What is the function of the Transmission Shaft?

• A. To support the engine in the frame.
• B. Transmits the Power of the turbine to the main transmission.
• C. Controls N1 speed.
• D. Links to rotor head.

Answer: (B)

The transmission shaft's main job is to transfer the turbine's mechanical power to the main transmission. It serves as the drive link in the drivetrain, taking the high-speed output from the turbine and delivering it to the reduction gearbox so the rotor can be driven at the correct speed and torque. This shaft must handle high torque, bending moments, and maintain proper alignment, with bearings and seals supporting it. It does not support the engine in the frame (that’s done by engine mounts), it doesn’t control N1 speed (that’s managed by fuel control and limiter systems), and while it ultimately works through the drivetrain to reach the rotor, it doesn’t directly connect to the rotor head.