Hey guys, I thought I'd pass on another useful tid-bit I've always taken for granted:
My buddy who just bought a pretty new Citabria went for a ride with me in my '69 Citab. He noticed that I always start my engine on the left magneto and then turn on the right after the engine is running. I've always done that as I recall because my IA said there was something advanced on the right mag. that makes it a little harder to start with both on. My Citab buddy is a "by the book" guy and said the manual says to start on both.
So I checked with my IA and this is what he confirmed:
"there is a good reason, as you mentioned. The left mag has the impulse coupling on it which retards and strengthens the spark during the low "cranking" rpms. The right mag fires in it's normal advanced mode all the time. If it is on during starting, it will fire as the piston is approaching TDC and can cause the prop to kick-back in the wrong direction. It can even damage the ring gear in extreme cases.
On most aircraft with only one impulse mag, like yours, but that have a key ignition, the right mag is actually electrically disabled when the key is in the "start" position, so the engine is started only on the left mag. As soon as it fires and you release the key, the right mag is then activated."
My buddy who just bought a pretty new Citabria went for a ride with me in my '69 Citab. He noticed that I always start my engine on the left magneto and then turn on the right after the engine is running. I've always done that as I recall because my IA said there was something advanced on the right mag. that makes it a little harder to start with both on. My Citab buddy is a "by the book" guy and said the manual says to start on both.
So I checked with my IA and this is what he confirmed:
"there is a good reason, as you mentioned. The left mag has the impulse coupling on it which retards and strengthens the spark during the low "cranking" rpms. The right mag fires in it's normal advanced mode all the time. If it is on during starting, it will fire as the piston is approaching TDC and can cause the prop to kick-back in the wrong direction. It can even damage the ring gear in extreme cases.
On most aircraft with only one impulse mag, like yours, but that have a key ignition, the right mag is actually electrically disabled when the key is in the "start" position, so the engine is started only on the left mag. As soon as it fires and you release the key, the right mag is then activated."