Torque, in a helicopter context, can refer to the tendency of the helicopter to yaw opposite the rotation of the main rotor, a concept captured by which term?

• A. Thrust Line
• B. Torquemeter
• C. Torque
• D. Thrust

Answer: (C)

When the engine turns the main rotor, it applies a torque to the rotor mast. By Newton’s third law, the helicopter fuselage experiences an opposite torque, causing the helicopter to yaw in the direction opposite the rotor’s rotation. This yaw tendency is described by the term torque (often called torque reaction). In other words, the rotor’s torque creates a reactive effect on the airframe that the helicopter must counteract with anti-torque control.

Other terms describe different things: thrust line refers to where the lifting force acts, a torquemeter is a device that measures torque, and thrust is the lifting force itself. So the concept that captures the yaw tendency is torque.