The Pratt & Whitney Canada PW100 aircraft engine family is a series of turboprops manufactured by Pratt & Whitney Canada. Pratt & Whitney Canada dominates the turboprops market with 89% of the turboprop regional airliner installed base in 2016, leading GE Aviation and Allison Engine Company. Development The engine was first introduced as a technology demonstrator in 1977. The PW100 was first tested in March 1981, made its initial flight in February 1982 on a Vickers Viscount testbed aircraft, and then entered service in December 1984 on a Dash 8 regional aircraft for NorOntair. The PW150 engine was introduced on 24 April 1995, when Bombardier selected the engine for the launch of its de Havilland Dash 8-400 regional turboprop. The PW150 was a higher-power version of the PW100 series, with the low-pressure compressor changed from a single-stage centrifugal compressor to a three-stage axial compressor, and the turbine modified to have improved cooling. The power rating was increased from in the PW127 to in the PW150, although the engine was thermodynamically capable of . At the 2021 Dubai Air Show, Pratt & Whitney Canada introduced the PW127XT (extended-time-on-wing) series. The PW127XT, which is intended to replace the PW127M variant, reduces the number of engine overhauls within 10 years to two from three. The engine maintenance interval (time-on-wing) is increased from 14,000 hours to 20,000 hours and would use three percent less fuel than the PW127M. The engine series will premiere as the standard powerplant on all new ATR 42 and ATR 72 aircraft, with a launch order from Air Corsica using the PW127XT-M engine model. The PW127XT-N variant, which is designed for the ATR 72-600, has the same mechanical power rating as the PW127XT-M but has a higher thermodynamic power rating. Design Originally called the PT7, the PW100 uses a relatively unusual three-shaft engine configuration. In the PW100, a centrifugal low-pressure (LP) impeller (except for the PW150, which uses a 3-stage axial LP compressor), driven by a single-stage LP turbine, supercharges a contra-rotating centrifugal high-pressure (HP) impeller, driven by a single-stage HP turbine. Power is delivered to the offset propeller reduction gearbox through a third shaft, connected to a two-stage free (power) turbine. The gearbox has two stages, yielding a reduction ratio between 15.4 and 17.16. The first stage uses double helical gears, followed by a second stage with straight spur gears. Variants The last two digits of each variant model