Date: 201206
Local time of day: 0601-1200
Location: ZZZZ.Airport, FO
Light: Daylight
Aircraft: A330
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Fuel Quantity-Pressure Indication
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Troubleshooting; Communication Breakdown; Situational Awareness; Confusion
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Manuals; Procedure
Primary problem: Aircraft

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.

Callback: Reporter stated he is a Technician working the Technical Support Desk. The whole event and flight cancellation started at the departure gate when the flight crew was reviewing the MEL deferral for the Left Inner Tank High [Fuel] Level Detection System. They were also watching the fuel indications and trying to determine where 2;000 LBS of metered off fuel had gone. The Fuel Totalizer showed the increase; but no increase in fuel levels were indicated in the other fuel tanks.Reporter stated after the flight canceled and the aircraft was repositioned; all fuel indications and quantities were normal; including the missing 2;000 LBS and the 'known' metered fuel in 1;000 LBS increments he requested Maintenance to perform. The aircraft was released the next morning. He still believes water in the fuel tanks is responsible for some of the indication failures; even though there are no faults showing up in the Aircraft Condition Monitoring System (ACMS) data. Their aircraft are flying constantly; with short turnarounds on the ground. Water in the fuel just doesn't have enough time to settle down to where the Water Extraction System can remove the water; or even manually sumping the tanks is not adequate; because the water just hasn't settled. On one of their aircraft; ten gallons of water had been drained (sumped) from a single fuel tank during an Overnight Check.



Synopsis: 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.