Allison Model 250
The Model 250 powers a large number of helicopters, small aircraft and even a motorcycle (MTT Turbine Superbike).The combustion products expand axially forward through the two-stage (single-stage on early engines) high-pressure turbine section, which is connected to the compressor via the HP shaft.The combustion products continue to expand through the two-stage power turbine which generates shaft horsepower for the aircraft.An important design feature of the Model 250 engine is its modular construction which greatly simplifies maintenance and repair activity.One of the latest versions of the Model 250 is the -C40, which has only a centrifugal compressor producing a pressure ratio of 9.2:1, at an airflow of 6.1 lb/s (2.8 kg/s), and develops, at the shaft, 715 hp (533 kW).