B747-400 DISPATCHED WITH A LIGHT FUEL LOAD AND STRUCTURAL CHK FUEL IN THE CTR TANK DEVELOPS AN OUT OF LIMITS QUANTITY DIFFERENTIAL BTWN THE INBOARD AND OUTBOARD MAIN TANKS.

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WE WERE DISPATCHED WITH A NON STANDARD FUEL LOAD. TOTAL FUEL LOADED WAS APPROX 64.8 WITH JUST UNDER 17.0 IN THE CTR TANK. THE FLT MANUAL LIMITATION SECTION NOTES: FUEL IN THE CTR TANK IS ALLOWED ONLY WHEN ALL MAIN AND RESERVE TANKS ARE FULL EXCEPT WHEN CTR TANK FUEL IS PAYLOAD OR STRUCTURAL. THE FLT PLAN DID NOT INDICATE THAT THE CTR TANK FUEL WAS PAYLOAD OR STRUCTURAL. I CHALLENGED THE DISPATCHER AND AFTER HE CHKED WITH LOAD PLANNING THE RELEASE WAS AMENDED TO INCLUDE THE CTR TANK FUEL AS STRUCTURAL AND COULD BE BURNED. ONCE INFLT AND AFTER THE CTR TANK FUEL WAS BURNED TO APPROX 3000 LBS; WE CONFIGURED THE FUEL SYS TO TANK TO ENG. HOWEVER; THE SCAVENGE PUMPS IN THE CTR TANK DELIVERED FUEL TO TANKS #2 AND #3. TANKS #2 AND #3 BEGAN TO INCREASE AS TANKS #1 AND #4 DECREASED. IN AN ATTEMPT TO BAL THE FUEL LOAD; I OPENED THE OUTBOARD XFEED VALVES AND TURNED ON THE OVERRIDE/JETTISON IN TANKS #2 AND #3. THE OVERRIDE FUEL PUMPS WOULD NOT PROVIDE ADEQUATE FUEL PRESSURE BECAUSE THEY WERE BELOW STANDPIPE FUEL LEVEL. WHILE WE WERE TRYING TO FIGURE THIS ALL OUT; THE OUTBOARD XFEED FUEL VALVES WERE OPEN. SINCE TANKS #1 AND #4 ARE HIGHER THAN TANKS #2 AND #3; TANKS #1 AND #4 PROVIDED FUEL TO ALL ENGS FURTHER EXACERBATING THE PROB. WE ENDED UP GETTING OUT OF BAL WITH AN EICAS MESSAGE 'FUEL IMBAL 2-3.' THIS WHOLE EVENT OCCURRED DURING A BUSY TIME DEVIATING AROUND TSTMS AND CLOSE TO THE TOP OF DSCNT. ONCE ON THE GND; I BRIEFED THE DUTY MGR; DISPATCH; AND MAINT. SUPPLEMENTAL INFO FROM ACN 697541: AFTER COMPLETION OF FLT; CAPT CALLED ME AND ADVISED THEY HAD A HARD TIME KEEPING THE PLANE IN BAL LIMITATIONS WITH SUCH A LOW CLRED FUEL NUMBER; APPROX 61.3. ONCE CTR TANK FUEL WAS BURNED DOWN TO 3.0; CAPT TURNED ON SCAVENGE PUMPS TO #2 TANK; BUT DUE TO LOW FUEL LEVELS IN ALL MAIN TANKS; OVERRIDE PUMPS WERE UNCOVERED AND THEY WERE UNABLE TO MAINTAIN PROPER BAL.