Narrative:

Ceilings at my destination were overcast 300 ft with less then 1 SM visibility. Tried one shot at the GPS 36 approach and executed the missed approach. Talked to approach for the ILS 24 at a nearby airport. During the vectoring and set up for that approach; I noticed that the battery voltage had fallen from around 14 volts to around 12 volts indicating no alternator output. I tried recycling the alternator switch and checked the circuit breakers. Nothing changed. I stared to shed some of the electrical load at that point to extend battery life. I asked approach if there were any VFR airports nearby; but there were none. In asking this; I also alerted approach to my alternator failure. The controller then asked if I would rather do the ILS 33 since I was almost on top of the approach course. I agreed. The controller mentioned that the ceilings were down to overcast 100 and asked if I still wanted to do the approach. I felt like I didn't have much choice but to execute the approach perfectly and get on the ground so I told the controller I needed to make this approach work. I had 1.5-2 hours of fuel remaining; but I did not want to fly 50-100 NM away and lose electrical power on the way only to have to execute another instrument approach with no panel navigation equipment functioning. The controller clearly declared an emergency on my behalf (much appreciated) and gave me all relevant information (frequencies; altitudes and distances) for the approach as I was setting it up. I flew the approach to decision height whereupon I had ground contact; but no runway. After another 100 ft; I could see the green runway end lights and some of the edge lights right in front of me clear enough for a normal and safe landing with no unusual maneuvering. I let the approach controller (with me the whole way) know I had landed safely (with half the runway to spare) and contacted ground to parking. My mechanics are on the job now to diagnose and fix the problem.

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Original NASA ASRS Text

Title: A PA28 Private Pilot on an IFR flight plan found his destination airport below minimums and his electrical system failing. Expert assistance from an Approach Controller and good airmanship by the reporter got him safely on the ground at another airport with marginal ceiling and visibility.

Narrative: Ceilings at my destination were overcast 300 FT with less then 1 SM visibility. Tried one shot at the GPS 36 approach and executed the missed approach. Talked to Approach for the ILS 24 at a nearby airport. During the vectoring and set up for that approach; I noticed that the battery voltage had fallen from around 14 volts to around 12 volts indicating no alternator output. I tried recycling the alternator switch and checked the circuit breakers. Nothing changed. I stared to shed some of the electrical load at that point to extend battery life. I asked Approach if there were any VFR airports nearby; but there were none. In asking this; I also alerted Approach to my alternator failure. The Controller then asked if I would rather do the ILS 33 since I was almost on top of the approach course. I agreed. The Controller mentioned that the ceilings were down to overcast 100 and asked if I still wanted to do the approach. I felt like I didn't have much choice but to execute the approach perfectly and get on the ground so I told the Controller I needed to make this approach work. I had 1.5-2 hours of fuel remaining; but I did not want to fly 50-100 NM away and lose electrical power on the way only to have to execute another instrument approach with no panel navigation equipment functioning. The Controller clearly declared an emergency on my behalf (much appreciated) and gave me all relevant information (frequencies; altitudes and distances) for the approach as I was setting it up. I flew the approach to Decision Height whereupon I had ground contact; but no runway. After another 100 FT; I could see the green runway end lights and some of the edge lights right in front of me clear enough for a normal and safe landing with no unusual maneuvering. I let the Approach Controller (with me the whole way) know I had landed safely (with half the runway to spare) and contacted ground to parking. My mechanics are on the job now to diagnose and fix the problem.

Data retrieved from NASA's ASRS site as of April 2012 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.