GB953473A - Improvements in control systems - Google Patents

Abstract

953,473. Protective arrangements. VICKERSARMSTRONGS (AIRCRAFT) Ltd., and D. I. ROBERTSON. Nov. 30, 1961 [Dec. 22, 1960], No. 44120/60. Heading H2K. In a control system, e.g. a triplicated aircraft autopilot control system, having a plurality of signal transmission channels A ... C for separately transmitting control signals from a common input to a common output, fault detection apparatus comprises a plurality of signal responsive devices C AB , C BC , C CA to which are applied different combinations of the control signals taken two at a time. Each device C AB , C BC , C CA produces an output signal in response to a predetermined difference between the two control signals applied thereto. Switch means, including two sets of normally-closed contacts, associated with each channel are operative in response to the simultaneous appearance of output signals from the devices fed from that channel to render that channel inoperative. In the arrangement shown, the switch means comprise electromagnetic relays RAB/2, RBC/2, RCA/2 each having two normally-closed sets of contacts, one set in a path of each of the channels from which signals are applied to the associated signal responsive device. Thus in the event of a fault in a channel, e.g. channel A, device C AB RAB provides an output to relay which opens 2 its contacts rab1 in channel A and its contacts RCA rab2 in channel B. Similarly relay opens 2 contacts rca2 and rca1 in channels A and C respectively. Channel A is now interrupted whilst channels B and C remain operative. Should the fault be in a signal responsive device or in a relay, none of the channels are interrupted.