Patent GB-932684-A (GB)
Title: Improvements in or relating to ground based flight training or flight simulating apparatus
Inventor: LONGLEY BERNARD EDGAR
IPC: G09B9/28
Filed: 1961-08-02
Abstract: 932,684. Grounded aircraft trainers. COMMUNICATIONS PATENTS Ltd. Aug. 2, 1961, No. 28006/61. Class 4. Ground based flight training or simulating apparatus comprising manually operable flight controls, a computer for simulating autopilot control, and a switch for selecting manual control or autopilot control, the apparatus providing feel on the flight controls, comprises also motor means having an output member connected to displace a flight control during autopilot operation, and providing a controllable load when driven by the output member. In Fig. 1, a dummy control column 10, movable in opposite directions as shown by arrows 20, 20<SP>1</SP>, for simulated elevator displacement, operates the wiper 12<SP>1</SP> of a potentiometer 12 to provide an input signal for the conventional flight parameter computer (not described). A distortable U-member 13 connects a rod 11 pivoted to the control column 10, and a rod 11<SP>1</SP> movable by a hydraulic jack 14 operated by a valve 15 controlled by an electro-dynamic unit 16 energized by a summing amplifier 17. Inputs to the amplifier during manual control are derived from a transducer 25 measuring the distortion of member 13, and thus the force applied by the trainee to column 10, from a potentiometer 27 measuring the jack displacement, and from a transducer 33 measuring the valve displacement, which is proportional to the rate of displacement of the jack, this last input being added for antihunting purposes. The potentiometer 27 may be non-linear. Thus in the equilibrium state the displacement of jack 14 is proportional or otherwise dependent on the force applied by the trainee to the control column. During auto pilot operation, a signal from the autopilot computer 28, described below, energizes a relay 26, to close contacts 30 and 31, and feed a demanded pitch change signal to amplifier 17. If the trainee flies " hands-off ", the signal from transducer 25 is zero, and in the equilibrium state the jack 14 will move the control column 10 to a position corresponding to the demanded pitch change signal. If the trainee attempts to deflect the control column from this position he will experience a biasing force proportional to the deflection. Apparatus similar to the above for the aileron and rudder control systems is shown in block form at 37 and 38. Fig. 2 shows the autopilot computer 28 and the trainee's dummy autopilot control unit 29. Conventional pitch (#), roll (Ï), yaw (#), side slip (#) and height (h) computers are indicated at 53, 107, 123, 131 and 54 respectively. The unit 29 has an autopilot ON/OFF switch 57, a switch 80 selecting pitch lock or height lock during autopilot control, an ILS ON/OFF switch 88, a heading lock ON/OFF switch 95, and pitch and yaw autopilot trim controls 56 and 108. The switches 80, 88, and 95 are mechanically interconnected so that ILS-ON can only be chosen when switch 80 is in height lock position, and the heading lock switch 95 is at OFF. During manual control, the contacts of switch 57 are made as shown. With ILS off (switch 88 as shown) and pitch lock selected (switch 80 as shown), the inputs to an amplifier 58 of an electromechanical servo system 55 are a # signal from computer 53 over contact 75, and an answer signal from the servo driven potentiometer 68 over contact 74. The usual damping rate feedback signal is provided by the servo tachometer generator 67. Thus the servo output shaft follows up the value of # as given by computer 53. If now the autopilot is engaged, by changing over the contacts of switch 57, a winding 71<SP>1</SP> is energized from a D.C. source 81 over contacts 77 and 73, to operate on clutch 71 and connect a potentiometer 69 to the servo, the wiper of this potentiometer being at a central, earthed, position at the time of connection. The inputs to amplifier 58 are now an answer signal from potentiometer 69, the trainee's pitch datum signal from potentiometer 56, and the damping rate feedback. The signal from potentiometer 68 is thus the simulated pitch at the time of autopilot engagement, as trimmed by the trainee. This signal is fed to input terminal 84 of an amplifier 50, together with a computed pitch signal and a damping pitch rate signal on terminals 85 and 87 from computer 53. The amplifier output is fed over terminal 36 (see now Fig. 1) as the demanded pitch change signal, whereby amplifier 17 operates unit 16, valve 15, and jack 14, to deflect the control column and produce simulated elevator deflection. The jack displacement signal on potentiometer 27 is fed over terminal 35 (see now Fig. 2) as an answer to amplifier 50. The apparatus thus operates to hold the computed pitch at the trimmed datum pitch value by simulated elevator deflection made apparent by deflection of the control column. Relay 26, Fig. 1, is energized during autopilot operation over terminal 34 (see now Fig. 2) and contact 72 from D.C. source 81. If switch 80 is put into the height lock position the winding 96<SP>1</SP> of an electromagnetic clutch 96 is energized over contact 78 from D.C. source 81. A potentiometer 82, the wiper of which is initially in a central, earthed, position, is thereby connected to the height servo 54 and its signal is thus proportional to the departure of the computed height from that at the time of " height lock ON." This height error signal is fed over contacts 79, and 90 to input terminal 61 of amplifier 58, and also through limiter 98 to input terminal 86 of amplifier 50. When the autopilot is engaged, and height lock is ON. there is no answer signal from servo 55 to amplifier 58, whereby the servo integrates the height error signal, the integrand signal on potentiometer 68 being fed to terminal 84 of amplifier 50. As before, an output signal from amplifier 50 results in simulated elevator deflection and control column deflection, so that the computed value of h is held to that prevailing at the time of " height lock ON." The integrated error signal ensures that small persistant height errors are detected and rectified. The roll control system is, during autopilot operation, controlled by amplifier 51, having, during heading look OFF a computed Ï input on terminal 104 from computer 107, and stabilizing rate inputs on terminals 102, 103, so as to maintain Ï zero. The rudder is controlled to provide co-ordinated turns with no side slip, by amplifier 52, having a Ï input on terminal 128, answered by a # signal from computer 123 on terminal 127. In addition, a # signal from computer 131 is fed to terminal 125. Stabilizing rate signals are also added. Closure of the heading lock switch 95 energizes the winding 122<SP>1</SP> of a clutch 122, and connects potentiometer 121 to the servo 123. The potentiometer wiper is initially in a central, earthed position, and derives a signal representing the heading error from the heading at the time of heading lock ON. This signal is fed to the rudder control amplifier 52, and also over contacts 93 and 92 to one input terminal 112 of amplifier 109, and to the input terminal 115 of an integrating servo 134, the output of which is connected to the other input terminal 111 of amplifier 109. The amplifier output is fed through a limiter 110 to terminal 105 of roll control amplifier 51. Any heading error signal thus produces co-ordinated aileron and rudder deflection. Any trainee's yaw trim signal from potentiometer 108 is fed to input terminal 106 of amplifier 51. Small persistent errors of yaw build up the integrand of servo 134, to produce a corrective action. When switch 88 is put in the ILS-ON position, simulated vertical and lateral displacement signals from glide path and localizer beam computers 100, 100<SP>1</SP> are substituted for the height error and heading error signals respectively.