Narrative:

Upon arrival at the aircraft, the fuel on board was approximately 32000#. This was more than our dispatch release called for, so rather than defuel, we received a second release showing the actual fuel on board. At takeoff the aircraft attempted to roll to the left and required substantial control input to maintain wings level. During climb at 230 KIAS, 3.5 units of rudder and 1.5 units of aileron trim were required to relieve most control pressure. I elected to return to the departure airport and we completed the abnormal flight controls checklist. Fuel balance was checked within limits (right wing tank indicated 300 pounds more fuel than the left fuel tank). All flight control position indicators checked normal. As a precaution, I requested that the emergency equipment standby for our landing. On approach at 180 KIAS, 4 units of rudder and 3.5 units of aileron trim were used. (The best trim combo seemed to be a combination of aileron and rudder which produced a slight skid.) I carried a speed of 15 KTS above reference to T/D and the landing was otherwise uneventful. We released the emergency equipment and taxied to the gate. At engine shutdown we noted that the fuel gauges were apparently operating normally and the balance was within limits (left wing approximately 9000 pounds and the right wing approximately 9100 pounds). We were provided another airplane in which we completed the flight. I have not received a final maintenance report at this time, but a subsequent verbal report to me stated that the fuel tanks were drip-checked after our return to the gate revealing 9000 pounds of fuel in the left wing tank and 2000# in the right tank (the fuel gauge readings at shutdown were approximately 9000 pounds left and 9100 pounds right). That report further stated that prior to our flight, maintenance had transferred fuel from the wing tank, or tanks to the center tank, to obtain a proper cg to tow the aircraft. There is at this time no explanation for the fuel imbalance of 7000 pounds, since there was no maintenance carry-over item (mco) indicating any fuel system indication discrepancy, nor any known reason for the right wing tank fuel gauge to indicate 7000 pounds higher than the actual amount of fuel in the tank. Supplemental information from acn 107553: all fuel gauges worked properly when press-to-test was done. Callback conversation with reporter revealed: extra fuel above flight plan fuel was determined by adding fuel gauge readings apparently without reference to the fuel added form. Suspect the ground crew moved fuel from tank #3 to tank #2, but did no rebalance the fuel distribution after towing the aircraft to the line. A faulty fuel transmitter in #3 tank caused the flight crew to think they had 6000 pounds extra fuel when in fact the fuel load was correct, but the #3 tank was not indicating the correct fuel load. The FAA investigated the incident and have absolved the flight crew of any error.

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Original NASA ASRS Text

Title: ACFT DEPARTED WITH VERY LARGE UNEXPLAINED FUEL LOAD BALANCE. REPORTER ELECTED TO RETURN AND LAND BECAUSE OF THE OUT OF TRIM CONDITION REQUIRED AND THE INABILITY TO EXPLAIN IT.

Narrative: UPON ARR AT THE ACFT, THE FUEL ON BOARD WAS APPROX 32000#. THIS WAS MORE THAN OUR DISPATCH RELEASE CALLED FOR, SO RATHER THAN DEFUEL, WE RECEIVED A SECOND RELEASE SHOWING THE ACTUAL FUEL ON BOARD. AT TKOF THE ACFT ATTEMPTED TO ROLL TO THE LEFT AND REQUIRED SUBSTANTIAL CONTROL INPUT TO MAINTAIN WINGS LEVEL. DURING CLB AT 230 KIAS, 3.5 UNITS OF RUDDER AND 1.5 UNITS OF AILERON TRIM WERE REQUIRED TO RELIEVE MOST CONTROL PRESSURE. I ELECTED TO RETURN TO THE DEP ARPT AND WE COMPLETED THE ABNORMAL FLT CONTROLS CHKLIST. FUEL BAL WAS CHKED WITHIN LIMITS (RIGHT WING TANK INDICATED 300 LBS MORE FUEL THAN THE LEFT FUEL TANK). ALL FLT CONTROL POS INDICATORS CHKED NORMAL. AS A PRECAUTION, I REQUESTED THAT THE EMER EQUIP STANDBY FOR OUR LNDG. ON APCH AT 180 KIAS, 4 UNITS OF RUDDER AND 3.5 UNITS OF AILERON TRIM WERE USED. (THE BEST TRIM COMBO SEEMED TO BE A COMBINATION OF AILERON AND RUDDER WHICH PRODUCED A SLIGHT SKID.) I CARRIED A SPD OF 15 KTS ABOVE REF TO T/D AND THE LNDG WAS OTHERWISE UNEVENTFUL. WE RELEASED THE EMER EQUIPMENT AND TAXIED TO THE GATE. AT ENG SHUTDOWN WE NOTED THAT THE FUEL GAUGES WERE APPARENTLY OPERATING NORMALLY AND THE BAL WAS WITHIN LIMITS (LEFT WING APPROX 9000 LBS AND THE RIGHT WING APPROX 9100 LBS). WE WERE PROVIDED ANOTHER AIRPLANE IN WHICH WE COMPLETED THE FLT. I HAVE NOT RECEIVED A FINAL MAINT RPT AT THIS TIME, BUT A SUBSEQUENT VERBAL RPT TO ME STATED THAT THE FUEL TANKS WERE DRIP-CHKED AFTER OUR RETURN TO THE GATE REVEALING 9000 LBS OF FUEL IN THE LEFT WING TANK AND 2000# IN THE RIGHT TANK (THE FUEL GAUGE READINGS AT SHUTDOWN WERE APPROX 9000 LBS LEFT AND 9100 LBS RIGHT). THAT RPT FURTHER STATED THAT PRIOR TO OUR FLT, MAINT HAD TRANSFERRED FUEL FROM THE WING TANK, OR TANKS TO THE CENTER TANK, TO OBTAIN A PROPER CG TO TOW THE ACFT. THERE IS AT THIS TIME NO EXPLANATION FOR THE FUEL IMBALANCE OF 7000 LBS, SINCE THERE WAS NO MAINT CARRY-OVER ITEM (MCO) INDICATING ANY FUEL SYS INDICATION DISCREPANCY, NOR ANY KNOWN REASON FOR THE RIGHT WING TANK FUEL GAUGE TO INDICATE 7000 LBS HIGHER THAN THE ACTUAL AMOUNT OF FUEL IN THE TANK. SUPPLEMENTAL INFO FROM ACN 107553: ALL FUEL GAUGES WORKED PROPERLY WHEN PRESS-TO-TEST WAS DONE. CALLBACK CONVERSATION WITH RPTR REVEALED: EXTRA FUEL ABOVE FLT PLAN FUEL WAS DETERMINED BY ADDING FUEL GAUGE READINGS APPARENTLY WITHOUT REF TO THE FUEL ADDED FORM. SUSPECT THE GND CREW MOVED FUEL FROM TANK #3 TO TANK #2, BUT DID NO REBALANCE THE FUEL DISTRIBUTION AFTER TOWING THE ACFT TO THE LINE. A FAULTY FUEL XMITTER IN #3 TANK CAUSED THE FLT CREW TO THINK THEY HAD 6000 LBS EXTRA FUEL WHEN IN FACT THE FUEL LOAD WAS CORRECT, BUT THE #3 TANK WAS NOT INDICATING THE CORRECT FUEL LOAD. THE FAA INVESTIGATED THE INCIDENT AND HAVE ABSOLVED THE FLT CREW OF ANY ERROR.

Data retrieved from NASA's ASRS site as of August 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.