Narrative:

Alternator failed due to failure of brushes in alternator, resulting in depletion of battery charge and absence of electrical supply to navigation and communications equipment. The problem was discovered when unable to contact orl approach following handoff from ZJX at 4000'. After shutting down all unnecessary electrical equipment and still having insufficient power to communicate with orl approach, I squawked transponder code 7700 for 1 min, followed by 7600. After approximately 5 mins, I shut the master switch off for a period of 5 mins to permit the battery to regenerate, then contacted orl approach and declared an emergency. Orl approach provided vectors and a clearance for ILS 09 approach to sanford airport, however during the approach, the charge in the battery was again depleted, resulting in unreliable instrument reading. I aborted the approach, climbed to visibility meteorological conditions at 3000' and circled with the master switch off for a period of 5 mins, after which I again contacted orl approach to explain my actions and proposed course of action. Orl approach did assist with ASR advisories during the approach, contact with approach lights made at approximately 400' AGL. At conclusion of the rollout, there was insufficient power remaining in the battery to contact orl ground control on the frequency given by orl approach. The alternator was repaired and reinstalled. The situation occurred as a result of unanticipated and unforeseeable mechanical failure. It would have been helpful to have noticed the volt meter showing a discharge prior to total loss of navigation and communications equipment, which would have permitted an earlier shutdown of nonessential electrical equipment. A more comprehensive review of the instruments, specifically including the volt meter, would be a recommended procedure.

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Original NASA ASRS Text

Title: GA SMA HAD LOW ELECTRICAL CHARGE DUE WORN BRUSHES AND HAD TO ALTERNATELY SHUT DOWN ACFT ELECTRICAL POWER TO BUILD UP BATTERIES FOR AN INSTRUMENT APCH.

Narrative: ALTERNATOR FAILED DUE TO FAILURE OF BRUSHES IN ALTERNATOR, RESULTING IN DEPLETION OF BATTERY CHARGE AND ABSENCE OF ELECTRICAL SUPPLY TO NAV AND COMS EQUIP. THE PROB WAS DISCOVERED WHEN UNABLE TO CONTACT ORL APCH FOLLOWING HDOF FROM ZJX AT 4000'. AFTER SHUTTING DOWN ALL UNNECESSARY ELECTRICAL EQUIP AND STILL HAVING INSUFFICIENT PWR TO COMMUNICATE WITH ORL APCH, I SQUAWKED XPONDER CODE 7700 FOR 1 MIN, FOLLOWED BY 7600. AFTER APPROX 5 MINS, I SHUT THE MASTER SWITCH OFF FOR A PERIOD OF 5 MINS TO PERMIT THE BATTERY TO REGENERATE, THEN CONTACTED ORL APCH AND DECLARED AN EMER. ORL APCH PROVIDED VECTORS AND A CLRNC FOR ILS 09 APCH TO SANFORD ARPT, HOWEVER DURING THE APCH, THE CHARGE IN THE BATTERY WAS AGAIN DEPLETED, RESULTING IN UNRELIABLE INSTRUMENT READING. I ABORTED THE APCH, CLBED TO VIS METEOROLOGICAL CONDITIONS AT 3000' AND CIRCLED WITH THE MASTER SWITCH OFF FOR A PERIOD OF 5 MINS, AFTER WHICH I AGAIN CONTACTED ORL APCH TO EXPLAIN MY ACTIONS AND PROPOSED COURSE OF ACTION. ORL APCH DID ASSIST WITH ASR ADVISORIES DURING THE APCH, CONTACT WITH APCH LIGHTS MADE AT APPROX 400' AGL. AT CONCLUSION OF THE ROLLOUT, THERE WAS INSUFFICIENT PWR REMAINING IN THE BATTERY TO CONTACT ORL GND CTL ON THE FREQ GIVEN BY ORL APCH. THE ALTERNATOR WAS REPAIRED AND REINSTALLED. THE SITUATION OCCURRED AS A RESULT OF UNANTICIPATED AND UNFORESEEABLE MECHANICAL FAILURE. IT WOULD HAVE BEEN HELPFUL TO HAVE NOTICED THE VOLT METER SHOWING A DISCHARGE PRIOR TO TOTAL LOSS OF NAV AND COMS EQUIP, WHICH WOULD HAVE PERMITTED AN EARLIER SHUTDOWN OF NONESSENTIAL ELECTRICAL EQUIP. A MORE COMPREHENSIVE REVIEW OF THE INSTRUMENTS, SPECIFICALLY INCLUDING THE VOLT METER, WOULD BE A RECOMMENDED PROC.

Data retrieved from NASA's ASRS site as of August 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.