Definition
A turbine stage in a turboshaft or turboprop engine that is mechanically independent of the gas generator turbine and exists solely to extract energy from the hot exhaust gases to drive an output shaft, which in turn powers a propeller, rotor, or other load through a reduction gearbox.
Plain English
A second, separate turbine wheel placed in the exhaust stream whose only job is to spin the shaft that drives the propeller or helicopter rotor. It is not connected to the compressor; it just catches the leftover energy in the hot gases and turns it into useful shaft power.
Context Anchor
Seen in turbine-engine discussions, especially turboprop and turboshaft engine descriptions.
Derivation
Called a 'power' turbine because, unlike the turbine that drives the compressor (which uses energy just to keep the engine running), this turbine's entire output is delivered as usable power to the aircraft.
Why Pilots Care
It allows the engine to deliver usable power to the propeller without mechanically linking the propeller load to the compressor, improving efficiency and reducing compressor stall risk.
Grounding Statement
Hot gas flows through the power turbine, spins it, and that spinning is used to turn the aircraft’s propeller or other driven part.
Intuition Check
Power turbine does not mean the whole engine or the throttle control. It means a specific spinning turbine section that turns gas energy into useful shaft power.
Example Sentence 1
In a free-turbine turboprop, the power turbine spins the propeller through a reduction gearbox while the gas generator runs at its own speed.
Example Sentence 2
In the PT6 engine, exhaust gases pass through the power turbine before exiting the tailpipe.