OPERATIONS MANUAL

Fuel System
Center Tank Operation:
If the center tank contains less than 1800 kg (4000 lb) before engine start, the center tank
pumps must remain off on the ground and through the entire flight. Otherwise, center tank
pump operation will be allowed under the respective conditions A, B, or C:
Condition A 1800 - 7600 kg (4000 - 16900 lb) in center tank before engine start:
Stage EICAS message Required crew action
Set both pump switches to OFF 1)
Cruise begins >FUEL OVD CTR () Set both pump switches to ON
At ~1300 kg (3000 lb) >FUEL LOW CTR () Set both pump switches to OFF
1)
If the pumps were to run from engine start on, beginning at a quantity below
7700 kg (17000 lb), the quantity might decrease to the climb-attitude-specific limit of
3200 kg (7000 lb) already shortly after takeoff. Reaching that limit in climb would require the
crew to switch the pumps off. To relieve the crew during this high-workload flight phase, the
center tank pumps must remain off from start until cruise.
Condition B 7700 - 22600 kg (17000 - 49900 lb) in center tank before engine start:
Stage EICAS message Required crew action
Set both pump switches to ON
At ~3200 kg (7000 lb) in climb >FUEL LOW CTR () Set both pump switches to OFF 2)
Cruise begins >FUEL OVD CTR () Set both pump switches to ON
At ~1300 kg (3000 lb) >FUEL LOW CTR () Set both pump switches to OFF
2)
This effect is possible only if the aircraft pitch is above 5°.
Condition C At least 22700 kg (50000 lb) in center tank before engine start:
Stage EICAS message Required crew action
Set both pump switches to ON
At ~1300 kg (3000 lb) >FUEL LOW CTR () Set both pump switches to OFF
The initial quantity of 22700 kg (50000 lb) is so high that it cannot decrease to the critical
minimum before the cruise begins, hence the above items 1) and 2) are irrelevant in this case.
When the center tank pumps shut down, the FSMCs activate the O/J pumps in main tanks
2 and 3, so that main tank 2 supplies the left wing engines, and main tank 3 supplies the right
wing engines.
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