Narrative:

This report covers a perceived malfunction west/in the fuel system. Where fuel was being drawn from only 1 tank, by observing the fuel qty indicators, when the cockpit fuel panel was calling for fuel feed from all 3 tanks to their respective engines. The problem was first called to my attention by the second officer as we climbed through FL190 for FL220. At takeoff, the fuel qty indicators read 7200, 7400, 7300 #. They now read 7000, 3800, 7000 #. All the fuel was coming from the #2 tank. The fuel panel was in the normal confign, i.e., all pumps on, #1 and #3 xfeed valve switches off and #2 xfeed valve switch open. I observed a decrease in the #2 fuel qty indication equivalent to the burn of all 3 engines and no decrease in the qty indicators of the #1 and #3 tanks. When the #2 pumps were turned off for 2 min, a decrease in the fuel qty indications was seen in all 3 fuel qty indicators. It was determined that fuel from #1 and #3 tanks could be used to feed the #2 engine. With situation stabilized, the flight operated in somewhat normal tank to engine confign except for the #2 tank pumps off. Something had happened! Immediate focus was on the #1 and #3 xfeed valve switch position during climb. The second officer states positively that these valves were not in any other position during climb then closed. I have no knowledge or belief to disbelieve his statement. The second officer further states that if he had had these valves open during climb, he would have admitted this as this is not that big of a problem. Except if it led to engine flame out. Again, if a mistake had been made at the second officer panel, it could have been quickly and quietly rectified by him alone, possibly even west/O my knowledge. This aircraft is equipped with standard fuel pumps and so, if the xfeeds are open and all pumps are on, very little if any xfeeding is supposed to occur until another tank's pumps have been turned off. Something happened! I have no knowledge if anything like this has ever happened before. If so, who would know, and what was the problem? The aircraft fuel system was checked west/O finding any malfunction. Not the first time that a system has ground checked ok! I flew this aircraft 3 more legs that day west/O a recurrence.

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Original NASA ASRS Text

Title: MYSTERIOUS FUEL BURN PROBLEM ON AN LGT DURING CLIMB. ENGINES #1 AND #2 REPORTEDLY SET TANK TO ENGINE BURNED FUEL FROM #2 TANK.

Narrative: THIS RPT COVERS A PERCEIVED MALFUNCTION W/IN THE FUEL SYS. WHERE FUEL WAS BEING DRAWN FROM ONLY 1 TANK, BY OBSERVING THE FUEL QTY INDICATORS, WHEN THE COCKPIT FUEL PANEL WAS CALLING FOR FUEL FEED FROM ALL 3 TANKS TO THEIR RESPECTIVE ENGS. THE PROB WAS FIRST CALLED TO MY ATTN BY THE S/O AS WE CLBED THROUGH FL190 FOR FL220. AT TKOF, THE FUEL QTY INDICATORS READ 7200, 7400, 7300 #. THEY NOW READ 7000, 3800, 7000 #. ALL THE FUEL WAS COMING FROM THE #2 TANK. THE FUEL PANEL WAS IN THE NORMAL CONFIGN, I.E., ALL PUMPS ON, #1 AND #3 XFEED VALVE SWITCHES OFF AND #2 XFEED VALVE SWITCH OPEN. I OBSERVED A DECREASE IN THE #2 FUEL QTY INDICATION EQUIVALENT TO THE BURN OF ALL 3 ENGS AND NO DECREASE IN THE QTY INDICATORS OF THE #1 AND #3 TANKS. WHEN THE #2 PUMPS WERE TURNED OFF FOR 2 MIN, A DECREASE IN THE FUEL QTY INDICATIONS WAS SEEN IN ALL 3 FUEL QTY INDICATORS. IT WAS DETERMINED THAT FUEL FROM #1 AND #3 TANKS COULD BE USED TO FEED THE #2 ENG. WITH SITUATION STABILIZED, THE FLT OPERATED IN SOMEWHAT NORMAL TANK TO ENG CONFIGN EXCEPT FOR THE #2 TANK PUMPS OFF. SOMETHING HAD HAPPENED! IMMEDIATE FOCUS WAS ON THE #1 AND #3 XFEED VALVE SWITCH POS DURING CLB. THE S/O STATES POSITIVELY THAT THESE VALVES WERE NOT IN ANY OTHER POS DURING CLB THEN CLOSED. I HAVE NO KNOWLEDGE OR BELIEF TO DISBELIEVE HIS STATEMENT. THE S/O FURTHER STATES THAT IF HE HAD HAD THESE VALVES OPEN DURING CLB, HE WOULD HAVE ADMITTED THIS AS THIS IS NOT THAT BIG OF A PROB. EXCEPT IF IT LED TO ENG FLAME OUT. AGAIN, IF A MISTAKE HAD BEEN MADE AT THE S/O PANEL, IT COULD HAVE BEEN QUICKLY AND QUIETLY RECTIFIED BY HIM ALONE, POSSIBLY EVEN W/O MY KNOWLEDGE. THIS ACFT IS EQUIPPED WITH STD FUEL PUMPS AND SO, IF THE XFEEDS ARE OPEN AND ALL PUMPS ARE ON, VERY LITTLE IF ANY XFEEDING IS SUPPOSED TO OCCUR UNTIL ANOTHER TANK'S PUMPS HAVE BEEN TURNED OFF. SOMETHING HAPPENED! I HAVE NO KNOWLEDGE IF ANYTHING LIKE THIS HAS EVER HAPPENED BEFORE. IF SO, WHO WOULD KNOW, AND WHAT WAS THE PROB? THE ACFT FUEL SYS WAS CHKED W/O FINDING ANY MALFUNCTION. NOT THE FIRST TIME THAT A SYS HAS GND CHKED OK! I FLEW THIS ACFT 3 MORE LEGS THAT DAY W/O A RECURRENCE.

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