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Z-14 with dual Lightspeed III and SD-8

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Feb 01, 2009 6:47 pm Post subject: Z-14 with dual Lightspeed III and SD-8

At 03:28 PM 1/31/2009, you wrote:

 	  Quote: 	
		  

<bob.condrey(at)baesystems.com>



Food for thought for those with dual LSE ignitions (like me).  I was 

talking with Klaus about his CB recommendation vs fuses and he said 

that the ignitions (at least the Plasma IIIs that I have) have an 

internal crowbar circuit to protect the ignition from an overvoltage 

event.  Reason for the CB recommendation was so that in the unlikely 

case of an OV event the pilot could pull the alternator CBs, reset 

the ignition CBs and continue flight.


	


  That is unfortunate. Is this feature

  mentioned in the installation literature?

  Under the right conditions of alternator

  size, battery condition and system loads,

  an OV event could trip BOTH ignition systems

  leaving you with a cold engine.



  The whole idea behind the 20V, 1-Second surge

  test under DO-160 was to open an OV

  shutdown opportunity as big as a barn door. Any

  product designed with rudimentary attention

  to DO-160 in mind will not even have to grunt

  hard during an OV detection and shutdown.

  Response to OV conditions are best handled

  by devices crafted to slay the dragon in his

  cave as opposed to chasing him down in the

  wild.



 	  Quote: 	
		  This was the first time I'd ever heard this and it scared me A LOT 

because I've got mine wired through my battery buss fuse blocks 

(Z-14).  While I've never had a problem and haven't heard of anybody 

else having a problem, I plan to redo the ignition power wiring and 

switch to CBs.


	


  It would scare me too. It's unfortunate

  that a feature of this accessory drives

  the installer's system architecture. Bottom

  line is you gotta do what you gotta do

  . . . even if it sucks for air.



        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

bcondrey

Joined: 03 Apr 2006
Posts: 580

Posted: Mon Feb 02, 2009 7:52 am Post subject: Re: Z-14 with dual Lightspeed III and SD-8

Bob,



Direction to use CBs is in the installation literature, however no specific or caution against fuses is not.  This came up during a conversation when I mentioned driving the ignitions off the battery buss fuse blocks.  



Bob

longg(at)pjm.com
Guest

Posted: Mon Feb 02, 2009 9:05 am Post subject: Z-14 with dual Lightspeed III and SD-8

This whole thing gives me the willies, but I'm in the same boat and not

jumping off. I'm gonna buy 2 CB's and hog tie them to the battery. Oddly

enough they will be wired through a switch on the panel which is another

point of failure. Perhaps I'll braze the fast tabs on so they don't fly

off over a bump. We could also fly around with a spare battery at our

feet and two alligator clips drooping down from the panel. In an

emergency, just hook them up. I guess it's just a matter of what one is

comfortable with. Different strokes for different paranoia's.

 On a similar note, in the recent KitPlanes mag there is an article

about Precision's "near" FADEC system which requires the whole system is

wired to a separate battery. In this they are taking the next step to

completely isolate dependency on the primary battery components. 



Perhaps that is a good first step. Just add a battery in series and wire

the 2 CB's to it.



Glenn



--

Erich_Weaver(at)URSCorp.c
Guest

Posted: Tue Feb 03, 2009 9:36 am Post subject: Z-14 with dual Lightspeed III and SD-8

I dont think I am fully understanding this discussion. Bob, perhaps you could provide a simple summary of the issue and concerns here for the less enlightened?  There are a lot of folks out here with single or dual lightspeed ignitions.  Under what circumstances are they at risk?  Any suggested course of action?  A lot of concern seems to have been expressed without much direct input from the manufacturer.

 

 erich  [quote][b]

msausen

Joined: 25 Oct 2007
Posts: 559
Location: Appleton, WI USA

Posted: Tue Feb 03, 2009 11:55 am Post subject: Z-14 with dual Lightspeed III and SD-8

Thanks Bob for uncovering this.  I had the same basic plan as you, using a fuse off each of the two main batteries running up each side of the fuselage to the two LSEIII’s.  

   

  I think knowing this now I will use a slightly larger fuse off the battery, say 15amp with the appropriate wire of course, and then use breaker switches for the LSE’s.  My batteries are in the back and I certainly don’t want two separate, unprotected wires running up the length of the fuselage.  If it’s an OV and not enough to blow the 15amp fuses then I can reset the LSE’s using the switch breakers.  If it’s something else that blows the 15amp, probably won’t make a difference at that point as it’s either a fried component or a shorted wire.  Does this sound like a workable solution to everyone?  

   

Michael  

      [quote][b]

mprather(at)spro.net
Guest

Posted: Tue Feb 03, 2009 12:52 pm Post subject: Z-14 with dual Lightspeed III and SD-8

I suspect such series protection will always blow the fuse and not the

breaker - if they both have the same rating.  The time constant for

blowing most standard breakers is much slower than for fuses.  You might

be able to upsize the wiring and fuse and get something to work - by

operating the fuse at a much smaller percentage of it's fault current

rating than the breaker.  You could also pick a device with a slower blow

time than a normal ATC fuse.  An MDL maybe?



The behavior of the system might also depend on how "good" the short is

that is presented by the LSE's internal crow bar.  The peak current

wouldn't likely be anywhere close to that of connecting copper straight

across the battery terminals.  The impedance of the crowbar comes into

play.



One question I can't remember being asked/answered is what voltage the

LSE's crowbar is designed to trip at.  I suspect it might be quite high as

I think the systems are allowed to be run from a 24(2V bus - the manual

lists proper operation up to 35V.  When using an LSE on an airplane with a

12(14)V buss, the alternator's OV crowbar might be depended on to trip

sooner than the LSE crowbar.

Regards,



Matt-



 	  Quote: 	
		     Thanks Bob for uncovering this.  I had the same basic plan as you, using

 a fuse off each of the two main batteries running up each side of the

 fuselage to the two LSEIII's.



   I think knowing this now I will use a slightly larger fuse off the

 battery, say 15amp with the appropriate wire of course, and then use

 breaker switches for the LSE's.  My batteries are in the back and I

 certainly don't want two separate, unprotected wires running up the

 length of the fuselage.  If it's an OV and not enough to blow the 15amp

 fuses then I can reset the LSE's using the switch breakers.  If it's

 something else that blows the 15amp, probably won't make a difference at

 that point as it's either a fried component or a shorted wire.  Does

 this sound like a workable solution to everyone?



 Michael

msausen

Joined: 25 Oct 2007
Posts: 559
Location: Appleton, WI USA

Posted: Tue Feb 03, 2009 1:44 pm Post subject: Z-14 with dual Lightspeed III and SD-8

Like I said, slightly larger fuse.    Normal operation lists an LSEIII at 7.5AMP requirement with a 10Amp fuse.  My reasoning is that doubling the initial fuse would allow the breaker to go first under normal circumstances.  I do agree that a slo-blo type fuse would probably decrease the likeliness of the fuse blowing first.



  I would just assume deal with this back at the batteries but it's not practical to have the CB's back there with no easy way to reset when I'm flying alone troubleshooting an overly quiet engine.  I could feed one LSE from the main bus and the second directly from a battery which would probably cover most circumstances.



Michael



--

frank.hinde(at)hp.com
Guest

Posted: Tue Feb 03, 2009 2:35 pm Post subject: Z-14 with dual Lightspeed III and SD-8

Absolutely..Then ditch the mechanical fuel pump and put the electric pumps in the wingrrots.



You now have a vapour lock proof fuel system that will run on just about anything, including ethanol.



Slightly off topic but you'd be amazed at how many builders balk at two electric fuel pumps, but two EI's is perfectly acceptable.



Frank



RV7a..IFR All electric, fuel pumps included.



--

Sam

Joined: 18 May 2008
Posts: 135

Posted: Tue Feb 03, 2009 8:00 pm Post subject: Z-14 with dual Lightspeed III and SD-8

I seem to remember that a CB was used, so you could easily disconnect the power from the always hot bus, for example, when performing maintenance.



I once had a conversation with Klaus about some problems I was having during installation and told him I took power off a bus.  He was adamant that I follow the installation instructions and take power directly off the battery.  It ultimately turned that my problem was caused by too much clearance between the Hall sensor and the rotating magnets.

 

Sam

www.samhoskins.blogspot.com

 	  Quote: 	
		  	




On Tue, Feb 3, 2009 at 7:24 PM, bcondrey <bob.condrey(at)baesystems.com (bob.condrey(at)baesystems.com)> wrote:

 [quote]--> AeroElectric-List message posted by: "bcondrey" <bob.condrey(at)baesystems.com (bob.condrey(at)baesystems.com)>

  

 I actually don't have an issue with this behavior (crowbar design) as long as it's a published design feature.  Lacking that, there's nothing providing any clues to somebody installing these units that use of a CB vs a fuse should be considered mandatory.

  

 Text from the LSE Plasma III install instructions section 2.6:

 •       When connecting the power supply, route the positive lead to a 5A pull-able circuit breaker and then to the battery plus terminal, bypassing any electrical buss or master solenoid.  Refer to the Input Connector Diagram.

  

 At this point not having specifics about voltage level, duration, etc. that causes a crowbar event within the ignition is really just academic curiosity to me.  Real point is that there is apparently a crowbar circuit internal to the units that is meant to trip a CB if overvoltage is detected (maybe also overtemp?) and using an inaccessible fuse instead of a CB is just flat unacceptable (to me).  I haven't grounded the plane simply because I've got redundancy with a 12 volt Z-14 implementation with B&C alternators and regulators.  Not sure if the regulators are faster than the Plasma III, but since the Plasma III will accept 28 volt power I suspect the 12 volt regulator would trip an offending alternator offline before the Plasma III crowbarred.  Even if something went really wrong with an alternator/regulator and an ignition popped the fuse, I've still got a second, isolated system.  I will however be reconfiguring the ignition power supply wiring in the next couple of mont!

   hs.

 

 I hope nobody interprets me being sour on LSE, I actually love the ignitions!  Klaus can be a little difficult to deal with and I can also accept that.  My purpose was simply to inform of a failure mode.  Given that there are a lot of LSE ignitions in the field and a lot of those are being powered through, this can't be that big of a problem - except for the poor soul that has an overvoltage condition which then causes the big fan up front to stop.

  

 Bob

 

 

 

 

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Sam Hoskins
www.samhoskins.blogspot.com

hotwheels

Joined: 01 Jun 2007
Posts: 240

Posted: Wed Feb 04, 2009 9:26 am Post subject: Re: Z-14 with dual Lightspeed III and SD-8

Existing dual LSE systems may not have any way to alert the pilot of problems without the addition of the warning indicators.



Note this info posted at http://www.lsecorp.com/News/News.htm. 



start quote ---



All dual systems should have this warning feature. New Ignition Indicator Lights for Dual Plasma CDI Installations.



This simple application of 2 LED warning lights will alert the pilot when one of the systems is disabled either by the power switch, a failed breaker, or in the event of an internal problem.



Since the engine runs extremely well on one PLASMA CDI alone, a failure in the power supply, for example, might go unnoticed.  These ignition indicator lights give the pilot immediate notice that the engine is running on only one ignition system.



end quote ---



It would be tempting fate to install dual LSE without two isolated power sources and adequate circuit protection. It's also apparent that proper mounting / cooling are just as important as providing power. This information is adequately described in the LSE install manual although admittedly the crowbar circuit wasn't disclosed except via a side conversation.



It's prudent to follow the intent of the manufacturer's installation instructions or risk the consequences and end up as a feature story on the evening news.



Regards,

Jay

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