Rotating airfoil is attached to a jet engine through what?

• A. turbo shaft
• B. nozzle
• C. reduction gear assembly
• D. fan blade

Answer: (C)

The important idea is how to drive a rotating external airfoil, like a propeller, from a jet engine. The engine core runs at very high speeds, but a propeller needs to turn much more slowly to be efficient and to avoid excessive tip speeds. A reduction gear assembly sits between the engine and the rotating airfoil and lowers the rotational speed while increasing torque. This gear train lets the turbine or engine shaft deliver power to the propeller at a practical RPM.

In other words, the gearbox converts high-speed, low-torque output from the engine into lower-speed, higher-torque output suitable for the propeller. The other parts mentioned—nozzle governs exhaust flow, the turbo shaft is the shaft itself, and the fan blade is part of the engine’s internal rotating assembly—do not provide the necessary speed reduction mechanism to drive an external rotating airfoil.