AIRCRAFT GROUND PROXIMITY WARMING SYSTEM

摘要

1479120 Aircraft warning indicators SUNDSTRAND DATA CONTROL Inc 26 Sept 1975 [1 Nov 1974] 39456/75 Heading B7W An aircraft ground proximity warning system for generating a warning signal when the aircraft is below a predetermined safe altitude comprises a function generator for generating a signal representative of minimum altitude over terrain as a function of the speed of the aircraft which signal is combined with a signal representing the actual altitude over the terrain whereby if the aircraft is below said minimum altitude a warning signal is generated. A circuit is provided to inhibit the warning signal when the aircraft overflys another aircraft. The system is designed to receive a Mach number speed signal as a 400 Hz A.C. signal from a Mk II air data computer 16 or as 0-12 D.C. voltage from a Mk. III air data computer 18, explanatory references for the two computers being given in the Specification. A voltage source 40 generates a 26 volt exitation signal fed on lines 42, 44 to points D and E on a circuit board 26 and thence to an isolation transformer 46 the output of which is transmitted through resistor 48, limited by a negative 15 volt D.C. voltage applied through a diode 52 over line 50 and through diode 54. This is combined with an output through resistor 56 from a buffer amplifier 28 to turn a transistor 38 on and off in synchronism with the input to transformer 46. The input to amplifier 28 is the 400 Hz signal generated by synchro 20 fed over lines 22, 24 and resistors 30, 32. The output from transistor 38, modified by resistors 58 and 60 is a D.C. signal on line 62 proportional to Mach number and this is used as input to the negative terminal of a bias amplifier 64, the positive terminal being grounded through a resistor 66. The output of amplifier 64 is transmitted through a diode 68 to a summing junction 72 and will increae in linear relationship with increase in Mach number, to be combined with a biasing signal on a line 76 which represents an altitude of 500 ft. The output from junction 72 is applied to the positive terminal of a comparator 78 which receives also a signal on line 80 from a radio altimeter h representing actual height and the output from comparator 78 is fed to an AND gate 82 to operate over line 86 a warning signal. An input over line 84 is taken from an undercarriage switch to deactivate gate 82 during a landing manoeuvre. When plugged in to the Mk. III computer 18 the input is fed over lines 221, 241 and through transistors 100, 102 that modify the circuit to accept a D.C. instead of an A.C. input. A circuit 200 has an input signal h1 which represents the rate of change in altitude with respect to time, obtained by differentiating the radio altimeter signal h and its output on line 218 is of a sufficiently high voltage to suppress any signal output from biasing amplifier 64 thereby inhibiting the warning system when the aircraft overflys another aircraft.