Patent GB-829739-A (GB)
Title: Aircraft control systems
IPC: G05D1/06
Filed: 1957-02-15
Abstract: 829,739. Automatic control systems for aircraft. SPERRY RAND CORPORATION. Feb. 15, 1957 [March 15, 1956], No. 5235/57. Class 38 (4). In an aircraft elevator servo-system the elevator servomotor is controlled by signals dependent on (a) deviation of pitch from a reference value, (b) the integral of signals produced by adjustment of a manual controller, and (c) deviation of altitude from a value which is continuously adjusted at a rate dependent on integral (b). In Fig. 1, by operating knob 30 of a ganged switch 29 to the appropriate position an aircraft control system may be arranged to maintain one of the following flight conditions constant:- (a) Pitch attitude.-In position 5 of switch 29 deviations of pitch attitude from a desired value are automatically corrected by signals from the pitch pick-off of a gyro-vertical 83 which are applied to a servo-system 50 controlling elevators 52. The desired pitch attitude is set by temporarily applying force to a manual control column 100 to produce corresponding signals from a signal generator 99 which are modified in dependence on Mach number by a computer 41 and applied to an amplifier 88 of an integrating type motor 90 operating a signal generator to apply datum shifting signals to elevator servo-system 50. The signals dependent on Mach number required for computer 41 are obtained from pick-offs 11, 73 associated with bellows 6, 62 responsive to static and dynamic pressures respectively. The signals from pick-offs 11, 73, respectively control motors 10, 56 which apply restoring forces to the bellows through gearing 18, 66 and, by virtue of logarithmic cams 22, 68, take up positions representative of the logarithms of the static and dynamic pressures, the difference between which is representative of Mach number. When it is desired to operate the elevators mechanically by means of control column 100 a switch 97 is moved from the position shown to disconnect automatic control and control motor 90 so that the signals from generator 87 continuously cancel the signals from the gyro vertical in readiness for reversion to automatic control. (b) Altitude.-In position 2 of switch 29 deviations of altitude from a desired value are automatically corrected by static pressure signals from pick-off 11 which are applied both directly and through integrator 90 to elevator servo-system 50. Stabilizing signals are also applied to integrator 90 from an accelerometer 94<SP>1</SP> responsive to acceleration normal to the longitudinal axis of the aircraft in this and the following methods of control. (c) Rate of climb.-In position 1 of switch 29 an increasing force is applied through gearing 18 to static pressure bellows 6 by motor 10 to produce a climb. The speed of motor 10, which is controlled by a tachometer generator 17 is determined by the setting of a potentiometer 36 the position of which is controlled through a motor 37 by signals produced by control column 100. Force is therefore manually applied to control column until the desired rate of climb is attained. (d) Airspeed.-In position 4 of switch 29 devitions of airspeed from a desired value are automatically corrected by signals from pick-off 73 of dynamic pressure bellows 62 which are applied both directly and through integrator 90 to elevator servo-system 50. Airspeed is set by moving a switch 75<SP>1</SP> to its other position and operating knob 82 of a signal generator 81 to cause motor 56 to apply force to bellows 62. (e) Mach number.-In position 3 of switch 29 movements of motor 10 with changes in altitude produce, through selsyns 32, 33, signals which cause motor 56 to apply force to bellows 62 so that airspeed is modified in dependence on altitude to maintain constant Mach number. Gearing 18, 66 is electrically controlled to increase the reduction ratios for this method of control. The desired Mach number is set by operating knob 82 with switch 75<SP>1</SP> in its other position in a manner similar to that for setting airspeed. Specifications 612,804 and 829,740 are referred to.