777 AIRCRAFT MAINTENANCE MANUAL
A/C -EQUIPMENT COOLING -OPERATION
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A/C -EQUIPMENT COOLING -GROUND TESTS
General
You select the equipment cooling ground tests from ATA 21 Environmental Control System.
Equipment Cooling
This test makes sure that these equipment cooling LRU installations are correct:
*
Sensors
*
Valves
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Fans. The test takes 2 to 5 minutes.
This test shows for these ground test types:
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System test
*
LRU replacement test.
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777 AIRCRAFT MAINTENANCE MANUAL
A/C -EQUIPMENT COOLING -GROUND TESTS
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777 AIRCRAFT MAINTENANCE MANUAL
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21-30-00
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AIR CONDITIONING -PRESSURIZATION -INTRODUCTION
Purpose
The cabin pressurization system controls cabin altitude and protects the fuselage structure against internal and external overpressurization.
Abbreviations and Acronyms
*
actr -actuator
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ADIRS -air data inertial reference system
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ADIRU -air data inertial reference unit
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AFDS -autopilot flight director system
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AGS -air/ground system
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AIMS -airplane information management system
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alt -altitude
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ARINC -Aeronautical Radio, Inc.
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ASCPC -air supply cabin pressure controller
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auto -automatic
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brk -brake
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capt -captain
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CMCF -central maintenance computing function
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decr -decrease
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ECS -environmental control system
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EEC -electronic engine control
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EFIS -electronic flight instrument system
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elex -electronics
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ELMS -electrical load management system
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F/O -first officer
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flt -flight
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FMCF -flight management computing function
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fwd -forward
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incr -increase
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ldg -landing
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man -manual
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max -maximum
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mgmt -management
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MFD -multi-function display * ofv -outflow
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OPAS -overhead panel ARINC 629 system
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PDF -primary display function
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pnl -panel
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pos -position
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press -pressure
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PSI -pounds per square inch
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pwr -power
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RVDT -rotary variable differential transformer
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sol -solenoid
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snsr -sensor
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stby -standby
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VCU -valve control unit
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vlv -valve
*
WOW -weight-on-wheels
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AIR CONDITIONING -PRESSURIZATION -INTRODUCTION
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AIR CONDITIONING -PRESSURIZATION -GENERAL DESCRIPTION
General
These are the two parts of the pressurization system:
*
cabin pressure control
*
cabin pressure relief.
The cabin pressure control system controls the amount of air that flows out of the airplane. This keeps the cabin air pressure in limits at altitude.
The cabin pressure relief system keeps the internal pressure of the airplane to a limit.
The pneumatic system usually supplies more than a sufficient quantity of air through the air conditioning packs to pressurize the airplane. Outflow valves in the forward and aft areas of the airplane control the amount of air that goes out of the airplane. This keeps the cabin air pressure within limits.
Outflow Valves
You can set the outflow valve control to automatic or manual mode from the flight deck. The forward and aft outflow valves can each be set to automatic or manual mode independent of the mode set for the other valve. When you set the two outflow valves to the automatic mode, the usual position of the valves is so that 20 percent of the total air outflow goes out through the forward outflow valve and 80 percent goes out through the aft outflow valve.
In the manual mode, you control the position of one or both of the valves.
Pressure Relief
Positive pressure relief valves and negative pressure relief vents, in the forward part of the airplane keep the difference between cabin pressure and ambient pressure in limits.
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