Helicopter Yaw Control: Review of Royal Aeronautical Society Conference

TORQUE reaction, control and yaw stabilisation are three essential requirements for helicopters and the means by which these are satisfied has been the subject of considerable development over the years. A conference on this area of activity was held recently at the Royal Aeronautical Society when the various solutions were considered, ranging from conventional tail rotors to bearingless rotors, ring fin, fenestron and recent NOTAR advances. An overview of conventional tail rotors by Westland Helicopters outlined the three tasks to be performed. The torque from the main rotor is reacted back through the transmission and into the aircraft structure and a force in the yawing direction is produced, in the most common configuration, by a small horizontal axis rotor outside the main rotor disc at the rear of the helicopter. The yaw movement arm is large and thus the torque reaction force required is small.