Pratt & Whitney Canada PT6

"PT6" redirects here. For other uses, see PT6 (disambiguation).
A PT6A-20 on display at the Canada Aviation and Space Museum
Type Turboprop / turboshaft
National origin Canada
Manufacturer Pratt & Whitney Canada
First run 1960[1]
Major applications Beechcraft Super King Air
de Havilland Canada DHC-6 Twin Otter
Pilatus PC-12
Sikorsky S-76
Number built 51 thousand (as of November 2015)[2]
Unit cost PT6A-60A: $955,000; PT6A-68: $855,000[3]
Variants Pratt & Whitney Canada PT6T

The Pratt & Whitney Canada PT6, produced by Pratt & Whitney Canada, is one of the most popular turboprop aircraft engines in history.[4] The PT6 family is known for its reliability with an in-flight shutdown rate of 1 per 333000 hours since 1963,[5] 1 per 651,126 hours over 12 months in 2016.[6] Time between overhauls are between 3600 and 9000 hours and hot section inspections between 1800 and 2000 hrs.[7]

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

In 1956, PWC's President, Ronald Riley, foreseeing the need for engines with much higher power-to-weight ratio, ordered engineering manager Dick Guthrie to establish a development group to create a turboprop engine designed to replace piston engines. Demand for the Wasp radial engine was still strong and its production line's output was robust and profitable. Riley gave Guthrie a modest budget of C$100,000. Guthrie recruited young engineers from the National Research Council in Ottawa and from Orenda Engines in Ontario. In 1958, the group began development of a turboprop engine intended to deliver 450 shaft horsepower. The first engine was powered up and run successfully in February 1960.[1][8] 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 the 40th anniversary of its maiden flight in 2001, over 36,000 PT6As had been delivered, not including the other versions.[9] The engine is used in over 100 different applications.

All versions of the engine consist of two sections that can be easily separated for maintenance: a gas generator supplies hot gas to a free power turbine.[10] The starter has to accelerate only the gas generator, making the engine easy to start, particularly in cold weather.[10] Air enters the gas-generator 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 a folded annular combustion chamber, and finally through a single-stage turbine that powers the compressors at about 45,000 rpm. Hot gas from the gas generator flows into the power turbine, which turns at about 30,000 rpm. It has one stage on the small engines and two stages on the medium and large ones. 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. The 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 aids maintenance by allowing the entire power section to be removed along with the propeller, exposing the gas-generator section. To facilitate rough-field operations, foreign objects are diverted from the compressor intake by inertial separators in the inlet.[11]

Several other versions of the PT6 have appeared over time. The Large PT6 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.[12]

When de Havilland Canada asked for a much larger engine, roughly twice the power of the Large PT6, 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. Turboprops such as the PT6 and PW100 may have a bypass ratio over 50,[13][14][15] although propeller airflow is slower than for turbofans.[16][17]

In-flight shutdown rate was 1 per 127,560 hours in 2005 in Canada,[18] 1 per 333,333 hours up to October 2003, with 31,606 delivered engines flown more than 252 million hours.[19] The PT6 family logged 400 million flight hours from 1963 to 2016 while power-to-weight ratio was improved by 50%, brake specific fuel consumption by 20% and overall pressure ratio reached 14:1.[5]

Its development continues and while today its high-level configuration is the same as in 1964, P&WC updated the PT6 including single-crystal turbine blades in the early 1990s, and FADEC should be introduced. Its pressure ratio is 13:1 in the AgustaWestland AW609 tiltrotor.[20]



A PT6A-67D engine on a Beechcraft 1900D. The size of the turbine exhaust is prominent.

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

variant equivalent
PT6A-6 525 eshp 500 shp
PT6A-11AG 528 eshp 500 shp Air Tractor AT-400
Schweizer Ag-Cat G-164B Turbine
PT6A-15AG 715 eshp 680 shp Air Tractor AT-400
Air Tractor AT-501
Frakes Turbocat
Schweizer Ag-Cat G-164B Turbine
PT6A-20 579 eshp 550 shp
PT6A-21 580 eshp 550 shp Beechcraft King Air C90A/B/SE
Beechcraft Bonanza (turbine conversion)
PT6A-25, -25A 580 eshp 550 shp
PT6A-25C 783 eshp 750 shp Embraer EMB 312 Tucano
Pilatus PC-7/PC-7 MKII Turbo Trainer
PZL-130 Orlik / TC-II Turbo-Orlik
PT6A-27 715 eshp 680 shp Beechcraft Model 99A, B99
de Havilland Canada DHC-6 Twin Otter 300
Harbin Y-12
Embraer EMB 110 Bandeirante
Let L-410 Turbolet
Pilatus PC-6/B Turbo-Porter
PT6A-28 715 eshp 680 shp
PT6A-29 778 eshp 750 shp
PT6A-34 783 eshp 750 shp Embraer EMB 110 Bandeirante/111
Embraer EMB 821 Carajá
Grumman Mallard (turbine conversion)
Quest Kodiak
Vazar Dash 3 Turbine Otter
Viking DHC-6 Twin Otter 400
PT6A-34AG 783 eshp 750 shp Air Tractor AT-502B
Frakes/Grumman Turbo-Cat Model A/B/C
Pacific Aerospace 750XL
PZL-Okecie PZL-106 Turbo Kruk
Schweizer Ag-Cat G-164B/D Turbine
Thrush Model 510P
PT6A-35 787 eshp 750 shp Blue 35
PT6A-36 783 eshp 750 shp
PT6A-38 801 eshp 750 shp
PT6A-110 502 eshp 475 shp
PT6A-112 528 eshp 500 shp
PT6A-114 632 eshp 600 shp
PT6A-114A 725 eshp 675 shp Cessna 208 Caravan
PT6A-116 736 eshp 700 shp
PT6A-121 647 eshp 615 shp
PT6A-135 787 eshp 750 shp Beechcraft King Air F90-1/C90GT/C90GTi/C90GTx
Blackhawk XP135A Cheyenne Series
Blackhawk XP135A Conquest I
Blackhawk XP135A King Air 90 Series
Cessna Conquest I
Lancair Evolution
Silverhawk 135/StandardAero C90/E90
StandardAero Cheyenne Series
StandardAero King Air F90
T-G Aviation Super Cheyenne
Vazar Dash 3 Turbine Otter
variant equivalent
PT6A-40 749 eshp 700 shp
PT6A-41 903 eshp 850 shp Beechcraft King Air 200/B200
Piper Cheyenne III/IIIA
PT6A-42 903 eshp 850 shp Beechcraft C-12 HuronF
Beechcraft King Air 200/B200
Blackhawk XP42 King Air 200
StandardAero King Air 200
Blackhawk XP42A C-208 Caravan Series (-42A)
Piper Meridian
PT6A-45 1070 eshp 1020 shp
PT6A-50 1022 eshp 973 shp
PT6A-52 898 eshp 850 shp Beechcraft King Air B200GT/250
Blackhawk XP52 King Air 200/B200
Enhanced Aero B200GTO
StandardAero King Air 200/B200
PT6A-60, -60A 1113 eshp 1050 shp Beechcraft Super King Air 300/350
PT6A-60AG 1081 ehsp 1020 shp Air Tractor AT-602
Ayres Thrush 550P/660
PT6A-61 902 eshp 850 shp
PT6A-62 950shp[23] KAI KT-1/KO-1
Pilatus PC-9 Turbo Trainer
variant equivalent
PT6A-64 747 eshp 700 shp EADS Socata TBM 700
PT6A-65B, -65R[21] 1249 eshp 1173 shp Beechcraft 1900/1900C
Polish Aviation Factory M28 Skytruck
PT6A-65AG, -65AR[21] 1298 eshp 1220 shp Air Tractor AT-602
Air Tractor AT-802/802A/802AF/802F
Ayres Thrush 660/710P
PT6A-66, -66A, -66D 905 eshp 850 shp National Aerospace Laboratories SARAS
Piaggio P.180 Avanti
Ibis Ae270 HP (-66A)
EADS Socata TBM 850
PT6A-66B 1010 eshp 950 shp Piaggio P180 Avanti II
PT6A-67, -67A, -67B, -67P 1272 eshp 1200 shp Beechcraft Starship
Epic LT
IAI Heron TP
Pilatus PC-12 (-67B)
Pilatus PC-12NG (-67P)
PT6A-67D 1285 eshp 1214 shp Beechcraft 1900D
PT6A-67AF, -67AG, -67R, -67T 1294 eshp 1220 shp Air Tractor AT-802/802A/802AF/802F (-67AG)
Ayres Thrush 710P (-67AG)
Basler Turbo BT-67 (-67R)
Shorts 360 / 360-300 (-67R)
PT6A-67F 1796 eshp 1700 shp Air Tractor AT-802/802A/802AF/802F
PT6A-68 1324 eshp 1250 shp T-6A Texan II
Pilatus PC-21 (-68B)
Embraer EMB-314 Super Tucano (-68C)
United States military designation for the PT6A-20/27, used in the Beechcraft U-21 Ute.
United States military designation for the T101-CP-100 / PT6A-45R, used in the Shorts 330 and Shorts C-23 Sherpa.
United States military designation for the T101-CP-100 / PT6A-45R, used in the Shorts 330 and Shorts C-23 Sherpa.


The PT6B-9 is a 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).


The PT6C is a 1600 to 2300 horsepower (1190 to 1720 kW) engine for helicopters and tiltrotors.


The PT6D-114A is 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.[25]
Soloy Dual Pac
2x PT6D-114A engines driving a single propeller through a combining gearbox, capable of independent operation.


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


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.
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.[26]


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.[27][28]








Engines on display

Cutaway of a PT6 engine, McGill University

Specifications (PT6A-6)

Data from Jane's 62-63,[30] helicopter annual 2009[31]

General characteristics



Name Width Height Length weight maximum continuous fuel consumption
PT6A-11AG 483 mm 483 mm 1.58 m 740 hp (552 kW)
PT6A-50 483 mm 483 mm 1.73 m 425 lb (193 kg) 945 hp (705 kW) 0.580 lb/hp/h (353 g/kW/h)
PT6A-68C 483 mm 483 mm 1.83 m 1576 hp (1175 kW)
PT6B-36A 495 mm 495 mm 1.50 m 384 lb (174 kg) 981 hp (732 kW) 887 hp (661 kW) 0.581 lb/hp/h (353 g/kW/h)
PT6B-37A 495 mm 894 mm 1.63 m 385 lb (175 kg) 1002 hp (747 kW) 872 hp (650 kW) 0.593 lb/hp/h (361 g/kW/h)
PT6C-67A 525 mm 525 mm 1.67 m 418 lb (190 kg) 1940 hp (1447 kW) 1675 hp (1249 kW)
PT6C-67B 584 mm 584 mm 1.50 m 447 lb (203 kg) 1200 hp (895 kW)
PT6C-67C 571 mm 571 mm 1.50 m 415 lb (188 kg) 1679 hp (1252 kW) 1531 hp (1142 kW) 0.507 lb/hp/h (308 g/kW/h)
PT6C-67D 571 mm 571 mm 1.50 m 446 lb (202 kg) 1692 hp (1262 kW) 1585 hp (1182 kW) 0.507 lb/hp/h (308 g/kW/h)
PT6C-67E 584 mm 584 mm 1.52 m 1775 hp (1324 kW) 0.602 lb/hp/h (366 g/kW/h)
PT6T-3B 1105 mm 825 mm 1.67 m 660 lb (300 kg) 1800 hp (1342 kW) 1600 hp (1193 kW) 0.600 lb/hp/h (365 g/kW/h)
PT6T-6B 1105 mm 825 mm 1.67 m 673 lb (305 kg) 1970 hp (1469 kW) 1745 hp (1301 kW) 0.591 lb/hp/h (359 g/kW/h)

See also

Related development
Comparable engines
Related lists


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