Patent GB-790272-A (GB)
Title: Automatic control systems for aircraft
Inventor: TRIBKEN EVERETT R
IPC: G05D1/04
Filed: 1956-02-13
Abstract: 790,272. Automatic steering control systems. SPERRY RAND CORPORATION. Feb. 13, 1956, No. 4471/56. Class 38 (4). In an aircraft autopilot, heading is automatically stabilized by one servosystem, bank angle is automatically stabilized by a second servo-system, and, during a turn, a control signal is injected to select an appropriate angle of bank, the heading being continuously modified automatically in dependence on the control signal, the apparent gravity angle and the heading error. In Fig. 2 heading deviations of an aircraft are detected by a magneticallyslaved directional gyro 14, electrical signals from the inductive pick-off 13 of which are applied through a selsyn 12 to control a follow-up type servomechanism 9 operating a rudder 8 to correct the heading. Similarly, deviations from a selected bank angle are detected by a gyro vertical 7, electrical signals from the inductive pick-off 6 of which are applied through a selsyn 5 to control a servo-mechanism 2 operating ailerons 1 to correct the bank angle. The ailerons may be trimmed by manual operation of a potentiometer 42, the output of which applies a further signal to servo-mechanism 2. Turn of the aircraft is initiated by manual operation of a knob 15 of a potentiometer 16, the output of which is applied through an amplifier 19 to run an electric motor 20, the speed and final position of which corresponds to the position of knob 15 by virtue of feedback from a tachometer generator 21 and an inductive device 22. Motor 20 positions selsyn 5 so that the aircraft is banked at an angle corresponding to the position of knob 15. The signal from inductive device 22, dependent on the sense and magnitude of bank, is also applied through a variable inductive device 27 and an amplifier 29 to run an electric motor 30 in a corresponding direction and at a corresponding speed by virtue of feedback from a tachometer generator 31. Motor 30 continuously adjusts selsyn 12 so that the rudder is moved at a rate designed to suit the angle of bank. Feedback of the heading signal from selsyn 12 to the input of amplifier 29 reduces the possibility of sideslip. Such side-slip is, however, detected by a pendulum 34, pivoted about the fore and aft axis near the centre of gravity of the aircraft. Electric signals derived from an inductive pickoff 36 associated with the pendulum are applied through an amplifier 38 to run an electric motor 39 adjusting inductive device 27 and hence the amount of rudder deflection to reduce sideslip. Compensation of the side-slip detector for variations of rudder angle and aileron trim is obtained by applying signals from selsyn 12 and potentiometer 42 to amplifier 38 through transformers 58 and 57 respectively. To ensure that the sense of adjustment of motor 39 is correct for aircraft turns in either sense a switch 65 operated by motor 20 controls a relay 63 to change over a switch 45 reversing the input to amplifier 38. To compensate for the characteristics of an aircraft which cause it to turn more or less than it should initially, a signal from tachometer generator 21 corresponding to rate of roll is also applied to amplifier 29 in the appropriate sense. After a turn has been made, manual centring of knob 15 closes a switch 68 to energize a relay 69 after a delay determined by a thermal unit 71. A function of this relay is to rearrange amplifier 38 so that motor 39 is driven to a suitable intermediate position in readiness for future use. When a manual switch 88 is operated to disengage the rudder and ailerons from the system by controlling electromagnetically-operated clutches 47 and 89, a relay 90 is operated to rearrange amplifiers 19 and 29 so that selsyns 5 and 12 are driven into correspondence with their respective gyros so that no error signals exist upon reengagement of the control system.