Narrative:

Normal cruise flight FL360 approximately 20 mins after reaching ZZZZ center airspace the left generator drive light began to flicker at irregular intervals. This was sometimes accompanied by a left generator drive message on the upper EICAS screen. QRH was reviewed and an attempt to start the APU accomplished. APU would not start. Descended to FL320 for second APU start attempt. APU still would not start. APU fault EICAS on the upper EICAS screen and APU door status message on the lower EICAS screen. Dispatch was advised and maintenance control was consulted. Maintenance control advised no history on either the left idg or APU and recommended continuing as long as light did not remain on steady. System seemed to settle down with fewer events of the generator drive light cycling on/off. Approximately 60-90 mins later the generator drive light began to flicker at regular intervals as described above. After about 15 mins of this the generator drive light came on steady with the accompanying left generator drive message on the upper EICAS screen. The idg was disconnected in accordance with QRH procedures. We immediately turned toward the nearest suitable airport; ZZZZ1 and tried multiple APU start attempts at different flight levels in accordance with recommended QRH procedures. Dispatch was advised via satcom. An emergency was declared due to single power source status of the electrical system and a landing was accomplished at the nearest suitable airport. Although I did declare an emergency I did not have to exercise my emergency command authority/authorized to deviate from any company procedures or ATC clrncs. A normal approach and landing was accomplished at ZZZ1.

Related reports:

Google
 

Original NASA ASRS Text

Title: B767 FLT CREW REPORTS GENERATOR DRIVE FAILURE AND INABILITY TO START APU; CAUSING DIVERSION TO NEAREST SUITABLE ARPT.

Narrative: NORMAL CRUISE FLT FL360 APPROX 20 MINS AFTER REACHING ZZZZ CTR AIRSPACE THE L GENERATOR DRIVE LIGHT BEGAN TO FLICKER AT IRREGULAR INTERVALS. THIS WAS SOMETIMES ACCOMPANIED BY A L GENERATOR DRIVE MESSAGE ON THE UPPER EICAS SCREEN. QRH WAS REVIEWED AND AN ATTEMPT TO START THE APU ACCOMPLISHED. APU WOULD NOT START. DSNDED TO FL320 FOR SECOND APU START ATTEMPT. APU STILL WOULD NOT START. APU FAULT EICAS ON THE UPPER EICAS SCREEN AND APU DOOR STATUS MESSAGE ON THE LOWER EICAS SCREEN. DISPATCH WAS ADVISED AND MAINT CTL WAS CONSULTED. MAINT CTL ADVISED NO HISTORY ON EITHER THE L IDG OR APU AND RECOMMENDED CONTINUING AS LONG AS LIGHT DID NOT REMAIN ON STEADY. SYS SEEMED TO SETTLE DOWN WITH FEWER EVENTS OF THE GENERATOR DRIVE LIGHT CYCLING ON/OFF. APPROX 60-90 MINS LATER THE GENERATOR DRIVE LIGHT BEGAN TO FLICKER AT REGULAR INTERVALS AS DESCRIBED ABOVE. AFTER ABOUT 15 MINS OF THIS THE GENERATOR DRIVE LIGHT CAME ON STEADY WITH THE ACCOMPANYING L GENERATOR DRIVE MESSAGE ON THE UPPER EICAS SCREEN. THE IDG WAS DISCONNECTED IN ACCORDANCE WITH QRH PROCS. WE IMMEDIATELY TURNED TOWARD THE NEAREST SUITABLE ARPT; ZZZZ1 AND TRIED MULTIPLE APU START ATTEMPTS AT DIFFERENT FLT LEVELS IN ACCORDANCE WITH RECOMMENDED QRH PROCS. DISPATCH WAS ADVISED VIA SATCOM. AN EMER WAS DECLARED DUE TO SINGLE PWR SOURCE STATUS OF THE ELECTRICAL SYS AND A LNDG WAS ACCOMPLISHED AT THE NEAREST SUITABLE ARPT. ALTHOUGH I DID DECLARE AN EMER I DID NOT HAVE TO EXERCISE MY EMER COMMAND AUTH TO DEVIATE FROM ANY COMPANY PROCS OR ATC CLRNCS. A NORMAL APCH AND LNDG WAS ACCOMPLISHED AT ZZZ1.

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.