Patent GB-806083-A (GB)
Title: Automatic control systems for aircraft
IPC: G05D1/08
Filed: 1956-10-12
Abstract: 806,083. Automatic steering-control systems. SPERRY BAND CORPORATION. Oct. 12, 1956 [Oct. 20, 1955], No. 31158/56. Class 38 (4). [Also in Group XXXVIII] An automatic control system for aircraft derives signals from an azimuth gyro 5, a vertical gyro 18, a magnetic compass 15 and setting controls for heading and pitch 20, 40. The shaft 22 is controlled from the heading setting 20 via the synchros 21, 21<SP>1</SP>, limiter, amplifier 23 and follow-up motor 24. The differential synchro 25 compares the position of this shaft with the reading of the flux-valve compass 15 and passes the difference signal to the gyro synchro 26, which is fixed to the gimbal ring 12 (and thus to the frame of the aircraft) in such a way that the windings are at 90 degrees to those of the flux valve 15. The gyro and magnetic compass thus mutually correct one another in respect of slow drift of the gyro and sudden changes of heading, and the rotor of synchro 26 then receives a signal dependent in amplitude and sense on the difference between the actual heading and the desired heading. This signal is passed to the heading torque 14 to cause precession of the y axis (normally athwartships) to bring it into agreement with the reference provided by the flux valve. At the same time the generator 19 produces a signal for the resolver 27 and the usual servo system to control the rudder; a cross-control is provided for the elevator for the reasons described-in Specification 621,121. The other gyro 18 is maintained vertical by the gravity-responsive devices 55 which act on torquers 57, 58 and provide signals corresponding to the pitch and roll attitudes of the aircraft from the generators 42, 17 respectively. The former is energized from the pitch setting control 40 and transmits a signal via the resolver 43 to the rudder and elevators when the aircraft is desired to climb or descend. No pitch resolver is required as the signal from the synchro 26 is a measure of the heading error times the cosine of the pitch angle, this being the required signal for direct control of the rudder. The roll generator 17 is coulped with the synchro 36 on the gyro 5 and any difference in position between the two causes the torquer 16 to precess about the x axis (fore-and-aft) until the signal is zero. Thus the spin axis of the gyro 5 is maintained horizontal and the heading error signal will be unaffected by rolling and pitching. A further signal is obtained from the heading setting 20 via the synchros 28, 30, 31 and associated limiter, amplifier 29 and motor 33, whereby the shaft 32 is rotated. The position of this shaft, in association with the signal from the roll generator 17, causes the synchro 34 to provide a signal for operating the ailerons to ensure a correct angle of bank when turning. A mechanical stop 50 and slip-clutch 51 prevent this angle from exceeding a predetermined value, and within these limits the angle will be proportional to the heading error. Pitching of the aircraft while banking will be corrected by a signal passed from synchro 34 to synchro 36, which actuates the torquer 16 and maintains the plane of the gimbal ring vertical. If the turn is unco-ordinated, the rotation of the shaft 22 and of the magnetic vector produced by the flux-valve will not keep in step; sideways slipping is sensed by the accelertometer 35 which provides a signal for the motor 24 to turn the shaft 22 appropriately. The differential synchro 25 will then give an output signal to operate the rudder via synchros 26 and 19. As the new heading is approached the heading and bank angle signals will gradually be reduced in amplitude and the aircraft will finally proceed on its new course in level and steady flight. The shaft 22 may carry a pointer and compass card to show the actual heading of the craft, and a similar dial may be fitted to the control 20 to facilitate setting.