Continuing the saga of my AOG back in August... we were flying back from AR and we started getting the surging engine again. We were pretty close to our fuel stop, so I continued, and the problem also continued to get worse. This time though I was able to isolate the issue to the left magneto. Engine ran smooth on the right only and nearly died on the left. All egt's would drop, which again pointed to a bad mag rather than a few fouled plugs.
Here's where the plot thickens...at low power in the descent to land, the engine ran smoothly. I did a runup on the taxiway as soon as I pulled off and both mags ran smooth with drops within spec.
Fueled up, took a break, and decided to continue home. I know this will be a controversial decision, but it was a 30 minute flight, it was running perfectly on the ground, I was on a hair trigger to abort, and I had 3 airports to fly over to get home. Of course the engine ran perfectly.
At least it did until I was about 5 min out, at which point it began to display the same symptoms of the left mag dropping out. This seems to confirm my suspicion that something is causing the left mag to fail when it's hot. My money is on the coil or the capacitor, but I don't know a lot about magnetos beyond the theory of operation.
The left set of points (bearing in mind this is a d3000 "dual mag") looked like it may have been arcing, but it's hard to tell. I believe that would point to the capacitor breaking down? Plugs, harnesses, and everything else looked good. Mag has about 125 hours since it was overhauled a year ago. We sent it back to poplar grove.... anyone hazard a guess on what they'll find?
Here's where the plot thickens...at low power in the descent to land, the engine ran smoothly. I did a runup on the taxiway as soon as I pulled off and both mags ran smooth with drops within spec.
Fueled up, took a break, and decided to continue home. I know this will be a controversial decision, but it was a 30 minute flight, it was running perfectly on the ground, I was on a hair trigger to abort, and I had 3 airports to fly over to get home. Of course the engine ran perfectly.
At least it did until I was about 5 min out, at which point it began to display the same symptoms of the left mag dropping out. This seems to confirm my suspicion that something is causing the left mag to fail when it's hot. My money is on the coil or the capacitor, but I don't know a lot about magnetos beyond the theory of operation.
The left set of points (bearing in mind this is a d3000 "dual mag") looked like it may have been arcing, but it's hard to tell. I believe that would point to the capacitor breaking down? Plugs, harnesses, and everything else looked good. Mag has about 125 hours since it was overhauled a year ago. We sent it back to poplar grove.... anyone hazard a guess on what they'll find?