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Z13-8 modification and LSE ignition wiring

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Sep 22, 2020 6:06 pm Post subject: Z13-8 modification and LSE ignition wiring

 	  Quote: 	
		  My reasoning is that should the battery fail somehow, the battery can be isolated and the SD8 could run the E buss, it could also be used to charge the battery with the alternate feed relay closed and the main battery relay open/alt off. I plan on incorporating the self energizing circuit for the SD8 (is this required with the newer SD8 system?). 	




   In 45 years of herding electrons on aircraft

   I cannot recall a single instance of an FMEA

   analysis that considered in flight 'battery failure'.

   Now there ARE airplanes fitted with battery over

   temperature warning systems that activate

   when a REGULATOR or some other system fault

   abuses an otherwise good battery.



   The battery is generally regarded as the most

   reliable source of energy on the airplane because

   it is sized and maintained to meet endurance

   design goals that far exceed it's ability to

   crank an engine.



   So, if (1) your engine started for this particular

   flight and (2) it recently demonstrated capacity 

   conforming to design goals, then what is the

   likelihood of it suddenly going TU in the next

   3 or 4 hours of flight?



   Further, if it's assumed to offer such risks,

   then what are the data supporting what

   failure mode? Field history? Observed limitations

   in fabrication? Limited manufacturer's

   warranty? Personal experience? The point being

   if there is a real, risk . . . then

   would it not be prudent to select another

   battery?



   Finally, suppose the battery does succumb to

   some failure while your cruising along. How

   would that failure manifest in the cockpit. What

   indication would you observe that points

   only to the battery causing you to initiate a

   plan developed to mitigate that condition?



 

 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Sep 23, 2020 12:09 pm Post subject: Z13-8 modification and LSE ignition wiring

 	  Quote: 	
		  

 I am aware of the need to be able to shut off power near the source but cannot think of a reliable way to do this with ignitions connected to a battery buss, surely don’t want to use a relay (for reliability) and the switches will be about 4’ of wire away from the battery on the firewall, as to using diodes “instead” of switches, one switch is certainly required to be able to shut off the ignition so I was thinking of using one single pole on/off/on switch to be able to select either power source, this allows power source selection without adding another switch to the circuit. I see the benefit of diodes but they would also be added to the switch in the circuit so would allow auto-switching but not increase reliability...what am I missing?

 	


   How big are the battery bus fuses?  Taking the

   system 'max cold' at the source is a crash

   safety issue. The regs allow TC aircraft to

   carry always hot feeders protected at no

   more than 5A.  Given that fuses are MANY

   times faster than breakers, I'd comfortably

   extend that feeder size to 7A.



   Anything protected at that level or below

   may enjoy long, un-switched feeders.



   Why the 'auto switching'? The engine will

   run on one ignition quite nicely. What

   are the probabilities for dual failures

   of single power paths? Assuming you've 

   detected an unacceptable probability,

   then do you have steps in the pre-flight

   check list to insure that all contingency

   paths are functioning? In such cases,

   it's better to design out the failure

   condition than to add automatic features

   that contribute their own burdens to

   work load. 



 



 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Sep 23, 2020 12:18 pm Post subject: Z13-8 modification and LSE ignition wiring

 	  Quote: 	
		  

 To protect the wire itself, I like using fusible links. For light consumers like the ignitions, a few inches of 22ga wire at the battery bus (sleeved with a fiberglass jacket) soldered to 18ga wire feeding the switch/ignition will protect the always-hot section of wire from catastrophic faults. 	


   but doesn't satisfy the crash safety condition



   Fusible links are generally limited to use in

   areas protected by battery master but included

   to isolate hard-faulted feeders from the remainder

   of normally functioning distribution.



   The battery bus should (1) drive fuse or breaker

   protected feeders at 7A or smaller -OR- if protection

   is larger, then a relay at the bus to manage that

   feeder's crash safety recommendations.



 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Sep 23, 2020 5:39 pm Post subject: Z13-8 modification and LSE ignition wiring

From the Lightspeed installation manual. I was working toward improving on the factory recommendation in this document. While a fusible link won't be as fast as a fuse, it seems better than a 5 or 6 foot long always hot wire to the CB.



  LSE ignitions were installed on the N811HB

  accident aircraft and decidedly not wired with

  due diligence to competent FMEA or best practices.

  Nor were they wired to LSE instructions.



  Kluse and I worked on that case and discussed his

  power source recommendations (then 10 years

  old or more).  He didn't disagree with recommendations

  and reasoning explained in the 'Connection but

  wasn't interested in refining his instructions.

  He cited a long successful field history.



  Klause is an accomplished performance guy and

  has an impressive record of marketing success.

  But he is not a systems integrator. We've been

  hashing over the Z-figures here on the List

  for almost 30 years.  I suggest they've

  evolved in ways that makes the system more

  robust while striving for simplicity of pilot

  workload, elegant FMEA outcomes and lowest

  cost of ownership while meeting design

  goals.



  I'm the first to admonish, "When in doubt follow

  the manufacturer's instructions." The flip side

  of that coin is, "If you've done the homework,

  modifications that go to a more elegant configuration

  at equal or less risk, go for it."



  Elegant, low risk craftsmanship is what we strive

  for here.



 

   Bob . . .

Tailwind1

Joined: 05 Sep 2020
Posts: 7
Location: GREYBULL, WY

Posted: Thu Sep 24, 2020 4:35 am Post subject: Re: Z13-8 modification and LSE ignition wiring

 	  nuckolls.bob(at)aeroelect wrote: 	
		   	  Quote: 	
		  

 To protect the wire itself, I like using fusible links. For light consumers like the ignitions, a few inches of 22ga wire at the battery bus (sleeved with a fiberglass jacket) soldered to 18ga wire feeding the switch/ignition will protect the always-hot section of wire from catastrophic faults. 	


   but doesn't satisfy the crash safety condition



   Fusible links are generally limited to use in

   areas protected by battery master but included

   to isolate hard-faulted feeders from the remainder

   of normally functioning distribution.



   The battery bus should (1) drive fuse or breaker

   protected feeders at 7A or smaller -OR- if protection

   is larger, then a relay at the bus to manage that

   feeder's crash safety recommendations.



 

   Bob . . . 	




Bob, am I understanding correctly from your above statement that fusible links are NOT a good alternative for a fuse block AT the battery bus in this case?



I was looking at the links to simplify and avoid the extra fuse block but are the links too slow for the crash safety aspect of this (say a 22AWG link and 18 AWG feeder wire with the 5A pullable breaker at the cockpit end as per the LSE recomendation)?. I will install a fuse block for the batt bus items if this is the recommended procedure. 



Also, what are your thoughts on the LSE manual procedure of using the wire shield as a ground return versus a separate conductor? Seems to be possibly be less robust?



Thanks, Tim M

_________________
Flying Sonerai II with A80 Continental. Wittman W10 Tailwind under construction, O360, dual LSE electronic ignition, airframe complete and covered, engine hung, cowl built. Working on electrical, instrumentation, and other details.

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Sep 24, 2020 5:16 am Post subject: Z13-8 modification and LSE ignition wiring

 	  Quote: 	
		  

 Bob, am I understanding correctly from your above statement that fusible links are NOT a

 good alternative for a fuse block AT the battery bus in this case? 	


   Correct



  	  Quote: 	
		  I was looking at the links to simplify and avoid the extra fuse block but are the links

 too slow for the crash safety aspect of this (say a 22AWG link and 18 AWG feeder

 wire with the 5A pullable breaker at the cockpit end as per the LSE recomendation)?.

 I will install a fuse block for the batt bus items if this is the recommended procedure. 

 	


   Installing those breakers in the cockpit

   on extended feeders from the battery bus

   has no foundation in physics or practice.

   Feeder protection needs to be a close as

   practical to the energy source that puts

   the feeder at risk. The time constant for

   operating that protection should be

   consistent with protection of that feeder

   from anticipated threats discovered in

   the FMEA for protection of that feeder.

   The crash safety issue is stacked on top

   of feeder protection intended to limit the

   electrical energy that raises risks of

   post crash fire ignited by always hot

   feeders.



   Hence the 5A limit (FARS) or my own suggestion

   for 7A fuses which would limit fault energy

   to much less than breakers.



  	  Quote: 	
		  Also, what are your thoughts on the LSE manual procedure of using the

 wire shield as a ground return versus a separate conductor? Seems

 to be possibly be less robust? 	


   You are correct. I had some discussion with

   Klause with respect to shields in his system.

   I inquired as to any testing or analysis done

   that called for shielding his wires as either

   potential victims or antagonists.



   He admitted to no such testing but thought

   it wasn't hard to do and was good insurance.

   Powering the hall sensors through twisted

   pair shields is probably a good thing to

   do. Shielding the power leads makes no sense.

   Those paths are not (or at least should

   never be) bad actors in the ship's electro-

   magnetic compatibility study.



   If ANYONE says that shielding power wires

   into or out of his product is a necessary

   thing, then they've admitted that their

   design falls short of some fundamental

   and easily achieved requirements of DO-160.

   Shielding breaks electro-static coupling

   which is very weak. No such risks exist on

   DC power feeders. 



   Klause wasn't claiming that it was necessary,

   only easy and a good thing to do.



   The recommended DC power feeder to the LSE system is

   a mish-mash of electrical joints that add

   complexity and failure points without

   adding EMC value. Asking for direct

   connections to batteries is also without

   foundation in physics or practice.



   You will never see such a recommendation

   in TC aircraft designs. I would ground the

   ignition electronics via wire to the firewall

   ground bus; feed DC power through contemporary,

   FAST protection at the battery bus and then

   through what ever switch is selected. Fuses

   are fine . . . if a fuse pops, something is

   broke and there is no value in fiddling

   with them in flight. That breaker-on-the-

   panel thing is simply not well thought out.

   



 

   Bob . . .

Tailwind1

Joined: 05 Sep 2020
Posts: 7
Location: GREYBULL, WY

Posted: Thu Sep 24, 2020 7:06 pm Post subject: Re: Z13-8 modification and LSE ignition wiring

When asked , Klaus stated that his reasoning for the pullable breakers at the panel was that an overvoltage or lightening strike could open the breaker and it could be reset whereas a fuse could not, any thoughts on this? 



Tim M

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Sep 25, 2020 7:28 am Post subject: Z13-8 modification and LSE ignition wiring

At 10:13 AM 9/25/2020, you wrote:

  	  Quote: 	
		  Well, for one thing I don't think fuses react to voltage. I think they react to current.



 



 On Thu, Sep 24, 2020 at 7:17 PM Tailwind1 <timmikus38(at)gmail.com (timmikus38(at)gmail.com)> wrote:

   --> AeroElectric-List message posted by: "Tailwind1" <timmikus38(at)gmail.com (timmikus38(at)gmail.com)>

 

  When asked , Klaus stated that his reasoning for the pullable breakers at the panel was that an overvoltage or lightening strike could open the breaker and it could be reset whereas a fuse could not, any thoughts on this? 	
 

   When and if a lightning strike opens a

   breaker . . . the airplane is toast.

   Similarly, ov conditions do not open

   breakers.



   



 

   Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan

Posted: Fri Sep 25, 2020 9:16 am Post subject: Re: Z13-8 modification and LSE ignition wiring

Overvoltage will not open a breaker either.  Over current will, but wait until

safely on the ground before resetting any breaker.

_________________
Joe Gores

Tailwind1

Joined: 05 Sep 2020
Posts: 7
Location: GREYBULL, WY

Posted: Mon Sep 28, 2020 4:23 am Post subject: Re: Z13-8 modification and LSE ignition wiring

Thank you all for your replies to the questions.



T Mikus

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