Patent GB-929491-A (GB)
Title: Improvements in or relating to flight simulators
IPC: G09B9/20
Filed: 1959-06-19
Abstract: 929,491. Grounded aircraft trainers. GENERAL PRECISION Inc. June 19, 1959 [June 19, 1958], No. 21170/59. Class 4. Flight simulator apparatus comprises means for selecting a first input signal value to represent air temperature at a reference altitude (e.g. sea level), means for selecting a second input signal value to represent temperature lapse rate, means for multiplying the second signal by a function of simulated aircraft altitude to derive a third signal which is summed with the first signal to give a signal representing simulated ambient air temperature, and means having the last signal and a signal representing airspeed as inputs, to derive a signal representing Mach number. In the Figure, Mach number is computed as M = V p  /#Ta where Vp is the true airspeed and Ta the ambient temperature. Ta is computed as To + 273À18 + a. h. where T 0  is the sea level temperature in degrees centrigrade, the term 273 À 15 converts to degrees absolute (Kelvin), a is the temperature lapse rate with altitude, and h is the altitude. An instructor's control 16 operates a constantly energized potentiometer R-16 to derive a signal representing sea level temperature fed over resistor R-18 to an ambient air temperature servo M-20. A second input to the servo is derived from a constant signal source at terminal 18 over resistor R-20 to represent the term 273À18. An instructor's control 32 operates a constantly energized potentiometer R-24 to derive a signal representing temperature lapse rate a. This signal energizes a potentiometer R-32 driven by a pressure altitude servo M-34, to derive a signal a h fed over resistor R-22 to servo M-20, which also has a balancing feed-back input from potentiometer R-38 driven by the servo, so that the servo shaft position represents Ta. A-V p  signal from a terminal 4, derived in a conventional manner, is fed over resistor R-60 to an amplifier U-62, the feedback network of which includes a square root law potentiometer R-66 driven by the Ta servo M-20, so that amplifier U-62 solves -Vp +M#Ta = O, and its output M energizes a Mach number servo M-72. The dynamic pressure is also computed as a function of To, a, h, and Vp as in Specification 928,223. Ram air temperature is computed by a servo M-92. A constantly energized potentiometer R-82 driven by the air temperature servo M-20 derives a signal fed over resistor R-90 as one input to servo M-92, and also fed over resistor R-86 to potentiometer R-80 driven by the Mach number servo M-72, to derive a signal f(M, Ta) fed to servo M-92 over resitor R-94. The shaft position of servo M-92 is repeated in ram air temperature indicator 106. Indicated air speed is computed by an amplifier U-128. A potentiometer R-110 driven by the Mach number servo M-72 derives a signal fed over resistor R-120 to amplifier U-128 and also energizing a potentiometer R-118 driven by the pressure altitude servo M-34 to derive a signal fed over resistor R-122 to amplifier U-128. These two inputs, together with a constant input on resistor R-126 are added by amplifier U-128 and the resultant energizes an i.a.s. servo M-134 driving an indicator 142.