Narrative:

On the night of jun/thu/03, aircraft X, an MD88, arrived at the gate with an inbound write-up for fuel migration from the left to right main tanks. I initially checked the log history and found 2 similar write-ups in the past 3 days. After the first write-up, the technicians flushed the check valves on the right tank boost pumps to ensure they were sealing. After the work was performed, during refueling, they found the right tank was continuing to fill after the right fueling valve was turned off. They assumed the fueling valve was defective and not closing completely, and because no parts were available they deferred the item to maintenance. In the second write-up the pilots didn't directly mention fuel migration, but rather the left tank was empting faster than the right, which we now know was because the fuel was migrating. And because of this, the write-up was treated as a possible left tank leak, and was signed off as no leaks found after an extensive check. So after researching these previous items and knowing that the right tank fueling valve was already on deferred item status, I incorrectly assumed that fuel was entering the right tank through the bypassing right fueling valve when the aircraft's fuel manifold was pressurized. I accidentally overlooked the fact that this would only be possible if the xfeed and defueling valves were open. So I checked that the proper procedures had been taken to previously place the right fueling valve on deferred item status checked for any possible leaks, and released the aircraft for service awaiting the new fueling valve to arrive in stock. On the first flight the next morning, the migration problem was again present and the aircraft was ferried back to atlanta for further troubleshooting. After entering the right fuel tank, the technician found a loose fitting on the fuel manifold that was allowing fuel to enter the tank, and that in fact the right fueling valve was working properly. And as of jun/tue/03, this has appeared to fix the problem. I realize now that I should not have trusted another technician's evaluation of the right fueling valve, and I should have found that a bypassing fueling valve could not have caused this condition in the first place.

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Original NASA ASRS Text

Title: AN MD88 WAS DISPATCHED IN NON COMPLIANCE WITH THE INCORRECT VALVE DEFERRED AS LEAKING CAUSING FUEL MIGRATION IN FLT.

Narrative: ON THE NIGHT OF JUN/THU/03, ACFT X, AN MD88, ARRIVED AT THE GATE WITH AN INBOUND WRITE-UP FOR FUEL MIGRATION FROM THE L TO R MAIN TANKS. I INITIALLY CHKED THE LOG HISTORY AND FOUND 2 SIMILAR WRITE-UPS IN THE PAST 3 DAYS. AFTER THE FIRST WRITE-UP, THE TECHNICIANS FLUSHED THE CHK VALVES ON THE R TANK BOOST PUMPS TO ENSURE THEY WERE SEALING. AFTER THE WORK WAS PERFORMED, DURING REFUELING, THEY FOUND THE R TANK WAS CONTINUING TO FILL AFTER THE R FUELING VALVE WAS TURNED OFF. THEY ASSUMED THE FUELING VALVE WAS DEFECTIVE AND NOT CLOSING COMPLETELY, AND BECAUSE NO PARTS WERE AVAILABLE THEY DEFERRED THE ITEM TO MAINT. IN THE SECOND WRITE-UP THE PLTS DIDN'T DIRECTLY MENTION FUEL MIGRATION, BUT RATHER THE L TANK WAS EMPTING FASTER THAN THE R, WHICH WE NOW KNOW WAS BECAUSE THE FUEL WAS MIGRATING. AND BECAUSE OF THIS, THE WRITE-UP WAS TREATED AS A POSSIBLE L TANK LEAK, AND WAS SIGNED OFF AS NO LEAKS FOUND AFTER AN EXTENSIVE CHK. SO AFTER RESEARCHING THESE PREVIOUS ITEMS AND KNOWING THAT THE R TANK FUELING VALVE WAS ALREADY ON DEFERRED ITEM STATUS, I INCORRECTLY ASSUMED THAT FUEL WAS ENTERING THE R TANK THROUGH THE BYPASSING R FUELING VALVE WHEN THE ACFT'S FUEL MANIFOLD WAS PRESSURIZED. I ACCIDENTALLY OVERLOOKED THE FACT THAT THIS WOULD ONLY BE POSSIBLE IF THE XFEED AND DEFUELING VALVES WERE OPEN. SO I CHKED THAT THE PROPER PROCS HAD BEEN TAKEN TO PREVIOUSLY PLACE THE RIGHT FUELING VALVE ON DEFERRED ITEM STATUS CHKED FOR ANY POSSIBLE LEAKS, AND RELEASED THE ACFT FOR SVC AWAITING THE NEW FUELING VALVE TO ARRIVE IN STOCK. ON THE FIRST FLT THE NEXT MORNING, THE MIGRATION PROB WAS AGAIN PRESENT AND THE ACFT WAS FERRIED BACK TO ATLANTA FOR FURTHER TROUBLESHOOTING. AFTER ENTERING THE R FUEL TANK, THE TECHNICIAN FOUND A LOOSE FITTING ON THE FUEL MANIFOLD THAT WAS ALLOWING FUEL TO ENTER THE TANK, AND THAT IN FACT THE R FUELING VALVE WAS WORKING PROPERLY. AND AS OF JUN/TUE/03, THIS HAS APPEARED TO FIX THE PROB. I REALIZE NOW THAT I SHOULD NOT HAVE TRUSTED ANOTHER TECHNICIAN'S EVALUATION OF THE R FUELING VALVE, AND I SHOULD HAVE FOUND THAT A BYPASSING FUELING VALVE COULD NOT HAVE CAUSED THIS CONDITION IN THE FIRST PLACE.

Data retrieved from NASA's ASRS site as of July 2007 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.