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TRAILING EDGE FLAPS -ALTERNATE FLAPS PANEL

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777 AIRCRAFT MAINTENANCE MANUAL

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TRAILING EDGE FLAPS -FLAP/SLAT ELECTRONICS UNIT (FSEU)

General

The two flap/slat electronics units (FSEUs) control the flaps and slats in the primary and secondary modes. Only one FSEU is in control of the flaps and slats at a time. The other FSEU does not send commands to the flaps and slats. The FSEUs automatically transfer control to the other FSEU after a post-flight self-test of the FSEUs or after disengagement from the alternate mode. There is also an automatic transfer after a fault in the FSEU in control.
Physical Description

The two FSEUs are the same and interchangeable. Each FSEU contains two independent channels: the control channel and the monitor channel. The two channels have different microprocessors, made by different manufacturers. The microprocessors have different part numbers. The two channels have the same capabilities and operate with the same software.
Program pins on each FSEU supply information on FSEU location and software. Cooling for both FSEUs is passive.
Channel Functions

The control channel and the monitor channel of each FSEU has:
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A set of HLCS sensor inputs

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An analog to digital (A/D) converter

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A set of control laws

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A failure monitor

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A cross-channel monitor

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A lane monitor

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Separate interfaces with the ARINC 629 buses.

HLCS Sensor Inputs
Each channel receives inputs from the HLCS sensors. Failure of a sensor can cause the control to change to the other FSEU.
A/D Converter
The FSEU changes the analog inputs to digital format before using them in the control laws.
Control Laws
The FSEUs use control laws to calculate the commands for the flaps and slats in the primary and secondary modes. Each channel sends the commands to output drivers. Both channels must agree on the commands to permit the FSEU to supply a ground for the flap and slat solenoids or relays.
Failure Monitor
Each channel monitors the HLCS for these conditions:
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Flap position failure

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Slat position failure

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Slat loss.

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TRAILING EDGE FLAPS -FLAP/SLAT ELECTRONICS UNIT (FSEU)

If the FSEU detects one of these conditions, the FSEU stops the commands to the failed surface.
Cross-Channel Monitor

The cross-channel monitor compares the commands from the control and monitor channels. The output command signals to control the flaps and slats go to the opposite channel for comparison. If the commands disagree, then the FSEU stops all commands. Control then changes to the other FSEU.
The alternate arm switch position signals to the FSEU directly disable the output commands. If this switch is in the ARMED position, the FSEU stops all commands.
Lane Monitor

The lane monitor compares the input signals to both channels in each FSEU. The lane monitor receives the inputs from the other FSEU in two ways.
One way is through the cross-lane ARINC 429 buses. The other way is through the systems ARINC 629 buses. If the input signals to the FSEU in control fails, then the control changes to the other FSEU.
ARINC 629 Buses
Each channel transmits and receives data from the systems ARINC 629 buses. Each channel transmits its own commands, and receives commands from the other channel and from the other FSEU. Each channel receives data from two of the systems buses for redundancy.
Training Information Point
Use the maintenance access terminal (MAT) to load the software for the FSEUs. After you load the software, push the alternate flaps arm switch to the ARMED then NOT ARMED position. This removes any EICAS messages for the HLCS.

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TRAILING EDGE FLAPS -FLAP/SLAT ELECTRONICS UNIT (FSEU)

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TRAILING EDGE FLAPS -FLAP PRIMARY CONTROL VALVE

Purpose

The flap primary control valve controls hydraulic power to the hydraulic motor. In the primary mode, this valve controls the direction and speed of movement of the flap drive system. In the secondary and alternate modes, this valve prevents hydraulic power to the hydraulic motor.
　
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