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.
2.20.10 D615Z003-TBC
• both flow sensors fail, or
• in flight, low airflow is detected, or
• in flight, excessive temperature is detected in the forward equipment
cooling system, or
• smoke is detected in the forward equipment cooling system or the forward
cargo area, or
• the FWD CARGO FIRE ARM switch is ARMED
In the override mode, the forward cargo heat and overboard vent valves are closed,
the vent fan and both supply fans are commanded off, and the forward equipment
cooling override valve is commanded to the override position.
Cabin differential pressure draws air through the flight deck panels and the
forward E/E equipment racks to create a reverse flow of air across the equipment,
then exits through the override valve to an overboard venturi.
The override mode supplies adequate cooling while the airplane is in cruise, but
the airflow decreases as the airplane descends as the cabin pressure differential
decreases.
In flight, the FWD EQUIP COOLING switch in OVRD aids smoke evacuation
from the flight deck.
On the ground, the EICAS advisory message EQUIP COOLING FWD is
displayed and the ground crew call horn in the wheel well sounds if the forward
equipment cooling system is inoperative.
Aft Equipment Cooling
The aft equipment cooling system is similar in layout and functionality to the
forward equipment cooling system. It provides cooling and ventilating air for the
aft E/E equipment compartment and heating/ventilating air for aft cargo
compartment.
The aft system uses internal fans and valves to direct cabin air to the aft equipment
bay and ventilates the warm exhaust air to a dedicated overboard exhaust valve or
aft cargo compartment. There are two cooling system supply fans, a primary and
a backup. If the primary supply fan fails, the backup supply fan operates
automatically.
The aft system reconfigures automatically to an override mode when:
• the AFT EQUIP COOLING switch is selected to OVRD, or
• in flight, both supply fans fail, or
• both flow sensors fail, or
• in flight, low airflow is detected, or
• in flight, excessive temperature is detected in the forward equipment
cooling system, or
February 15, 2010
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