AIR CONDITIONING -CABIN PRESSURE RELIEF SYSTEM -POSITIVE PRESS RELIEF VALVE AND FILTER

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AIR CONDITIONING -CABIN PRESSURE RELIEF SYSTEM -NEGATIVE PRESS RELIEF VENT

Purpose
The negative pressure relief vent opens when cabin pressure is less than ambient pressure. This prevents negative cabin pressure. Too much negative cabin pressure could damage the fuselage structure.
Physical Description
The negative pressure relief vent is a spring-loaded door. The door starts to open at a differential pressure of 0.2 psi. It is full open at a differential pressure of 0.5 psi.
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AIR CONDITIONING -CABIN PRESSURE RELIEF SYSTEM -NEGATIVE PRESS RELIEF VENT

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777 AIRCRAFT MAINTENANCE MANUAL

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21-40-00

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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.

AIR CONDITIONING -HEATING -INTRODUCTION

Purpose
Heat sources add heat to cabin areas and cargo compartments to keep temperatures at necessary levels.
Forward Cargo Heating
The forward cargo compartment uses warm air from the equipment cooling system to keep temperature in limits. See the forward cargo compartment heating section for more information about the forward cargo compartment heating (SECTION 21-43).
Aft and Bulk Cargo Heating
The aft and bulk cargo compartments use air from the pneumatic system to keep temperature in limits. See the aft and bulk cargo compartment heating section for more information about the aft and bulk cargo compartment heating (SECTION 21-44).
Supplemental Heating
These areas use electric heaters to keep temperature in limits.
*
Flight deck foot and shoulder heaters

*
Door heaters

*
Galley heaters.

See the supplemental heating section for more information about the supplemental heating system (SECTION 21-45).
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777 AIRCRAFT MAINTENANCE MANUAL

AIR CONDITIONING -HEATING -INTRODUCTION

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AIR CONDITIONING -HEATING -AIR SYNOPTIC DISPLAY AND MAINTENANCE PAGE
General
The air synoptic display and the maintenance page show this cargo compartment temperature data:
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Target temperature, set on the flight deck

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Actual compartment temperature.

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AIR CONDITIONING -HEATING -AIR SYNOPTIC DISPLAY AND MAINTENANCE PAGE

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AIR CONDITIONING -HEATING -GROUND TESTS

General
These are the heating ground tests that show when you select ATA 21 Environmental Control System:
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Aft cargo heat

*
Bulk cargo heat

*
Door area heater.

Aft Cargo Heat
This test makes sure that these LRU installations are correct:
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Aft cargo heat shutoff valve

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Aft cargo heat temperature control valve

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Aft cargo compartment temperature sensor.

You must pressurize the pneumatic system for this test. During this test, hot air comes out of the aft cargo heat duct. This test takes approximately 2-5 minutes.
This test shows for these ground test types:
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System test

*
LRU replacement test.

Bulk Cargo Heat
This test makes sure that these LRU installations are correct:
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Bulk cargo heat shutoff valve

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Bulk cargo heat temperature control valve

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Bulk cargo ventilation fan

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Bulk cargo compartment temperature sensor.

You must pressurize the pneumatic system for this test. During this test, hot air comes out of the bulk cargo heat duct. This test takes approximately 2-5 minutes.
This test shows for these ground test types:
*
System test

*
LRU replacement test.

Door Area Heater
This test makes sure that all passenger door area heater installations are correct.
　
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