Ignition switch, what happen when Left or Right is selected

wrote in message
ups.com...
Exactly. I learned to fly in the early '70s and they didn't
teach us to look for a hot mag. I learned that when upgrading some
years ago. Doing this, I found that one of our 172's mag switches would
allow the mags to keep firing if the key was forced against the "Off"
stop, and upon investigation found an AD against any of those switches
that did that (76-07-12). Bet there are still a lot of them out there.


Well, I certainly had occasion to turn the key to "OFF" on a 172 and hand it
to my instructor in the right seat while the prop kept spinning. We
reported it (and it was returned "fixed") at least 3 times on that aircraft
before somebody finally managed to isolate and *really* fix the problem.

Otherwise the RPM drop for each mag was consistent, so both mags were
"grounding", but not in the OFF position.