Well, I went out to fly my Dakota to my mechanics field for an oil change (the first since owning - I want to see it done a time or two before doing it myself) and to look at a couple of minor squawks - one of which turned out to be not so minor - and honestly should never had been considered minor. After spending an hour waiting for the sun to melt the frost and the pre-start engine warmup I discovered that my left magneto was completely dead - not rough running, but d.e.a.d dead. I called my mechanic to let him know, he gave me a couple of 'try this' things to do - neither worked.
Oh, the lesson learned. I had experience a brief period of surging power on my last flight (short, but enough to give me pause to ask - 'did that really just happen???') I discussed this with my mechanic and his first thought was the prop governor was acting up and we would look at today. As it turns out we think now it was the left mag cutting in/out on its way to dead... so technically not a surge in power, but several momentary losses and return of the left mag - which results in about 100 rpm drop - right? So the lesson, know your airplane, if something doesn't seem, sound or smell right - do not rationalize and justify it. Determine the cause definitively.
In this case, I am not sure how I would have known the mag was failing short of doing my mag check this morning. The magnetos in my aircraft are about 400 hours since last overhaul. Thoughts on how to know a mag is going bad? A brief power oscillation in flight is at the top of my list right now....
Oh, the lesson learned. I had experience a brief period of surging power on my last flight (short, but enough to give me pause to ask - 'did that really just happen???') I discussed this with my mechanic and his first thought was the prop governor was acting up and we would look at today. As it turns out we think now it was the left mag cutting in/out on its way to dead... so technically not a surge in power, but several momentary losses and return of the left mag - which results in about 100 rpm drop - right? So the lesson, know your airplane, if something doesn't seem, sound or smell right - do not rationalize and justify it. Determine the cause definitively.
In this case, I am not sure how I would have known the mag was failing short of doing my mag check this morning. The magnetos in my aircraft are about 400 hours since last overhaul. Thoughts on how to know a mag is going bad? A brief power oscillation in flight is at the top of my list right now....
