Patent GB-486788-A (GB)
Title: Improvements relating to automatic pilots for aircraft
IPC: G05D1/08
Filed: 1936-12-11
Abstract: 486,788. Fluid-pressure servomotor-control systems. SPERRY GYROSCOPE CO., Inc. Dec. 11, 1936, No. 34070. Convention date, Dec. 11, 1935. [Class 135] In automatic control apparatus for aircraft in which one or more of the control stafaces are operated by a long period gravity responsive device, for example a gyrovertical, to maintain the craft in a definite altitude, one or more short period gravity responsive devices slowly change the altitude maintained by the long period device. Thus any tendency of an aircraft maintained in level flight by a gyro-vertical to descend or climb may be frustrated by a short period device such as a pendulum or a liquid level device. By means of a further pendulum device, the craft may be banked automatically when it turns. Fig. 1 shows a gyro-vertical in which the rolling and pitching movements are controlled respectively by rotary disc valves 5, 7 differentially controlling ports 6, 6<1> and 10, 10<1> as described in Specification 416,813, [Group XXXIII]. The levelling pendulum device 23a and the banking pendulum device 23b are both shown in elevation, the former being also turned through 90. The two devices are of similar construction and comprise a pendulum 18 or 39 pivoted at 19 on member 20, Fig. 2, itself pivoted by a boss 32 in an air-tight casing 23. The member 20 carries a worm sector 27 so as to be adjustable by a worm 26 operated by an external knob 24, or 65. The member 20 is held in place by a spring 28 acting on a washer 33 whilst the pendulum is constrained to move in a vertical plane by a strap 34. The pendulum differentially controls ports 21, 21<1> in the member 20 through which air passes via a vent port 44 and a recess 18<1> to pipes 35, 35<1> and thence to nozzles 36, 36<1> acting oppositely on turbine wheels 37, 37<1> respectively. This pendulum control operates by means of a gear 16 on a sleeve 17 carrying the ports 10, 10<1> through the same differential 15 as the follow-up connection from the elevator E which connection comprises cables 13 acting on a drum 14. The banking pendulum 39 in a similar manner controls turbine wheels 40 acting through a differential 38 on the part carrying the ports 6, 6<1>, the follow-up connection 13<11>, 14<11> from the ailerons A acting through the same differential. Control by the pendulum 18 is continuous but the control by the pendulum 39 is operative only when the knob 42<1> of the hand control valve 42, Figs. 5, 6, is moved from its central position. In the positions marked " BANK," one of the ports 48 communicates with a port 49 so that air is admitted to the casing 23b, by a pipe 43 and the pendulum 39 takes control. In the positions marked " TURN " the ports 48 still communicate with the port 49 but in addition a small port 50 allows air to pass through the open-ended valve sleeve 47 and by one of pipes 46, 46<1> to one of the nozzles 51, 52 respectively. Air from the latter acts on opposed turbine wheels 53 which through gearing including a differential 58 controls an element 54 of the pick-up of a directional gyroscope 75. The follow-up connection 13<1>, 14<1> from the rudder R also acts through the differential 58. The valve 42 is @oved back into the appropriate " BANK " position after a turn has been made, until level flight is again attained when the knob 421 mav be moved to the " off " position. The craft may be turned when the valve is in a " BANK " position by a knob 64 acting through the differential 58. The control elements or pick-ups 61, 7, 5 operate the rudder R, ailerons A, elevator E respectively through relay valves 62, 62<1>, 62<11> controlling hydraulic servomotors 63, 63<1>, 63<11>. The two gyroscopes with their pick-ups are arranged in air-tight casings 70 from which air is continuously pumped.