Narrative:

Flight mci phx B737-300. Subject: unintentional transfer of fuel beyond the amount needed to balance wing tanks. While at FL310 on the above mentioned flight. Just prior to top of descent, the captain began to transfer fuel to balance out the wing tanks. I was unaware at the time that he had started to balance the fuel, as no verbal statement was made to me as I was on the radio talking to ZAB. The captain was then distracted by a flight attendant coming into the cockpit to ask a question. We were flying into a bright afternoon sun, and had used the checklist as a sun shade instead of putting it between the two throttle levers as a reminder that fuel xfeed was taking place. We were arriving into phx during the afternoon 'bank' of flts and our workload began to greatly increase. I got busy talking to company on the #2 radio and the captain became distracted from the fuel imbal, as he was both flying the aircraft and handling the radio work with ATC. ATC started giving numerous clrncs to use, ie, speed and altitude restrs and some heading changes. We landed uneventfully and upon calling our 'on and in' times to company at the gate, the crew noticed that the fuel imbal had exceeded the afm limit of 1000 pounds. We had been flying night trips the first 2 days of our pattern, and now we were back on a day trip. I feel fatigue contributed heavily to this fuel imbal occurrence.

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Original NASA ASRS Text

Title: CAPT NOTICES FUEL IMBAL, BEGINS TRANSFER. DISTR AND FORGETS, TRANSFER CONTINUES TO CAUSE OPPOSITE IMBAL.

Narrative: FLT MCI PHX B737-300. SUBJECT: UNINTENTIONAL TRANSFER OF FUEL BEYOND THE AMOUNT NEEDED TO BAL WING TANKS. WHILE AT FL310 ON THE ABOVE MENTIONED FLT. JUST PRIOR TO TOP OF DSCNT, THE CAPT BEGAN TO TRANSFER FUEL TO BAL OUT THE WING TANKS. I WAS UNAWARE AT THE TIME THAT HE HAD STARTED TO BAL THE FUEL, AS NO VERBAL STATEMENT WAS MADE TO ME AS I WAS ON THE RADIO TALKING TO ZAB. THE CAPT WAS THEN DISTRACTED BY A FLT ATTENDANT COMING INTO THE COCKPIT TO ASK A QUESTION. WE WERE FLYING INTO A BRIGHT AFTERNOON SUN, AND HAD USED THE CHKLIST AS A SUN SHADE INSTEAD OF PUTTING IT BTWN THE TWO THROTTLE LEVERS AS A REMINDER THAT FUEL XFEED WAS TAKING PLACE. WE WERE ARRIVING INTO PHX DURING THE AFTERNOON 'BANK' OF FLTS AND OUR WORKLOAD BEGAN TO GREATLY INCREASE. I GOT BUSY TALKING TO COMPANY ON THE #2 RADIO AND THE CAPT BECAME DISTRACTED FROM THE FUEL IMBAL, AS HE WAS BOTH FLYING THE ACFT AND HANDLING THE RADIO WORK WITH ATC. ATC STARTED GIVING NUMEROUS CLRNCS TO USE, IE, SPD AND ALT RESTRS AND SOME HDG CHANGES. WE LANDED UNEVENTFULLY AND UPON CALLING OUR 'ON AND IN' TIMES TO COMPANY AT THE GATE, THE CREW NOTICED THAT THE FUEL IMBAL HAD EXCEEDED THE AFM LIMIT OF 1000 LBS. WE HAD BEEN FLYING NIGHT TRIPS THE FIRST 2 DAYS OF OUR PATTERN, AND NOW WE WERE BACK ON A DAY TRIP. I FEEL FATIGUE CONTRIBUTED HEAVILY TO THIS FUEL IMBAL OCCURRENCE.

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.