What is the primary function of the tail rotor on a helicopter?

The primary function of the tail rotor on a helicopter is to control torque. When the main rotor spins, it generates torque that tends to cause the helicopter body to rotate in the opposite direction. The tail rotor counteracts this rotational motion by exerting a force that stabilizes the aircraft and maintains heading. By varying the pitch of the tail rotor blades, the pilot can effectively control the amount of torque compensation, allowing for smooth and controlled flight.

This function is critical for a helicopter's stability and maneuverability, as unopposed torque would create uncontrollable yaw. The coordination of the main rotor and tail rotor is essential for safe operation, especially during takeoffs, landings, and hovering where torque effects are most pronounced.