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Magneto failure in general, Was: Re: P Mags

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nuckollsr(at)cox.net
Guest

Posted: Thu Feb 22, 2007 1:29 pm Post subject: Magneto failure in general, Was: Re: P Mags

At 11:11 AM 2/22/2007 -0700, you wrote:



 	  Quote: 	
		  



Hello Bob,



I have read/been-told that cycling the mag switch while at high power

settings might cause the engine to backfire if one mag is dead and the

other is turned back on, and that such a backfire might damage components

of the intake and exhaust systems..  What do you think about this?


	


    That is a risk. Magenetos will do it too but is it a

    "backfire"???  When the engine is totally deprived of

    ignition it continues to pull stoichiometric mixture through

    the plumbing. Then when any source of ignition returns, there's

    a volume full of unburned mixture that includes the entire

    exhaust system and any cylinder with an exhaust valve open

    at the time this volume gets lit off.



    I've experienced this on the ground when doing mag checks

    where I inadvertently turned off both mags during a run-up

    and then got them back on while the engine was still

    turning. Folks have done this in their cars too and I've

    heard of mufflers being split open from the resulting

    explosion.  Hmmm . . . guess we need to agree on the word

    "backfire" which I use as ignition on the intake side of the

    cylinders. Does this make the exhaust side explosion a

    "foreward fire"?????



    In the common public vernacular, a loud report from a

    vehicle is referred to as "backfire" . . . I suppose because

    it blows flames out the back of the car . . .



    Oh well, I THINK we know what we're talking about!!!!



    Bob . . .

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nuckollsr(at)cox.net
Guest

Posted: Thu Feb 22, 2007 1:30 pm Post subject: Magneto failure in general, Was: Re: P Mags

At 01:50 PM 2/22/2007 -0500, you wrote:



 	  Quote: 	
		  Good Afternoon Matt,



The procedure, as taught, is to be very sure you DO NOT turn on the 

remaining good magneto if the engine does quit. The drill then is to put 

the mixture in full lean, count to ten, turn on the magneto and slowly 

richen the mixture until the engine starts.



I have never had it happen that way and I am sure it will take a lot of 

discipline to wait those few seconds for the engine to clear itself before 

the magneto is placed back in service!



It does help if the operator has experience deliberately running fuel 

tanks dry.



That procedure is another one that is rarely taught these days, but having 

run a tank dry often does instill confidence in the restart procedure.


	




   Hadn't heard that one. Makes a lot of sense. Something

   to check my instructor on at the next checkride!



   Bob . . .

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dsleepy47(at)hotmail.com
Guest

Posted: Thu Feb 22, 2007 3:58 pm Post subject: Magneto failure in general, Was: Re: P Mags

In FAA terms a backfire would be fire in the intake which would go "back" through the carb or throttle body. "afterfiring" or "afterburning" is the term for burning in the exhaust. From a mechanics standpoint it would be nice to keep them straight because the items to check for damage after a backfire are different than an afterfire.

  

 Deems





   

 > Date: Thu, 22 Feb 2007 15:25:52 -0600

 	  Quote: 	
		   To: aeroelectric-list(at)matronics.com

 From: nuckollsr(at)cox.net

 Subject: Re: Magneto failure in general, Was: Re: P Mags


	


 	  Quote: 	
		   

 I've experienced this on the ground when doing mag checks

 where I inadvertently turned off both mags during a run-up

 and then got them back on while the engine was still

 turning. Folks have done this in their cars too and I've

 heard of mufflers being split open from the resulting

 explosion. Hmmm . . . guess we need to agree on the word

 "backfire" which I use as ignition on the intake side of the

 cylinders. Does this make the exhaust side explosion a

 "foreward fire"?????

 

 In the common public vernacular, a loud report from a

 vehicle is referred to as "backfire" . . . I suppose because

 it blows flames out the back of the car . . .

 

 Oh well, I THINK we know what we're talking about!!!!

 

 Bob .=====

 

 

 


	


Explore the s=7+wonders+world&mkt=en-US&form=QBRE' target='_new'>Learn more!  [quote][b]

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