UH60 Crew Chief Practice Test

The key idea is that the tail rotor provides anti-torque yaw control, and hydraulic power is what makes pedal inputs translate into precise tail rotor blade pitch changes. If the tail rotor hydraulic system fails, you lose that authority over tail rotor thrust. The main rotor torque is still acting on the helicopter, so without hydraulic control you can’t reliably counteract it, leading to yaw that is uncommanded or directional control is lost. The aircraft may begin to yaw unpredictably rather than responding predictably to pedals. The other options imply perfect control, stability with no effect, or elimination of yaw, which isn’t consistent with losing tail rotor authority.