Definition
A turbine engine in which most of the power produced by the expanding gases is used to drive a shaft rather than to produce thrust through the exhaust. The shaft typically drives a rotor system in a helicopter, a propeller through a reduction gearbox, or another mechanical load such as an auxiliary power unit.
Plain English
A jet-style engine that, instead of pushing the aircraft along with exhaust, uses its turbines to spin a shaft. That shaft then turns something useful — most often a helicopter rotor.
Context Anchor
Seen in turbine engine discussions, especially when comparing helicopter engines with turbojet, turbofan, and turboprop engines.
Derivation
‘Turbo’ comes from the Latin turbo, meaning a spinning or whirling thing — the same root behind ‘turbine.’ ‘Shaft’ is the rotating rod that carries the power out of the engine. So the name simply describes what the engine does: a turbine that delivers its power through a shaft.
Why Pilots Care
Turboshaft engines supply the high torque at moderate RPM needed to turn helicopter rotors efficiently, making vertical flight practical with good power-to-weight performance.
Intuition Check
Do not read “turboshaft” as “a turbocharger on a shaft.” Here it means a complete turbine engine whose main job is to turn an output shaft.
Example Sentence 1
The helicopter is powered by a single turboshaft engine driving the main and tail rotors through a reduction gearbox.
Example Sentence 2
During preflight, the pilot checks the turboshaft oil level and N1 and N2 gauges before starting.