B777-200
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Fuel Issue
Flight Crew Diverted; Flight Crew Landed As Precaution
Aircraft
Enroute to [an international destination] an overweight landing and diversion to [a suitable alternate] became necessary due to a sudden loss of fuel. We had been ahead of flight plan fuel estimates by approximately 700 lbs at previous waypoints and fuel balance and quantity had been checked approximately 5 minutes prior to getting the Fuel Imbalance EICAS warning due to right wing fuel quantity suddenly being approximately 5000 lbs below left tank fuel. The Fuel Imbalance checklist was accomplished and we were now going to be 4900 lbs below flight plan fuel estimate at next waypoint and it appeared we must have developed a fuel leak. Because we still had lots of fuel and were not yet fuel critical I first coordinated with dispatch regarding a divert because of this fuel disparity. The Relief Pilot was awakened early to inspect the wings and engines for evidence of a fuel leak; and we then notified ATC of our intentions and needs. We then requested and received an inspection and escort to the gate by Fire/ARFF after an uneventful overweight landing. The performance of all of my crew; including Flight Attendants was great and I have no suggestions at this time to anyone involved in our handling of this event to have improved our situation. The diversion and landing although busy and task saturated; went smoothly.
Reporter stated follow up conversation with Maintenance suggested the problem was a fuel quantity indicator error.
[Report narrative contained no additional information.]
B777 flight crew reported diverting to an alternate after experiencing an apparent fuel leak.