Which of the following is one of the three major categories of Unanticipated Yaw?

• A. Tail Rotor Noise Increase
• B. Main Rotor Thrust Loss
• C. Tail Rotor Drag Increase
• D. Loss of Tail Rotor Authority

Answer: (D)

Unanticipated yaw happens when the helicopter’s anti-torque system can no longer produce the expected yaw control, so the aircraft yaws in an uncommanded way. There are three major ways this can occur: loss of tail rotor authority, tail rotor drag increase, and loss of main rotor thrust. Loss of tail rotor authority is the direct anti-torque failure: if the tail rotor can’t produce the needed thrust to counter the main rotor torque, heading control is effectively lost and yaw can occur without the pilot’s intended input. The other two are real mechanisms that can drive yaw as well—tail rotor drag increase changes the tail rotor from thrust to drag, and loss of main rotor thrust changes the torque load the tail rotor must counter—but the clear, fundamental anti-torque failure is the loss of tail rotor authority, which is why this option is the best answer. Tail rotor noise increase is not itself one of the major yaw categories.