Narrative:

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 between the 2 inboard main tanks of 1000 kgs or so. These tanks were supplying all engines via the x-feed valve system 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 west/left caption when switched off. Thus, believing all was well, we cancelled the fuel synoptic. Several hours later, we had a 'low fuel' caution via upper EICAS. The outboard tanks had been feeding their respective engines and were now at approximately 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 engine. There is no way of transferring fuel outboard via the jettison system as on the jurassic widebody transport. Needless to say, we watched the fuel synoptic for the remainder of the flight, and certainly learned something from that one! Callback conversation with reporter revealed the following information: in a conversation with a pilot who flew the same model widebody transport, analyst learned that the incident cited was a simple oversight on the part of the flight crew. He could not think of anything that should be done to avoid a repetition.

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Original NASA ASRS Text

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

Narrative: 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.

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