Patent GB-875800-A (GB)
Title: Improvements in or relating to flight simulation apparatus
Filed: 1957-09-06
Abstract: 875,800. Grounded aircraft trainers. GENERAL PRECISION Inc. Sept. 6, 1957 .[Sept. 21, 1956], No. 28217/57. Class'4. Flight training apparatus for simulating the operation of high speed aircraft comprises means for deriving a quantity commensurate with the acceleration of the simulated aircraft along its flight path, means for modifying said quantity in accordance with a function of simulated altitude and means for integrating the modified quantity to provide simulated Mach number. A Mach number servo is shown at 210 in Fig. 2 wherein an amplifier U 201  receives a plurality of input voltages (to be described), and provides an output signal via rectifier X 201 , to a magnetic amplifier U 202  the signal from which energises the control winding 211 of a servomotor M. The stator winding 212 is energised from an A.C. supply connected to terminals XX, and the rotor 213 of motor M drives a D.C. tachometer generator 214 which drives shaft 215 to adjust the arms of a number of potentiometers and a simulated Mach meter I-M. Input potentials to amplifiers of Mach number servo 210 aircraft acceleration. Simulated engine thrust potentials are derived in " Left " and " Right " engine computers 311 and 310, Fig. 1, the " Left " engine signal being applied through summing resistor R 101  to amplifier U 101  which energises a potentiometer R 102  adjusted by an "aircraft weight " servo M 200 , which may be a conventional integrating servo, to provide an input to amplifier U 101  via resistor R 103  so that the amplifier gives an output potential related to the ratio between simulated " left " engine thrust and simulated aircraft weight, i.e. simulated acceleration. This acceleration signal is supplied through terminal 191 and summing resistor R 201 , Fig. 2, to the input circuit of amplifier U 201 . The " Right " engine thrust is similarly divided by simulated weight by amplifier U 102  and potentiometer R 104  the resulting acceleration signal being applied through terminal 192 and summing resistor R 202  to amplifier U 201 . The aforementioned inputs to amplifier U 201  represent acceleration with reference to the aircraft longitudinal axis and to represent the effects of climb or sideslip to give a true computation of Mach number, the input signals may be modified by cosine resolvers positioned by conventional angle of attack and sideslip angle servos. The input signals to servo M 200  are from terminal 102 via resistor R 108  representing simulated rate of fuel flow Wf and from potentiometer R 105  the arm of which is set by an instructor's control knob 101 to provide a signal representative of filling of the fuel tanks. The sum of these potentials fed respectively through resistors R 108  and R 107  represent rate at which aircraft weight is changing as fuel consumption or refuelling takes place. A further potentiometer R 106 , adjusted by knob 101 and a tapping from terminal 102 respectively supply signals through resistors R 109  and R 110  to an electronic integrator I 201  provided with an integrating shunt capacitor C 102  which provides an output representing the time integral of the fuel flow rate and filling or draining rate potentials applied to the integrator and this output potential may operate a simulated fuel quantity meter I-F. Acceleration of aircraft along flight path due to gravity. A fixed potential at terminal 103, Fig. 1, is applied in opposite polarities to excite sine resolver R 112  positioned by a flight path angle servo 312 to produce a signal sin γ commensurate with elevation angle y and this is fed via terminal 193 to resistor R 212 , Fig. 2, which scales the signal to make the input to amplifier U 201  commensurate with g. sin y where g is a constant representing acceleration of gravity. Simulated rolling friction and braking force of aircraft during landing. A switch S 101 , Fig. 1, operated by a conventional altitude servo closes when simulated altitude becomes zero to energise a " weight-on-wheels" relay K 101  which closes its contact c to apply a fixed potential, representing simulated rolling friction of the aircraft, from source 120 through resistor R 132 , terminal 195 and resistor R 203 , Fig. 2, to amplifier U 201 . Wheel braking effect is provided from a fixed potential which excites potentiometers R 213  and R 214 , Fig. 2, the arms of which are adjusted by left and right brake pedals 317 and 318 respectively to provide outputs which are routed through contacts a and b of relay K 101  and summing resistors R 205  and R 206  to the input circuit of amplifier U 201 . Simulated deceleration due to aerodynamic drag. A wing-flaps motor 315, Fig. 2, positions arms of potentiometers R 216  and R 217  and the negative potential from R 216  excites potentiometer R 218  which is positioned by Mach number servo shaft 215 to supply a " deflected wing flaps " potential modified in accordance with Mach number, to amplifier U 203  via resistor R 225 , adjustable feedback being provided by resistor R 231 . Similarly an undercarriage motor 316 adjusts potentiometer R 221  to derive an " undercarriage deflection " potential modified by a function of Mach number by potentiometer R 220  and applied via resistor R 227  to amplifier U 203 . To simulate the drag effect of windmilling engines, " Left Engine Fired " relay K 103 L and " Right Engine Fired " relay K 103 R (inoperative when the simulated engines are firing) are energised by a fixed potential from terminal 216 and connected through resistor R 229  and /or resistor R 230  to amplifier U 203  to simulate increase in drag coefficient due to engine windmilling. The output from U 203  is passed via terminal 188 to excite potentiometer R 11 l, Fig. 1, and, indirectly potentiometer R 129  respectively positioned by " weight " servo M 200  and a simulated dynamic pressure servo M 201 . The output from potentiometer R 111  is fed back to amplifier U 203  via terminal 189 and resistor R 224  and it energises also potentiometer R 129 , the output of which is fed through terminal 190 and resistor R 208  to amplifier U 201  as a signal commensurate with simulated deceleration due to aerodynamic drag. Coefficient of lift. CL is given as Cla + Clo + Clffw. The first terms relate to angles of attack of α and o respectively, and as functions of Mach number may be designated f2(M) and f3(M) respectively. The third term is a function related to extended wing flaps and since flaps are lowered in a speed range in which the coefficient varies little the term need not be modified by Mach number. Potentiometers R 238 , Fig. 2, and R 150 , Fig. 1, respectively provide f 2 (M) and f 3 (M) potentials when adjusted by Mach number servo shaft 215. Angle of attack servo 320, Fig. 2, adjusts potentiometer R 265  which supplies an angle of attack potential to potentiometer R 238 . The resulting angle of attack potential as modified by Mach number is then applied via resistor R 235  to summing amplifier U 204 . Potentiometer R 150 , Fig. 1, energised by a constant negative potential also supplies to amplifier U 204  an input representing f 3 (M) via terminal 262 and resistor R 236  the resultant output of the amplifier being applied through resistor R 244  to summing amplifier U 244  together with a "wing flaps" signal from terminal 260 derived at potentiometer R 217 . The signal from amplifier U 244  operates servo 319 to position a shaft 280 as a function of total coefficient of lift. Shaft 280 positions a feed back potentiometer R 239  and also potentiometer R 240  forming part of an induced drag circuit described below. Deceleration due to induced drag is simulated by applying a potential representative of vertical aerodynamic acceleration to terminal 270, Fig. 2, to energise potentiometer R 243  via a circuit including an isolation amplifier U 271 , diode U 272 , feedback resistor R 273  and an earthed resistor R 242 . The diode prevents the deceleration potential due to simulated induced drag from appearing as an acceleration potential during simulated dives and resistor R 273  provides scaling. The total coefficient of induced drag is simulated as a function of Mach number by adjustment of the wiper of potentiometer R 243  by shaft 215 and the output is applied to potentiometer R 240  which in turn supplies to amplifier U 201  via resistor R 207  a potential commensurate with deceleration of the simulated aircraft resulting from induced drag. The potentials previously described and applied to amplifier U 201  are each commensurate with simulated acceleration of a simulated aircraft along its flight path. Additionally, a rate-ofchange-of-Mach-number potential is derived by tachometer generator 214, Fig. 2, and applied through resistor R 210  ; a potential is derived by applying the output from generator 214 via resistor R 209  and terminal 194 to excite potentiometer R 134 , Fig. 1, the arm of which is positioned by altitude servo 314 to derive a potential applied via terminal 196 and resistor R 204  to amplifier U 201 . The output shaft 215 of the Mach number servo drives further potentiometers as follows : R 120 , Fig. 1, excited by a constant voltage applies a potential commensurate with Mach number to potentiometer R 117 , adjusted by altitude servo 314 to represent variation in the speed of sound with altitude. The resulting modification of Mach number potential by the speed of sound at simulated altitude provides an output commensurate with simulated airspeed and this may be resolved at 313 into ground track velocities VN and VE to operate ground track recorders. The output from R 117  also is applied to sine resolver R 113  positioned by elevation angle servo 312 to derive a rate of 114 change of altitude signal which is applied via scaling resistor R 114  to altitude servo 314 and also via resistor R 115 , resistors R 130  and R 131  and capacitor C 101  to operate a simulated rate of climb meter I-BC. A