Patent GB-616702-A (GB)
Title: Improvements in and relating to automatic control mechanisms for aircraft
IPC: G05D1/04
Filed: 1946-01-01
Abstract: 616,702. Controlling aircraft. BRITISH THOMSON-HOUSTON CO., Ltd. Jan. 1, 1946, No. 54. Convention date, Jan. 1, 1945. [Class 4] [Also in Group XXXV] In an automatic pilot for aircraft, the ailerons are subject to two controls, one dependent on the turning control and the other dependent on the extent to which the aircraft vertical deviates from the correct apparent vertical during turns and operated through a reversible motor. The outer gimbal ring 43 of the turn gyroscope 13, is connected to the rotor 57 of a transmitter motor 56 which is fed from a common A.C. supply 1, 2 and whose stator winding is connected to the input of an amplifier 17. The output of the motor 56 is such that it varies in phase and magnitude according to the direction and extent of movement of the rotor from its central position and, since the anodes of valve 31 are also fed from the source 1, 2, any such output is differentiated in the two halves of the amplifier and causes the solenoids 29, 30 to move the valve piston 21 in the corresponding direction. The valve passes oil under pressure from supply 22 to the rudder servomotor 19 which consequently moves the rudder in the appropriate direction to correct any deviation from the set course. A follow-up action is provided by a transmitter motor 67 whose rotor is mechanically coupled to the rudder and which generates an output proportional to the movement of the rudder and in opposition to the output of the transmitter 56. The rudder therefore moves until the two outputs are balanced and is then set in a position proportional to the movement of the rotor 57. The bank and pitch control gyroscope 14 is set with its rotor axis vertical and it actuates an aileron control transmitter 65 and elevator control transmitter 66, both of which operate their control surfaces 11, 12 respectively through follow-up transmitters 68, 69 and individual amplifiers as in the rudder system. Manual control of the aircraft's flight is introduced by a universally mounted control switch 80 which completes circuits through fixed contacts 85, 86, 87, 88 according to the direction in which it is moved. Movement to the left or right influences pole-changing contactors 101, 102 to cause a turn control motor 92 to run in a corresponding direction and, through reduction gearing 100, to set the rotors of transmitters 94, 95. These introduce unbalance signals in the rudder and aileron circuits such as to cause turns with a predetermined corresponding bank angle. During such turns the turn gyroscope 13 is caged, and so rendered ineffective, by energization of a solenoid 53 through a switch 120 operated by a cam on the shaft of motor 92. The gyroscope 14 is, however, left free and the bank angle is automatically stabilized at the point where the outputs of transmitters 95 and 65 balance. A similar reversible motor 92a, controlled by contacts 85, 86 of the switch 80, actuates a transmitter 69 in the elevator control circuit to produce changes in the pitch attitude and in each case the motor 92, 92a runs until the switch 80 is restored to centre and it maintains the resultant setting until the knob 82 is momentarily depressed to make contact between plate 89 and contact 90. When this is done, relay 110 is energized and locks over. motor-actuated contacts 111, at the same time completing a circuit through motor-driven change-over contact 115 to drive the motor back to its central position, whereupon contact 111 opens and relay 110 is released. Similar functions are carried out by the pitch controller. Final correction of the bank angle during a turn, to allow for various air speeds, is effected by a pendulum contact 129 swinging about a fore and aft axis. The pendulum lies along the correct apparent vertical and if the aircraft is incorrectly banked during a turn it completes a circuit through one of fixed contacts 130, 131, causing running of reversible motor 127 in a manner similar to motor 92. This actuates a further transmitter 125 in the aileron circuit and introduces the necessary correction into the signals therein. The system also incorporates a rate-of-turn gyroscope 134, comprising a rotor 135 so mounted as to precess about a longitudinal axis DD against spring restoring means 137 whenever the aircraft turns. The mounting ring 136 is coupled to the rotor of a transmitter motor 133 connected in the rudder circuit so as to introduce a signal of similar polarity to a correcting signal from transmitter 56, but of magnitude dependent on the rate of turn. During straight flight, this has a damping effect on the stabilization in azimuth, since it augments the rudder correction until the aircraft commences to respond, after which it reduces the extent of rudder movement and prevents overshooting. During controlled turns it again tends to oppose the turn and ensures that the ultimate rate of turn is proportional to the time the control switch is displaced, the output of the transmitter 133 ultimately balancing that of transmitter 56, at the same time restoring the rudder as the aircraft goes - into the turn. Specification 616,777, [Group XXXV], is referred to.