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Circuit lesson

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emrath(at)comcast.net
Guest

Posted: Sat Nov 29, 2008 3:59 pm Post subject: Circuit lesson

Bob,

Why do we feed power to the starter contactor thru the master contactor?

Could one run a short hot lead from the always hot terminal on the master

contactor to the starter contactor. Thus eliminating the voltage drop and

stress on the master contactor when starting.  Interested in your comments.



Marty RV-6A Brentwood TN

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ceengland(at)bellsouth.ne
Guest

Posted: Sat Nov 29, 2008 8:37 pm Post subject: Circuit lesson

Emrath wrote:

 	  Quote: 	
		   



 Bob,

 Why do we feed power to the starter contactor thru the master contactor?

 Could one run a short hot lead from the always hot terminal on the master

 contactor to the starter contactor. Thus eliminating the voltage drop and

 stress on the master contactor when starting.  Interested in your comments.



 Marty RV-6A Brentwood TN


	


I'm not Bob, but the master contactor is a backup disconnect if the 

starter contactor fails 'on'. It makes it possible to kill all 

electrical energy from the battery except the (hopefully short) run from 

the battery + to the master contactor. (Except the 'endurance bus, of 

course.)



Charlie

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nuckolls.bob(at)cox.net
Guest

Posted: Sun Nov 30, 2008 8:55 am Post subject: Circuit lesson

At 05:58 PM 11/29/2008, you wrote:

 	  Quote: 	
		  



Bob,

Why do we feed power to the starter contactor thru the master contactor?

Could one run a short hot lead from the always hot terminal on the master

contactor to the starter contactor. Thus eliminating the voltage drop and

stress on the master contactor when starting.  Interested in your comments.



Marty RV-6A Brentwood TN


	


   You've already seen a good answer to this. I would elaborate

   by sharing two tense moments in OBAM aircraft where the starter

   contactor stuck closed (it's the most abused contactor in the

   airplane) and the battery master was not wired to shut down the

   starter. In one case, the starter survived but the 17 a.h. battery

   case melted. In the other case, the pilot was able to get out,

   pull the cowl and disconnect the battery before anything smoked

   or melted.



   Type certificated aircraft have always been wired such that

   EVERYTHING other than battery-bus power goes through the battery

   master contactor. Turning off the battery switch gets the electrical

   system the most benign condition possible.



   Bob . . .

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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