Right magneto is "hot" (ungrounded). The "OFF" position grounds
both
mags.


I know from personal experience that a lot of pilots continue to have
serious misconceptions about such things, but it still bothers me. This
is
the sort of thing that is part of every run-up, and therefore should
have
been part of the aircraft systems knowledge requirement to get the
license--not necessarily the grounding issue, but which magneto actually
fires its set of plugs.



I don't get the connection. Why would the licenced pilot need to know
which
mag and which set of plugs is firing on Left or Right key position? Know
why
the mag check is important and what to watch for during the mag check,
yes.


No, but he should know that that the Right mag is hot (firing plugs) and the
Left mag is cold (not firing) when the switch is in the "R" position, and
that the Right mag is cold (not firing) and the Left mag is hot (firing
plugs) when the switch is in the "L" position. That much systems knowledge
would seem usefull for a safe and reasonable Go/NoGo decision prior to
take-off, and also to explain a problem to an efficient manner.

Knowledge of the specifics of how the ignition system works could be very
usefull in the case of "stealing your oun airplane" because you lost the key
at a remote hunting/fishing spot; but I can not imagine that being part of
an accredited licensing test.

Peter