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Sky-tec starters - elimination of Starter Contactor

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nuckolls.bob(at)aeroelect
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Posted: Wed Feb 18, 2009 9:43 am Post subject: Sky-tec starters - elimination of Starter Contactor

At 10:16 AM 2/18/2009, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Vern Little" <rv-9a-online(at)telus.net>



 Bob, Sky-tec's web site has information on wiring up their starters without starter contactors.  In addition, they seem to directly contradict the recommendation of Van's aircraft on how to wire a starter contactor if one is used.



 See  http://www.skytecair.com/Wiring_diag.htm  for more information. 	


   With all due respect to Skytec . . . the diagram offered

   by Van's is technically correct and practical solution

   for eliminating delayed starter dis-engagement reported

   by many builders . . . 



 [img]cid:.0[/img]



 



 



 

  	  Quote: 	
		  I plan on using an automotive relay instead of a 30A pushbutton switch to activate the solenoid as they recommend, but the principle is the same. 	


   Correct. You can do without external contactor providing

   a robust current control path for the extra-ordinary inrush

   demands of the built in contactor



   See also . . .



  http://www.aeroelectric.com/articles/strtctr.pdf



  http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z22-23K.pdf

 

   http://www.aeroelectric.com/PPS/Engine/Starter/PM_Starter_w_RunOn_Relay.pdf 



 

  	  Quote: 	
		  The folklore that I'm used to is that you need an upside-down starter contactor to be immune from large G-loads activating the starter. 	


   Urban myth . . .



  	  Quote: 	
		   Seems if you eliminate the contactor, this is not a problem.  Of course, this all depends on the design and reliability of the Sky-tec internal solenoid. 	


   I have no reason to suspect that the built in

   contactor on a Skytec is any better/worse than

   any other built in contactor. 



 

   See also . . .



  http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z22-23K.pdf

 

 

  	  Quote: 	
		  I've asked Sky-tec for clarification on the potential failure mechanisms of their solenoids (G loading etc.), but have had no response. 	


   G-loading concerns for contators are bogus.



 

  	  Quote: 	
		  Any opinions on elimination of the contactor?  For bonus marks, how about commenting on Van's recommendation of using the I contact in the starter contactor to feed the starter motor solenoid (both pics on the link above)? 	


   It's a slick implementation of features offered in

   automotive contacts and has much to recommend it.



 

        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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rv-9a-online(at)telus.net
Guest

Posted: Wed Feb 18, 2009 10:57 am Post subject: Sky-tec starters - elimination of Starter Contactor

Thanks, Bob.  I am using Z22 with diodes (like  your last figure), only the ground of the relay goes to an oil pressure switch  to prevent accidental operation of the starter when the engine is running (don't  ask!).

  

 I understand the run-on problem is due to  self-generation of the starter, and Van's prevents this by splitting the  solenoid current from the primary feed.  Clever use of the "I" terminal on  the contactor.

  

 Since Skytec is pretty adamant in their wiring  diagrams, I suspect that they have not experienced run-on problems... but who  knows?

  

 My choice of a relay vs. contactor comes down to  whether I want a hot battery lead connected to the starter for the full duration  of flight.   I suppose that if it ever came off the starter and  shorted that bad things may happen.  I just have to mitigate or accept this  risk.

  

 Thanks for your help.

 Vern

  

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