flight control system for helicopter with coaxial rotors

摘要

A helicopter having coaxial counterrotating rotors is provided with a reversible yaw control system which is required due to airflow reversal through the rotors in autorotation. The system includes a sensing means responsive to engine torque and to the position of the collective pitch control stick for operating a reversing device disposed between a foot pedal operated input link and a differential collective pitch control output link. The reversing device comprises a slotted link pivotally mounted at its midpoint and pivotally connected at one end to said input link by a pin slidable in the slot and pivotally connected at its opposite end to the output link. An actuator for said input link moves said slidable pin into the extreme ends of the slot on one side or the other of the midpivot point for the slotted link to reverse the direction of movement of the output link and thus reverse the collective pitch of the two rotors. The actuator, comprising cooperating cylinder and piston elements, includes a mechanical locking device for locking the actuator in its normal flight position. The actuator is hydraulically controlled by said sensing means.