Equiptment Cooling

Question 1

Equipment cooling provides cooling air for what compartment/systems?

Answer 1

• Flight deck equipment
• Electrical and electronic (E & E) compartment equipment racks.
FCOM, VOL 2; 2.20.20

Question 2

When is warm equipment cooling air ducted overboard on the ground?

Answer 2

• Engines not operating
• Equipment cooling selector in NORM
• Ambient temperature is moderate or high.
FCOM, VOL 2; 2.20.14; 2.20.18

Question 3

When does the equipment cooling system configure for flight?

Answer 3

• One or more engines on each wing is operating, or
- The EQUIP COOLING selector in STBY.
- LLCCAFR selector is OFF, FWD LOW, BOTH LOW OR FWD HIGH,
and temperature selected 10C or higher selected,
- Engines not running and LOWER than normal temperatures on
the ground.

FCOM, VOL 2; 2.20.14

Question 4

How can you manually configure the equipment cooling system for flight?

Answer 4

• Positioning the Equipment Cooling Selector to STBY.

FCOM, VOL 2; 2.20.14

Question 5

Which valve is closed when equipment cooling is in closed loop mode?

Answer 5

• Inboard exhaust valve

FCOM, VOL 2; 2.20.14

Question 6

What is the source of equipment cooling air for the flight deck?

Answer 6

• With two or three packs operating, the flight deck equipment
cooling source valve directs conditioned air into the flight deck
electrical equipment.
FCOM, VOL 2; 2.20.15

Question 7

Describe the operation of the equipment cooling system with the Equipment Cooling Selector in OVRD?

Answer 7

• Internal supply and exhaust fans are not powered.
• Smoke/override valve opens.
• All other valves close, no air flow to forward cargo.
• Cabin differential pressure draws air from the panels area on the flight deck,
through the equipment cooling ducts to the E&E equipment racks,
to create a reverse flow of air across the equipment, then through
the supply duct, then overboard.
FCOM, VOL 2; 2.20.15.

Question 8

Under what conditions would the equipment cooling system revert to closed loop mode?

Answer 8

• EQUIPT COOLING selector in NORM or STBY with a single internal fan fault, or
• LLCCAFR Selector in FWD LOW, BOTH LOW, FWD HIGH, with a forward
lobe temp selector set LOWER than 10C.
• When the MAIN CARGO FIRE ARM switch is pushed. (ARMED)
FCOM, VOL 2; 2.20.14/8.10.6

Question 9

When does equiptment cooling go into smoke override?

Answer 9

• Inflight with both internal fans failed,
• FWD or AFT CARGO FIRE ARM switch armed, or
• OVRD selected by the EQUIP COOLING selector.