WDB CREW CAUSES FUEL TO BE DRAWN FROM THE WRONG TANKS CAUSING THOSE TANKS TO GET A 'LOW FUEL' WARNING.

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A CASE OF SEEING WHAT YOU EXPECT TO SEE; NOT WHAT IS THERE. SHORTLY AFTER START OF CRUISE IT WAS NOTICED THAT THERE WAS AN IMBAL OF FUEL BTWN THE 2 INBOARD MAIN TANKS OF 1000 KGS OR SO. THESE TANKS WERE SUPPLYING ALL ENGS VIA THE X-FEED VALVE SYS AND PWRED BY THE OVERRIDE/JETTISON PUMPS. ACCORDINGLY; THE OVERRIDE/JETTISON ON THE LOW TANK WERE SWITCHED OFF AND THE FUEL SYNOPTIC WAS CONTINUOUSLY MONITORED UNTIL THE TANKS WERE ONCE AGAIN LEVEL. AT THIS POINT; THE OTHER OVERRIDE/JETTISONS WERE SWITCHED OFF INSTEAD OF THE PREVIOUSLY DE-ACTIVATED ONES BEING REACTIVATED. BECAUSE WE NOW HAD BALANCED TANKS AND A TIDY SYMMETRICAL SYNOPTIC WE DID NOT SPOT OUR ERROR. ON THE OVERHEAD PANEL THE OVERRIDE/JETTISON SWITCHES DO NOT HAVE A LOW PRESSURE W/L CAPTION WHEN SWITCHED OFF. THUS; BELIEVING ALL WAS WELL; WE CANCELLED THE FUEL SYNOPTIC. SEVERAL HRS LATER; WE HAD A 'LOW FUEL' CAUTION VIA UPPER EICAS. THE OUTBOARD TANKS HAD BEEN FEEDING THEIR RESPECTIVE ENGS AND WERE NOW AT APPROX 1000 KGS EACH. THE INBOARDS STILL HAD 25000 KGS EACH. THUS; IF EITHER OUTBOARD X-FEED VALVE CHOSE TO FAIL SHUT (SMALL CHANCE); WE WOULD RAPIDLY LOSE THAT ENG. THERE IS NO WAY OF TRANSFERRING FUEL OUTBOARD VIA THE JETTISON SYS AS ON THE JURASSIC WDB. NEEDLESS TO SAY; WE WATCHED THE FUEL SYNOPTIC FOR THE REMAINDER OF THE FLT; AND CERTAINLY LEARNED SOMETHING FROM THAT ONE! CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: IN A CONVERSATION WITH A PLT WHO FLEW THE SAME MODEL WDB; ANALYST LEARNED THAT THE INCIDENT CITED WAS A SIMPLE OVERSIGHT ON THE PART OF THE FLC. HE COULD NOT THINK OF ANYTHING THAT SHOULD BE DONE TO AVOID A REPETITION.