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are prevented from opening to decrease APU and ground source bleed air demand.
Air Distribution Diagram
Pilot Auxiliary Heat
Flight crew shoulder heat is provided by electric elements in the side window and
pilot shoulder air diffusers. The foot heaters have electric heating elements under
the pilot foot area. Shoulder heat and foot heat are available in flight.
Equipment Cooling
The equipment cooling system provides cooling air for flight deck equipment and
the electrical and electronic (E & E) compartment equipment racks. The system
uses internal fans and valves to direct cool cabin air from inside the lower fuselage
into the equipment racks. The warm exhaust air is ducted into the forward cargo
compartment, recirculated in a closed loop mode through the E & E compartment
cooling racks, or ducted overboard.
On the ground, with the engines not operating, the Equipment Cooling selector in
NORM, and ambient temperatures moderate or high, the warm exhaust air is
ducted overboard through the ground exhaust valve. With lower ambient
temperatures, the ground exhaust valve is closed and the system is configured for
flight.
On the ground, when one or more engines on each wing are operating, the system
configures for flight to allow cabin pressurization. Positioning the Equipment
Cooling selector to STBY closes the overboard exhaust valve to manually
configure the airplane for flight.
In flight configuration, the inboard exhaust valve is open and the warmed
equipment cooling exhaust air discharges into the forward cargo compartment.
With the Equipment Cooling selector in NORM or STBY, the system normally
configures to closed loop mode if a single internal fan fails. In closed loop mode,
the inboard exhaust valve is closed.
Equipment Cooling Non-Normal Operation
With the Equipment Cooling selector in NORM, the airplane on the ground, and
with one or more engines on each wing operating, the EICAS alert message
EQUIP COOLING is displayed if the equipment cooling system is not configured
for flight. Positioning the selector to STBY configures the system for flight.
April 01, 2001
747 Operations Manual
Air Systems -
Air Conditioning System
Description
Copyright © The Boeing Company. See title page for details.
D6-30151-425 2.20.5
An override mode provides equipment cooling in flight if internal fans are
inoperative. With the Equipment Cooling selector in OVRD, the internal fans
deactivate and the smoke/override valve opens with all other valves closed. The
smoke/override valve opens to an overboard vent allowing cabin differential
pressure to draw air from the panels area on the flight deck, through the equipment
cooling ducts to the E & E compartment equipment racks, to create a reverse flow
of air across the equipment, then through the supply duct, and overboard.
April 01, 2001
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
2.20.6 D6-30151-425
Air Systems -
Air Conditioning System
Description
Equipment Cooling Control Diagram
ELECTRICAL/ELECTRONIC (E/E)
EQUIPMENT COMPARTMENT
FLIGHT DECK
ELECTRICAL
EQUIPMENT
TO FORWARD
SMOKE/OVERRIDE
VALVE
EQUIPMENT
SUPPLY
VALVE
GROUND
EXHAUST
VALVE
INBOARD
EXHAUST
VALVE CABIN
AIR CARGO HEAT
STBY OVRD
NORM
STBY OVRD
NORM
STBY OVRD
NORM
• Normal Operation
• Normal Operation includes
reconfiguring after supply
and exhaust fan failure
to maintain E/E equipment
cooling:
- Inboard Exhaust valve closes
- no airflow to forward cargo
- no EICAS message displayed
• Cooling system operates in
reverse flow using differential
pressure to exhaust cooling air
through Smoke/Override valve
• No cooling exhaust airflow to
Above 45`F (7`C),
Smoke/Override valve
Ground Exhaust valve
closes and Inboard
Exhaust valve opens
opens.
Equipment Supply valve
and Ground Exhaust
valve close.
Ground Exhaust valve
opens and Inboard
Exhaust valve closes.
Below 45`F (7`C),
Ground Exhaust valve
closes and Inboard
Exhaust valve opens.
SYSTEM OPERATION
EQUIPMENT COOLING
VALVE CONFIGURATION
EQUIPMENT COOLING
SWITCH POSITION
Inboard Exhaust valve,
Condition: - Normal Operation
• two or more packs
operating
• one or more engines on
each wing operating
forward cargo
April 01, 2001
747 Operations Manual
Air Systems Chapter 2
　
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