Narrative:

While performing an ETOPS check before departure, the engine oils were checked per the airline check sheet. I visually checked the oils and completed a sniff check for fuel with no discrepancies found. No oil was added to either engine and both caps were verified installed and locked. About 3 hours into the flight, the pilot reported low oil quantity and returned to the field. Upon inspection by maintenance personnel, the cap on the #1 engine was found off, along with a failed check valve in the filler neck and damaged o-ring seal on the cap. Items repaired and aircraft returned to service. Callback conversation with reporter revealed the following information: the reporter stated the company had a disciplinary hearing on the oil loss and it was argued by the union that failure of the filler neck check valve was the direct cause. The reporter said that he was aware of a manufacturer's service bulletin relating to check valve failure but is unable to get a copy from the company engineering staff.

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Original NASA ASRS Text

Title: A B767-200 IN CRUISE DECLARED AN EMER AND DIVERTED DUE TO LOSS OF OIL IN #1 ENG CAUSED BY THE OIL FILLER CAP SUSPECTED NOT BEING SECURED.

Narrative: WHILE PERFORMING AN ETOPS CHK BEFORE DEP, THE ENG OILS WERE CHKED PER THE AIRLINE CHK SHEET. I VISUALLY CHKED THE OILS AND COMPLETED A SNIFF CHK FOR FUEL WITH NO DISCREPANCIES FOUND. NO OIL WAS ADDED TO EITHER ENG AND BOTH CAPS WERE VERIFIED INSTALLED AND LOCKED. ABOUT 3 HRS INTO THE FLT, THE PLT RPTED LOW OIL QUANTITY AND RETURNED TO THE FIELD. UPON INSPECTION BY MAINT PERSONNEL, THE CAP ON THE #1 ENG WAS FOUND OFF, ALONG WITH A FAILED CHK VALVE IN THE FILLER NECK AND DAMAGED O-RING SEAL ON THE CAP. ITEMS REPAIRED AND ACFT RETURNED TO SVC. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE COMPANY HAD A DISCIPLINARY HEARING ON THE OIL LOSS AND IT WAS ARGUED BY THE UNION THAT FAILURE OF THE FILLER NECK CHK VALVE WAS THE DIRECT CAUSE. THE RPTR SAID THAT HE WAS AWARE OF A MANUFACTURER'S SVC BULLETIN RELATING TO CHK VALVE FAILURE BUT IS UNABLE TO GET A COPY FROM THE COMPANY ENGINEERING STAFF.

Data retrieved from NASA's ASRS site as of July 2007 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.