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Z-14 implementation

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foghorn757(at)gmail.com
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Posted: Sun Feb 02, 2020 12:10 pm Post subject: Z-14 implementation

Here is what I’m working on for my SDS powered RV8. This is a work in progress. I’m not sure about the diodes to the ENG BUS since I can control power through the switches from the BATT BUSs one at a time. The main ALT is a PP 60A internally regulated, until it fails, then I’m going to switch to a B&C externally regulated ALT. For now I’m going to give the PP and VPX the opportunity to run the show. 

Ok I’m here to learn so help me get smarter.

Jeff Parker



  	  Quote: 	
		  On 2Feb, 2020, at 13:45, Krea Ellis <krea.ellis(at)gmail.com (krea.ellis(at)gmail.com)> wrote:

Clearly, my emails are getting through even though I get a reply from the server that they are being rejected.

Thanks for all the valuable information and thoughtful responses. 



You're not going to be comfortable with your system until you're  comfortable with it. But it might be worth stepping back and looking  'big picture' for a bit. Checking every detail should happen, but  sometimes our initial premise may need re-evaluation. There are one or  two of my basic premises I'm currently rethinking a bit....  Charlie



Agreed and I am stepping back and working hard to overcome the concerns about multiple redundancies. Years of flying big iron I guess and a fear about new ground (at least for me) with SDS.



How would that happen? EVERY branch feeder in Z-14    is QUAD sourced until some component fails in flight    (an exceedingly rare event). Two distribution    busses (main and aux) remain at least DUAL sourced    and sometimes TRIPLE sourced depending on nature of failure.     Complete loss of power on either bus just doesn't    happen . . . Z-12 (revised) is another solid    option where a single bus is TRIPLE fed and no    less than DUAL fed after loss of a single    component.



I need to keep things in perspective. In 1000 hours of GA flying and multiple thousands of large airplanes, any electrical problems I have had have been totally controllable and I have never had total electrical failure - although there are plenty of anecdotal stories of that happening.  So the risk is probably very small. 



I guess things are quad sourced if you assume you can close the cross tie contactor.  I was hoping to do that only for start and only in a dire emergency in flight. But if the only source of power to the injectors has failed, not much to lose by closing the cross tie and hope it powers up.  Screens in front are backed up by an IBBS battery and the G5 has an internal battery, so we can keep the shiny side up no matter if we are a glider.  



Can you suggest that SDS contact me with a    goal of collaborating on a unified approach    to minimizing risks? 



I will absolutely do that a greatly appreciate your willingness to help me (and others) through this.



I am coming to the conclusion quickly that a single injector bus fed by one of the two battery busses and with a good battery and an externally regulated alternator is probably the best compromise of simplicity and reliability. I’d still like to consider a slightly more redundant approach too. 



Krea

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nuckolls.bob(at)aeroelect
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Posted: Sun Feb 02, 2020 12:18 pm Post subject: Z-14 implementation

 	  Quote: 	
		   

 I guess things are quad sourced if you assume you can close the cross tie contactor.  I was hoping to do that only for start and only in a dire emergency in flight. 	


   The whole reason for the cross-feed contactor

   is to PREVENT a 'dire emergency' . . . not

   react to one.



   If system components never failed, FBOs would

   be out of business. Tires and batteries wear

   out. Radios go belly up. 



  	  Quote: 	
		    But if the only source of power to the injectors has failed, not much to lose by closing the

 cross tie and hope it powers up. 	


   Okay, failure of WHAT component would prompt closing

   the cross-tie? Will failure of that component result

   in instant loss of engine?



  	  Quote: 	
		     Screens in front are backed up by an IBBS battery and the G5 has an internal battery,

  so we can keep the shiny side up no matter if we are a glider.  	


   Batteries which, in my never humble opinion,

   only add cost of ownership and offer little

   benefit in terms of mission reliability.



   If one of these batteries is ever called

   upon to do it's job, it's because you

   probably DO HAVE a real EMERGENCY borne

   of poor design and/or craftsmanship.



  	  Quote: 	
		  Can you suggest that SDS contact me with a 

 goal of collaborating on a unified approach 

 to minimizing risks? 



 I will absolutely do that a greatly appreciate your willingness to help me (and others) through this.



 I am coming to the conclusion quickly that a single injector bus fed by one of the two battery busses and with a good battery and an externally regulated alternator is probably the best compromise of simplicity and reliability. I’d still like to consider a slightly more redundant approach too. 	


   Define 'slightly' and articulate the

   sequence of failure events that would

   bring that benefit into play.



   This is what failure mode effects analysis

   is all about. You need to have confidence

   in your minimally configured, well considered

   constellation of airframe systems. Otherwise,

   the benefit of a 'slightly more redundant'

   feature is reduced to the same utility

   as carrying a rabbit's foot.



   What you're going through here is equivalent

   to a process I've participated in dozens of

   times. They're called Preliminary and Critical

   Design Reviews. I've stood in front of a

   Power Point screen many times in a room full

   of Navy engineers, technicians, pilots and

   program managers along with other members

   of my project group.



   In my later years, I 'ran the gauntlet'

   and sold the idea(s) most of the time.

   On occasion, I took some hits. But in

   any case, the process was invaluable

   in that it prevented bad ideas from

   going to production.



   I suggest that what we're doing here

   has the same goals. Another goal is to

   eliminate the word 'emergency' from the

   lexicon of electrics-speak . . . we're

   just not going to have one.



 

 

   Bob . . .

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