Ignition switch, what happen when Left or Right is selected

BTIZ wrote:
and now the other part of that question... for most key switches that have
"Off" "Left" "Right" "Both" "Start" positions.. what happens when you go to
the "Start" position.?.

Depends on the switch. Some switches ground out the RIGHT mag, some
leave both on. It also provides a contact for the starter solenoid.

Some more thoughts on selecting the correct mag for starting -

The impulse function on a mag provides a both a substantial timing
delay and a velocity enhancement for starting purposes. Both are
important. The timing delay of the impulse prevents an engine from
kicking back. That's why starting is done on one (the impulse) mag
only. Most aircraft have only one mag with an impulse, but even a
non-impulse mag may generate a spark at cranking speeds if the mag is
in good condition.

Two things to consider are

1) Be sure the only correct mag is selected if hand propping - and
never put your fingers over the back of the blade. I didn't once on a
TriPacer and still have a fortunately small scar on the tip of my index
finger when it kicked back mightily.

2) Consider that possibly the mag p leads might get reversed in
maintenance. The starter may be able to handle the cranking on the
wrong mag but it could be a hand propping accident waiting to happen.

That's why I won't hand prop a strange airplane for the first time.

Just running down the list in my head, I am going to take the opposite
position. Most aircraft have BOTH mags with an impulse; a small minority
have only one with an impulse.

Jim


Most aircraft have only one mag with an impulse

RST Engineering wrote:
Just running down the list in my head, I am going to take the opposite
position. Most aircraft have BOTH mags with an impulse; a small minority
have only one with an impulse.

Jim

Most aircraft have only one mag with an impulse

Not sure to whom you are responding. I don't see that exact text in my posting,
but I did say something like that.

....but I defer to your greater experience.

Dave

I'm not saying I am right, just that off the top of my head without going
down the list with a pencil and paper, it seems that most (if not all)
Cessnas from the 120 to the 210 have both mags impulsed, most Pipers also,
and that is 90% of the fleet right there.

However, I'm also willing to be corrected by my greasywrench colleagues who
are more into engine work than I.

Jim



"Dave Butler" wrote in message
news:1116429660.228058@sj-nntpcache-5...
RST Engineering wrote:
Just running down the list in my head, I am going to take the opposite
position. Most aircraft have BOTH mags with an impulse; a small minority
have only one with an impulse.

Jim

Most aircraft have only one mag with an impulse

Not sure to whom you are responding. I don't see that exact text in my
posting, but I did say something like that.

...but I defer to your greater experience.

Dave

Almost all of the make/models that you mention below have an impulse
mag on the left side only.


On Wed, 18 May 2005 09:00:21 -0700, "RST Engineering"
wrote:

I'm not saying I am right, just that off the top of my head without going
down the list with a pencil and paper, it seems that most (if not all)
Cessnas from the 120 to the 210 have both mags impulsed, most Pipers also,
and that is 90% of the fleet right there.

However, I'm also willing to be corrected by my greasywrench colleagues who
are more into engine work than I.

Jim



"Dave Butler" wrote in message
news:1116429660.228058@sj-nntpcache-5...
RST Engineering wrote:
Just running down the list in my head, I am going to take the opposite
position. Most aircraft have BOTH mags with an impulse; a small minority
have only one with an impulse.

Jim

Most aircraft have only one mag with an impulse

Not sure to whom you are responding. I don't see that exact text in my
posting, but I did say something like that.

...but I defer to your greater experience.

Dave

Perhaps those Lycoming powered that came off the production line after the
service bulletin advising to make that switch, but prior to that date they
were double impulse mags.

Let's take just two examples with which I am intimately familiar, since I
just did a mag rebuild on both of them. The Continental O-470L with Bendix
magnetos has dual impulse mags. (Cessna 182 et al)

The Continental O-300D with Bendix magnetos has dual impulse mags. (Cessna
172 et al)

I suppose we can go down the list of every aircraft that was ever made and
start a table. I'm not going to waste my time doing that.

Jim




"Bill Zaleski" wrote in message
news
Almost all of the make/models that you mention below have an impulse
mag on the left side only.


On Wed, 18 May 2005 09:00:21 -0700, "RST Engineering"
wrote:

I'm not saying I am right, just that off the top of my head without going
down the list with a pencil and paper, it seems that most (if not all)
Cessnas from the 120 to the 210 have both mags impulsed, most Pipers also,
and that is 90% of the fleet right there.

However, I'm also willing to be corrected by my greasywrench colleagues
who
are more into engine work than I.

Jim

In article ,
says...


Just running down the list in my head, I am going to take the opposite
position. Most aircraft have BOTH mags with an impulse; a small minority
have only one with an impulse.




Well, I certainly can't contest that, but Lycoming did issue a service
instruction some years ago, indicating that motors with two impulse coupled
magnetos should have the right one replaced with a plain magneto.
Implementation at owner's discretion.

Assuming lawyers drive every technical decision nowdays, I wonder why
they did that (recommend switching to single impulse mags)?