B767-300 relief pilot reported that they observation of fuel streaming from the trailing edge of the...

Attributes
ACN	1504683
Time
Date	201712
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZZ.Airport
State Reference	FO
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B767-300 and 300 ER
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Oceanic
Flight Plan	IFR
Component
Aircraft Component	Fuel Tank Cap
Person 1
Function	Relief Pilot
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 20000 Flight Crew Type 7000
Events
Anomaly	Aircraft Equipment Problem Less Severe Flight Deck / Cabin / Aircraft Event Other / Unknown Inflight Event / Encounter Fuel Issue

Narrative:

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.

Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

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.