An air carrier B737 flight crew experiences an electrical fault on bus #1. They were able to restore...

Attributes
ACN	382767
Time
Date	199710
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : orf
State Reference	VA
Altitude	msl bound lower : 35000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc tower : mht
Operator	common carrier : air carrier
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : atp pilot : cfi
Experience	flight time last 90 days : 150 flight time total : 6800 flight time type : 1400
ASRS Report	382767
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	controller : issued new clearance none taken : anomaly accepted other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

On a flight (B737-400) from isp to pbi, climbing through 34000 ft for 35000 ft, loss of both generator busses occurred. The captain became the PF and we referred to the aircraft checklist. The generator bus #2 was restored by deselecting generator bus #1. All electrical was restored, except what was on generator bus #1. After starting the APU, it was selected for generator bus #1. Loss of both generator busses occurred again. Deselecting the APU, generator bus #2 came back on line. After calling dispatch and discussing our options, we continued to proceed to pbi. The #2 generator was powering all electrical (except generator bus #1), without excess load or temperature. There was no need to divert since all standby power and battery indications were normal, plus the APU could supply the #2 generator bus (if necessary). The only change to our flight was the routing. Instead of flying overwater from diw to pbi, we rerouted along the coast. WX was VFR along the route to our destination. Forecast showers at our destination had moved to the south. The flight was completed without further incident. We surmised that xfer relays from generator bus #1 to xfer bus #1 were defective. Aircraft capabilities allowed generator bus #2 automatic connection to xfer bus #1, which it did within generator load limits. No navigation or other system degradation occurred in this confign. Only redundant items on the generator bus #1 were inoperative.

Original NASA ASRS Text

Title: AN ACR B737 FLC EXPERIENCES AN ELECTRICAL FAULT ON BUS #1. THEY WERE ABLE TO RESTORE PWR TO BUS #2 AND USED THE AUX PWR UNIT AS A BACKUP SOURCE.

Narrative: ON A FLT (B737-400) FROM ISP TO PBI, CLBING THROUGH 34000 FT FOR 35000 FT, LOSS OF BOTH GENERATOR BUSSES OCCURRED. THE CAPT BECAME THE PF AND WE REFERRED TO THE ACFT CHKLIST. THE GENERATOR BUS #2 WAS RESTORED BY DESELECTING GENERATOR BUS #1. ALL ELECTRICAL WAS RESTORED, EXCEPT WHAT WAS ON GENERATOR BUS #1. AFTER STARTING THE APU, IT WAS SELECTED FOR GENERATOR BUS #1. LOSS OF BOTH GENERATOR BUSSES OCCURRED AGAIN. DESELECTING THE APU, GENERATOR BUS #2 CAME BACK ON LINE. AFTER CALLING DISPATCH AND DISCUSSING OUR OPTIONS, WE CONTINUED TO PROCEED TO PBI. THE #2 GENERATOR WAS POWERING ALL ELECTRICAL (EXCEPT GENERATOR BUS #1), WITHOUT EXCESS LOAD OR TEMP. THERE WAS NO NEED TO DIVERT SINCE ALL STANDBY PWR AND BATTERY INDICATIONS WERE NORMAL, PLUS THE APU COULD SUPPLY THE #2 GENERATOR BUS (IF NECESSARY). THE ONLY CHANGE TO OUR FLT WAS THE ROUTING. INSTEAD OF FLYING OVERWATER FROM DIW TO PBI, WE REROUTED ALONG THE COAST. WX WAS VFR ALONG THE RTE TO OUR DEST. FORECAST SHOWERS AT OUR DEST HAD MOVED TO THE S. THE FLT WAS COMPLETED WITHOUT FURTHER INCIDENT. WE SURMISED THAT XFER RELAYS FROM GENERATOR BUS #1 TO XFER BUS #1 WERE DEFECTIVE. ACFT CAPABILITIES ALLOWED GENERATOR BUS #2 AUTO CONNECTION TO XFER BUS #1, WHICH IT DID WITHIN GENERATOR LOAD LIMITS. NO NAV OR OTHER SYS DEGRADATION OCCURRED IN THIS CONFIGN. ONLY REDUNDANT ITEMS ON THE GENERATOR BUS #1 WERE INOP.

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.

An air carrier B737 flight crew experiences an electrical fault on bus #1. They were able to restore power to bus #2 and used the auxiliary power unit as a backup source.