Which engine module reduces the power turbine RPM and transfers power forward to the power output flange?

• A. Accessory gearbox
• B. Reduction gearbox
• C. Turbine governor
• D. Fuel control unit

Answer: (B)

The main idea is that turbine engines spin far too fast for their output shaft, so a reduction mechanism is used to make the speed usable. The reduction gearbox takes the high-speed rotation of the power turbine and steps it down to a slower, appropriate RPM, transmitting the resulting power to the power output flange where the shaft connects to the rest of the drivetrain or rotor. This gear reduction keeps the torque at a workable level while protecting the engine and connected components from overspeed.

The accessory gearbox is meant to drive auxiliary parts like pumps and generators, not to provide the main power to the output shaft. The turbine governor and fuel control unit regulate speed and fuel delivery, respectively, rather than transferring mechanical power to the output flange.