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2.10.12 Boeing Proprietary
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787 Flight Crew Operations Manual
Air Systems Chapter 2
Air Conditioning System Description Section 20
Boeing Proprietary 2.20.1
2.20 Air Systems-Air Conditioning System Description Introduction
The air conditioning system supplies conditioned outside air and recirculated
cabin air at a controlled temperature throughout the airplane.
The system supplies conditioned air to the flight deck shoulder heaters.
The system supplies ventilation for the passenger cabin:
• lavatories
• galleys
The system supplies ventilation for the:
• overhead crew rest compartments
Pack control, zone temperature control, cabin air recirculation, fault detection, and
overheat protection are all automatic. Backup system control modes operate
automatically in the event of system failures.
The airplane is divided into seven temperature zones: the flight deck and six
passenger cabin zones.
Note: Zones A and B contain sub-zones A1 and B1 not depicted on the air
synoptic.
Air Conditioning Packs
Outside air is supplied to four electric cabin air compressors (CAC) through two
dedicated ram scoops located in the wing to fuselage fairing. The air is pressurized
and flow-regulated by the CACs and supplied to two identical air conditioning
packs. Two CACs are dedicated to each pack. A single CAC provides sufficient
air to operate its associated pack in all operating modes. Packs are controlled by
two identical pack control systems. If one system fails, pack control switches
automatically to the other system.
Air flow to the packs is controlled by regulating the cabin air compressors. CAC
output is increased automatically during high demand periods (to compensate for
a failed pack), or is limited during electrical load shed conditions to ensure
sufficient electrical power is available to other critical systems. During normal
operation, outside airflow is controlled to ensure that a minimum ventilation rate
is maintained.
Pack Ground Operation
Both air conditioning packs are normally selected to AUTO for ground operations.
To maximize system efficiency, one CAC on each side is off when the APU is the
power source. For normal engine starts, the CACs will be commanded
787 Flight Crew Operations Manual
Air Systems -
Air Conditioning System
Description
2.20.2 Boeing Proprietary
off immediately. For an engine start in flight, power is also removed from the
CACs immediately to maximize availability of power for an engine start.
A ground source of conditioned air may be used to supply conditioned air directly
to the cabin distribution system, eliminating the need for pack operation.
Pack Non–Normal Operation
Pack control, fault detection, and overheat protection are all automatic. If an
overheat or other significant pack fault is detected, the pack shuts down
automatically and the EICAS advisory message PACK (L, R) is displayed. An
attempt to restore pack operation may be made by pressing the AIR
CONDITIONING RESET switch.
Standby Cooling Mode
For certain internal malfunctions, pack control automatically uses standby cooling
mode as a backup to normal mode. In standby cooling mode, the EICAS advisory
message PACK MODE (L, R) is displayed, and STBY COOLING is displayed in
amber on the AIR synoptic.
If one pack is in standby cooling and the other pack is operating normally, the pack
in standby cooling mode shuts down at lower altitudes and higher outside air
temperatures when ambient conditions do not permit standby cooling. The pack
restarts automatically when altitude and outside air temperatures are suitable for
standby cooling.
In standby cooling mode, pack cooling capacity may be less than in normal mode
and may result in warm flight deck or cabin temperatures at lower altitudes.
Air Distribution
Recirculation fans assist the packs to maintain a constant ventilation rate through
the cabin. The fans draw cabin air through filters, then reintroduce the air into the
conditioned air distribution system.
The flight deck receives 100% conditioned outside air and the passenger cabin
receives a mix of outside air and recirculated air. Flight deck pressure is
maintained slightly higher than the passenger cabin pressure to prevent smoke
from entering the flight deck. Some recirculated air is supplied to the flight deck
if one pack is off and its associated lower recirculation fan is on.
Outside air flow is reduced during failure conditions and electrical load shed
conditions to protect the electrical power distribution system and to ensure that
sufficient electrical power is available to other critical aircraft systems. Cabin
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787机组操作手册Flight Crew Operations Manual 1(126)
