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A B747 developed a fuel imbalance about 3.5 hours after takeoff which could not be balanced and lead to an assumed fuel leak. While returning to the departure airport and jettisoning fuel; the imbalance remained during the overweight landing.
| Attributes | |
| ACN | 1302839 |
| Time | |
| Date | 201510 |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Make Model Name | B747 Undifferentiated or Other Model |
| Flight Phase | Cruise |
| Component | |
| Aircraft Component | Fuel System |
| Person 1 | |
| Function | First Officer Pilot Not Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 180 Flight Crew Total 10000 Flight Crew Type 650 |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical Inflight Event / Encounter Fuel Issue |
Narrative:
I was in the bunk asleep while this was building up to a divert. When I was woken up and made aware of the situation; we collectively; as a crew decided; along with input from dispatch; to divert back to [departure airport]. Evidently; there was a fuel score discrepancy of 6K from the flight plan;early in the flight; with no other mitigating circumstances. Initially a fuel imbalance checklist was accomplished. I think between tanks 1 and 4. This eventually lead to the fuel leak checklist. At any rate; we diverted to the departure airport. We had to jettison fuel to land under max landing weight. During the jettison; an imbalance occurred. The jettison was stopped to resolve the imbalance; as the checklist gave no guidance for an imbalance during jettison operations. We did not want to go into no man's land trying to balance during jettison operations; with no checklist guidance. I believe as a function of stopping the jettison early; to balance; we ended up landing just a little bit over max landing weight. Not sure on that. Fire trucks rolled. Landing uneventful.
Original NASA ASRS Text
Title: A B747 developed a fuel imbalance about 3.5 hours after takeoff which could not be balanced and lead to an assumed fuel leak. While returning to the departure airport and jettisoning fuel; the imbalance remained during the overweight landing.
Narrative: I was in the bunk asleep while this was building up to a divert. When I was woken up and made aware of the situation; we collectively; as a crew decided; along with input from dispatch; to divert back to [departure airport]. Evidently; there was a fuel score discrepancy of 6K from the flight plan;early in the flight; with no other mitigating circumstances. Initially a fuel imbalance checklist was accomplished. I think between tanks 1 and 4. This eventually lead to the fuel leak checklist. At any rate; we diverted to the departure airport. We had to jettison fuel to land under max landing weight. During the jettison; an imbalance occurred. The jettison was stopped to resolve the imbalance; as the checklist gave no guidance for an imbalance during jettison operations. We did not want to go into no man's land trying to balance during jettison operations; with no checklist guidance. I believe as a function of stopping the jettison early; to balance; we ended up landing just a little bit over max landing weight. Not sure on that. Fire trucks rolled. Landing uneventful.
Data retrieved from NASA's ASRS site 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.