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.