AFDC -FLIGHT CONTROLS ARINC 629 BUSES INTERFACE
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AFDS -ARINC 429 DATA BUS INTERFACE
Mode Control Panel
The mode control panel (MCP) has three 429 input data buses and two 429 output data buses.
The MCP receives mode requests and target values from the three AFDCs on separate data buses.
The MCP sends this information to the three AFDCs:
*
Autopilot engage requests
*
Mode requests
*
Target values
*
Maintenance data.
The MCP sends LNAV and VNAV mode requests and maintenance data to the AIMS cabinets.
Instrument Landing System (ILS)
Each multi-mode receiver (MMR) sends runway course and ILS deviation data to the on-side AFDC.
Radio Altimeter (RA) Transceiver
Each radio altimeter transceiver sends radio altitude data to the on-side AFDC.
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777 AIRCRAFT MAINTENANCE MANUAL
AFDS -ARINC 429 DATA BUS INTERFACE
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AFDS -CROSS-CHANNEL DATA INTERFACE
Cross Channel Bus and Discrete Information
Each AFDC receives digital data on cross-channel (X-CH) buses for monitor, signal selection, and synchronization functions.
Each AFDC continuously sends an AFDC ALIVE discrete to the other AFDCs if it does not detect any internal faults.
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777 AIRCRAFT MAINTENANCE MANUAL
AFDS -CROSS-CHANNEL DATA INTERFACE
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AFDS -MISCELLANEOUS ANALOG DISCRETES INTERFACE
General
Th discrete inputs to the AFDC are from these switches:
*
Autopilot disconnect switches
*
Takeoff/go-around (TO/GA) switches
*
Autopilot disengage bar.
Interface
Each control wheel has an autopilot disconnect switch. These switches supply the A/P disengage and A/P warning reset discretes to each AFDC.
Two takeoff go-around (TO/GA) switches on the left and right thrust levers supply a discrete to each AFDC. The left discrete goes to both AIMS cabinets.
The disengage bar on the MCP supplies a secondary method to disengage the AFDCs. When the bar is in the up position, the disengage switches supply power to the engage relay in the AFDCs. When the bar is in the down position, the disengage switches supply a ground to this relay.
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AFDS -MISCELLANEOUS ANALOG DISCRETES INTERFACE
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AFDS -WARNING ANALOG DISCRETES INTERFACE
Warning Electronic System
These signals go to the warning electronic units (WEUs) when there is an autopilot disconnect:
*
Autopilot disconnect warning normal (A/P DISC WARN NORM)
*
Autopilot disconnect warning battery 1 (A/P DISC WARN BAT 1)
*
Autopilot disconnect warning battery 2 (A/P DISC WARN BAT 2).
When the WEUs receive at least two of the three warning signals, they make the master warning lights show and the siren sounds.
AIMS
The A/P DISCONNECT WARN BAT 2 discretes are connected together outside of the AFDCs and go to the two AIMS cabinets. The primary display function of AIMS shows a warning message on EICAS.
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AFDS -WARNING ANALOG DISCRETES INTERFACE
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AFDS -ILS ANALOG DISCRETES INTERFACE
Tune Inhibit Discrete
During an approach with the flight director or autopilot engaged, the AFDCs send a tune inhibit discrete to the multi-mode receivers (MMRs). The tune inhibit discrete inhibits flight crew from tuning the MMRs.
Antenna Switch Interface
Each AFDC controls its antenna switches for the LOC and G/S antennas.
The LOC antenna request discrete signal controls a localizer antenna switch that connects the LOC antenna to the MMR. One set of switch contacts sends feedback to the AFDC to show the position of the relay.
The G/S capture antenna request discrete signal controls a glideslope antenna switch that connects the G/S track antenna to the MMR. One set of switch contacts sends feedback to the AFDC to show the position of the relay.
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