Narrative:

Approximately 2 hours into the flight; we got an EICAS message that the left generator had tripped. We ran the engineering checklist and was unable to recover the generator. Per the checklist; we started the APU to recover the lost power to the aircraft. After completion of the checklist; we contacted dispatch to discuss the generator failure and the fuel considerations with running the APU for the remainder of the flight. We rang up dispatch on the satphone and had them get maintenance control on the line. I was concerned about other electrical component failures because the maintenance history had shown a problem with the elms system on the previous flight. We had no indications other than the generator failure and maintenance control showed no additional downloaded information on the aircraft maintenance history system. With that in mind; we had dispatch work up fuel burn numbers for the entire flight with the APU running. Maintenance control in turn forwarded the MEL card for dispatching with the generator inoperative to the aircraft printer. I suggested to dispatch that we cruise at economy speeds with a cost index of zero to conserve the most fuel. The economy fuel burn numbers allowed us to arrive into ZZZZ with a comfortable amount of fuel and well within our scheduled arrival time. Since there were no maintenance considerations with the generator inoperative and since our arrival fuel was adequate; we all agreed it was safe to continue to our destination. We also kept it in the back of our minds that if we did not have adequate fuel at our re-dispatch point we would land and refuel before continuing on to ZZZZ. While working the generator problem we got a call from the flight attendants complaining about the loss of galley power. I explained that the power interruption was due to the loss of the generator and that it would be restored shortly. Along with the loss of galley power the flight attendant told me that there was a vibration in and around the business class area of the aircraft with the worst of it behind the business class galley. We had no indication of a problem in the cockpit; but there was a faint vibration in the cockpit floor. The relief pilots were about to return from their rest break; so I had them walk through the aircraft and see if they could pinpoint the vibration. The vibration was pronounced but not excessive and it seemed to be coming from the wing box area. As I went on break I had the relief pilots turn off the recirculation fans to see if the vibration was somehow related to the air conditioning system. The recirculations had no effect on the vibration; so I suggested it might be related to the generator failure on the left engine. I then instructed the relief pilots to call dispatch and get a phone patch with maintenance control to discuss disconnecting the idg for the left generator. Dispatch and maintenance control thought it was a good idea; so while I stood by door 2L on the interphone; they disconnected the left idg. Unfortunately; it had no effect on the vibration. I suggested they continue to work with maintenance control to see if he had any additional thoughts as to where the vibration might be coming from and to keep me abreast of any developments. Maintenance control reviewed the aircraft maintenance history and discovered 2 snapshots of engine parameters; one taken during takeoff and the other during cruise flight. The one during takeoff was normal; but the cruise snapshot showed excessive vibration in the fan stage and N1 rotor. After much deliberation between maintenance control; dispatch; and the relief pilots; a decision had to be made as to whether we should continue and just monitor the engine or divert. I was still on break at this time so the relief pilots summoned me back to the cockpit to help make a decision. I was informed by maintenance control that with the excessive vibration; components could start to fail on the engine. At this point in time; we were over foreign airspace with over 8 hours left in the flight and our routing had us traveling over more foreign airspace. We all agreed that the safest course of action was to divert the aircraft to ZZZ; where we could have the engine properly inspected. Dispatch; maintenance control; the flight operations duty manager; and crew saw no issues in making an overweight landing. The WX was VFR and the landing performance numbers showed plenty of margin; so we planned for an overweight landing at 25000 pounds over maximum at 485.0 K. We informed the passenger of the situation and briefed the flight attendants about the overweight landing and issued a cabin advisory to them. The remainder of the flight was uneventful with the conclusion of a smooth landing. Upon inspection; the engine was determined to have suffered internal damage. The aircraft was then taken OTS and scheduled for an engine change.

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Original NASA ASRS Text

Title: A B777-200 CAPTAIN REPORTS THE LEFT GENERATOR (IDG) HAD TRIPPED. LEFT ENG VIBRATION NOTED IN CABIN. ACFT DIVERTED. ENG HAD SUFFERED INTERNAL DAMAGE; REQUIRING ENGINE CHANGE. MAINT HISTORY SHOWED AN ELMS SYSTEM PROBLEM ON THE PREVIOUS FLIGHT.

Narrative: APPROX 2 HRS INTO THE FLT; WE GOT AN EICAS MESSAGE THAT THE L GENERATOR HAD TRIPPED. WE RAN THE ENGINEERING CHKLIST AND WAS UNABLE TO RECOVER THE GENERATOR. PER THE CHKLIST; WE STARTED THE APU TO RECOVER THE LOST PWR TO THE ACFT. AFTER COMPLETION OF THE CHKLIST; WE CONTACTED DISPATCH TO DISCUSS THE GENERATOR FAILURE AND THE FUEL CONSIDERATIONS WITH RUNNING THE APU FOR THE REMAINDER OF THE FLT. WE RANG UP DISPATCH ON THE SATPHONE AND HAD THEM GET MAINT CTL ON THE LINE. I WAS CONCERNED ABOUT OTHER ELECTRICAL COMPONENT FAILURES BECAUSE THE MAINT HISTORY HAD SHOWN A PROB WITH THE ELMS SYS ON THE PREVIOUS FLT. WE HAD NO INDICATIONS OTHER THAN THE GENERATOR FAILURE AND MAINT CTL SHOWED NO ADDITIONAL DOWNLOADED INFO ON THE ACFT MAINT HISTORY SYS. WITH THAT IN MIND; WE HAD DISPATCH WORK UP FUEL BURN NUMBERS FOR THE ENTIRE FLT WITH THE APU RUNNING. MAINT CTL IN TURN FORWARDED THE MEL CARD FOR DISPATCHING WITH THE GENERATOR INOP TO THE ACFT PRINTER. I SUGGESTED TO DISPATCH THAT WE CRUISE AT ECONOMY SPDS WITH A COST INDEX OF ZERO TO CONSERVE THE MOST FUEL. THE ECONOMY FUEL BURN NUMBERS ALLOWED US TO ARRIVE INTO ZZZZ WITH A COMFORTABLE AMOUNT OF FUEL AND WELL WITHIN OUR SCHEDULED ARR TIME. SINCE THERE WERE NO MAINT CONSIDERATIONS WITH THE GENERATOR INOP AND SINCE OUR ARR FUEL WAS ADEQUATE; WE ALL AGREED IT WAS SAFE TO CONTINUE TO OUR DEST. WE ALSO KEPT IT IN THE BACK OF OUR MINDS THAT IF WE DID NOT HAVE ADEQUATE FUEL AT OUR RE-DISPATCH POINT WE WOULD LAND AND REFUEL BEFORE CONTINUING ON TO ZZZZ. WHILE WORKING THE GENERATOR PROB WE GOT A CALL FROM THE FLT ATTENDANTS COMPLAINING ABOUT THE LOSS OF GALLEY PWR. I EXPLAINED THAT THE PWR INTERRUPTION WAS DUE TO THE LOSS OF THE GENERATOR AND THAT IT WOULD BE RESTORED SHORTLY. ALONG WITH THE LOSS OF GALLEY PWR THE FLT ATTENDANT TOLD ME THAT THERE WAS A VIBRATION IN AND AROUND THE BUSINESS CLASS AREA OF THE ACFT WITH THE WORST OF IT BEHIND THE BUSINESS CLASS GALLEY. WE HAD NO INDICATION OF A PROB IN THE COCKPIT; BUT THERE WAS A FAINT VIBRATION IN THE COCKPIT FLOOR. THE RELIEF PLTS WERE ABOUT TO RETURN FROM THEIR REST BREAK; SO I HAD THEM WALK THROUGH THE ACFT AND SEE IF THEY COULD PINPOINT THE VIBRATION. THE VIBRATION WAS PRONOUNCED BUT NOT EXCESSIVE AND IT SEEMED TO BE COMING FROM THE WING BOX AREA. AS I WENT ON BREAK I HAD THE RELIEF PLTS TURN OFF THE RECIRCULATION FANS TO SEE IF THE VIBRATION WAS SOMEHOW RELATED TO THE AIR CONDITIONING SYS. THE RECIRCULATIONS HAD NO EFFECT ON THE VIBRATION; SO I SUGGESTED IT MIGHT BE RELATED TO THE GENERATOR FAILURE ON THE L ENG. I THEN INSTRUCTED THE RELIEF PLTS TO CALL DISPATCH AND GET A PHONE PATCH WITH MAINT CTL TO DISCUSS DISCONNECTING THE IDG FOR THE L GENERATOR. DISPATCH AND MAINT CTL THOUGHT IT WAS A GOOD IDEA; SO WHILE I STOOD BY DOOR 2L ON THE INTERPHONE; THEY DISCONNECTED THE L IDG. UNFORTUNATELY; IT HAD NO EFFECT ON THE VIBRATION. I SUGGESTED THEY CONTINUE TO WORK WITH MAINT CTL TO SEE IF HE HAD ANY ADDITIONAL THOUGHTS AS TO WHERE THE VIBRATION MIGHT BE COMING FROM AND TO KEEP ME ABREAST OF ANY DEVELOPMENTS. MAINT CTL REVIEWED THE ACFT MAINT HISTORY AND DISCOVERED 2 SNAPSHOTS OF ENG PARAMETERS; ONE TAKEN DURING TKOF AND THE OTHER DURING CRUISE FLT. THE ONE DURING TKOF WAS NORMAL; BUT THE CRUISE SNAPSHOT SHOWED EXCESSIVE VIBRATION IN THE FAN STAGE AND N1 ROTOR. AFTER MUCH DELIBERATION BTWN MAINT CTL; DISPATCH; AND THE RELIEF PLTS; A DECISION HAD TO BE MADE AS TO WHETHER WE SHOULD CONTINUE AND JUST MONITOR THE ENG OR DIVERT. I WAS STILL ON BREAK AT THIS TIME SO THE RELIEF PLTS SUMMONED ME BACK TO THE COCKPIT TO HELP MAKE A DECISION. I WAS INFORMED BY MAINT CTL THAT WITH THE EXCESSIVE VIBRATION; COMPONENTS COULD START TO FAIL ON THE ENG. AT THIS POINT IN TIME; WE WERE OVER FOREIGN AIRSPACE WITH OVER 8 HRS LEFT IN THE FLT AND OUR ROUTING HAD US TRAVELING OVER MORE FOREIGN AIRSPACE. WE ALL AGREED THAT THE SAFEST COURSE OF ACTION WAS TO DIVERT THE ACFT TO ZZZ; WHERE WE COULD HAVE THE ENG PROPERLY INSPECTED. DISPATCH; MAINT CTL; THE FLT OPS DUTY MGR; AND CREW SAW NO ISSUES IN MAKING AN OVERWT LNDG. THE WX WAS VFR AND THE LNDG PERFORMANCE NUMBERS SHOWED PLENTY OF MARGIN; SO WE PLANNED FOR AN OVERWT LNDG AT 25000 LBS OVER MAX AT 485.0 K. WE INFORMED THE PAX OF THE SITUATION AND BRIEFED THE FLT ATTENDANTS ABOUT THE OVERWT LNDG AND ISSUED A CABIN ADVISORY TO THEM. THE REMAINDER OF THE FLT WAS UNEVENTFUL WITH THE CONCLUSION OF A SMOOTH LNDG. UPON INSPECTION; THE ENG WAS DETERMINED TO HAVE SUFFERED INTERNAL DAMAGE. THE ACFT WAS THEN TAKEN OTS AND SCHEDULED FOR AN ENG CHANGE.

Data retrieved from NASA's ASRS site as of May 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.