Patent GB-873088-A (GB)
Title: Improvements in or relating to grounded aircraft trainers or flight simulators
IPC: G06G7/70
Filed: 1957-07-22
Abstract: 873,088. Grounded aircraft trainers. GENERAL PRECISION Inc. July 22, 1957 [July 27, 1956], No. 23134/57, Class 4. [Also in Group XXXVI] A grounded aircraft trainer has a computer for deriving an output obtained from a comparison of two quantities involving different powers of the same variable, and comprises means for computing one quantity in which the power is other than positive unity, including an electronic function generator providing an output signal representative of the variable raised to that power, and having the variable as an input signal. Fig. 2 shows a circuit for computing the light path elevation angle from the equation dγ/dt = v [psoL/2m-g cos Ï cos γ/v<SP>2</SP>] where y is the flight path elevation angle, v is the true airspeed, p is the. air density, S is the nominal wing area, C L  is the left coefficient m. is the aircraft mass, g is the acceleration due to gravity, and Ï is the angle of bank. The effects due to sideslip and a small component of the propulsive thrust are neglected. In the above equation, errors in the divisor V<SP>2</SP> due to hysteresis loss, friction, time lag, and finite resolution of potentiometers which occur in electro-mechanical servointegrators may result in oscillation of the computed value of y, particularly in simulated steady flight (dγ/dt = o). The integrators and the circuit for deriving 1/v<SP>2</SP> from v are therefore electronic. The value of C 2  is derived in Fig. 4, from CL = f, (M) [α + f2 (M) #WF + f3 (M) #DB] where f1 (M), f 2  (M), fs (M) are appropriate functions of the simulated Mach number, α is the angle of attack, #WF is the wing flap deflection, and #DB is the dive brake deflection. Potentials representing #WF and #DB are derived by the trainee's simulator controls 16 and 17 controlling the sliders of constantly energized potentiometers R 402  and R 404 . These potentials energize potentiometers R 409  and R 408 , the sliders of which are driven by a conventional flight computer Mach number servo 15, to derive potentials #WF f2 (M) and #DB fs (M), which are fed to amplifier U 401  through summing resistors R 403  and R 405 . A potential representing dα/dt from a conventional flight computer (preferably computed as dα/dt = q<SP>1</SP> + K [Az /v + ges Ï /v] where q is the rate of pitch, Az is vertical acceleration, and K a constant) is applied to terminal 401 and the integrand from integrator I 201  is fed to amplifier U 401  over summing resistor R 401 . The output of amplifier U 401  energizes a potentiometer R 407 , the slider being driven by the servo 15, contoured to represent f1 (M), whereby the potential at terminal 202 represents CL. This signal is fed over resistor R 200  to amplifier U 201 , Fig. 2, the feed back circuit of which includes a potentiometer R 201  driven by a conventional aircraft mass servo 11, whereby if the potentiometers are suitably sealed, the output of amplifier U 201  represents -SCL/M. This potential energizes a potentiometer R 204 , the slider of which is driven by a conventional computer altitude servo 12, and which is contoured so that the derived potential represents -#SCL/M, fed to amplifier U 204  over summing resistor R 205 . An input g cos Ï cos #/v2 derived as explained below is also fed to amplifier U 204 , the output of which is thus (dy/dt)/v. This potential energizes a potentiometer R 208 , the slider of which is driven by the simulated velocity servo M 201 , to derive a potential dy/dt fed to integrator I 203 , the output of which energizes a y servo M 200 . A potential -dv/dt from a conventional flight computer (preferably computed from mdv/dt = T cos α - D - mg sin y where T is the thrust and D the drag) is applied over terminal 201 to. integrator I 204 , the v output of which energizes the v servo M 201  referred to above, and is the input over resistor R 214  to a function generator circuit (see Group XXXVI) providing an output -<SP>1</SP>/v<SP>2</SP> on line 210. This energizes a cosine resolver R 213  driven by the y servo Mzoo, derived a potential - cosγ/v2, energizing a cosine resolver R 225  driven by a conventional bank servo 14, to derive a signal representing - cos Ï cos γ/V2, which is reversed in polarity by amplifier U 202  and fed to amplifier U 204  over resistor R 201  as a term in the computation of dγ/dt as explained above the content g being taken into account by scaling the summing resistors. The angle of pitch # may be computed from α and y. Alternatively, the simulator may solve equations in # and α, and then derive y.