In a free turbine engine, what percentage of the total thrust is typically extracted by the gas generator turbine?

In a free turbine engine, the gas generator is primarily responsible for converting fuel into energy, which is then directed to the power turbine. The unique design of a free turbine engine allows the gas generator turbine to operate independently of the power turbine, which is responsible for generating the thrust that propels the aircraft.

Typically, the gas generator turbine only extracts a small portion of the total thrust, as its main role is to provide the necessary power for the compressor and other accessory components rather than directly contributing to thrust. The range of 5-20% is consistent with the functioning of many free turbine engines, where the power turbine does most of the work in generating thrust.

In this context, higher percentages would imply greater contributions from the gas generator, which is not characteristic of free turbine designs, as they are structured to maximize thrust generation from the power turbine while minimizing the demand on the gas generator.