What was found
AFTER T/O OUT OF SJU, F.O. NOTIFIED CAPT AIRCRAFT WAS REQUIRING ALMOST FULL AILERON TO MAKE LEFT TURN ON DEPARTURE. FUEL QTY #3 WAS INOP AND FUELED TO KNOWN QTY. AFTER REVIEWING FUEL SLIPS AND ESTIMATING FUEL QTY #3 FROM PREVIOUS CREW, WE SUSPECT #3 FUEL QTY TO BE APPROXIMATELY 10.0 HIGHER THAN TANK #1. TALKED WITH GOCC/MOCC/DUTY OFFICER/MD11 TECH PILOT ABOUT ISSUE. I ELECTED TO CONTINUE TO KMEM (WINDS) AND TRANSFER 2,800 LBS OF FUEL FROM TANK #3 TO TANK #1. UPON ARRIVAL INTO KMEM, WE DECLARED AN EMERGENCY AND HAD AN UNEVENTFUL LANDING. AT BLOCK IN CHECKED #1 AND #3 TANK FUEL QTY. USING MLI'S. FOUND TIP COMPT. FULL ON BOTH WINGS , BUT #3 TANK HAD APPROX. 2,000 LBS HIGHER THAN #1 TANK. TRANSFERRED FUEL FROM #3 TANK TO #2 TANK AND FOUND #3 TANK CONTAINED THE AMOUNT CALCULATED FROM THE MLI. POWERED ALL FLT. CONTROLS AND PERFORMED VISUAL CHECK OF AILERONS RUDDER AND SPOILERS. NO FAULTS FOUND.