Narrative:

There was an MEL 28-25-03b for the left inner tank high level detection system inoperative. But no other faults for the fuel quantity or fuel system faults. I explained to the captain that the fuel quantity system (fqs) is very accurate and if no faults were displayed that there was nothing wrong with the system. The magnetic level indicator (mli) system [fuel sticks]; as per the fuel manual for the inner tanks are accurate to +/- 5% of their indication. If there was an error between the fuel quantity indicating system (fqis) or the mli system; I would say that the mli system would be in error with the human factor of not reading the [fuel] charts or sticks correctly.there were no real time aircraft condition monitoring system (acms) faults and no faults in the fqis. Therefore I could apply the MEL for the mli system. They metered in 2;000 pounds [of fuel] supposedly into the left inner tank and the three pilots watched the indication for that left inner tank and it did not increase. The total fuel increased; but to their knowledge there was no indication that it went to the left inner tank or other tanks. Therefore; they were saying that their six eyes were more believable than the aircraft's fuel indicating system. The mli [fuel] sticks for the left inner tank did show an increase for the metered fuel added. The left inner tank indication could not be MEL'd due to the pre-existing MEL for the left inner tank detection system was inoperative. The flight was canceled. I instructed maintenance to transfer fuel in 1;000 pound increments to the left inner tank and to verify fuel increased in that tank only and not the other tanks. However; before they accomplished this; they repositioned aircraft. After tow [of aircraft]; the left inner tank had increased by the 2;000 pounds that was not showing previously. After completing their fuel transfer; all indications checked normal and no other faults could be found. No parts were replaced. Aircraft was fueled to 112;000 pounds for correct distribution.I suspect improper sumping; not necessarily on maintenance behalf; but rather on extremely short turn times these aircraft experience during heavy summer flying season/schedule. [Fuel] tanks [were] sumped after flight canceled and aircraft was moved to remote area. At that time; fuel quantity indicating system (fqis) showed proper increase in fuel load. [Suggest] allowing more time on ground for water to settle; allowing proper sumping.

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Original NASA ASRS Text

Title: An A330 aircraft had fuel quantity indication failures that did not show up as fuel faults in the Aircraft Condition Monitoring System (ACMS). Only after flight cancellation and repositioning of the aircraft did 2;000 LBS of missing fuel reappear. Technician believes water in the fuel tanks may be a factor.

Narrative: There was an MEL 28-25-03b for the Left Inner Tank high level detection system inoperative. But no other faults for the fuel quantity or fuel system faults. I explained to the Captain that the Fuel Quantity System (FQS) is very accurate and if no faults were displayed that there was nothing wrong with the system. The Magnetic Level Indicator (MLI) System [Fuel Sticks]; as per the Fuel Manual for the inner tanks are accurate to +/- 5% of their indication. If there was an error between the Fuel Quantity Indicating System (FQIS) or the MLI System; I would say that the MLI System would be in error with the human factor of not reading the [fuel] charts or sticks correctly.There were no real time Aircraft Condition Monitoring System (ACMS) faults and no faults in the FQIS. Therefore I could apply the MEL for the MLI System. They metered in 2;000 LBS [of fuel] supposedly into the Left Inner Tank and the three pilots watched the indication for that Left Inner Tank and it did not increase. The Total Fuel increased; but to their knowledge there was no indication that it went to the Left Inner Tank or other tanks. Therefore; they were saying that their six eyes were more believable than the aircraft's Fuel Indicating System. The MLI [fuel] sticks for the Left Inner Tank did show an increase for the metered fuel added. The Left Inner Tank Indication could not be MEL'd due to the pre-existing MEL for the Left Inner Tank Detection System was inoperative. The flight was canceled. I instructed Maintenance to transfer fuel in 1;000 LB increments to the Left Inner Tank and to verify fuel increased in that tank only and not the other tanks. However; before they accomplished this; they repositioned aircraft. After tow [of aircraft]; the Left Inner Tank had increased by the 2;000 LBS that was not showing previously. After completing their fuel transfer; all indications checked normal and no other faults could be found. No parts were replaced. Aircraft was fueled to 112;000 LBS for correct distribution.I suspect improper sumping; not necessarily on Maintenance behalf; but rather on extremely short turn times these aircraft experience during heavy summer flying season/schedule. [Fuel] Tanks [were] sumped after flight canceled and aircraft was moved to remote area. At that time; Fuel Quantity Indicating System (FQIS) showed proper increase in fuel load. [Suggest] allowing more time on ground for water to settle; allowing proper sumping.

Data retrieved from NASA's ASRS site as of July 2013 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.