B747 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 180; Flight Crew Total 10000; Flight Crew Type 650
Time Pressure; Situational Awareness; Confusion; Training / Qualification; Workload
Aircraft Equipment Problem Critical; Inflight Event / Encounter Fuel Issue
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; Flight Crew Took Evasive Action; General Maintenance Action
Aircraft; Procedure; Manuals
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.
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.