A turboshaft engine's a form of gas turbine which's optimized to produce shaft power, rather than jet thrust. In principle, a turboshaft engine's similar to a turbojet, except the former features additional turbine expansion to extract heat energy from the exhaust and convert it into output shaft power. Turboshaft engines are commonly used in applications which require a sustained high power output, high reliability, small size and light weight. These include helicopters, auxiliary power units… (More on Turboshaft)