Narrative:

During flight planning I noticed a deferral for a discrepancy between FMC calculated and totalizer fuel. Read deferral and reviewed history and went to plane. During setup and review of MEL card pilot actions I had a question as to whether the individual tank quantity gauges would work in this case as some of the history indicated there was some 'blanking'. I called the dispatcher jim hansen from the jetway; patched to maintenance and specifically asked if the individual tank gauges were ok in case the FMC calculated readings failed and was told that they were. Back to cockpit and did preflight; and MEL card items to check sensors and manually enter calculated fuel from fuel slip. At this point all gauges including the overhead totalizer were working fine. About two hours into flight I noticed we had an EICAS status message that said fuel quantity indicator; and later we received a fuel quantity channel status message. Looked on the overhead and noticed the totalizer which was deferred inoperative was blank as was the center tank quantity gauge. We were still burning from the center tank and we knew we had some 8000 pounds of fuel remaining in there but I didn't expect the center gauge to go blank. Didn't seem like a big deal yet as I knew we had full wing tanks and could ascertain when they would start to deplete but then I noticed the left and right fuel gauges did not reflect full tanks. They showed various amounts of fuel from 14.8 (full) to 11.2 etc. The split between left and right was as great as 1400 pounds with no corresponding fuel configuration message-(not sure if that is gauge generated or not and the values to trigger the fuel configuration message have been removed from our manuals- I think it is 1500 # though) this got my attention now though since I really would not have any way of monitoring my fuel quantity if the left and right gauges were not accurate. Coupled with that was weather at our destination and we were at a low altitude 300 for rough rides and I started to become concerned about continuing past a mid point divert airport or there abouts when I knew my center tanks would be empty. Patched to dispatch and maintenance--discussed problem. Agreed to monitor and reevaluate with thoughts of diverting. Did lots of manual calculations and we were actually up on our fuel. Felt pretty good about it in general but feeling was if the gauges were still acting up we would divert. After about 45 minutes of this the gauges all seemed to go back to normal except for the intermittent blanking of the center and totalizer. Quantity in center depleted as per flight plan and left and right gauges were accurate and all status messages went away. Pressed on with normal indications and landed with about 9.0 pounds. I suspect the deferral we had was not as comprehensive as the problem and should have had a deferral on the gauges which would probably have not permitted dispatch. Spoke to maintenance folks next am and expressed concern along with dispatcher. We also received a fuel configuration warning at one point with the weird gauge readings but the quantity showed balanced and within limits. I'm not sure of what the original write ups said but this might have been a case of poor first officer write ups leading to a less than complete deferral of a problem.

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Original NASA ASRS Text

Title: A B757 fuel quantity system was MELed; presented a FUEL CONFIG EICAS message and an inaccurate quantity when only the center fuel tank quantity was creating the totalizer anomaly.

Narrative: During flight planning I noticed a deferral for a discrepancy between FMC calculated and totalizer fuel. Read deferral and reviewed history and went to plane. During setup and review of MEL card pilot actions I had a question as to whether the individual tank quantity gauges would work in this case as some of the history indicated there was some 'blanking'. I called the dispatcher Jim Hansen from the jetway; patched to maintenance and specifically asked if the individual tank gauges were OK in case the FMC calculated readings failed and was told that they were. Back to cockpit and did preflight; and MEL card items to check sensors and manually enter calculated fuel from fuel slip. At this point all gauges including the overhead totalizer were working fine. About two hours into flight I noticed we had an EICAS status message that said fuel quantity indicator; and later we received a fuel quantity channel status message. Looked on the overhead and noticed the totalizer which was deferred INOP was blank as was the center tank quantity gauge. We were still burning from the center tank and we knew we had some 8000 pounds of fuel remaining in there but I didn't expect the center gauge to go blank. Didn't seem like a big deal yet as I knew we had full wing tanks and could ascertain when they would start to deplete but then I noticed the left and right fuel gauges did not reflect full tanks. They showed various amounts of fuel from 14.8 (full) to 11.2 etc. The split between left and right was as great as 1400 pounds with no corresponding FUEL CONFIG message-(not sure if that is gauge generated or not and the values to trigger the FUEL CONFIG message have been removed from our manuals- I think it is 1500 # though) this got my attention now though since I really would not have any way of monitoring my fuel quantity if the left and right gauges were not accurate. Coupled with that was weather at our destination and we were at a low altitude 300 for rough rides and I started to become concerned about continuing past a mid point divert airport or there abouts when I knew my center tanks would be empty. Patched to dispatch and maintenance--discussed problem. Agreed to monitor and reevaluate with thoughts of diverting. Did lots of manual calculations and we were actually up on our fuel. Felt pretty good about it in general but feeling was if the gauges were still acting up we would divert. After about 45 minutes of this the gauges all seemed to go back to normal except for the intermittent blanking of the center and totalizer. Quantity in center depleted as per flight plan and left and right gauges were accurate and all status messages went away. Pressed on with normal indications and landed with about 9.0 pounds. I suspect the deferral we had was not as comprehensive as the problem and should have had a deferral on the gauges which would probably have not permitted dispatch. Spoke to maintenance folks next AM and expressed concern along with Dispatcher. We also received a FUEL CONFIG warning at one point with the weird gauge readings but the quantity showed balanced and within limits. I'm not sure of what the original write ups said but this might have been a case of poor First Officer write ups leading to a less than complete deferral of a problem.

Data retrieved from NASA's ASRS site as of April 2012 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.