E120 crew had both emergency dc electrical busses fail.

Attributes
ACN	410333
Time
Date	199807
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : flo
State Reference	SC
Altitude	msl bound lower : 23000 msl bound upper : 23000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zjx tower : fat
Operator	common carrier : air carrier
Make Model Name	Brasilia EMB-120 All Series
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other other other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi pilot : instrument
Experience	flight time last 90 days : 240 flight time total : 4500 flight time type : 3000
ASRS Report	410333
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : declared emergency flight crew : overcame equipment problem other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

In cruise flight, just prior to descent, we experienced loss of both emergency dc busses. Followed checklist to find no solution. Declared an emergency. Checklist advised that the following items were not available. Nosewheel steering inoperative, antiskid brakes inoperative, reverse (beta) range inoperative, normal landing gear extension inoperative, captain's altimeter inoperative, engine torque and engine gauges (T6) inoperative, autofeather system inoperative, altitude alerter, autoplt -- all inoperative. Only first officer's altimeter worked. May have oscillated through assigned altitudes (we did our best). Only first officer's headsets for all communications (no cockpit speakers or captain's headset) manual freefall of gear. All emergency checklists and normal checklists completed. Landing was uneventful. Taxied to gate and shut down engines. Decision to land in ilm based on length of runway (runway 24), sun was setting, fuel low (but still landed with IFR minimums). Maintenance inspection concluded some transient (electrical) must have popped the main breakers which are not accessible to pilots. CRM played a big factor in the success of this incident. Passenger were not inconvenienced at all. NTSB was notified as required under NTSB 830, FAA and poi also advised. Callback conversation with reporter revealed the following information: there have been a number of electrical items added to the emergency busses over the yrs. It finally reached the point that the circuit breakers reached their load limit. This aircraft had a left emergency bus fail 3 days prior to this incident. The reporter knows of other aircraft with similar problems. The air carrier, in coordination with the FAA, NTSB, and embraer, have started a modification program which replaces the circuit breakers with a different type. The captain knows of no further problems on aircraft which have been modified. Reporter was favorably impressed with the speed with which all parties responded to this problem. He also stated that the guidance in the aircraft flight manual was excellent.

Original NASA ASRS Text

Title: E120 CREW HAD BOTH EMER DC ELECTRICAL BUSSES FAIL.

Narrative: IN CRUISE FLT, JUST PRIOR TO DSCNT, WE EXPERIENCED LOSS OF BOTH EMER DC BUSSES. FOLLOWED CHKLIST TO FIND NO SOLUTION. DECLARED AN EMER. CHKLIST ADVISED THAT THE FOLLOWING ITEMS WERE NOT AVAILABLE. NOSEWHEEL STEERING INOP, ANTISKID BRAKES INOP, REVERSE (BETA) RANGE INOP, NORMAL LNDG GEAR EXTENSION INOP, CAPT'S ALTIMETER INOP, ENG TORQUE AND ENG GAUGES (T6) INOP, AUTOFEATHER SYS INOP, ALT ALERTER, AUTOPLT -- ALL INOP. ONLY FO'S ALTIMETER WORKED. MAY HAVE OSCILLATED THROUGH ASSIGNED ALTS (WE DID OUR BEST). ONLY FO'S HEADSETS FOR ALL COMS (NO COCKPIT SPEAKERS OR CAPT'S HEADSET) MANUAL FREEFALL OF GEAR. ALL EMER CHKLISTS AND NORMAL CHKLISTS COMPLETED. LNDG WAS UNEVENTFUL. TAXIED TO GATE AND SHUT DOWN ENGS. DECISION TO LAND IN ILM BASED ON LENGTH OF RWY (RWY 24), SUN WAS SETTING, FUEL LOW (BUT STILL LANDED WITH IFR MINIMUMS). MAINT INSPECTION CONCLUDED SOME TRANSIENT (ELECTRICAL) MUST HAVE POPPED THE MAIN BREAKERS WHICH ARE NOT ACCESSIBLE TO PLTS. CRM PLAYED A BIG FACTOR IN THE SUCCESS OF THIS INCIDENT. PAX WERE NOT INCONVENIENCED AT ALL. NTSB WAS NOTIFIED AS REQUIRED UNDER NTSB 830, FAA AND POI ALSO ADVISED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THERE HAVE BEEN A NUMBER OF ELECTRICAL ITEMS ADDED TO THE EMER BUSSES OVER THE YRS. IT FINALLY REACHED THE POINT THAT THE CIRCUIT BREAKERS REACHED THEIR LOAD LIMIT. THIS ACFT HAD A L EMER BUS FAIL 3 DAYS PRIOR TO THIS INCIDENT. THE RPTR KNOWS OF OTHER ACFT WITH SIMILAR PROBS. THE ACR, IN COORD WITH THE FAA, NTSB, AND EMBRAER, HAVE STARTED A MODIFICATION PROGRAM WHICH REPLACES THE CIRCUIT BREAKERS WITH A DIFFERENT TYPE. THE CAPT KNOWS OF NO FURTHER PROBS ON ACFT WHICH HAVE BEEN MODIFIED. RPTR WAS FAVORABLY IMPRESSED WITH THE SPD WITH WHICH ALL PARTIES RESPONDED TO THIS PROB. HE ALSO STATED THAT THE GUIDANCE IN THE ACFT FLT MANUAL WAS EXCELLENT.

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.