B757-200 lost electrical power to both main busses; and aircraft reverted to standby power. One gene...

Attributes
ACN	755188
Time
Date	200709
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 36000
Aircraft 1
Controlling Facilities	artcc : zzz.artcc tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 170 flight time total : 11000 flight time type : 4000
ASRS Report	755188
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 300 flight time total : 14000 flight time type : 4000
ASRS Report	754931
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : overcame equipment problem
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Both AC buses suddenly fell off line leaving aircraft on standby power. Standby engine instruments indicated 0.0 on both EPR gauges which led us initially to believe we had dual engine failure. The captain took control of aircraft and started the APU while I started to run loss dual engine failure qrc. Moving the throttles toward idle provided us with good engine indications except for EPR and I abandoned the qrc and headed for loss of AC bus(es) checklist in FM. About this time the APU generator came on line and pwred just the left electrical system. We had an isol light on the right isol bus and the right generator was still off line. I reset the right generator and the bus isol switch and both reset. At this time; all electrical power was restored except for the left generator which would not reset. We also had a left generator drive light and I attempted to disconnect per the checklist. After completing generator drive light checklist and loss of AC power checklist we confirmed with maintenance over commercial radio. We all decided to press on to ZZZ since we had 2 AC power sources available and ZZZ now was the closest field. Approach and landing were uneventful.

Original NASA ASRS Text

Title: B757-200 LOST ELECTRICAL PWR TO BOTH MAIN BUSSES; AND ACFT REVERTED TO STANDBY PWR. ONE GENERATOR RESET AND THE APU WAS STARTED; RESTORING PWR.

Narrative: BOTH AC BUSES SUDDENLY FELL OFF LINE LEAVING ACFT ON STANDBY PWR. STANDBY ENG INSTS INDICATED 0.0 ON BOTH EPR GAUGES WHICH LED US INITIALLY TO BELIEVE WE HAD DUAL ENG FAILURE. THE CAPT TOOK CTL OF ACFT AND STARTED THE APU WHILE I STARTED TO RUN LOSS DUAL ENG FAILURE QRC. MOVING THE THROTTLES TOWARD IDLE PROVIDED US WITH GOOD ENG INDICATIONS EXCEPT FOR EPR AND I ABANDONED THE QRC AND HEADED FOR LOSS OF AC BUS(ES) CHKLIST IN FM. ABOUT THIS TIME THE APU GENERATOR CAME ON LINE AND PWRED JUST THE L ELECTRICAL SYS. WE HAD AN ISOL LIGHT ON THE R ISOL BUS AND THE R GENERATOR WAS STILL OFF LINE. I RESET THE R GENERATOR AND THE BUS ISOL SWITCH AND BOTH RESET. AT THIS TIME; ALL ELECTRICAL PWR WAS RESTORED EXCEPT FOR THE L GENERATOR WHICH WOULD NOT RESET. WE ALSO HAD A L GENERATOR DRIVE LIGHT AND I ATTEMPTED TO DISCONNECT PER THE CHKLIST. AFTER COMPLETING GENERATOR DRIVE LIGHT CHKLIST AND LOSS OF AC PWR CHKLIST WE CONFIRMED WITH MAINT OVER COMMERCIAL RADIO. WE ALL DECIDED TO PRESS ON TO ZZZ SINCE WE HAD 2 AC PWR SOURCES AVAILABLE AND ZZZ NOW WAS THE CLOSEST FIELD. APCH AND LNDG WERE UNEVENTFUL.

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.

B757-200 lost electrical power to both main busses; and aircraft reverted to standby power. One generator reset and the APU was started; restoring power.