Patent GB-662857-A (GB)
Title: Automatic pilot for aircraft
IPC: G05D1/00
Filed: 1949-03-22
Abstract: 662,857. Automatic control systems for aircraft. BENDIX AVIATION CORPORATION. March 22, 1949 [June 30, 1948], No. 7807/49. Class 38 (iv). In an automatic pilot for aircraft wherein the rudder, ailerons and elevators are controlled by direction and vertical gyros through follow-up servomotor systems, provision is made whereby bank trim of the aircraft is corrected in accordance with the sudden forces and pitch attitude is temporarily maintained when the automatic pilot is switched in so as to facilitate smooth levelling off of the aircraft. The system also provides for the reversal of the direction signals upon a 90 degrees climb and the bank signals upon a 90 degrees climb or dive so that these signals are automatically corrected for inverted flight. When the aircraft is under the control of the gyrocompass 25, direction signals from the transmitter 11 and "rate of turn " signals from the gyro 12 are combined in resistor 44 and passed through amplifier 40 to a reactor amplifier 50 which is movably balanced. The output of amplifier 50 controls the variable phase of a two-phase servomotor 13 controlling the rudder 68. Follow-up signals from the rudder are transmitted by 72 and injected in opposition to the control signals into amplifier 40. Similar control channels are provided for the ailerons 106 and elevators 181 and controlled by the gyro vertical 130, the bank signals for the ailerons being passed via transmitter 18 and amplifiers 101, 102 and those for the elevators via transmitter 17 and amplifiers 150, 162. Bank trim in accordance with the direction signals produced by any tendency for the aircraft to fly off-course is provided by an integrator 90 comprising heaters 91, 92 associated with resistors 93, 94 in a bridge circuit, the output of which is fed to the amplifier 101 in the aileron channel. Any deviation from the correct trim attitude will disturb the balance of the bridge and thereby introduce a correction in the aileron channels. An integrator 166 of type similar to 90 is also included in the elevator channel and is short-circuited by relay 200 when the automatic pilot is switched in, the time delay due to cooling when this takes place allowing persistance of the pitch signal so that gentle levelling off of the aircraft under automatic control is facilitated.  When due to a 90 degrees climb prior to inverted flight, the gyro's " tumble " contacts 35, 210 are operated to pull-up relays 33, 135 and thereby reverse the direction and bank signals respectively. Overriding control of the aircraft is accomplished by a stick controller 16, movement athwartships operating transmitter 80 which provides a rudder control signal at 85 and a bank signal at 117. Movement of the stick through more than a predetermined angle breaks at switch 124 the circuit for a relay 120 which short-circuits the " trim " integrator 90. Fore-and-aft movement of the stick controls a transmitter 205 for the elevator channel. During stick control a magnetic clutch 23 is released to disconnect the directional gyro 25. A switch 123 is operated by a push button on the stick to disconnect the gyro 25 when trimming the craft for direction. The system is brought into operation by a switch 201 in circuit with the relays 120, 200, the compass clutch 126 and the servomotor clutches 70, 110, 180, a time delay 203 being included to provide a interval for heating up the valve amplifiers. Specification 662,831 is referred to.