The force causing the fuselage to rotate opposite the rotor is:

• A. Drag
• B. Torque
• C. Lift
• D. Thrust

Answer: (B)

This question is about reaction torque. When the engine applies torque to turn the rotor, the rotor, in turn, exerts an equal and opposite torque on the fuselage. That opposite torque tends to spin the fuselage in the direction opposite to the rotor’s rotation unless something counters it. This is why helicopters have anti-torque measures like a tail rotor to balance the yaw.

Drag refers to resistance on the rotor blades and is part of energy losses, not the direct cause of the fuselage’s opposite rotation. Lift is the vertical force produced by the rotor that supports weight, not the yaw tendency. Thrust is the axial force the rotor produces to move the aircraft forward, not the yaw reaction.