For a free power turbine engine

A、the gas generator is free to run at a constant speed while the power turbine changes speed in response to changes in drag on the main rotor blades.
B、the compressor driving the main transmission is mechanically independent from the power turbine.
C、pilot control of the engine is limited to the selection of OFF, GROUND IDLE and FLIGHT, leaving the engine to automatically respond to rotor demands.
D、the turbine driving the main rotor transmission is mechanically independent from the gas generator.