Joined: 11 Dec 2005
|Posted: Mon Aug 06, 2012 9:46 am Post subject: Fuel System (Technical Notes)
|Fuel Imbalance Indications
A fuel imbalance pointer is displayed on the expanded fuel quantity display next to the low tank quantity for the following imbalance conditions.
A solid white pointer is displayed if:
main tank fuel differs more than 500 kilograms
main tank fuel differs more than 100 kilograms and a crossfeed valve is open.
A solid amber fuel imbalance pointer replaces the white pointer if the FUEL IMBALANCE message is displayed. The difference in fuel quantity which causes the FUEL IMBALANCE message to be displayed varies with total main tank fuel quantity.
Center Fuel Pumps
The center tank fuel pumps will shut off automatically after 15 seconds of continuous low pressure. The auto-shutoff feature is disabled during jettison.
When the center fuel pump switches are off, the switch PRESS lights and pump pressure EICAS messages are inhibited (this is not the case with main pumps).
On the ground, both center fuel pumps operate only when two electrical power sources are available.
With only one power source available and the center fuel pump switches on, the switch PRESS light on the nonpowered side is illuminated and the pump pressure EICAS message is inhibited.
Before start, with center tank quantity more than 4,800 kilograms, the center tank switches should be pushed ON.
With the main tank pumps ON, a scavenge system operates automatically to transfer any remaining center tank fuel to the main tanks.
For fuel transfer:
Center tank quantity must be below 15,900 kilograms.
Either main tank quantity is less than 13,100 kilograms for AP-BGJ-AP-BGL, AP-BHX (777-200ER) and 23,900 kilograms for AP-BGY - AP-BHW, AP-BID (777-200LR and 777-300ER)
Fuel Tank Capacities
Based on a Fuel Density of 0.8029 kilograms per liter.
AP-BGJ - AP-BGL, AP-BHX (777-200ER)
Center 79,300 Kg
Main 29,100 Kg x 2
AP-BGY - AP-BHW, AP-BID (777-200LR and 777-300ER)
Center 82,900 Kg
Main 31,300 Kg x 2
DC and Left Forward AC Fuel Pump
On the ground, with the APU switch ON and no AC power available, the DC pump runs automatically. With AC power available, the left forward AC fuel pump operates automatically, regardless of fuel pump switch position, and the DC fuel pump turns off.