*
Automatically select a good AFDC for master after a failure disengages the autopilot.
The AFDS does not use the master/slave function in autoland.
Selection Process
The AFDCs use these methods to select the master AFDC:
*
The right AFDC is the master when the AFDS gets power
*
The master AFDC changes each time the autopilot disengages and re-engages.
Master AFDC Function
The master AFDC does these functions:
*
Column and wheel backdrive actuator selection and control in cruise
*
Wheel backdrive actuator selection during BAP
*
Control of AFDS modes
*
Sends AFDS mode data to the slave AFDCs
*
Calculate pitch, roll and yaw commands.
If the master AFDC cannot do these functions, the autopilot disengages. You can engage the autopilot again with a different AFDC as the master.
The MCP microprocessor in control follows the master AFDC selection when:
*
The left AFDC is the master, MCP microprocessor A writes to all the MCP displays
*
The right AFDC is the master, MCP microprocessor B writes to all the MCP displays.
Slave AFDC Function
The slave AFDC does these functions:
*
Calculate pitch, roll and yaw commands
*
Receives AFDS mode data from the master AFDC
*
Limits the AFDS pitch and roll commands to safe values.
If a slave AFDC cannot do its functions, the PFCs do not use autopilot commands from that AFDC.
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AFDS -FUNCTIONAL DESCRIPTION -ENGAGE INTERLOCKS MASTER/SLAVE SELECTION
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AFDS -ILS ANTENNA SWITCHING LOGIC
ILS Antenna Switching
The autopilot flight director computers (AFDCs) select the position of their onside localizer and glideslope antenna switches.
ILS Tune Inhibit
The AFDCs prevent tuning of the multi-mode receivers (MMRs) when the airplane makes an autopilot engaged approach. The AFDCs also prevent tuning of the MMRs when the pilot makes a flight director only approach and the airplane is below 500 feet of radio altitude.
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777 AIRCRAFT MAINTENANCE MANUAL
AFDS -ILS ANTENNA SWITCHING LOGIC
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AFDS -FUNCTIONAL DESCRIPTION -WARNING AND ANNUNCIATION INTRODUCTION
General The AIMS also turns on the master caution light and causes the
WES to make the caution aural. The AFDCs warning and annunciation functions send normal and non-normal indications of AFDS performance to:
*
The AIMS cabinets
*
The warning electronic system (WES).
Description
Each AFDC sends this normal data to the AIMS cabinets:
*
Mode
*
Status
*
Flight director commands
*
Autoland status.
AIMS shows this data on the primary flight displays (PFDs).
Each AFDC sends this non-normal data to AIMS:
*
Autopilot disconnect warning
*
Autopilot caution
*
Autoland status
*
Mode fail
*
Flight director (F/D) fail.
Each AFDC sends the disconnect warning discrete to the WES. This causes the master warning lights and the siren to come on.
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AFDS -FUNCTIONAL DESCRIPTION -WARNING AND ANNUNCIATION INTRODUCTION
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AFDS -FUNCTIONAL DESCRIPTION -WARNING AND ANNUNCIATION -PFD AND ND DISPLAYS
General
The primary flight displays (PFDs) show AFDS modes, status messages, and flight director (F/D) information. The PFD also shows selected mode control panel (MCP) data.
Display Priority
The AIMS uses the validity of the three AFDCs and the MCP A and B processors to find the priority for the displays.
This is the AFDC priority for the captain PFD:
*
left AFDC if valid
*
Center AFDC if left AFDC is not valid
*
Right AFDC if left and center AFDCs are not valid.
This is the AFDC priority for the first officer PFD:
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