*
Priority selection for signals with two sources (left, right). For example, the air data inertial reference unit (ADIRU) is the normal source of air and inertial reference data. If the ADIRU fails, the AFDC selects the secondary attitude air data reference unit (SAARU).
*
Forced selection for airplane information management system (AIMS) data. AIMS tells the AFDC which signal to use.
AFDC Processors
The AFDC has three processors. Processors A and B receive digital backdrive commands from the primary flight computers (PFCs). They convert the digital backdrive commands into analog. Processor C calculates the autopilot and flight director control laws. Processor C also does these functions:
*
Test and data load.
*
Engage/disengage logic
*
Failure detection/fault response monitor
Power Supplies
The logic power supply sends +5v dc, +15v dc, -15v dc, and +28v dc to internal components of the AFDC. It also sends +28v dc disengage power to the mode control panel (MCP).
The backdrive clutch power supply sends +28v dc to the backdrive clutch engage logic and relays.
Three backdrive power supplies send drive signals to the wheel, column, and rudder pedal backdrive actuators. Each power supply is a variable voltage push-pull power supply that sends +/-50v dc to each backdrive actuator. Commands from the A and B processors control the variable output of the power supplies.
The center AFDC does not connect to backdrive actuators and does not use its backdrive power supplies.
The battery warning power supply sends +28v dc to the battery warning logic.
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AFDS -AUTOPILOT FLIGHT DIRECTOR COMPUTER -FUNCTIONAL BLOCK DIAGRAM
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AFDS -AUTOPILOT DISCONNECT SWITCH
Purpose
The autopilot disconnect switches are on the outboard side of each control wheel. The example shows the captain’s control wheel. The first officer has the switch on the right side of the wheel. Each switch has a push-button and multiple contacts. These switches manually disconnect all AFDCs.
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777 AIRCRAFT MAINTENANCE MANUAL
AFDS -AUTOPILOT DISCONNECT SWITCH
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AFDS -BACKDRIVE ACTUATOR INSTALLATION -1
Purpose
The backdrive actuators are variable torque motors. They move the control columns, control wheels, and rudder pedals during autopilot operation. This movement gives the flight crew an indication of the autopilot commands that go to the primary flight computers (PFCs).
A control wheel backdrive actuator also operates when the bank angle protection (BAP) function operates. The actuator supplies a variable torque to the roll control system if the airplane bank angle exceeds 35 degrees. BAP is available with the autopilot engaged or disengaged.
There are two backdrive actuators for each of the control columns, control wheels, and rudder pedals. The backdrive actuators are interchangeable.
Location
The six backdrive actuators are below the floor in the 41 section. Access to the control wheel and rudder pedal backdrive actuators is by the main equipment center access door. Access to the control column backdrive actuators is through the forward equipment center access door.
Physical Description
Each actuator weighs about 8 lbs (3.6 kg) and attaches to the airplane structure with four bolts.
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AFDS -BACKDRIVE ACTUATOR INSTALLATION -1
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AFDS -BACKDRIVE ACTUATOR INSTALLATION -2
General
The right control column backdrive actuator is below the flight deck floor. Access is through the forward equipment center.
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AFDS -BACKDRIVE ACTUATOR INSTALLATION -2
EFFECTIVITY BEJ ALL 22-11-00 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：777 AMM 飞机维护手册 自动飞行 Autoflight(11)
