B767-300 and 300 ER
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 200; Flight Crew Total 20000; Flight Crew Type 7000
Workload; Troubleshooting; Distraction
Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Other / Unknown; Inflight Event / Encounter Fuel Issue
Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft
About 20 minutes after takeoff; Lead flight attendant called the flight deck to inform us that a passenger observed fluid coming from the right wing. I asked; what color of fluid the passenger had seen; she informed me clear fluid.As relief pilot; I exited the flight deck about 10 minutes later to observe the right wing. I observed what I would judge to be about 1 or 2 gallon per minute of fluid streaming from the trailing edge of the right wing; and could trace the origin to the mid-wing fuel cap. I called the flight deck to inform the Captain of the situation. About 15 minutes later; the Captain called back to the cabin to ask me to reassess the leak. I observed no change in the situation.I returned to the flight deck to find the duty crew had initiated fuel dumping and had coordinated a diversion. I assisted in calculating our landing fuel; ACARS communication with dispatch; informing the flight attendants and passengers; and reviewing the QRH; as well as making logbook entries.After an uneventful landing; we were able to get the fuel cap O-ring replaced. Flight attendant duty time was an issue but they voluntarily waved their limit and we were on our way within about 4 hours. Remainder of the flight was uneventful.
B767-300 Relief Pilot reported that they observation of fuel streaming from the trailing edge of the right wing. It was determined that the source of the leak was a wing-tank fuel cap; and an uneventful return to the departure airport was accomplished.