Narrative:

During cruise; about 3 hours from landing; I returned from my break. My first officer briefed me and advised me that we had 2 status messages. One was 'left engine fire loop' and the other was 'left engine overheat detection.' as these were status messages; there was no action required. During descent; about 30 mins prior to landing; we discussed the left engine vibration. It was in the 4-5 range and was indicating N2 vibration. The relief first officer mentioned that it also read high during cruise. There was no noticeable vibration in the cockpit or in the cabin and all other engine indications were normal. As we were on base leg for the approach to runway 27R at ZZZ; the first officer noticed oil quantity decreasing. We discussed the possibility of a single engine approach and landing. I asked the relief first officer to review the checklist for loss of oil quantity or pressure. Moments later; the oil pressure began to drop; followed by an 'engine oil pressure left' EICAS alert message. We declared an emergency and completed the 'engine oil pressure left' electronic checklist. We asked ATC to send out the emergency equipment. A call was made to the purser to inform her of the situation. The relief first officer made a brief PA. No communication was made to the company in-flight due to our close proximity to the airport. The landing was uneventful. I taxied the aircraft off the runway and came to a stop. The relief first officer made another announcement to the passenger explaining the presence of emergency vehicles. A visual inspection of the left engine from the emergency crews indicated nothing abnormal. We proceeded to the gate and the passenger were deplaned. I called dispatch from the aircraft and provided details of the incident to him and then to the duty flight manager. I called the maintenance controller engine controller to discuss the details of the incident. I learned that they were reviewing engine data during the cruise portion of our flight. It had already been determined that there may be some damage to a turbine blade. A borescope was planned after arrival in chicago. I questioned as to why it was thought not necessary to inform the crew as to the status of the engine if it was determined that there was a problem. It was explained to me that this was not the type of situation that was expected to result in an in-flight shutdown. The worst case considered was the inability to ferry the aircraft back to san francisco from chicago. In retrospect; I believe that the 2 status messages and the engine vibration were related. A call to maintenance controller/dispatch from us or from maintenance controller/dispatch to us in the cockpit may have been a useful discussion. Callback conversation with reporter revealed the following information: the reporter stated the maintenance action is unknown as no final report has been released by maintenance. The plans by maintenance control were to immediately borescope the engine and the findings of the borescope inspection would determine the maintenance action. I never followed up with maintenance after leaving the terminal.

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Original NASA ASRS Text

Title: A B777-200 ON FINAL AT 5000 FT DECLARED AN EMER DUE TO LOSS OF L ENG OIL PRESSURE AND QUANTITY. ENG INDICATING HIGH N2 VIBRATION. CAUSE UNKNOWN.

Narrative: DURING CRUISE; ABOUT 3 HRS FROM LNDG; I RETURNED FROM MY BREAK. MY FO BRIEFED ME AND ADVISED ME THAT WE HAD 2 STATUS MESSAGES. ONE WAS 'L ENG FIRE LOOP' AND THE OTHER WAS 'L ENG OVERHEAT DETECTION.' AS THESE WERE STATUS MESSAGES; THERE WAS NO ACTION REQUIRED. DURING DSCNT; ABOUT 30 MINS PRIOR TO LNDG; WE DISCUSSED THE L ENG VIBRATION. IT WAS IN THE 4-5 RANGE AND WAS INDICATING N2 VIBRATION. THE RELIEF FO MENTIONED THAT IT ALSO READ HIGH DURING CRUISE. THERE WAS NO NOTICEABLE VIBRATION IN THE COCKPIT OR IN THE CABIN AND ALL OTHER ENG INDICATIONS WERE NORMAL. AS WE WERE ON BASE LEG FOR THE APCH TO RWY 27R AT ZZZ; THE FO NOTICED OIL QUANTITY DECREASING. WE DISCUSSED THE POSSIBILITY OF A SINGLE ENG APCH AND LNDG. I ASKED THE RELIEF FO TO REVIEW THE CHKLIST FOR LOSS OF OIL QUANTITY OR PRESSURE. MOMENTS LATER; THE OIL PRESSURE BEGAN TO DROP; FOLLOWED BY AN 'ENG OIL PRESSURE L' EICAS ALERT MESSAGE. WE DECLARED AN EMER AND COMPLETED THE 'ENG OIL PRESSURE L' ELECTRONIC CHKLIST. WE ASKED ATC TO SEND OUT THE EMER EQUIP. A CALL WAS MADE TO THE PURSER TO INFORM HER OF THE SIT. THE RELIEF FO MADE A BRIEF PA. NO COM WAS MADE TO THE COMPANY INFLT DUE TO OUR CLOSE PROX TO THE ARPT. THE LNDG WAS UNEVENTFUL. I TAXIED THE ACFT OFF THE RWY AND CAME TO A STOP. THE RELIEF FO MADE ANOTHER ANNOUNCEMENT TO THE PAX EXPLAINING THE PRESENCE OF EMER VEHICLES. A VISUAL INSPECTION OF THE L ENG FROM THE EMER CREWS INDICATED NOTHING ABNORMAL. WE PROCEEDED TO THE GATE AND THE PAX WERE DEPLANED. I CALLED DISPATCH FROM THE ACFT AND PROVIDED DETAILS OF THE INCIDENT TO HIM AND THEN TO THE DUTY FLT MGR. I CALLED THE MAINT CTLR ENG CTLR TO DISCUSS THE DETAILS OF THE INCIDENT. I LEARNED THAT THEY WERE REVIEWING ENG DATA DURING THE CRUISE PORTION OF OUR FLT. IT HAD ALREADY BEEN DETERMINED THAT THERE MAY BE SOME DAMAGE TO A TURBINE BLADE. A BORESCOPE WAS PLANNED AFTER ARR IN CHICAGO. I QUESTIONED AS TO WHY IT WAS THOUGHT NOT NECESSARY TO INFORM THE CREW AS TO THE STATUS OF THE ENG IF IT WAS DETERMINED THAT THERE WAS A PROB. IT WAS EXPLAINED TO ME THAT THIS WAS NOT THE TYPE OF SIT THAT WAS EXPECTED TO RESULT IN AN INFLT SHUTDOWN. THE WORST CASE CONSIDERED WAS THE INABILITY TO FERRY THE ACFT BACK TO SAN FRANCISCO FROM CHICAGO. IN RETROSPECT; I BELIEVE THAT THE 2 STATUS MESSAGES AND THE ENG VIBRATION WERE RELATED. A CALL TO MAINT CTLR/DISPATCH FROM US OR FROM MAINT CTLR/DISPATCH TO US IN THE COCKPIT MAY HAVE BEEN A USEFUL DISCUSSION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE MAINT ACTION IS UNKNOWN AS NO FINAL RPT HAS BEEN RELEASED BY MAINT. THE PLANS BY MAINT CTL WERE TO IMMEDIATELY BORESCOPE THE ENG AND THE FINDINGS OF THE BORESCOPE INSPECTION WOULD DETERMINE THE MAINT ACTION. I NEVER FOLLOWED UP WITH MAINT AFTER LEAVING THE TERMINAL.

Data retrieved from NASA's ASRS site as of January 2009 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.