Which component connects the engines to the transmission system, driving the main and tail rotor systems?

• A. Free-wheeling unit
• B. Driveshaft sections
• C. Tail gearbox
• D. Main gearbox/Main Transmission

Answer: (B)

Power from the engines must reach the rotor drives through a path that starts with a shaft network. The driveshaft sections are the components that physically connect the engine output to the transmission system, transmitting torque to the input of the main gearbox so the rotor system can be driven. These shafts are designed in sections to accommodate engine location and helicopter movement while keeping power flow continuous. Once the engine torque is on the main gearbox, the gears reduce speed and distribute power to the main rotor, with a separate drive path from the transmission to the tail rotor via the tail gearbox and its drive shaft. The free-wheeling unit is a one-way clutch that disconnects the engine from the rotor during autorotation or engine failure, not the normal connection. The tail gearbox drives the tail rotor, and the main gearbox is the reduction/transmission for the main rotor; the driveshaft sections specifically provide the link from engine to that transmission system.