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Electronic ignition feed circuit.

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tim2542(at)sbcglobal.net
Guest

Posted: Thu Aug 05, 2010 6:18 pm Post subject: Electronic ignition feed circuit.

Bob; I’m still digestion the question of un-fused wires running more than a few inches, so this question comes to mind. I have a rear engine/rear battery. The mfg calls for a pull-able breaker on the panel.  3 options I see are:   

1. Run the wire from the Bat Bus forward to the C/B, then on to it’s business. Now I am open to problems with an unintentional ground and a burning wire, but I can reset in flight in an emergency.  

2. Install a 10 amp fuse at the Bus and then a 5 Amp CB in the panel. My thought is the CB would always trip first and I can reset it, the fuse is there to protect from a problem between the Buss and the CB. Now I have 2 fail points.  

3. Use a fuse only at the Bus and no CB in the panel. Now I can’t reset it in flight.  

If I understand you correctly you would say use #1 and just use good practices. Is that correct?  

This same issue comes up a few times in my project, like the nose lift for example. The mfg wants a un-switched 10A feeder to it.  

Thanks & Yes I have a copy of the Aerolectric’!  

Tim Andres  

 (rnbraud(at)yahoo.com)   

   

       [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 05, 2010 8:31 pm Post subject: Electronic ignition feed circuit.

At 09:11 PM 8/5/2010, you wrote:

  	  Quote: 	
		   Bob; I’m still digestion the question of un-fused wires running more than a few inches, so this question comes to mind. I have a rear engine/rear battery. The mfg calls for a pull-able breaker on the panel.  3 options I see are: 	


   You must be talking about Light Speed.

   You can wire as he suggests. No doubt

   many hundreds of airplanes have been wired

   thusly. An accident I'm working involves

   wiring that was NOT done to LS drawings . . .

   but not to mine either. The airplane

   suffered simultaneous loss of both ignition

   systems because the folks making decisions

   THOUGHT they were building in some sort of

   super-redundancy.



   If it were my airplane, each ignition would

   be fed with a 5A fuse and 20AWG wire to a 

   switch on the panel. One fuse on a battery

   bus, the other on the main bus.



  	  Quote: 	
		   1. Run the wire from the Bat Bus forward to the C/B, then on to it’s business. Now I am open to problems with an unintentional ground and a burning wire, but I can reset in flight in an emergency.

 2. Install a 10 amp fuse at the Bus and then a 5 Amp CB in the panel. My thought is the CB would always trip first and I can reset it, the fuse is there to protect from a problem between the Buss and the CB. Now I have 2 fail points.

 3. Use a fuse only at the Bus and no CB in the panel. Now I can’t reset it in flight. 	


   Yeah, but you have TWO of them and the engine

   runs really fine on one. Likelihood of

   resetting a breaker being even a choice

   is low . . . likelihood of it being useful

   is even lower . . . likelihood that you

   pop a fuse on one ign (which means it's

   dead anyhow) and then having a second

   system go down.



   In fact, if I were in an endurance mode

   flying battery only with two ignition systems,

   I'd shut one of them off.



  	  Quote: 	
		   If I understand you correctly you would say use #1 and just use good practices. Is that correct?

 This same issue comes up a few times in my project, like the nose lift for example. The mfg wants a un-switched 10A feeder to it.

 Thanks & Yes I have a copy of the Aerolectric’! 	


   and no doubt many airplanes have been wired

   that way too.



   All I can offer you is that there are "rules

   of the wiring" that have been developed over

   nearly a century of wiring airplanes. They

   represent proven recipes for success validated

   in hundreds of thousands of airplanes. There

   are other recipes that will have different risks.

   The risks are probably low . . . after all, how

   many hours of the rest of your life to you expect

   to be airborne in this machine?



   So it's a toss-up . . .



 

   Bob . . .    [quote][b]

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