Narrative:

During descent with vectors to the ILS runway 040 ama airport, I lost radio communication with ama approach. I was VFR at the time and had trade wind airport assured so I landed at trade wind. I called ama tower and approach control as soon as possible to let them know what had happened. They said ok, but they would need to report this to the FAA. I put the airplane in the shop at trade wind the next day. I explained to the shop I had no indication of the electrical problem. The shop tested the airplane and found that 2 events had happened. 1) the alternator capacitor had come lose and fallen off the alternator, which caused transmitting problems, and 2) when it fell off it shorted the alternator so that it only partly worked. This allowed my ammeter to read normal, but was draining my electrical system. When I keyed my microphone to report the bases as requires by approach, I became aware of the problem. This airplane has an engine-driven alternator and in the event of a partial loss, there should be a low voltage warning light system and the capacitors should be fixed to the fire wall, not to the alternator itself.

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Original NASA ASRS Text

Title: GA SMA LOST RADIO POWER AND COULD NOT COMMUNICATE WITH AMA TRACON WHILE ON VECTORS FOR ILS. PLT HAD TDW IN SIGHT AND LANDED AT TDW.

Narrative: DURING DSCNT WITH VECTORS TO THE ILS RWY 040 AMA ARPT, I LOST RADIO COM WITH AMA APCH. I WAS VFR AT THE TIME AND HAD TRADE WIND ARPT ASSURED SO I LANDED AT TRADE WIND. I CALLED AMA TWR AND APCH CTL AS SOON AS POSSIBLE TO LET THEM KNOW WHAT HAD HAPPENED. THEY SAID OK, BUT THEY WOULD NEED TO REPORT THIS TO THE FAA. I PUT THE AIRPLANE IN THE SHOP AT TRADE WIND THE NEXT DAY. I EXPLAINED TO THE SHOP I HAD NO INDICATION OF THE ELECTRICAL PROBLEM. THE SHOP TESTED THE AIRPLANE AND FOUND THAT 2 EVENTS HAD HAPPENED. 1) THE ALTERNATOR CAPACITOR HAD COME LOSE AND FALLEN OFF THE ALTERNATOR, WHICH CAUSED TRANSMITTING PROBLEMS, AND 2) WHEN IT FELL OFF IT SHORTED THE ALTERNATOR SO THAT IT ONLY PARTLY WORKED. THIS ALLOWED MY AMMETER TO READ NORMAL, BUT WAS DRAINING MY ELECTRICAL SYSTEM. WHEN I KEYED MY MICROPHONE TO REPORT THE BASES AS REQUIRES BY APCH, I BECAME AWARE OF THE PROBLEM. THIS AIRPLANE HAS AN ENGINE-DRIVEN ALTERNATOR AND IN THE EVENT OF A PARTIAL LOSS, THERE SHOULD BE A LOW VOLTAGE WARNING LIGHT SYSTEM AND THE CAPACITORS SHOULD BE FIXED TO THE FIRE WALL, NOT TO THE ALTERNATOR ITSELF.

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.