21-50-00

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AIR CONDITIONING -COOLING -GROUND TESTS

General
These are the cooling ground tests that show when you select ATA 21 Cabin Temperature Control System:
*
Left pack actuators

*
Left system air on

*
Left system air off

*
Right pack actuators

*
Right system air on

*
Right system air off.

Left and Right Pack Actuators
This test makes sure that the related cabin temperature controller can control these air conditioning pack LRUs:
*
Ram air inlet door

*
Turbine bypass valve

*
Low limit valve.

During this test, the related pack operation stops, and the ram air doors move. The test takes approximately 3-5 minutes.
This test shows for these ground test types:
*
System test

*
Operational test

*
LRU replacement test.

EFFECTIVITY
BEJ ALL

Left and Right System Air On
This test makes sure that the related cabin temperature controller can control these air conditioning pack and trim air LRUs:
*
Upper flow control valve

*
Lower flow control valve

*
Economy cooling valve

*
Air cycle machine

*
Trim air pressure regulation and shutoff valve.

During this test, the related pack operation stops, and the ram air doors move. The test takes approximately 5-10 minutes.
This test shows for these ground test types:
*
System test

*
Operational test

*
LRU replacement test.

Left and Right System Air Off
This test makes sure that the related cabin temperature controller can control these air conditioning pack LRUs:
*
Ram air inlet door

*
Turbine bypass valve

*
Low limit valve.

This test also makes sure that the related cabin temperature controller can control the trim air system on that side.
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AIR CONDITIONING -COOLING -GROUND TESTS

During this test, the related pack and trim air operation stops, and the ram air doors move. The test takes approximately 2-3 minutes.
This test shows for these ground test types:
*
System test

*
Operational test

*
LRU replacement test.

EFFECTIVITY BEJ ALL  21-50-00 
Page 18 
D633W101-BEJ  Sep 05/2002 

777 AIRCRAFT MAINTENANCE MANUAL

AIR CONDITIONING -COOLING -GROUND TESTS

EFFECTIVITY BEJ ALL  21-50-00 
Page 19 
D633W101-BEJ  Jan 05/2002 

AIR CONDITIONING -PACK FLOW CONTROL -INTRODUCTION

Purpose
The flow control system controls the quantity of air that goes from the pneumatic system into the air conditioning packs. These are the functions of the pack flow control system:
*
Pack air on/off control

*
Pack air flow regulation

*
Ozone converter bypass

*
Backup pack flow control

*
Engine air supply system bias.

The CTCs and the ASCPCs have logic that control the pack air flow. The ASCPCs have the backup pack flow control.
Components
The pack flow control system has these components:
*
Pack flow sensor

*
Upper flow control and shutoff valve

*
Lower flow control and shutoff valve

*
Primary heat exchanger inlet temp sensor.

The systems for the left and right packs are the same.
EFFECTIVITY BEJ ALL
Pack Air On/Off Control
With the air conditioning pack switch off, the two flow control and shutoff valves close. With the pack switch in AUTO, the flow control valves control pack air flow. The valves close if the pack fails, has an overheat condition, or if a higher priority bleed user is on.
Pack Air Flow Regulation
The flow control system makes decisions about the amount of air the packs can have. These decisions take into account the needs of other bleed air users and airplane operating conditions.
Ozone Converter Bypass
The ozone converter decreases the amount of atmospheric ozone that goes into the cabin. Ozone is in the atmosphere at high altitudes. The ozone converter is serviceable for a longer time if it operates only at high altitudes. At low altitudes the lower flow control valve closes and the upper valve controls flow. At high altitude the upper valve closes and the lower valve controls flow.
Backup Pack Flow Control
If only battery or standby power are available, the packs operate in a backup mode. The flow control system adjusts the pack air flow to keep the pack outlet temperature in limits.
　
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