Ignition switch settings

Here's a question that until yesterday I'd have thought was
obvious.

Cessna-style (and no doubt other) ignition switches have five
settings -- Off/Right/Left/Both/Start. When you're on the "Right"
setting, does it mean you are firing on the right magneto or
does it mean the right magneto is grounded?

In article .com,
"Tony Cox" wrote:

Here's a question that until yesterday I'd have thought was
obvious.

Cessna-style (and no doubt other) ignition switches have five
settings -- Off/Right/Left/Both/Start. When you're on the "Right"
setting, does it mean you are firing on the right magneto or
does it mean the right magneto is grounded?

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

On Mar 3, 8:34 am, Orval Fairbairn wrote:
In article .com,
"Tony Cox" wrote:

Here's a question that until yesterday I'd have thought was
obvious.

Cessna-style (and no doubt other) ignition switches have five
settings -- Off/Right/Left/Both/Start. When you're on the "Right"
setting, does it mean you are firing on the right magneto or
does it mean the right magneto is grounded?

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

That was my understanding too, but after arguing the
point with two very experienced pilots yesterday, I
wondered how prevalent the contrary view might be.

On Mar 3, 11:12 am, "Tony Cox" wrote:


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

That was my understanding too, but after arguing the
point with two very experienced pilots yesterday, I
wondered how prevalent the contrary view might be.

Most pilots don't understand much about aircraft systems,
and many who have automobile maintenance experience don't understand
magnetos. They make a lot of assumptions and sometimes harbour many
misconceptions. A magneto's primary winding is grounded to kill it, so
when the key is in the R position, the L magneto is grounded, and vice
versa. Even the terminals on back of the switch are labelled R and L
and when the appropriate positions are selected, the other terminal is
grounded. Can confuse someone trying to test the switch itself unless
they know what the principles are.
Another misconception: that the magneto is somehow connected
to the aircraft's electrical system. They're afraid to turn off the
master switch in flight lest it kill the engine.

Dan

On Mar 3, 11:09 am, "Tony Cox" wrote:
Here's a question that until yesterday I'd have thought was
obvious.

Cessna-style (and no doubt other) ignition switches have five
settings -- Off/Right/Left/Both/Start. When you're on the "Right"
setting, does it mean you are firing on the right magneto or
does it mean the right magneto is grounded?

Very good question. If we use the logic that "Both" means both magneto
circuits are open, and "Off" means both magneto circuits are closed,
that would imply that "Right" means the right magneto is open (and
hence firing).

But I am sure an A&P should be able to give a more authoritative
answer.

And I've been trying to learn for years why R is on the left and L is on the
right.

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

That was my understanding too, but after arguing the
point with two very experienced pilots yesterday, I
wondered how prevalent the contrary view might be.

Most pilots don't understand much about aircraft systems,
and many who have automobile maintenance experience don't understand
magnetos. They make a lot of assumptions and sometimes harbour many
misconceptions. A magneto's primary winding is grounded to kill it, so
when the key is in the R position, the L magneto is grounded, and vice
versa. Even the terminals on back of the switch are labelled R and L
and when the appropriate positions are selected, the other terminal is
grounded. Can confuse someone trying to test the switch itself unless
they know what the principles are.
Another misconception: that the magneto is somehow connected
to the aircraft's electrical system. They're afraid to turn off the
master switch in flight lest it kill the engine.

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.

On Mar 3, 4:21 pm, "Jon Woellhaf" wrote:
And I've been trying to learn for years why R is on the left and L is on the
right.

I wonder. Maybe because the ancient systems used two toggle
switches labelled "L" and "R" and they were connected to their
respective mags. When you turned off the L switch, you were running on
the R mag. It was self-evident. Our two Citabrias still have this
setup and I bet American Champion is still building them that way.
When Bendix came up with the combination starter/mag switch, the
internal mag-shorting contacts were set up in the same order but now
they had to label them opposite so that you knew which one you were
sparking on.
I'd rather have the toggles in my Jodel but it makes the
airplane so much easier to steal. If you can get in you can go.

Dan

"Peter Dohm" wrote in message
...
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.

On Mar 3, 5:11 pm, "Travis Marlatte"
wrote:

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.

Here's one reason (and this scenario initiated the post
in the first place). My 182 failed the run-up yesterday
on the "left" mag. I knew which cylinder it was through
my JPI. But which plug? The upper plug is easy to check, but
the lower requires removal of the lower cowling, which is
a 2-person job to replace.