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Pratt & Whitney Canada PT6

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"PT6" redirects here. For other uses, see PT6 (disambiguation).
PT6
A PT6A-20 on display at the Canada Aviation and Space Museum
Type Turboprop / turboshaft
National origin Canada
Manufacturer Pratt & Whitney Canada
First run 1961[1]
Major applications Beechcraft Super King Air
de Havilland Canada DHC-6 Twin Otter
Pilatus PC-12
Sikorsky S-76
Variants Pratt & Whitney Canada PT6T

The Pratt & Whitney Canada PT6 is one of the most popular turboprop aircraft engines in history,[2] and is produced by Pratt & Whitney Canada. The PT6 family is particularly well known for its extremely high reliability, with MTBO's on the order of 9000 hours in some models.[3] In US military use, they are designated as T74 or T101. The main variant, the PT6A, is available in a wide variety of models, covering the power range between 580 and 920 shaft horsepower in the original series, and up to 1,940 shp (1,450 kW) in the "large" lines. The PT6B and PT6C are turboshaft variants for helicopters.

Design and development

Development of the PT6 family started in the late 1950s, apparently as a modern replacement for the Pratt & Whitney Wasp radial engines they were producing at that time.[4] 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. By its 40th anniversary in 2001 over 36,000 PT6As had been delivered, not including the other versions.[5] The engine is used in over 100 different applications.

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. 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 up to 600 lbf (2,700 N) of jet thrust.[citation needed] The engine is arranged such that the power turbines are mounted inside the combustion chamber, reducing overall length.

Epicyclic reduction gears on Pratt & Whitney Canada PT6 gas turbine engine.

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.

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 (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 4,000 hp (3,000 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.[6]

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.

Variants

PT6A

A PT6A-67D engine on a Beechcraft 1900D. The jet nozzle on the exhaust is prominent.

The PT6A is a free turbine providing 500 to 1,940 shaft horsepower (433 to 1,447 kW).

PT6A-6
"Small" engine of 525 equivalent shaft horsepower (eshp) and 500 shaft horsepower (shp)[7]
PT6A-11
"Small" engine of 528 eshp and 500 shp[7]
PT6A-15AG
"Small" engine optimised for agricultural aircraft of 715 eshp and 680 shp[7]
PT6A-20
"Small" engine of 579 eshp and 550 shp[7]
PT6A-21
"Small" engine of 580 eshp and 550 shp[7]
PT6A-25
"Small" engine of 580 eshp and 550 shp (-25, -25A) or 783 eshp and 750 shp (-25C)[7]
PT6A-27
"Small" engine of 715 eshp and 680 shp[7]
PT6A-28
"Small" engine of 715 eshp and 680 shp[7]
PT6A-29
"Small" engine of 778 eshp and 750 shp[7]
PT6A-34
"Small" engine of 783 eshp and 750 shp[7]
PT6A-35
"Small" engine of 787 eshp and 750 shp[7]
PT6A-36
"Small" engine of 783 eshp and 750 shp[7]
PT6A-38
"Medium" engine of 801 eshp and 750 shp[7]
PT6A-40
"Medium" engine of 749 eshp and 700 shp[7]
PT6A-41
"Medium" engine of 903 eshp and 850 shp[7]
PT6A-42
"Medium" engine of 903 eshp and 850 shp[7]
PT6A-45
"Medium" engine of 1,070 eshp and 1,020 shp[7]
PT6A-50
"Large" engine of 1,022 eshp and 973 shp[7]
PT6A-52
"Large" engine of 898 eshp and 850 shp[7]
PT6A-60
"Large" engine of 1,113 eshp and 1,050 shp (-60, -60A) or 1,081 ehsp and 1,020 shp (-60AG)[7]
PT6A-61
"Large" engine of 902 eshp and 850 shp[7]
PT6A-62
"Large" engine of 1,218 eshp and 950 shp[8][dead link‍]
PT6A-64
"Large" engine of 747 eshp and 700 shp[9]
PT6A-65
"Large" engine of 1,249 eshp and 1,173 shp (-65B, -65R) or 1,298 eshp and 1,220 shp (-65AG, -65AR)[7]
PT6A-66
"Large" engine of 905 eshp and 850 shp (-66, -66A, -66D) or 1,010 eshp and 950 shp (-66B)[9]
PT6A-67
"Large" engine of 1,272 eshp and 1,200 shp (-67, -67A, -67B, -67P), 1,285 eshp and 1,214 shp (-67D), 1,294 eshp and 1,220 shp (-67AF, -67AG, -67R, -67T), or 1,796 eshp and 1,700 shp (-67F)[9]
PT6A-68
"Large" engine of 1,324 eshp and 1,250 shp[9]
PT6A-110
"Small" engine of 502 eshp and 475 shp[7]
PT6A-112
"Small" engine of 528 eshp and 500 shp[7]
PT6A-114
"Small" engine of 632 eshp and 600 shp (-114) or 725 eshp and 675 shp (-114A)[7]
PT6A-116
"Small" engine of 736 eshp and 700 shp[7]
PT6A-121
"Small" engine of 647 eshp and 615 shp[7]
PT6A-135
"Small" engine of 787 eshp and 750 shp[7]
PT6B
The PT6B is a 981 horsepower (732 kW) engine designed for helicopters.
PT6C
The PT6C is a 1600 to 2300 horsepower (1190 to 1720 kW) engine for helicopters and tiltrotors.
PT6D
The PT6D-114A is based on the PT6A-114A. The main difference is the deletion of the second stage

reduction gearing and output shaft, as the engine is intended for integration with a combining gearbox incorporating power turbine governors and a propeller output shaft.[10]

ST6
The ST6 is a variant of the PT6 that was originally developed as a powerplant for the UAC TurboTrain power cars, but later developed as a stationary power generator and auxiliary power unit.
ST6B
The ST6B-62 was a 550 bhp (410 kW) version of the PT6 developed for use in the STP-Paxton Turbocar, raced in the 1967 Indianapolis 500.[11]
STN 6/76
The STN 6/76 was a 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.[12][13]
T74
United States military designation for the PT6A-20/27, used in the Beechcraft U-21.
T101
United States military designation for the T101-CP-100 / PT6A-45R, used in the Shorts 330 and Shorts C-23 Sherpa.

Applications

PT6A

PT6B

PT6C

PT6D

ST6

Specifications

Name PT6A-11AG PT6A-50 PT6A-68C PT6B-36A PT6B-37A PT6C-67B PT6C-67C PT6C-67E PT6T-6B
Diameter 483 mm 483 mm 483 mm 825 × 495 mm 495 mm 584 mm 584 mm 584 mm 825 × 1105 mm
Length 1.58 m 1.73 m 1.83 m 1.5 m 1.63 m 1.50 m 1.50 m 1.50 m 1.67 m
Dry weight 193 kg 169 kg 172 kg
Power 550 kW (748 PS) 705 kW (958 PS) 1175 kW (1600 PS) 732 kW (995 PS) 747 kW (1015 PS) 895 kW (1217 PS) 1252 kW (1702 PS) 1324 kW (1800 PS) 1469 kW (2000 PS)
Specific fuel consumption 353 g/ekWh 0.581 lbs/shph 0.584 lbs/shph 0,602 lbs/shph

See also

Related development

Comparable engines

Related lists

References

  1. ^ [1]
  2. ^ United Technologies history
  3. ^ PT6A Model Specifications
  4. ^ PT6 engine - The Legend
  5. ^ Pratt & Whitney Canada's PT6 Turboprop Marks 40 Years of In-flight Success
  6. ^ "Pratt & Whitney PT6A-42 Turboprop" - primary source for the description
  7. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab Pratt & Whitney Canada PT6 Series Type Certificate retrieved 2009-11-28.
  8. ^ PT6A-62 data retrieved 2007-12-29[dead link‍]
  9. ^ a b c d PT6A -64/-66/-67/-68 Series Type Certificate retrieved 2009-11-28.
  10. ^ PT6 Type Certificate Data Sheet Information
  11. ^ 'The Big Engine That Almost Did' Popular Mechanics August 1967. Retrieved 26 June 2011
  12. ^ http://www.research-racing.de/Lotus56B-1.htm
  13. ^ http://www.f1technical.net/f1db/cars/271
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