The September Pilot has an article re mag checks. Personally I have a problem with the "dead' mag check. I always taught my students check the mags on shut down by going to 1200 rpm and then checking for a RPM drop with a left - both right -both and then mixture idle cut off. The reason for not turning both mags off with the engine running is that if the student isn't quick turning the mags back on, the engine will backfire and blow out all of the muffler baffles.
I was discussing this with an another instructor recently who strongly disagreed with me. My question to fellow ppruners is; has anyone ever seen a mag switch that would properly ground the mags when selected to left and right but leave a mag live when selected to off ?
Incidentally he did not know that the mag switch is designed so that the key can only be removed when the switch is in the off position. When I teach the shut down mag check I also tell the student to gently pull on the key when in the both, left and right position. On 2 occasions I have found switches that were worn enough that the key came off in the left position. It would be very easy to think you had turned the key all the way to the off position but instead left it in the left position with a mag live and the key out.
I also make a point of not wrapping your fingers around the blade if you have to reposition the prop to put in the tow bar.