Patent GB-656779-A (GB)
Title: Improvements in or relating to automatic control systems for aircraft
IPC: G05D1/00
Filed: 1947-09-12
Abstract: 656,779. Automatic control systems for aircraft. SPERRY GYROSCOPE CO., Inc. Sept. 12, 1947, No. 25056. Convention date, Sept. 14, 1946. [Class 38 (iv)] [Also in Group XXXVII] An automatic pilot controlling heading, attitude, and altitude of an aircraft, in which servomotors drive the control surfaces through clutches, has the clutch selectors and manual manoeuvring controls interlocked with a master switch to prevent incorrect operation. The output of a Selsyn 90, Fig. 5, attached to one frame of a gyro 85 is connected via an integrator 96 to a phase detector 95, wherein the phase of the signal voltage is compared with that of the supply voltage. The output of the phase detector is fed through a rate network 97 and a phase sensitive amplifier 98 to the splitfield winding of a generator 100 supplying servomotor 102 which operates the aileron control cables 107 through gearing and a clutch 105. Generator 100 is one of three coupled to motor 101 to supply each of the three servomotors. A follow-up signal obtained from a Selsyn 110 is fed back to the amplifier 98. An A.C. voltage tapped off potentiometer 72 is added to the automatic signal for manual control. The gyro 85 by a circuit 123, similar to that above, also controls a servomotor 126 operating the elevator control cables 130 through a clutch 128. Manual control is effected by a signal from a potentiometer 38, and a pick-off device 169 is energized when an altitude control, Fig. 7 (not shown), is switched in. A rudder servo, driving through a clutch, is similarly controlled by a directional gyro. Manual control is effected by a signal from a potentiometer added to the automatic signal. Power for the three servo systems is supplied by relays 196, 197, Fig. 3, energized by a master switch 10, which (see Group XXXVII), has an electromagnetic latch 11 supplied through contacts E, A, R, on the three clutch-engaging levers, Fig. 6 (not shown), and with contacts 67 on the manual turn control, Fig. 1 (not shown). Thus the latch is only energized to allow the master switch to be closed and hence the servos can only be energized when the contacts are in the position shown, i.e. the clutches are disengaged and the turn control is centralized. The servos then automatically align themselves with the control surfaces and the clutches may be engaged without disturbing the position of the aircraft. Closing the master switch 10 closes contacts 191, 192 which short-circuit the clutch switches and maintain the latch 11 energized when the clutches are engaged. If, however, the manual turn control is moved, opening contacts 67, when either the rudder or elevator clutch is not engaged, the master switch is tripped. Engaging the rudder clutch energizes relays 206 and 210 which connect the manual turn control potentiometer into the rudder circuit, and provide dynamic braking for a turn controller. Movement of the manual turn control changes over contact 68, releasing the brake and energizing relay 211 which disconnects erecting and levelling circuits from the gyro 85 during the turn. Engaging the elevator clutch energizes the latching electromagnet 76 of an altitude control switch of similar construction to the master switch. If the automatic altitude control is off, a magnetic clutch 57 is energized coupling the manual elevator control to the potentiometer 38, otherwise contact 217 energizes the automatic altitude control clutch 165.