Mags on BOTH
05-20-2010, 01:41 AM
#11
pants on the ground
Joined APC: Jan 2007
Position: back seat
Posts: 1,358
Originally Posted by 9kBud
The question I've always wondered is: why is the switch ordered off, R, L, Both, Start? Shouldn't "L" be on the left and "R" be on the right?
05-20-2010, 02:23 AM
#12
Gets Weekends Off
Joined APC: Oct 2007
Position: Sr. VP of button pushing
Posts: 2,730
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.
05-20-2010, 05:13 AM
#13
On Reserve
Joined APC: Jan 2010
Posts: 20
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
WildSmurf
P.S. If you ever have a student, this could and has happened.
05-20-2010, 05:51 AM
#14
Gets Weekends Off
Joined APC: Jun 2008
Position: USAF
Posts: 1,398
Originally Posted by WildSmurf
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
WildSmurf
P.S. If you ever have a student, this could and has happened.
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.
05-21-2010, 03:56 AM
#15
Line Holder
Thread Starter
Joined APC: Sep 2008
Position: Right
Posts: 55
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.
05-21-2010, 04:31 AM
#16
Flying Farmer
Joined APC: Jul 2006
Position: Turbo-props' and John Deere's
Posts: 3,160
Originally Posted by Airframe
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.
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.
05-21-2010, 05:24 AM
#17
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Joined APC: Dec 2009
Position: 127.0.0.1
Posts: 2,115
Mooney Shutdown Procedure
Originally Posted by WildSmurf
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.
05-21-2010, 05:37 AM
#18
On Reserve
Joined APC: Jan 2010
Posts: 20
Originally Posted by ryan1234
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.
"Pneumatic discharge and 'shower of sparks' for start"?
I have an idea how it works, but just might Google search to see exactly what that is.WildSmurf
05-22-2010, 02:25 AM
#19
Gets Weekends Off
Joined APC: Aug 2006
Posts: 511
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.
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.
05-22-2010, 06:51 AM
#20
Line Holder
Joined APC: Jan 2008
Posts: 27
Originally Posted by 9kBud
The question I've always wondered is: why is the switch ordered off, R, L, Both, Start? Shouldn't "L" be on the left and "R" be on the right?
So R, L, Both is the correct order (some don't have the start position
)
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