What is the function of the reduction gearbox?

The function of the reduction gearbox is to reduce the rotational speed of the power turbine output shaft and adjust it to the appropriate level for driving the propeller. In a turboprop engine like the one in the T-6B, the power turbine operates at high speeds, which are not suitable for directly turning the propeller. The reduction gearbox plays a crucial role by decreasing this speed to a level that allows the propeller to operate efficiently and produce thrust.

This mechanism ensures optimal propeller performance and contributes to overall aircraft performance, as the propeller needs to turn at a rate that maximizes thrust while still being manageable given the engine’s high-speed operation.