B757 captain reports a fuel imbalance developing shortly after takeoff which cannot be rectified. Wh...

Narrative:

During climb out and shortly after passing 10;000 ft; we became aware of a developing fuel imbalance between the left and right main fuel tanks. We attempted balancing the fuel using normal procedures with no success. This action did stabilize the imbalance for a while; but did not improve the imbalance. This was perplexing in that the engines' fuel flows were identical and fuel total compared to the ACARS info was accurate; ruling out a fuel leak. The QRH offered little guidance other than to use differential power. About 20 minutes into the flight the imbalance quickly increased from approximately 2;100 pounds to around 2;700 pounds. I declared an emergency and returned to departure airport. Arff responded and confirmed the absence of any leaking fuel so we continued to the gate. Maintenance concluded that a piece of debris in the fuel system may have caused one of the refueling valves to stick open causing fuel to transfer from the right tank to the left; thus causing the imbalance.

Original NASA ASRS Text

Title: B757 Captain reports a fuel imbalance developing shortly after takeoff which cannot be rectified. When imbalance reaches 2;700 LBS crew declares an emergency and returns to departure airport.

Narrative: During climb out and shortly after passing 10;000 FT; we became aware of a developing fuel imbalance between the left and right main fuel tanks. We attempted balancing the fuel using normal procedures with no success. This action did stabilize the imbalance for a while; but did not improve the imbalance. This was perplexing in that the engines' fuel flows were identical and fuel total compared to the ACARS info was accurate; ruling out a fuel leak. The QRH offered little guidance other than to use differential power. About 20 minutes into the flight the imbalance quickly increased from approximately 2;100 LBS to around 2;700 LBS. I declared an emergency and returned to departure airport. ARFF responded and confirmed the absence of any leaking fuel so we continued to the gate. Maintenance concluded that a piece of debris in the fuel system may have caused one of the refueling valves to stick open causing fuel to transfer from the right tank to the left; thus causing the imbalance.

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.

Attributes
ACN	950393
Time
Date	201105
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Fuel Distribution System
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical

B757 captain reports a fuel imbalance developing shortly after takeoff which cannot be rectified. When imbalance reaches 2;700 pounds crew declares an emergency and returns to departure airport.