The Pratt & Whitney Canada PT6 is a family of gas-turbine aircraft engines best known through the PT6A turboprop. The wider lineage also includes helicopter turboshaft engines. Pratt & Whitney Canada delivered the first production PT6A-6 in December 1963 to Beech Aircraft for the Beech 87, a precursor of the King Air.[1]The Legend Tells Its StoryPratt & Whitney · rtx.com · Accessed 2026-09-13Open source details
Architecture
The PT6A separates its gas generator from an independent power turbine. The compressor turbine drives the compressor, while the power turbine delivers mechanical power to the propeller through a reduction gearbox. Because the power turbine is not mechanically fixed to the compressor shaft, this arrangement is commonly described as a free-turbine design.[2]PT6A EnginePratt & Whitney · prattwhitney.com · Accessed 2026-09-13Open source details
The engine uses a reverse-flow layout, with the inlet toward the rear and the turbine section toward the front in the usual installation. Its compressor combines axial stages with a centrifugal stage. The arrangement supports a compact powerplant and makes the turbine section accessible for maintenance in many aircraft installations.[2]PT6A EnginePratt & Whitney · prattwhitney.com · Accessed 2026-09-13Open source details
Growth and applications
The first production engine established a design that could grow into more capable models. In 1973, the PT6A-41 introduced a second-stage power turbine, increasing power and efficiency. Other applications followed: an Air Tractor agricultural aircraft used PT6A power in 1979, and Cessna selected the PT6A-114A for its new Caravan in 1982.[1]The Legend Tells Its StoryPratt & Whitney · rtx.com · Accessed 2026-09-13Open source details
The PT6T Twin-Pac entered service in 1970. It couples two engine power sections into one package for helicopters, including the Bell 212 and its military UH-1N derivative. This rotary-wing application delivers power to a rotor transmission, while the PT6A turboprop supplies a propeller; both belong to the broader PT6 lineage.[1]The Legend Tells Its StoryPratt & Whitney · rtx.com · Accessed 2026-09-13Open source details
Power and installation
Pratt & Whitney groups PT6A models into small, medium and large series, with the overall range extending from roughly 500 to 1,900 shaft horsepower. These are product-family classes, not one engine's operating range. The manufacturer's tables also distinguish mechanical shaft power from equivalent shaft horsepower, the latter including an allowance for exhaust thrust.[2]PT6A EnginePratt & Whitney · prattwhitney.com · Accessed 2026-09-13Open source details
Electronic development
The PT6 E-Series brought a dual-channel integrated electronic engine and propeller control system into the lineage. Pratt & Whitney describes this as simplifying operation while adding data-management capabilities. The development combines control of the engine and propeller, extending the established mechanical architecture with electronic coordination and information for operators.[3]RTX's Pratt & Whitney Canada marks 60 years of the purpose driven PT6 engine familyPratt & Whitney · rtx.com · Accessed 2026-09-13Open source details