Patent GB-1291211-A (GB)
Title: Simulation of instruments in a fixed-base aircraft trainer
IPC: G09B9/16
Filed: 1971-04-19
Abstract: 1291211 Simulating aircraft instruments SINGER CO 19 April 1971 [27 March 1970] 23845/71 Heading B7W [Also in Division G4] A fixed base aircraft trainer has a flight computer generating electrical signals commensurate with the rate of change of flight variables which are fed to a digital integrator 36, 38, 40, Fig. 2, generating a digital value of a said flight variable which is fed to a comparator 42 which generates a pulse when said digital value corresponds to the value of an input from a digital master logic input 43, which pulse causes means 44 to sample the instantaneous value of a continuously variable analogue function and supply the instantaneous value as a D.C. voltage to drive an output member of a simulated instrument. The digital integrator receives signals representing the rate of change of pitch or roll or heading, or X or Y co-ordinates of the simulated aircraft; for example a signal in line 34 representing rate of change of pitch angle causes the comparator 42 to be supplied with a digital signal representing the simulated pitch angle. When the value from the master logic counter 50, Fig. 1, corresponds to this value pulses from the comparator cause sample/hold circuits 44 and 46 to sample respectively 400 Hz sine and cosine functions also supplied from the master logic, so that the phase angle of these functions is equal to the pitch angle, and the instantaneous amplitudes are fed to the orthogonal windings of D.C. synchro 48 which drives the pitch bar to indicate simulated aircraft pitch attitude. A pulse from the comparator 42 also causes sample/ hold circuit 49 to sample a ramp voltage (in line 56) generated by a digital/analogue converter 16, Fig. 1, in response to a signal from counter 50, and a corresponding D.C. voltage is fed to the motion system which physically orients the simulator cockpit. Punched cards programmed with data relating to fixed radio beacon transmitters or instrument landing systems (ILS) are located in card reader 10 and supply data relating to coordinates X and Y of a transmitter which are compared with co-ordinates X and Y of the simulated aircraft by a subtractor 14 to provide digital values #X, #Y of the distance of the aircraft from the transmitter, which are converted to analogue values by the converter 16 and fed to sample/hold circuit 20, Fig. 3, which samples the #X, #Y signals on receiving a pulse from frequency comparator 12, Fig. 1, indicating that the frequency set on a simulated radio receiver corresponds to that of the said transmitter, and applies the sampled voltages to a radio aids analogue computer 22, Fig. 3 to drive a simulated navigation instrument. Data representing factors such as magnetic variation, station elevation, runway bearing or field elevation are also fed by the card reader to the digital/analogue converter 16 and the resultant analogue values sampled and fed to the computer 22 when the simulated receiver is correctly tuned. An audio signal corresponding to the call letters of the station in Morse code is produced by means of code ID generator 26 and oscillator 28. Sampling of the ramp voltage in line 56 to produce outputs representing X and Y may be used to drive a recorder. The ramp voltage may also be compared by comparator 58, Fig. 3, with other flight variables where no integration is required, such as rate of climb, r.p.m., fuel pressure or flow and manifold air pressure, applied as a D.C. voltage at terminal 54. When the two correspond a single shot multivibrator 60 fires a pulse to cause circuits 62 and 64 to sample sine and cosine waves and apply the resultant D.C. voltages to a synchro 66 driving a simulated instrument. Signals representing #X, #Y, sin #, cos #, - sin # and - cos # (where #=heading angle) are supplied to a modulator 68 which produces a sine wave whose phase is commensurate with (#X/#Y - #), so that the sampling of sine and cosine waves by sample/hold circuits 74 and 76 indicates the difference between the bearing of the beacon and the heading of the aircraft which is shown on an instrument driven by D.C. synchro 78.