ACR LGT FUEL IMBALANCE CAUSED BY IMPROPER FUEL MANAGEMENT BY FLT CREW.

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WE PICKED UP THE ACFT; AN LGT; IN STL TO FLY STL-ORD-STL. DURING THE FLT FROM STL TO ORD I FOUND #2 THRUST LEVEL TO BE OUT OF RIG. I HAD THE FE ENTER THIS IN THE LOGBOOK AND PRESENT IT TO MAINT IN ORD. A RE-RIGGING AND FULL PWR RUN UP WAS REQUIRED TO CLEAR THE ITEM. THE MAINT REQUIRED DICTATED CANCELLATION OF OUR TURNAROUND REVENUE FLT. MAINT PEOPLE TOOK THE ACFT FOR RUNUP W/O FLC AND ACCOMPLISHED THE RE-RIGGING IN A RUNUP AREA. THE RETURN FLT TO STL WAS CONDUCTED PREDOMINANTLY IN IMC; AT NIGHT; WITH A RELEASE FUEL OF 26000#. DURING CLB AT 330 KTS A NOTICEABLE VIBRATION WAS FELT THROUGHOUT THE AIRFRAME. DEACTIVATION OF THE SPOILERS DID NOT RESULT IN ANY CHANGE; BUT CRACKING THE SPOILERS UP STOPPED THE PROB. STL WAS EXPERIENCING SIGNIFICANT TSTM ACTIVITY AND HOLDING DELAYS. IT BEARS MENTIONING THAT THROUGHOUT THE FLT THE CREW WAS WORKING INDIVIDUALLY AND TOGETHER AT A FAIRLY HIGH WORKLOAD. THERE WAS NO IDLE CONVERSATION. THROUGHOUT THE FLT I NOTICED THE ACFT REQUIRED CONSIDERABLE RETRIMMING. HOWEVER; THE YOKE REMAINED LEVEL AND THE SLIP INDICATOR WITHIN THE BARS. I DID NOT VISUALLY CHK THE TRIM WHEELS FOR DEFLECTION IN THE DARKENED COCKPIT. THERE WAS A CONSIDERABLE AMOUNT OF DISTR WITH LIGHTNING AND TURB. AN ILS TO 12R STL WAS FLOWN MANUALLY WITH FLT DIRECTOR GUIDANCE AND NO UNUSUAL CONTROL PRESSURES WERE REQUIRED. AFTER LNDG MAINT INFORMED OF THE SPOILER PROB. UPON EXITING THE COCKPIT I NOTICED THE AILERON AND RUDDER TRIM DEFLECTED 2-3 UNITS R (AN EXCESSIVE AMOUNT) AND THOUGHT IT THE RESULT OF COMPENSATION FOR A FLOATING SPOILER. ON THE DAY FOLLOWING THE FLT; I WAS NOTIFIED BY COMPANY FLT OPS THAT MAINT HAD FOUND THE FUEL TANKS UNBALANCED IN EXCESS OF THE LIMITS. TANK 1 HAD 8200 LBS; 2 HAD 4800# AND 3 HAD 2050#. THEY INFORMED ME THAT XFEED VALVE CONFIGN WAS #1 OPEN; #2 CLOSED AND #3 OPEN. WITH A 26000# FUEL LOAD ON THE FEED IS NORMALLY TANK TO ENG WITH XFEEDS SET #1 CLOSED; #2 OPEN (TO PRESSURIZED MANIFOLD); #3 CLOSED. A MIRROR IMAGE OF THE XFEEDS AS FOUND AFTER SECURE IN STL. A FUEL LOG IS NOT REQUIRED BY COMPANY POLICY ON STAGE LENGTHS WITH CRUISE LESS THAN 30 MINS AS THIS FLT WAS. ALSO THE FUEL TOTALIZER MAY BE USED AS REF FOR FUEL ON BOARD ON SHORTER LEGS; BUT DOES SPECIFY THAT THE INDIVIDUAL TANK QUANTITIES SHOULD BE XCHKED. IT SEEMS THAT THE FOLLOWING EXPLANATION MOST ACCURATELY DESCRIBES THE POSSIBLE CAUSES OF THIS INCIDENT. THE F/E CAME OFF THE PREVIOUS LEG WITH THE FAA ON BOARD CHKING HER FOR CHK AIRMAN STATUS. HIGH STRESS WITH HIGH VISIBILITY. MAINT IN ORD TOOK THE ACFT (PROPERLY CONFIGURED) AND PROBABLY RECONFIGURED THE XFEEDS FOR RUN UP. ACFT WAS DELIVERED TO THE FLC WITH XFEEDS IN MIRROR IMAGE. THE ENGINEER PROBABLY MISREAD THE VALVE CONFIGN AS CAN SO EASILY BE DONE WHEN A PATTERN IS WHAT YOU ARE LOOKING FOR. TANK #3 OVERPWRED 1 AND FED BOTH ENG 1 AND 3. THE HIGH WORKLOAD PRECLUDED THE OPPORTUNITY TO XCHK FUEL GAUGES AND THE TENDENCY WOULD BE TO ASSUME NORMAL BURN CONSIDERING TANK TO ENG CONFIGN. THE SPOILER PROB COMPOUNDED THE CONFUSION AND DIRECTED THE ENTIRE CREWS ATTN FROM THE TRIMMING IMBALANCE. THE SHORT LEG REQUIRED NO FUEL LOG TO BE KEPT ENRTE. PS: SUBSEQUENT INVESTIGATION SHOWED THAT: MAINT ORD HAD IN FACT RECONFIGURED THE XFEEDS AND RAN THE TANKS OUT OF BAL DURING RUN UP.