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Starter Contactor location on a Long-EZ

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jan 26, 2018 4:57 pm Post subject: Starter Contactor location on a Long-EZ

At 05:08 PM 1/26/2018, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Airdog77" <Airdog77(at)gmail.com>



 Bob,



 Roger... I'll go back and take a deeper look at all this. 	


   Is there a published failure analysis of

   what transpired in the unhappy event?



   A significant proportion of my career in aviation

   focused on what-went-wrong-and-why. In hind-sight,

   I wish I had kept a journal on the various inquiries,

   facts found and resolution of root causes.  I

   can state with confidence that a majority of

   failure events had root cause in 'somebody

   didn't read/understand some bit of history in

   design or application.



   A few instances, like the sticking trim relays on the

   Beechjet, involved new discoveries. But most unhappy

   events were founded on inattention to rudimentary

   details. I've worked some exceedingly expensive

   problems ($millions$) that had roots in $100

   decisions . . .



   Whatever you decide to do with your airplane,

   it NEVER hurts to take some pictures, post to

   the List and ask questions. The most elegant

   solutions are invariably a team effort by

   competent observers. You'll have a hard time

   finding a more capable group than right here . . .  



 

   Bob . . .

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michaelagarmon(at)gmail.c
Guest

Posted: Sat Jan 27, 2018 3:44 am Post subject: Starter Contactor location on a Long-EZ

Bob,There is an account of the incident on Brian Deford’s website located at http://deford.com/cozy/fire.html. 

I am also considering installing the starter solenoid on the inside (cabin side) of the firewall. I also plan on protecting alternator B leads with fusible links sized to protect the wire ( larger than the alternator capacity). In this way, any wire crossing the firewall will be protected.



Michael Garmon

Cozy Mk IV

Houston, TX

Sent from my iPad



On Jan 26, 2018, at 6:56 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 05:08 PM 1/26/2018, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Airdog77" <Airdog77(at)gmail.com (Airdog77(at)gmail.com)>



 Bob,



 Roger... I'll go back and take a deeper look at all this. 	


   Is there a published failure analysis of

   what transpired in the unhappy event?



   A significant proportion of my career in aviation

   focused on what-went-wrong-and-why. In hind-sight,

   I wish I had kept a journal on the various inquiries,

   facts found and resolution of root causes.  I

   can state with confidence that a majority of

   failure events had root cause in 'somebody

   didn't read/understand some bit of history in

   design or application.



   A few instances, like the sticking trim relays on the

   Beechjet, involved new discoveries. But most unhappy

   events were founded on inattention to rudimentary

   details. I've worked some exceedingly expensive

   problems ($millions$) that had roots in $100

   decisions . . .



   Whatever you decide to do with your airplane,

   it NEVER hurts to take some pictures, post to

   the List and ask questions. The most elegant

   solutions are invariably a team effort by

   competent observers. You'll have a hard time

   finding a more capable group than right here . . .  



 

   Bob . . .

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Airdog77

Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

Posted: Sat Jan 27, 2018 7:57 am Post subject: Re: Starter Contactor location on a Long-EZ

Bob,



I have to admit I'm puzzled on what appears to be sticking to the standard convention of mounting the starter contactor/solenoid on the firewall of a pusher aircraft when the A-to-Z of the power distribution configuration is different than a traditional tractor airplane.



If we look at the different configurations, which I spelled out in asking advice on this from some canard builder/fliers, it looks like this:



1.  Tractor:  FIREWALL >> Battery >> Battery Contactor >> shorter big wire >> Starter Contactor >> Starter



2.  "Standard" Pusher:  Battery >> Battery Contactor >> longer big wire >> FIREWALL >> Starter Contactor >> Starter



3.  "New" Cozy style: Battery >> Battery Contactor >> longer big wire >> Starter Contactor  >> FIREWALL >> Starter



Not to be critical of Brian in any way, and in the discussion I discovered in support of placing the starter solenoid on the cold side of the firewall, was a point made that he "didn't turn off the master" which controls the power flow through the big power cable, as is a prominent feature of #2 above.  I understand doing analysis on past events, and looking at standard practices in an attempt to mitigate potential issues (which is exactly what I'm attempting here), but Brian's scenario isn't the only reported instance of smoking wires in a pusher, it's simply the most tragic (that I know of).  



The second point in this discussion is that if control of the electron flow through the big cable ends at the cold side of the firewall (as is proposed), and the only (initial) action that results in electrons flowing across the firewall boundary is when the starter button is depressed... then very most likely only one action is required if there is any malcontent going on "back there" and that is simply to STOP pressing the starter button.  Then Step 2: TURN OFF THE MASTER is moved from the "critical" column to the "probably a good idea" column.



Moreover, the ancillary logistical benefits of moving the starter contactor to the cold/forward side of the firewall in routing wires is quite significant.  It simply makes for running less wires through the firewall, wire runs to the Hall Effect sensor for both the primary and SD-8 backup alternators are optimized, and it places more items in the rather empty Hell Hole area and gets them off a very crowded firewall.  In short, it just really appears on the face of it to make for an easier install and a safer operational setup.



And again, going back to my original statement, I'm not really sure why the starter contactor/solenoid should be on the hot side of the firewall in a pusher airplane.  Moreover, in looking at the pros/cons for moving the starter solenoid to the cold side, the pros vastly outweigh any cons that I could find.  Not that I am in any way the most knowledgeable on this stuff, but from what I know, have researched and discussed it appears to be the best option thus far.



Regards,

Wade

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_________________
Airdog
Wade Parton
Building Long-EZ N916WP
www.longezpush.com

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jan 28, 2018 10:46 am Post subject: Starter Contactor location on a Long-EZ

 	  Quote: 	
		  

 Not to be critical of Brian in any way, and in the discussion I discovered in support of placing the starter solenoid on the cold side of the firewall, was a point made that he "didn't turn off the master" which controls the power flow through the big power cable, as is a prominent feature of #2 above.  I understand doing analysis on past events, and looking at standard practices in an attempt to mitigate potential issues (which is exactly what I'm attempting here), but Brian's scenario isn't the only reported instance of smoking wires in a pusher, it's simply the most tragic (that I know of). 	


   But has there been any forensic analysis of

   cause/effect in any of these incidents? 

   If wires 'smoked', were they small wires

   improperly protected or fat wires improperly

   installed? Did quantitative analysis

   show that the 'incidents' were more prevalent

   in pushers as opposed to tractor airframes?



   I think the problem is being over-worried . . .

   concerns which are certainly understandable

   but for reasons based more on lack of information

   than from rational actions to reduce risk.



   To be sure, fire wall penetrations of all stripe

   have figured in failures.  I recall one incident

   on a tractor airplane where a bulkhead fitting

   on a fuel line did not receive the benefit of

   safety-wired flare-nuts.  The line leaked and

   an in-flight, fuel-fed fire ensued.



   I can recall dozens of articles in the aviation

   mags and publications by Tony B et. als. where

   reliable fire wall penetration is discuesed

   in detail. The air framers I've worked for had

   books of process and practice specifications

   for such things . . . books that have seen

   only minor revision over decades . . . 



   As a class of incident, these are way

   down the charts in frequency of occurrence.

   Virtually all such events have root cause in

   failure to observe legacy design rules that

   have served well on hundreds of millions of vehicles

   of all kind for over a century . . . not the

   least of which are airplanes.



 

 

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jan 29, 2018 3:48 pm Post subject: Starter Contactor location on a Long-EZ

 	  Quote: 	
		  



 I will say --and not that this is my reasoning for a go/no-go decision-- that I've learned over these past few days that placing the starter contactor on the cold side of the firewall is a VERY common practice in the canard community --again, for whatever reasons individual builders' have.  Actually, surprisingly common in fact.



 Perhaps some of that has to do with the inherent design of canards, wiring and space logistics (my overarching reason for going this route), tribal culture, or just individual preference.



 As you have alluded to many times, this flexibility is one of the outstanding characteristics of the OBAM world... to adjust when necessary to optimize one's build. 	


     . . . a well reasoned decision. My only concern about

     this thread (and similar threads in the past) was

     that some readers perceive value in moving their

     contactor as a prophylactic against having

     their airplane catch fire.



     My sense is that you've got a handle on the

     need/value/processes for risk management. A quality

     that has very little to do with architecture.



     May The Force be with you sir . . .



 

 

   Bob . . .

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Airdog77

Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

Posted: Sat Feb 03, 2018 5:14 pm Post subject: Re: Starter Contactor location on a Long-EZ

Thanks Bob!

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_________________
Airdog
Wade Parton
Building Long-EZ N916WP
www.longezpush.com

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