B777 Undifferentiated or Other Model
Flight Crew Last 90 Days 200; Flight Crew Total 8000; Flight Crew Type 600
Aircraft Equipment Problem Critical; Inflight Event / Encounter Fuel Issue
Flight Crew Diverted; Flight Crew Inflight Shutdown; Flight Crew Landed in Emergency Condition; General Declared Emergency; General Maintenance Action
Aircraft; Human Factors; Procedure
Enroute during maintenance ferry we received an EICAS message of fuel imbalance; we executed the checklist and noted how long it should take to balance the fuel based on fuel flow. It took half the expected time to balance the fuel; also we received another message of Fuel Disagree; After Electronic Checklist execution we now felt we had a possible fuel leak. We notified the Captain (who was on break) of the situation and he came to the cockpit. We inspected the left engine and noticed fuel was leaking from the fan section of the aircraft. We declared an emergency and initiated a turn towards a suitable diversion airport. We descended while executing the checklist which required engine shut down. We planned a single engine landing and the approach and landing were uneventful.
[Over the Pacific] heading east we had a Fuel Imbalance Checklist icon.Fuel Imbalance Checklist considered fuel leaks if one or more of the following was present: 1.  Fuel spray observed from an engine2.  A change in fuel imbalance of 1;000 or more within 30 minutes or less 3.  EICAS fuel remaining different than calculated fuel on the FMCWe had all three.We declared a mayday via both CPDLC and voice with ATC. [We] then requested and received a return clearance to ZZZZ via CPDLC as well as via voice on HF. We followed all checklists and notified all personnel. The checklist directed an engine shutdown to stop the fuel leak. It worked. We continued on the diversion with no other problems. Landed uneventfully. Taxiied (followed by the fire trucks) to the ramp where Maintenance met us and saw it was indeed a leak.
B777 flight crew experiences a fuel imbalance during a ferry flight over the Pacific Ocean. After rebalancing a Fuel Disagree message is displayed and the electronic checklist indicates a fuel leak is likely. Fuel is visually confirmed to be coming from the left engine which is shut down and the flight diverts to a suitable airport.