as a stationary power generator and auxiliary power unit.


550 bhp (410 kW) version of the PT6 developed for use in the STP-Paxton Turbocar, raced in the 1967 Indianapolis 500.


STN 6/76
500 bhp (370 kW) version of the PT6 developed for use in the Lotus 56, raced in the 1968 Indianapolis 500 and later in Formula One races, in 1971.



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Type: Turboprop
Length: 62 in (1,575 mm)
Diameter: 19 in (483 mm)
Dry weight: 270 lb (122.47 kg)
ComponentsCompressor: 3-stage axial + 1-stage centrifugal flow compressor
Combustors: Annular reverse-flow with 14 Simplex burners
Turbine: 1-stage gas generator power turbine + 1-stage free power turbine
Fuel type: Aviation kerosene to MIL-F-5624E / JP-4 / JP-5
Oil system: Split system with gear type pressure and scavenge pumps, with pressure to gearbox boosted by a second pump.
Maximum power output: 578 hp (431 kW) equivalent power at 2,200 output rpm for take-off
Overall pressure ratio: 6.3:1
Specific fuel consumption: 0.67 lb/hp/hr (0.408 kg/kW/hr)
Power-to-weight ratio: 2.14 hp/lb (3.52 kW/kg)


Diameter: 483 mm
Length: 1.58 m
Power: 550 kW (748 PS)


Diameter: 483 mm
Length: 1.73 m
Dry weight: 193 kg
Power: 705 kW (958 PS)
Specific fuel consumption: 353 g/ekWh


Diameter: 483 mm
Length: 1.83 m
Power: 1175 kW (1600 PS)


Diameter: 825 mm
Length: 1.5 m
Dry weight: 169 kg
Power: 732 kW (995 PS)
Specific fuel consumption: 0.581 lbs/shph


Diameter: 495 mm
Length: 1.63 m
Dry weight: 172 kg
Power: 747 kW (1015 PS)
Specific fuel consumption: 0.584 lbs/shph


Length: 1.87m
Diameter: 0.48m


Diameter: 584 mm
Length: 1.50 m
Power: 895 kW (1217 PS)


Diameter: 584 mm
Length: 1.50 m
Power: 1252 kW (1702 PS)


Diameter: 584 mm
Length: 1.50 m
Dry weight:
Power: 1324 kW (1800 PS)
Specific fuel consumption:


Diameter: 825 × 1105 mm
Length: 1.67 m
Dry weight:
Power: 1469 kW (2000 PS)
Specific fuel consumption: 0,602 lbs/shph







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