maybe the engineer had Dyslexia:D

It's a hold over from when you normally hand propped an engine. The impulse coupler is on the left mag and if you started on LEFT you wouldn't want to go through RIGHT to get to BOTH.

Just like to add, that this is why most aircraft, at least to all of my knowledge, you turn the aircraft off using the mixture, not just turning off the key. This then insurers that all the fuel in the cylinders is burned off. If you ever shut a plane down with just the key there will be fuel left in the engine. If this happened, better to keep the mixture out, then turn the key to start. The prop will spin a few times then come to a stop, but just imagine if you didn't do that. Some poor SOB could come along to push it and turn the prop, engine start, and then someones head/hand is gone.
The
WildSmurf

P.S. If you ever have a student, this could and has happened.

The CJ-6 and J-3 actually shut down using the mags - both for different reasons. The CJ calls for a pre-shut down run up to 1900rpm for 10 seconds and bringing the throttle and mix full aft (full rich) and then turning the mags off. It's weird...it pnuematic discharge and 'shower of sparks' for start.

The caveat is that if you don't have enough air for a start (in the bottle), you probably don't have enough air to operate your brakes - so hand propping requires a tie down or something.

As a radial it also requires the prop turned through about 9-10 times checking for hydraulic lock.

Thanks for the posts. I didn't think it would do anything to a C-172 other than the risk of starting the propeller when you least expect it. I've heard of one story of someone leaving the mags on a twin engine overnight and he killed the battery or left the mags too warm for too long and it did some sort of damage. Now I'm just trying to figure out the difference of turning on mags between lighter vs. larger aircraft.

There's no way.

Magneto's in any airframe, large, small, russian even etc.. work the same. They have no, none, nada, zip, zilch effect on the battery. Now if someone left the Master switch on, then yes, that's the battery switch. Master switch is not the Mag switch, and never have they been connected to my knowledge in the 100's of GA planes I've flown.

Mooney Shutdown Procedure
 

We pull the mixture slowly til the cylinder temps rise and then full cut off. This is supposed to prevent plug fouling on the "lean loving" close cowled fuel injected IO360 in the Mooney E Model.

Very interesting, I figured that there was some aircraft out there that would call for something other than pulling the mixture out.
"Pneumatic discharge and 'shower of sparks' for start"?:confused: I have an idea how it works, but just might Google search to see exactly what that is.

WildSmurf

all i have to say, is if you ever leave the mags on and an A&P comes to work on your plane, you will get an ear full. I always check before turning the prop but there is always the chance of me forgetting to check (swiss cheese model). This could easily result in my death, especially if someone turned the engine off by the mags.

and yes, the above posters are correct. the mags have absolutely, positively nothing to do with the battery or electrical system. they are an independent system for a reason.

The labels are for the mag that is active. So when you're in the R position, you're grounding the Left mag, therefore the Right one is operating.

So R, L, Both is the correct order (some don't have the start position :))