Patent GB-975540-A (GB)
Title: Improvements in or relating to monitoring and warning systems for aircraft
IPC: G05D1/00
Filed: 1962-09-20
Abstract: 975, 540. Electric measuring systems. BENDIX CORPORATION. Sept. 20, 1962 [Sept. 29, 1961], No. 35869/62. Heading G1N. A monitoring system for a craft comprises a control means having two operating positions, in the first of which two input members of a differential are respectively operated in accordance with the signals from two sensors responsive to a common variable being monitored, and in the second of which the connection between one sensor and the corresponding input member of the differential is interrupted and a connection is simultaneously provided from the output of the differential to an indicator which monitors the output of the second sensor relative to the output of the first at the instant when the control means is operated. In a third position of the control means the connection between the second sensor and the second input member is broken and a brake associated with that member is actuated. The Mach number of an aircraft is measured by an air condition sensing device 9 and by a Mach meter 101. The Mach meter continuously positions the armature 44 of a differential device, E-pickup 43. Device 9 positions the rotor of a synchro 11 and the resulting signal is transmitted through differential synchro 13 to receiver 12. A conventional servo loop including switch contacts 19, 20, amplifier 18, motor 25 and rate generator 27 positions the rotor of receiver 12 and simultaneously rotates shafts 28A and 28B. Shaft 28B positions E-core 105 of pickup 43 through a normally engaged clutch 30. If switch 21 is moved to its second position, the servo loop including contacts 19, 20 is broken and motor 25 is instead controlled by the output from differential 105 through contacts 113, 115 and 119, 20. Simultaneously contacts 192, 194 are closed connecting winding 38 of a normally open clutch 29 to power supply 73. The clutch engages so that shaft 28A actuates indicator 34, 35 and also positions the shaft 14 of differential synchro 13. Variations between the two sensors are thereby indicated. Scale 85 may be manually repositioned relative to the pointer by knob 300. The system may also warn of changes from a predetermined Mach number. For this mode switch 21 is in its first position and switch 125 is operated to close contacts 126, 127. Relay coil 129 is then energized to operate switch 78. Contacts 165, 167 close to energize clutch winding 40 to disengage clutch 30 and engage brake 173, locking E-core 105 and parallel shaft 67 through gears 65, 66. Contacts 76, 77 close to energize clutch winding 71 to engage clutch 68 so that shaft 69, gear 61 and idler gear 45 are locked. Idler gear 45 is rotatably mounted on shaft 28B and carries switches 53, 54, 85, 86 which are actuable by arm 47 on shaft 28B. Contacts 113, 145 close to apply the output of differential 43 to amplifier 151. When the differential output exceeds a predetermined value due to a change in the output of Mach meter 101, relay 149 is operated to energize bell 156 and lamp 158. A predetermined change in the output of sensor 9 rotates shaft 28B and arm 47 to close switch 53 or 54 and actuate bell 187 and lamp 185, or 186 and 184. Further rotation of shaft 28B closes limit switch 85 or 86 to actuate relay 72 and de-energize clutch 71, allowing idler 45 to be recentered by springs (not shown). Actuation of switch 21 to its second position nullifies the effect of switch 125 by opening contacts 135, 137 and indicator 34, 35 indicates the actual change in Mach number since switch 125 was closed. When switch 21 is released the system will continue to monitor flight at the new Mach number. Relay 149 may be replaced by a phase-sensitive relay having separate bells and lamps for energization when the Mach number increases or decreases excessively. Specifications 446,665 and 774,341 are referred to.