Narrative:

[It was] a normal flight with myself as pilot flying. I remember making a mental note of the fuel gauges during cruise; specifically remembering left and right tanks were in balance. Some time later; we both noticed a fuel imbalance: left tank roughly 3;100 pounds; right 9;000 pounds and center 12;100 pounds. We referenced our QRH's and attempted to stop what appeared to be a more greater than normal flow from the left tank. It did not fix the issue. Hence; we declared an emergency and I remained the pilot flying as we turned back to an airport we had just passed and time permitting continued to work on the fuel issue as well as communicate with ATC; operations; etc. It was an overweight landing and uneventful in VMC conditions on runway 31. I did notice that upon landing the left tank was roughly 1;500 pounds; but by the time we got to the gate it was about 1;200 pounds. Why the rapid decrease even still on the ground? I don't know.my only goal from noticing till landing was getting the aircraft safely on the ground. Upon arrival at the gate; things moved very quickly. There were the issues of maintenance log write-ups; crew duty days; the passenger service agents wanting answers; potential aircraft swaps; etc. The decision was made to switch aircraft and we continued uneventfully on a new aircraft.aircraft are machines subject to potential malfunction and we pilots who operate them are humans subject to potential human error. I have reviewed the most current electronic maintenance log write-ups and there appears to be some issues regarding this aircraft's fuel system and unwarranted fuel transfers. Moreover; a more quick or accurate log of the fuel numbers may have allowed an earlier decision point with which to deal with the unbalance. However; I am not certain though that a more accurate fuel log would have avoided the more normal than usual left tank decrease or divert. Either way; as a pilot who plans on remaining on the fleet; I have learned a valuable lesson to monitor more closely the fuel system like a hawk; to be cognizant of the age of the airplanes and to avoid what seems to be a problem with some of these aircrafts fuel issues that even other pilots have encountered!

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Original NASA ASRS Text

Title: A MD-83 fuel system developed a large fuel imbalance in flight; so an emergency was declared and the flight diverted to a nearby airport where it was removed from service.

Narrative: [It was] a normal flight with myself as pilot flying. I remember making a mental note of the fuel gauges during cruise; specifically remembering left and right tanks were in balance. Some time later; we both noticed a fuel imbalance: left tank roughly 3;100 LBS; right 9;000 LBS and center 12;100 LBS. We referenced our QRH's and attempted to stop what appeared to be a more greater than normal flow from the left tank. It did not fix the issue. Hence; we declared an emergency and I remained the pilot flying as we turned back to an airport we had just passed and time permitting continued to work on the fuel issue as well as communicate with ATC; OPS; etc. It was an overweight landing and uneventful in VMC conditions on Runway 31. I did notice that upon landing the left tank was roughly 1;500 LBS; but by the time we got to the gate it was about 1;200 LBS. Why the rapid decrease even still on the ground? I don't know.My only goal from noticing till landing was getting the aircraft safely on the ground. Upon arrival at the gate; things moved very quickly. There were the issues of maintenance log write-ups; crew duty days; the passenger service agents wanting answers; potential aircraft swaps; etc. The decision was made to switch aircraft and we continued uneventfully on a new aircraft.Aircraft are machines subject to potential malfunction and we pilots who operate them are humans subject to potential human error. I have reviewed the most current electronic maintenance log write-ups and there appears to be some issues regarding this aircraft's fuel system and unwarranted fuel transfers. Moreover; a more quick or accurate log of the fuel numbers may have allowed an earlier decision point with which to deal with the unbalance. However; I am not certain though that a more accurate fuel log would have avoided the more normal than usual left tank decrease or divert. Either way; as a pilot who plans on remaining on the fleet; I have learned a valuable lesson to monitor more closely the fuel system like a hawk; to be cognizant of the age of the airplanes and to avoid what seems to be a problem with some of these aircrafts fuel issues that even other pilots have encountered!

Data retrieved from NASA's ASRS site as of July 2013 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.