Narrative:

15000 ft cruise from tpa to mia in VMC conditions when the dc generator #1 faulted. Referencing the QRH checklist for the fault allowed for a reset of the generator. Once the generator was reset, the electrical system went 'bizerk.' all bells, chimes and warning lights in the cockpit activated simultaneously, as well as lights in the passenger cabin. We declared an emergency and initiated a descent to below 10000 ft due to loss of cabin pressure. Then we proceeded with dual dc generator failure checklist. Main battery power (which should have lasted approximately 43 mins) was lost within 1 min. The flight attendant came to the cockpit as soon as his cabin lighting started malfunctioning. We continued with the checklist, selecting override/undervoltage per the QRH in order to go to emergency battery power. The flight attendant was briefed in person. Contact with ATC (which had been lost with the main battery) was now re-established and we were given vectors to rsw. With the integrity of the emergency in question, we elected to perform a no flap landing. The landing was accomplished without incident, with emergency braking being satisfactory. Crash fire rescue equipment team and aircraft operations personnel met the aircraft as it exited the runway at taxiway A6. The fire marshall asked if we had experienced a main battery thermal runaway. Not having a battery temperature gauge, we told him that we had no way of knowing. He checked it (he was also an a&P rated mechanic) and said the battery was hot and should be removed immediately. The passenger were evacuate/evacuationed from the aircraft and the battery was removed to the grassy area adjacent to the taxiway. The aircraft was then towed to the cargo ramp to await inspection by the maintenance department. Callback conversation with reporter revealed the following information: the reporter stated the NTSB and the FAA have interviewed the crew recently. The reporter said the exact cause at this time is unknown but the following components were replaced: both engine dc generators, left engine generator wire harness, the left generator control unit and the main ship's battery. The reporter stated at no time was any electrical odor or smoke present in the cockpit.

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Original NASA ASRS Text

Title: AN ATR42-300 IN CRUISE AT 15000 FT DECLARED AN EMER AND DIVERTED DUE TO LOSS OF ENG DC ELECTRICAL PWR INCLUDING MAIN SHIP'S BATTERY, SWITCHED TO EMER BATTERY PWR.

Narrative: 15000 FT CRUISE FROM TPA TO MIA IN VMC CONDITIONS WHEN THE DC GENERATOR #1 FAULTED. REFING THE QRH CHKLIST FOR THE FAULT ALLOWED FOR A RESET OF THE GENERATOR. ONCE THE GENERATOR WAS RESET, THE ELECTRICAL SYS WENT 'BIZERK.' ALL BELLS, CHIMES AND WARNING LIGHTS IN THE COCKPIT ACTIVATED SIMULTANEOUSLY, AS WELL AS LIGHTS IN THE PAX CABIN. WE DECLARED AN EMER AND INITIATED A DSCNT TO BELOW 10000 FT DUE TO LOSS OF CABIN PRESSURE. THEN WE PROCEEDED WITH DUAL DC GENERATOR FAILURE CHKLIST. MAIN BATTERY PWR (WHICH SHOULD HAVE LASTED APPROX 43 MINS) WAS LOST WITHIN 1 MIN. THE FLT ATTENDANT CAME TO THE COCKPIT AS SOON AS HIS CABIN LIGHTING STARTED MALFUNCTIONING. WE CONTINUED WITH THE CHKLIST, SELECTING OVERRIDE/UNDERVOLTAGE PER THE QRH IN ORDER TO GO TO EMER BATTERY PWR. THE FLT ATTENDANT WAS BRIEFED IN PERSON. CONTACT WITH ATC (WHICH HAD BEEN LOST WITH THE MAIN BATTERY) WAS NOW RE-ESTABLISHED AND WE WERE GIVEN VECTORS TO RSW. WITH THE INTEGRITY OF THE EMER IN QUESTION, WE ELECTED TO PERFORM A NO FLAP LNDG. THE LNDG WAS ACCOMPLISHED WITHOUT INCIDENT, WITH EMER BRAKING BEING SATISFACTORY. CFR TEAM AND ACFT OPS PERSONNEL MET THE ACFT AS IT EXITED THE RWY AT TXWY A6. THE FIRE MARSHALL ASKED IF WE HAD EXPERIENCED A MAIN BATTERY THERMAL RUNAWAY. NOT HAVING A BATTERY TEMP GAUGE, WE TOLD HIM THAT WE HAD NO WAY OF KNOWING. HE CHKED IT (HE WAS ALSO AN A&P RATED MECH) AND SAID THE BATTERY WAS HOT AND SHOULD BE REMOVED IMMEDIATELY. THE PAX WERE EVACED FROM THE ACFT AND THE BATTERY WAS REMOVED TO THE GRASSY AREA ADJACENT TO THE TXWY. THE ACFT WAS THEN TOWED TO THE CARGO RAMP TO AWAIT INSPECTION BY THE MAINT DEPT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE NTSB AND THE FAA HAVE INTERVIEWED THE CREW RECENTLY. THE RPTR SAID THE EXACT CAUSE AT THIS TIME IS UNKNOWN BUT THE FOLLOWING COMPONENTS WERE REPLACED: BOTH ENG DC GENERATORS, L ENG GENERATOR WIRE HARNESS, THE L GENERATOR CTL UNIT AND THE MAIN SHIP'S BATTERY. THE RPTR STATED AT NO TIME WAS ANY ELECTRICAL ODOR OR SMOKE PRESENT IN THE COCKPIT.

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.