Which component carries engine torque to the main and tail rotor?

• A. Transmission and drive system
• B. Free-wheeling unit
• C. Driveshaft sections
• D. Accessory Gearboxes/Drives

Answer: (A)

Engine torque to the rotors is carried by the transmission and drive system. The engine’s output goes into the helicopter’s transmission, which reduces speed and increases torque as needed and then routes power to both rotors. The main rotor gets drive through the main drive shaft and its gear train inside the main gearbox, while the tail rotor gets power via a tail rotor drive shaft connected to the transmission and, if equipped, a tail gear box. The driveshaft sections are part of this path, forming the route from the transmission to the rotors. The free-wheeling unit sits between the engine and rotor system to allow autorotation by disengaging the engine from the rotor when power is not being applied, but it does not carry torque to the rotors in normal flight. Accessory gearboxes/drives power non-rotor systems (like generators and hydraulic pumps) and do not transmit rotor torque.