Patent GB-693293-A (GB)
Title: Improvements in or relating to craft guidance apparatus
IPC: G05D1/02
Filed: 1950-08-02
Abstract: 693,293. Radio navigation. SPERRY GYROSCOPE CO., Ltd., and RICHARDSON, C. A. July 11, 1951 [Aug. 2, 1950], No. 19301/50. Class 40 (vii). An aircraft navigational-aiding device comprises an indicator controlled by the resultant of a number of signals one of which represents the angular departure of the aircraft heading from a reference direction and means for changing the sensitivity of the indicator in response to a given angular departure. In one embodiment a cross-pointer meter 1 is used as an indicator, the horizontal plane deviation pointer 12 of which is moved under control of the signal output of azimuth combining channel 18 to which is fed the outputs of the gyro-magnetic compass 2, the roll pick-off of the gyro vertical 6<SP>1</SP>, and any signal fed by banks E and F of switch 8. Vertical deviation pointer 13 is similarly controlled by the output of elevation combining channel 20 to which is fed the output of an altitude-responsive device 3 over contacts 21 of relay 36, the output of gyro-vertical pitch pickoff 7 and any signal fed by bank G of switch 8. The pitch pick-off arrangement 7 comprises the actual pick-up 28 varying the position of the tapping point on potentiometer 27 and a manual pitch setting device 30 varying potentiometer 29 in accordance with the setting of knob 10 Potentiometers 27 and 29 combine to form a bridge circuit, the out-of-balance signal of which is fed to unit 20. In position A of switch 8 the output of radio localizer receiver 5 is fed over switch banks E and F to channel 18 so that the craft may be flown along the localizer path and no signal is fed over bank G to channel 20. In the B position of the switch no signal is fed either over banks E and F or G and the craft may be flown across country in accordance with the indications of its own instruments only. In position C the arrangement is the same as A except that the applied localizer signals are reversed for flight in the opposite direction along the localizer path. In any of the positions A, B and C, switch 9 controlling wipers 37 may be in a position to energize relay 36 in order to connect the altitude-control signal to channel 20 for constant altitude flight or not. In either position of wipers 37, relay 35 is energized to hold brake shoe 33 against drum 32 and maintain the pitch manually set by knob 10, however, on switching from one position to another, relay 35 is temporarily released, allowing springs 41 and 42 to return the control to zero or a small preset value. In the final (D) position of switch 8 localizer signals are fed to the channel 18, signals from a radio glide path receiver 4 are fed to the elevation channel 20, switch 9 is locked off (by mechanical means, not shown) to prevent the output of device 3 being fed to channel 20 and power supply to relay 35 switched off by bank K of the switch so that no manually-applied pitch bias is applied. This switch position is the one used for landing and clearly requires a much greater accuracy of control than is required when the other switch positions are in use. So, according to the invention, the meter inputs are shunted respectively by resistors 45 and 46 under control of relay 50 fed over switch bank H in switch positions A, B and C to reduce the indication sensitivity but full sensitivity is retained in position D when the shunts are disconnected.