What is the primary function of a reduction gear in a gas turbine propulsion system?

The primary function of a reduction gear in a gas turbine propulsion system is to reduce the rotational speed to meet propeller requirements. In gas turbine engines, the turbine operates at very high rotational speeds, often exceeding the optimal speed range for propellers.

The reduction gear allows the high-speed rotation of the turbine to be converted into a lower, more manageable speed that is suitable for the propeller or other components of the propulsion system. This reduction is crucial because propellers are designed to operate efficiently at specific speeds, and if they were directly connected to the gas turbine, they would not perform optimally.

By implementing a reduction gear, the system ensures that the propeller receives the correct rotational speed, enabling better thrust efficiency and overall performance of the aircraft. Without a reduction gear, the mismatch in speed would lead to excessive wear on the propeller and would not harness the full potential of the gas turbine's power output.

The other options do not accurately describe the role of the reduction gear in this context, focusing instead on functions that are either not applicable or are secondary to the main purpose of adapting rotational speeds.