Light transport has electrical dc bus failure. Emergency declared.

Attributes
ACN	271129
Time
Date	199405
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mfd
State Reference	OH
Altitude	msl bound lower : 19000 msl bound upper : 19000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob tower : fat
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other other other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 6000 flight time type : 1500
ASRS Report	271129
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : atp
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

Items that run off our left main dc bus started to intermittently fail. Then all dc items on captain side died. After switching control to first officer we began troubleshooting. Pressurization was lost, temperature control was lost. At full hot cargo and cabin door warning lights illuminated. An emergency was declared and a landing at mfd, oh, was made. Landing was normal. Everything pointed to a left dc bus failure, however, none of the appropriate caution lights were on. In talking to maintenance afterward, they said the left generator surged and popped numerous circuit breakers. The gcu which controls bus ties and turns on caution lights became inoperative. Because of this, our situation was not displayed on the annunciator panel. Numerous caution lights illuminated, but they had nothing to do with this electrical system, which confused our initial conclusion.

Original NASA ASRS Text

Title: LTT HAS ELECTRICAL DC BUS FAILURE. EMER DECLARED.

Narrative: ITEMS THAT RUN OFF OUR L MAIN DC BUS STARTED TO INTERMITTENTLY FAIL. THEN ALL DC ITEMS ON CAPT SIDE DIED. AFTER SWITCHING CTL TO FO WE BEGAN TROUBLESHOOTING. PRESSURIZATION WAS LOST, TEMP CTL WAS LOST. AT FULL HOT CARGO AND CABIN DOOR WARNING LIGHTS ILLUMINATED. AN EMER WAS DECLARED AND A LNDG AT MFD, OH, WAS MADE. LNDG WAS NORMAL. EVERYTHING POINTED TO A L DC BUS FAILURE, HOWEVER, NONE OF THE APPROPRIATE CAUTION LIGHTS WERE ON. IN TALKING TO MAINT AFTERWARD, THEY SAID THE L GENERATOR SURGED AND POPPED NUMEROUS CIRCUIT BREAKERS. THE GCU WHICH CTLS BUS TIES AND TURNS ON CAUTION LIGHTS BECAME INOP. BECAUSE OF THIS, OUR SIT WAS NOT DISPLAYED ON THE ANNUNCIATOR PANEL. NUMEROUS CAUTION LIGHTS ILLUMINATED, BUT THEY HAD NOTHING TO DO WITH THIS ELECTRICAL SYS, WHICH CONFUSED OUR INITIAL CONCLUSION.

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.