GB698031A - Improvements in or relating to apparatus for controlling a helicopter in azimuth - Google Patents

Abstract

698,031. Automatic control systems. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Nov. 12, 1948 [Nov. 14, 1947], No. 29404/48. Class 38 (iv). [Also in Group XX] Apparatus for the azimuth control of a helicopter having a steering propeller comprises a gyro responsive to the velocity of the helicopter about its turn axis for controlling pitch changing mechanism of the steering propeller and means for controlling the response of the gyro to the turn velocity. In Fig. 4 a lifting rotor LR of a helicopter and a reversible-pitch steering propeller SP, mounted aft with axis athwartships to prevent rotation of the fuselage, are each driven through a transmission 24 from an engine E, the lifting rotor being driven through a free-wheeling unit 24a. Pitch of the lifting rotor is under the control of two handles 27, 28 associated with a pitch control unit. Handle 27 also controls the engine throttle and ensures a lifting rotor pitch suited to the throttle opening. Handle 28 may be moved from a central position in the direction in which it is desired to travel to produce a cyclic variation of blade angle, during revolution of the lifting rotor, from a maximum at one point to a minimum at a point 180 degrees therefrom so that the rotor thrust has a horizontal component producing travel in the desired direction. Turn of the craft in azimuth is prevented by a rate-of-turn gyro (see Group XX), responsive to angular velocity and acceleration about a vertical axis, precession of which controls the position of a pair of contacts C1, C2 relative to a contact C3, vibrated by slight unbalance of the gyro rotor, to control the relative energization of opposed fields DF1, DF2 of a D.C. generator GEN so that a motor M supplied from the generator effects the appropriate adjustment of steering propeller pitch. The orientation of the craft in azimuth and hence its direction of travel may be set by operating pedals 29 to move the slider of a potentiometer P from its normally central position until the torque applied to the gyro by the differential adjustment of the energization of electromagnets P1, P2 establishes a new datum position. In a modification, Fig. 5 (not shown), gyro contacts C1 C3 only are used to control the energization of a spring-biased solenoid-operated valve of a hydraulic system controlling steering propeller pitch. In this arrangement to reduce the duty on the contacts the energization of a further winding of the solenoid-operated valve is made dependent on the throttle setting.