Narrative:

During cruise at FL320 a fuel imbalance occurred that was not able to be remedied by usual fuel management procedures; nor by QRH procedures. Strangely; with center tank fuel (both center boost pumps on) the right wing fuel quantity began decreasing. The imbalance was first noted to be 500 pounds; this was after cruising at cruise altitude for approximately 10 minutes. In the minutes that followed after unsuccessfully cross-feeding from the left tank; the imbalance reached 1000 pounds. Total fuel quantity was verified 'on target' so the question of a possible fuel leak was eliminated. An emergency was declared; and an immediate uneventful overweight landing was made at the nearest suitable airfield. The crew coordination was exemplary between cockpit and cabin. My first officer did a magnificent job flying the aircraft while I ran checklist; and communicated with our flight attendants and passengers. I landed the aircraft with a 2000 pounds fuel imbalance. ATC provided excellent assistance throughout. Post-flight revealed some interesting findings. While on the phone with our maintenance center; contract maintenance patiently awaited in the cockpit while I was on the phone. Technician had me verify all of the fuel boost pump circuit breakers (circuit breaker). What was found was that the placarded fuel boost pump (aircraft was dispatched with the left aft fuel boost pump inoperative) was not collared; but the operable fuel boost pump circuit breaker was pulled and collared. Technician then stated that on the previous overnight; maintenance most likely attempted to clear the placard; but after troubleshooting; 'didn't clean it up right' (paraphrased). The cbs (collared) were all verified 'in' on the originated preflight; so I feel that maintenance simply 'pushed-in' the wrong circuit breaker and it didn't pop until after airborne. (The original write-up; on placard for the previous two days; stated that the left hand aft fuel boost pump circuit breaker had popped in flight.) as a result of this event; I have sent in some recommendations for changes in our MEL directive (concerning and inoperative fuel boost pump) specifically instructing the pilot(s) to verify integrity of the operable boost pump. I also made a few other recommendations; as well. An overweight inspection was conducted by contract maintenance; and a maintenance crew drove in to repair the fuel system.

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Original NASA ASRS Text

Title: MD80 flight crew experienced a fuel imbalance shortly after leveling off at FL320. When QRH procedures did not correct the problem; the crew diverted to the nearest suitable airport.

Narrative: During cruise at FL320 a fuel imbalance occurred that was not able to be remedied by usual fuel management procedures; nor by QRH procedures. Strangely; with center tank fuel (both center boost pumps on) the right wing fuel quantity began decreasing. The imbalance was first noted to be 500 LBS; this was after cruising at cruise altitude for approximately 10 minutes. In the minutes that followed after unsuccessfully cross-feeding from the left tank; the imbalance reached 1000 LBS. Total fuel quantity was verified 'on target' so the question of a possible fuel leak was eliminated. An emergency was declared; and an immediate uneventful overweight landing was made at the nearest suitable airfield. The crew coordination was exemplary between cockpit and cabin. My First Officer did a magnificent job flying the aircraft while I ran checklist; and communicated with our flight attendants and passengers. I landed the aircraft with a 2000 LBS fuel imbalance. ATC provided excellent assistance throughout. Post-flight revealed some interesting findings. While on the phone with our Maintenance Center; contract maintenance patiently awaited in the cockpit while I was on the phone. Technician had me verify all of the fuel boost pump circuit breakers (CB). What was found was that the placarded fuel boost pump (aircraft was dispatched with the left Aft Fuel Boost pump inoperative) was not collared; but the operable fuel boost pump CB was pulled and collared. Technician then stated that on the previous overnight; maintenance most likely attempted to clear the placard; but after troubleshooting; 'didn't clean it up right' (paraphrased). The CBs (collared) were all verified 'in' on the originated preflight; so I feel that maintenance simply 'pushed-in' the wrong CB and it didn't pop until after airborne. (The original write-up; on placard for the previous two days; stated that the Left Hand Aft Fuel Boost pump CB had popped in flight.) As a result of this event; I have sent in some recommendations for changes in our MEL directive (concerning and inoperative fuel boost pump) specifically instructing the pilot(s) to verify integrity of the operable boost pump. I also made a few other recommendations; as well. An overweight inspection was conducted by contract maintenance; and a maintenance crew drove in to repair the fuel system.

Data retrieved from NASA's ASRS site as of April 2012 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.