Narrative:

An in-flight electrical failure occurred for the electrical charging system of the C172. The airplane just had an installation of a garmin 430 moving map, dautron digital clock, and garmin indicator. Aircraft checked out normally when preflted and run-up ammeter indicated normally when field switch turned off during ground checks. Battery had less than 10 hours of operation on it since new. Not much discharge occurred during the 5-6 circuits of field off. In cruise flight, discharge light was dimly lit. Alternator field rocker switch was cycled 3 times. System seemed to be behaving normally, but electrical equipment that was non essential was turned off. After 1 hour and 10 mins of flight, radio reception and transmission capability was lost. Squawked 7600 intermittently. When garmin GNS lbo went off line, communication reception was restored long enough to get vectors from greer approach to a localizer runway 1 at gmv. Navigation reception of #2 navigation/communication was lost while descending through clouds. Handheld garmin III pilot was used for emergency course guidance to localizer minimums at gmv. A normal landing at gmv was then executed once visual.

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Original NASA ASRS Text

Title: C172 INSTRUCTOR AND STUDENT HAD INDICATIONS OF ALTERNATOR FAILURE. THE ACFT OP WAS CONTINUED UNTIL THE BATTERY DIED.

Narrative: AN INFLT ELECTRICAL FAILURE OCCURRED FOR THE ELECTRICAL CHARGING SYS OF THE C172. THE AIRPLANE JUST HAD AN INSTALLATION OF A GARMIN 430 MOVING MAP, DAUTRON DIGITAL CLOCK, AND GARMIN INDICATOR. ACFT CHKED OUT NORMALLY WHEN PREFLTED AND RUN-UP AMMETER INDICATED NORMALLY WHEN FIELD SWITCH TURNED OFF DURING GND CHKS. BATTERY HAD LESS THAN 10 HRS OF OP ON IT SINCE NEW. NOT MUCH DISCHARGE OCCURRED DURING THE 5-6 CIRCUITS OF FIELD OFF. IN CRUISE FLT, DISCHARGE LIGHT WAS DIMLY LIT. ALTERNATOR FIELD ROCKER SWITCH WAS CYCLED 3 TIMES. SYS SEEMED TO BE BEHAVING NORMALLY, BUT ELECTRICAL EQUIP THAT WAS NON ESSENTIAL WAS TURNED OFF. AFTER 1 HR AND 10 MINS OF FLT, RADIO RECEPTION AND XMISSION CAPABILITY WAS LOST. SQUAWKED 7600 INTERMITTENTLY. WHEN GARMIN GNS LBO WENT OFF LINE, COM RECEPTION WAS RESTORED LONG ENOUGH TO GET VECTORS FROM GREER APCH TO A LOC RWY 1 AT GMV. NAV RECEPTION OF #2 NAV/COM WAS LOST WHILE DSNDING THROUGH CLOUDS. HANDHELD GARMIN III PLT WAS USED FOR EMER COURSE GUIDANCE TO LOC MINIMUMS AT GMV. A NORMAL LNDG AT GMV WAS THEN EXECUTED ONCE VISUAL.

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.