A B747-400 diverted to a suitable airport when the number two engine was shut down due to a probable fuel leak.
Synopsis
A B747-400 diverted to a suitable airport when the number two engine was shut down due to a probable fuel leak.
Narrative
Noted that the fuel score showed a decrease of 1800 # in the fuel on board over a period of 47 minutes. Looked at the fuel quantity in each tank and noted that main tank #2 was 4;000lb less than main tank #3. We were at the flight plan recommended altitude and the FMC optimum altitude. The winds and temperature were as forecast. We attempted to reconcile the discrepancy. FMC used fuel - within 100 # for all engines. Fuel Flow - within .1 for all engines. Fuel service form showed equal quantity in main tanks #2 and #3. All of these items did not show any reason for the over burn or the fuel imbalance. We accessed the Flight Manual fuel leak checklist and determined that there was a probable engine fuel leak; talked with Dispatch and engine Maintenance and they concurred. Received a clearance to descend to a lower altitude and shut the engine down per the procedure. Discussed with Dispatch and determined the nearest suitable airport to be ZZZ. Monitored the fuel and did not notice any further fuel loss. Landed uneventfully. Switched the passengers and cargo to another plane and continued to our original destination.
Second reporter narrative
I was asleep on my break and was awakened and when I came to the cockpit the flying crew had shut the #2 engine down per the checklist due to a suspected fuel leak. They had talked to Dispatch and Maintenance and we were now rerouted to land in ZZZ instead of our original destination. We reviewed what had happened; the current status of our fuel situation; weather; reroute; any additional things that we would have to address. After a thorough briefing the Captain and flying First Officer went on break and we proceeded on our new course to ZZZ. We kept the fuel balanced per the flight manual and monitored the fuel burn and did not have any further indications of fuel leaking. We stayed in fuel balance . The flying crew returned to the cockpit from their break early and we reviewed what had happened on our watch and landed without any further problems. We reviewed the flight with Maintenance at the gate.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.