787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Air Systems -
Air Conditioning System
Description
Copyright © The Boeing Company. See title page for details.
2.20.2 D615Z003-TBC
Pack Ground Operation
Both air conditioning packs are normally selected to AUTO for ground operations.
Each pack uses a ram fan to draw air through the ram air system for ground
operation cooling when sufficient main A/C Bus power is available. Normally, to
maximize system efficiency, only one CAC on each side runs when using the APU
as the power source. During cold weather operations both CACs are commanded
on.
For normal engine starts, all CACs are commanded off during initial start
sequence with corresponding PACK L and PACK R messages inhibited. Packs do
not restart until at least two minutes after the engine start sequence is initiated and
the engine is running. If both engines are started together, and the two minute limit
is met, packs restart immediately after the second engine is running.
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.
For an in-flight starter assisted engine start, only one CAC runs to maintain pack
operation and maximize power available for the engine cross start.
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.
February 15, 2010
To Next Page
Loading...
