Narrative:

In flight planning we noted that there was a gripe on the paperwork about a chronic fuel imbalance issue on takeoff. It could not be duplicated on deck. On takeoff we experienced the same event as previous crews. The difference was greater than 3000 pounds and set off the EICAS fuel alert on the upper EICAS. We monitored the fuel quantity as we climbed out as well as the imbalance. It decreased to within limits; EICAS went away and the fuel totals in the left and right tanks came back together over time (when the center tank fuel quantity low alert illuminated and we shut off the center tank pumps; the fuel was matched evenly). On the fuel maintenance synoptic on the right tank; we did notice that one of the values was out of line with the others; but as the fuel balanced itself then numbers remained the same so we did not write up the details. We did however hit the send function to transmit data to maintenance control. The values were in the #19 and #20 sensors and they showed 0.8 and 5.1 respectively while the rest were in the 20 range. As we continued to through the flight in the latter portion; the fuel began to show a split between the calculated value and the value off of the fuel synoptic. The relief first officer pointed out that it peaked at a roughly 3000 pound difference with the error being on the low side just prior to the top of descent. Meaning the tanks showed 19.4 while the totalizer showed 22.4 onboard. There was also a split in the fuel between tanks again. The split was approximately 2000 pounds. This split remained until touchdown. I changed the fuel in the FMC to manual to match the actual fuel from the gauges. At this point I am not sure as to which of the values is correct; manual or calculated but am concerned that this aircraft will continue to fly in the system without a thorough diagnosis of the problem as the schedule continues to dominate. We made sure to write up the 3000 pound difference in the log book to alert following crews to the possibility that they could end up with a split between manual and calculated values and to monitor both of them very closely as well as consider adding a bit of additional fuel; to preclude being short at destination. We had plenty of fuel even with 9 minute reroute due to mlitary airspace off coast of alaska.

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Original NASA ASRS Text

Title: B777-200 pilot extensively detailed fuel quantity indication anomalies.

Narrative: In flight planning we noted that there was a gripe on the paperwork about a chronic fuel imbalance issue on takeoff. It could not be duplicated on deck. On takeoff we experienced the same event as previous crews. The difference was greater than 3000 LBS and set off the EICAS fuel alert on the upper EICAS. We monitored the fuel quantity as we climbed out as well as the imbalance. It decreased to within limits; EICAS went away and the fuel totals in the left and right tanks came back together over time (when the center tank fuel quantity LOW alert illuminated and we shut off the center tank pumps; the fuel was matched evenly). On the fuel maintenance synoptic on the right tank; we did notice that one of the values was out of line with the others; but as the fuel balanced itself then numbers remained the same so we did not write up the details. We did however hit the send function to transmit data to Maintenance Control. The values were in the #19 and #20 sensors and they showed 0.8 and 5.1 respectively while the rest were in the 20 range. As we continued to through the flight in the latter portion; the fuel began to show a split between the calculated value and the value off of the fuel synoptic. The relief First Officer pointed out that it peaked at a roughly 3000 LB difference with the error being on the low side just prior to the top of descent. Meaning the tanks showed 19.4 while the totalizer showed 22.4 onboard. There was also a split in the fuel between tanks again. The split was approximately 2000 LBS. This split remained until touchdown. I changed the fuel in the FMC to manual to match the actual fuel from the gauges. At this point I am not sure as to which of the values is correct; manual or calculated but am concerned that this aircraft will continue to fly in the system without a thorough diagnosis of the problem as the schedule continues to dominate. We made sure to write up the 3000 LB difference in the log book to alert following crews to the possibility that they could end up with a split between manual and calculated values and to monitor both of them very closely as well as consider adding a bit of additional fuel; to preclude being short at destination. We had plenty of fuel even with 9 minute reroute due to mlitary airspace off coast of Alaska.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.