Quote:

Airplanes require two independantly powered ignition systems for safety reasons, nothing more. If your plane ran better when you switched the other mag in then your first mag setup has problems. Not that mags are all that great an ignition system.



Hmmm...yeah; I screwed up my first post. I inadvertently took off running on one magneto. You use both magnetos; switching each off in turn for the pretakeoff check. When I selected both "on" was when I picked up that little bit extra power.

I suppose safety is the reason behind the independent self-powered ignitions for airplane recip engines, but its a fact that you get a 50-75 RPM drop when switching one mag off during a runup.