Narrative:

While en-route; I noticed that my engine analyzer shut off (jpi edm-800). In the five years I have been flying this aircraft; I never experience this type of failure. I started to troubleshoot; including looking at the ammeter. Since I normally get my electrical status information from the engine analyzer; I was not used to seeing the ammeter needle in a 'normal' position. In this case; the needle was above zero (about a quarter of the way from zero to the maximum value). However; since it didn't seem to be showing a discharge; I assumed that the issue was with the engine analyzer; and not electrical in nature. Several minutes later; I noticed the pressure altitude on the transponder stopped working. Just as I was leaning over to troubleshoot; I heard a painfully loud; low tone noise in my headset. I could no longer hear my passengers; myself; or the radio. At the same time; my on board GPS shut off. I tried to contact center; however I could barely hear voices over the noise. I removed my headset and turned on the aircraft speaker; using the aircraft's microphone to attempt communication. I could still barely hear voices. I have no idea if I was transmitting or if center could hear me. I did hear the word 'ident'; which I did; making the assumption that center realized that I could not hear them (however that could have been for another aircraft). I could not make out any other words. With the need to focus on flying the airplane (at that point the autopilot; trim; and other electrical components were no longer functioning); I transmitted that I was canceling my IFR flight plan and continuing VFR. Since I could not hear a confirmation (still too much noise); I set my transponder to 1200 to confirm my intentions. I then shut off all electrical equipment with the exception of the transponder. The ammeter needle never moved from its 'about a quarter above zero' position. At this point; we still do not know what the failure mode was beyond the fact that it was electrical in nature. I had a significant delay in reacting to this electrical failure due to my initial reading of the ammeter. Even though I have a very accurate instrument which provides a tremendous amount of information; I need to be aware of what the 'old' instruments read when all conditions are normal.

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Original NASA ASRS Text

Title: PA28 pilot experienced an electrical failure at 6;000 FT on an IFR flight plan. First indications were loss of the engine analyzer which also provided electrical status information. The ammeter information could not be deciphered and the impending electrical failure was not detected until more components failed.

Narrative: While en-route; I noticed that my engine analyzer shut off (JPI EDM-800). In the five years I have been flying this aircraft; I never experience this type of failure. I started to troubleshoot; including looking at the ammeter. Since I normally get my electrical status information from the engine analyzer; I was not used to seeing the ammeter needle in a 'normal' position. In this case; the needle was above zero (about a quarter of the way from zero to the maximum value). However; since it didn't seem to be showing a discharge; I assumed that the issue was with the engine analyzer; and not electrical in nature. Several minutes later; I noticed the pressure altitude on the transponder stopped working. Just as I was leaning over to troubleshoot; I heard a painfully loud; low tone noise in my headset. I could no longer hear my passengers; myself; or the radio. At the same time; my on board GPS shut off. I tried to contact Center; however I could barely hear voices over the noise. I removed my headset and turned on the aircraft speaker; using the aircraft's microphone to attempt communication. I could still barely hear voices. I have no idea if I was transmitting or if Center could hear me. I did hear the word 'ident'; which I did; making the assumption that Center realized that I could not hear them (however that could have been for another aircraft). I could not make out any other words. With the need to focus on flying the airplane (at that point the autopilot; trim; and other electrical components were no longer functioning); I transmitted that I was canceling my IFR flight plan and continuing VFR. Since I could not hear a confirmation (still too much noise); I set my transponder to 1200 to confirm my intentions. I then shut off all electrical equipment with the exception of the transponder. The ammeter needle never moved from its 'about a quarter above zero' position. At this point; we still do not know what the failure mode was beyond the fact that it was electrical in nature. I had a significant delay in reacting to this electrical failure due to my initial reading of the ammeter. Even though I have a very accurate instrument which provides a tremendous amount of information; I need to be aware of what the 'old' instruments read when all conditions are normal.

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.