Narrative:

I was the check airman occupying the right seat. A passenger noticed fuel streaming from the top of the left wing. Flight attendants called us. The relief pilot just started break so we had him look at it and he saw fuel streaming from the top of the wing around the fuel cap. I pulled out the fuel leak checklist and got maintenance and dispatch on a conference call. I worked through the checklist and requested the relief pilot return to the flight deck. When he returned he said the leak stopped. We had taken off with the tank full 141;000 pounds for ZZZZ as an alternate. Dispatch and us contemplated pressing on since all we had was a 500 pounds difference between tanks and it was obviously coming from a very full tank. Maintenance said no we need to return to departure airport since it was a bad seal on the tank. We discussed going to ZZZ since we were a bit closer and the checklist said land at nearest suitable but all agreed that we didn't have a fuel leak any more just a return to airport for a maintenance issue. We discussed dumping fuel vs landing overweight. We all determined conditions were acceptable for an overweight landing. The relief pilot and myself worked the fuel checklist again in case we missed anything and received performance data from dispatch. We made PA's to the passengers; kept the flight attendants informed did a cabin advisory to be safe and had the equipment standing by for landing. ATC declared an emergency for us. Since we were overweight we landed flaps 25 took the last taxiway chocked the tires and let the brakes cool. Complied with the tow-in checklist and returned to the blocks under tow.

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Original NASA ASRS Text

Title: B767 flight crew was informed of fuel leaking from a wing cap at FL310. After discussions with maintenance it was decided to return to their departure airport for an overweight landing and repairs.

Narrative: I was the Check Airman occupying the right seat. A passenger noticed fuel streaming from the top of the left wing. Flight attendants called us. The relief pilot just started break so we had him look at it and he saw fuel streaming from the top of the wing around the fuel cap. I pulled out the fuel leak checklist and got Maintenance and Dispatch on a conference call. I worked through the checklist and requested the relief pilot return to the flight deck. When he returned he said the leak stopped. We had taken off with the tank full 141;000 LBS for ZZZZ as an alternate. Dispatch and us contemplated pressing on since all we had was a 500 LBS difference between tanks and it was obviously coming from a very full tank. Maintenance said no we need to return to departure airport since it was a bad seal on the tank. We discussed going to ZZZ since we were a bit closer and the checklist said land at nearest suitable but all agreed that we didn't have a fuel leak any more just a return to airport for a maintenance issue. We discussed dumping fuel vs landing overweight. We all determined conditions were acceptable for an overweight landing. The relief pilot and myself worked the fuel checklist again in case we missed anything and received performance data from Dispatch. We made PA's to the passengers; kept the flight attendants informed did a cabin advisory to be safe and had the equipment standing by for landing. ATC declared an emergency for us. Since we were overweight we landed flaps 25 took the last taxiway chocked the tires and let the brakes cool. Complied with the Tow-in Checklist and returned to the blocks under tow.

Data retrieved from NASA's ASRS site as of April 2012 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.