ACFT EQUIP PROB. FUEL TANK INDICATIONS INTERMITTENT AND ERRONEOUS.

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LOCATION: ORF. OVER ORF AT FL370. FUEL TANK TEMP MINUS 24. RIGHT OUTER TANK HAD BEEN READING ZERO QTY; INCREASED TO 4000 LBS AND TRIM TANK QTY INCREASED 1000 LBS. CGCC FAULTED. OUTER TANKS WERE EVEN AT 8800 LBS. 5 MINS LATER L OUTER TANK QTY WENT TO XX AND TRIM TANK QTY SHOWED A DASH IN HUNDREDS POS. DSNDED TO FL350 AND L OUTER QTY CAME BACK SHOWING SAME AS R OUTER QTY 8500 LBS. TRIM TANK AND L INNER STILL READING INCORRECTLY. DSNDED TO FL190 AND L OUTER QTY DROPPED TO 1000 LBS LESS THAN R OUTER. IT REMAINED THIS WAY ALL THE WAY TO ENG SHUTDOWN. WHEN LEVEL AT 3000 FT THE TRIM AND L OUTER QTY CORRECTED TO SHOW ZERO QTY. THIS MALFUNCTION OCCURS ON APPROX 40 PERCENT OF THE FLEET DURING THE WINTER. THE MAINT CORRECTIVE ACTION IS NOT SOLVING THE PROB. HOW WOULD WE BE ABLE TO DETECT A FUEL LEAK IN THIS SIT? HOW CAN WE TELL IF WE ARE IN BAL? IF WE HAD ANOTHER MALFUNCTION THIS PROB WOULD BE DISTRACTING. OTHER FLEETS OPERATING IN THE CARIBBEAN DO NOT SEEM TO HAVE THIS PROB. PERHAPS WE NEED TO CHANGE THE FUEL QTY SYS.