Patent GB-431328-A (GB)
Title: Improvements in piloting controls for aircraft
IPC: G05D1/00
Filed: 1933-10-05
Abstract: 431,328. Controlling aircraft. BENDIX AVIATION CORPORATION, 105, West Adams Street, Chicago, U.S.A. Oct. 5, 1933, No. 27471. Convention date, Oct. 6, 1932. [Class 4] An aircraft-control system includes automatic-control means and manual - control means arranged so that manual actuation of a control surface is prevented when the automatic means are energized but remain in their neutral position. The aileron controls are arranged so that manual control may be superimposed on the automatic control in any position of the automatic control. The ailerons, elevators and rudder of an aircraft are controlled by servomotors controlled by instruments preferably gyros, e.g. the aileron and elevator servomotors are controlled by an artificial horizon and the rudder by the ordinary directional gyroscope. Manual control is provided which can take over immediately on failure of the automatic system. The servomotors are supplied with fluid from a pump through a distributing- device 28 allowing excess fluid to return through a pipe 31 to a reservoir which device also acts as a shut-off valve to render all of the servomotors inoperative to permit of manual control. The servomotors are cut off from the pressure system by an electric switch arranged so that when it is closed the automatic control is operative. The servomotors 22, 26 for the elevator and rudder are identical and are controlled from current supply to solenoids 93, 94. Each servomotor 22, 26 includes a piston 53 moving in a cylinder 52 and connected to the operating-cables by its piston rod 54. Excess oil in the cylinder passes through holes 65 to the reservoir. The cylinder has ports 71, 711 communicating with a passage 69 in which a spring-pressed valve 72 is situated. Above the cylinder is situated a valve chamber 74 housing a balanced piston valve 76 which has cylindrical portions 77, 78 adapted when the valve is in its neutral position to close conduits 80, 82, 83, 84 communicating with the passage 69. The valve 76 is centred by springs 90 and is moved to the right or left by the solenoids 93, 94. Fluid is supplied from a pump to an orifice 103 which is controlled by an adjustable needle valve 104 into the space 105. When pressure is supplied oil may pass downwardly through a passage 108 and force the spring-pressed valve 72 (Fig. 4) to the left to close the passage 69 thus preventing the short circuiting of the oil flow from one side of piston 53 to the other. A slot 73 is provided to permit movement of the valve 72. Movement of the valve 76 to the right by energization of the solenoid 93 uncovers passages 80, 83, oil being forced from the space 105 through passages 83, 69 and 711 to force the piston 53 to the left to actuate the rudder or elevators, oil escaping through passages 71, 69, 80, 110 and return pipe 36 to the sump. On movement of the valve 76 to the left, passages 82, 84 will become respectively the supply and exhaust passages and the piston 53 is then moved to the right, oil on the right hand side of the piston being exhausted through ports 711, 84 and passages 113, 36 to the sump. The servomotor 14 is modified in that the cylindrical portions 121, 122 of the valve 76 cover in its mid position only passages 141, 133, the valve 72 being omitted and the passage 126 being in two parts. Movement of the valve 76 to the right by actuation of the solenoid 132 uncovers ports 123, 133, causing the piston 127 to be moved to the left, oil escaping through a port 134 and passages 126, 123, to the sump. Movement of the valve 76 to the left uncovers a supply port 141 and an exhaust port 124 to force the piston 127 to the right. As at least one of the exhaust ports 123, 124 is always open, manual control can always be superimposed on the automatic control. The distributing device includes a cylinder 151 in which is a spring- pressed piston 152. Oil enters from the pump through a pipe 157, the pressure of the fluid forcing piston 152 to the right to uncover a relief passage 158 communicating with the reservoir. The cylinder communicates through pipes 15, 30, with the servomotors. The inlet pipe 157 communicates with the outlet pipe 31 through a passage 167 which is opened and closed by a valve 168 normally held open by a spring but forced to its closed position, whereby the servomotors are supplied, by actuation of a solenoid, the core of which is connected to the valve by a lever.