Patent GB-622926-A (GB)
Title: Improvements in or relating to aircraft control apparatus
IPC: G05D1/00
Filed: 1945-12-13
Abstract: 622,926. Automatic aircraft control systems. MINNEAPOLIS-HONEYWELL REGULATOR CO. Dec. 13, 1945, No. 33760. Convention date, Dec. 30, 1944. [Class 38 (iv)] [Also in Group XXXVII] An automatic control system for an aircraft which has control surfaces each provided with a motor for controlling the aircraft about its roll, pitch, and turn axis respectively, and deviation sensing means responsive to movement about each axis for controlling the relative motor, is provided with a manual control device which can be used alternatively and comprises a motor controller that can be moved in one direction to effect the positioning of the ailerons and rudder, and in a direction at right-angles thereto to operate the elevator motor. These two directions of movement may be combined as in a joystick and, in addition, the control handle may 'be rotated axially to operate the rudder. An independent operation of the rudder may be effected by the latter action to produce skidding of the aircraft. A.C. motors 10-12 which operate the ailerons, rudder and elevator respectively, are controlled by signals received from amplifiers 13-15, the amplifiers being fed over lines 400, 409 and 416 in accordance with the magnitude and phase of signals derived from the unbalance of Wheatstone bridge circuits connected thereto. Under the automatic control system a deviation of the aircraft from course produces, through mechanical connections 67, 671 to the directional gyro 62, simultaneous movement of sliders 64, 66 over resistances 63, 65 in a bridge circuit 19 in the aileron control, and through a mechanical connection 67<SP>11</SP> moves a slider 125 over a resistance 124 in a bridge circuit 121 in the rudder control system. The various bridge circuits are energized by connecting them each to a separate secondary winding on a transformer provided with a primary winding 40. The arrangement of two sliders 64, 66 in bridge 19 provides across a trimming resistance 85 a voltage which is substantially an exponential function of the displacement of those sliders, its phase being dependent on the direction of displacement. The motor 10 operates to move the ailerons to bank the aircraft in turning to restore it to its course, and simultaneously displaces a slider 29 over a resistance 28 to re-balance the bridge 16. The movement of slider 125 over resistance 124 introduces into the network 120 a signal which is applied over line 409 to operate the rudder motor 11 and effect the necessary turn, and at the same time the motor displaces a slider 129 in a direction to rebalance the bridge, but before the turn is completed mechanical connections 261, 26<SP>11</SP> between the vertical gyro 27 and a potentiometer arm 98 produce a signal which opposes that introduced by the directional gyro on the potentiometer 121, thereby reducing the extent of rudder displacement and preventing skidding of the aircraft. Due to the banking of the aircraft during turning the vertical gyro 27 is caused to operate and, by a mechanical connection 26 between that gyro and slider 25 of the aileron control network, the slider is moved over resistance 24 and produces in the network a signal which assists the aileron motor 10 in moving slider 29 to rebalance the bridge 16. Rolling of the aircraft about its longitudinal axis causes the vertical gyro 27 to move the slider 25 of the aileron control potentiometer along the resistance 24, thereby producing a signal which operates the aileron control motor 10 to restore the aircraft to the desired attitude. At the same time mechanical connections 26<SP>1</SP>, 26<SP>11</SP> between the vertical gyro 27 and potentiometer slider 98 in the rudder control system produce over line 409 a signal which operates the rudder motor to deflect the rudder in a direction opposite to that in which it would normally tend to turn by reason of the bank. The operation of the vertical gyro also causes mechanical connection 26<SP>1</SP> to move a slider 194 over a potentiometer resistance 193 in a circuit 190 connected to the elevator control, the ends of resistance 193 being connected over leads 197, 198 to a common terminal of the transformer secondary line 199, so that the voltage impressed upon a resistance 207 is independent of the direction of movement of slider 194. This voltage is fed over line 416 to amplifier 15 which supplies current of predetermined phase to the motor 12, the phase being such that the motor is caused to tilt the elevators upwardly to tend to raise the aircraft and prevent it from losing altitude whenever it banks. An alteration in the pitch of the aircraft causes the vertical gyro 27 to operate a mechanical connection 249 to move slider 225 over a resistance 224 of a Wheatstone bridge circuit 220 so that the signal supplied to the amplifier 15 is of a phase such that it operates the motor 12 in a direction to tilt the aircraft back towards the desired course. As the aircraft is tilted back the displacement of slider 225 is decreased and the bridge is unbalanced in the opposite direction tb cause motor 12 to drive the elevators back towards their streamlined position. The bridge circuits are provided with trimming potentiometers, and in addition the control circuits of the three control surfaces are provided with ratio-adjusting rheostats 32, 132 and 232 respectively, whereby the effect of the motor-operated potentiometer arms 29, 129, and 229 relative to the associated gyroscope-controlled potentiometers can be varied. A turn control, operated manually,be a knob 173, is arranged to actuate a potentiometer arm 168 in a bridge circuit which includes potentiometer resistances 154, 156 associated with the aileron and rudder control systems, the direction of the turn being dependent on the direction of rotation of the knob. The employment of this control necessitates the locking of the automatic control, otherwise the directional gyro would tend to correct any change in course. An electromagnetic lock 69 is accordingly associated with the directional gyro 62 and energized by the closing of a battery circuit when the knob 173 is turned in either direction and actuates a cam 175 which closes contacts 176, 177. The vertical gyro 27 is not locked and remains free to operate the mechanical connection 26 to slider 25 in the aileron control circuit, and connections 26<SP>1</SP>, 26<SP>11</SP> to slider 98 in the rudder control. As the plane approaches the desired course the turn control is turned back to the normal position, and the various surfaces are deflected in the opposite directions. Operation of manual controller. The manual control lever comprises a rod 256 which terminates in a knob 330 and is located within a sleeve 327 pivoted on a rocking bar 336, Fig. 2, which in turn is pivoted at its ends, so that a compound swinging movement can be effected and, in addition, the rod 256 is rotatable and movable vertically within the sleeve 327 in opposition to the pressure of a spring 331 below the knob. The lower portion of the sleeve carries a resilient contact 266 (shown connected to it by dotted lines in Fig. 1) which moves over an arcuate resistance 265 when the lever is swung to the left or right and applies a voltage signal over a conductor 407 and tappings on resistors 154, 156 to the rudder and aileron control networks. At the same time the lock 69 of the directional gyro 62 is actuated by closing a pair of contact fingers 315, 316 in its energizing circuit, the latter action being effected by a cam surface 382 which bears upon a pin projecting from the lever rod 256 whereby the latter is caused to move downwardly to depress finger 315. When the lever is swung in the plane at right-angles to that aforesaid a contact arm 306 secured at one end of the rocking bar moves over an arcuate resistance 305 and causes a control signal to be sent into the elevator control system to change the pitch of the aircraft. The change in pitch is detected by the vertical gyro 27 which moves slider 225 in a direction to oppose the effect of the movement of slider 306 to return the elevator to the streamlined position, whereupon the knob 330 should be released. The movements of the control lever may be compounded to produce a control effect jointly on the three control surfaces of the aircraft. The knob 330 can also be rotated to turn the rod axially to move a contact finger 291 at its lower end over a circular resistance 290 and produce a signal in the rudder control system. When this is effected as a separate movement the aircraft is turned by means of the rudder alone. The directional gyro is simultaneously locked by effecting an axial movement of the rod 256, which results in a cam action when the rod is rotated, and closes contacts 315, 316.