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Bob Nuckolls's Z-14 with dual Lightspeed iii and SD-8

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jan 26, 2009 7:01 am Post subject: Bob Nuckolls's Z-14 with dual Lightspeed iii and SD-8

At 02:12 PM 1/25/2009, you wrote:

 	  Quote: 	
		  



Busy building an RV-8 with dual LS Plasma III (crank sensor) and 

would appreciate some input on Z 14 changes required for my set-up.



Engine drives a B & C 60 Amp main Alt, and a SD-8 as back-up .


	


   Don't recommend Z-14 for this combination of altenrators.

   Suggest you consider Z-13/8



 	  Quote: 	
		  I wish to install 2 x 17aH batteries as per Bob's drawings and  I 

would like to know whether:-

1) the 2 shunts depicted on Z14 need to be changed to 50mv/60A and 

..50mv/10A.?.


	


   The shunts should match their respective alternator ratings.

 	  Quote: 	
		  2) Klaus Savier recommends 2 x 5A "pull-able" C.B.s....Could I 

substitute these for fuses of 5A each?


	


   It's your airplane. 5A fuses on battery busses is a

   perfectly



 	  Quote: 	
		  3) Could these be placed as per Z14 , #1 on the Main Batt bus and on 

Aux Batt. the other?


	


   It's my recommendation that accessories for electrically

   dependent engines be powered from a battery bus.



 	  Quote: 	
		  4) Any other changes I should contemplate, as I would like the 

engine  to start only  from the grip of my Infinity stick.


	


   Are you planning on some means by which the starter

   button becomes disabled for flight?

 	  Quote: 	
		  5) I  am also installing a GRT HX  & EIS 4000..any caveats/advice on 

any additional systems/relays required on Z14 for these, or those below??


	




   Z-13/8 will offer overall system reliability that

   would exceed the contemporary single-engine airplane

   by at least an order of magnitude.

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jan 26, 2009 10:26 am Post subject: Bob Nuckolls's Z-14 with dual Lightspeed iii and SD-8

At 08:20 AM 1/26/2009, you wrote:

 	  Quote: 	
		  



Rob,



I am installing the same dual plasma III in my Lancair. I am however

using Z-13/8 with one battery instead of two. I have yet to hear a good

argument as to why two batteries are better than two alternators. LS

does recommend a 4.5 amp battery behind a Schottky diode which I may

consider paralleling with the main at some time. The diode is about

$2.00 and the battery about $35. This is an easier/lower cost solution

than fussing with all the extras on Z14.



I also found the answer to the constant whining of pilots over fuse

blocks and cb's - use both  You can tell Klaus's lawyers you had them

tied to cb's. If you use the below with the Bussman panel, you now have

the best of both worlds.



See...



https://www.alliedelec.com/Search/ProductDetail.aspx?SKU=6770385


	


    These are pretty cheesy breakers. They're

    also more massive than the fuses they replace which

    degrades longevity of the gas-tight grip on the

    connection tabs. I do not recommend their use.

 	  Quote: 	
		  Your shunt should be rated in conjunction with the alternator. No more,

no less. Use the ANL to drop amperage if desired and size the wire in

front and behind it accordingly. Think of the ANL as a step down

transformer, not the shunt.


	


    ??? The ANL is an exceedingly robust fuse . . . so

    robust that they call them "current limiters". What's

    NOT readily apparent in their marked ratings is just

    how robust they are. See:



http://aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ANL_Specs.pdf



    Note that a 35A rated ANL will carry 80A continuously

    at room temperature. A 60A rated device will sniff

    at about 160A continuous. Note further that a fault

    current of 250A opens both devices in 250 mS or less.

    The fault for which we use current limiters is the

    HARD fault that will load a BATTERY to hundreds if

    not 1000+ amps.



    To depend on the ANL for any other fault condition

    is to ignore the design goals that controlled its

    design.

 	  Quote: 	
		  You can install whatever battery/alt you choose. Z14 was designed as a

purely redundant system rather than an economical fly to safety system

like Z13/8.


	


    Correct. I suspect that less than 1% of OBAM aircraft

    flying can justify Z-14. Sadly, I suspect that way

    too many builders have installed Z-14 style systems

    with some notion that it adds to safety. This simply

    isn't so. Unless you spend a SIGNIFICANT percentage

    of your flight time pushing into the corners of pilot,

    aircraft and weather combinations . . . Z-14 only

    adds unjustifiable weight, cost, complexity and higher

    maintenance $time$ to an airplane that simply doesn't

    need it.

 	  Quote: 	
		  I'm not sure if they sell handi-capped switch for folks that can't reach

the panel from their seat to start the engine, but there's no reason you

couldn't do a relay for the starter switch and even a remote starter if

you have FADEC. For me, I'd rather just lean over, push button - go. $20

and 15 minutes to install a starter button. If you're really lazy you

could wire one of those remotes to open the hanger door, turn on the

lights and start the coffee in the hangar before you get up the hill.

All from the stick.


	


    Agreed. Starting the engine is a few seconds per flight

    cycle, even fewer seconds per flight hour. "Convenience"

    added at the expense of increased parts count only improves

    on the probability of having to fix some crapped-out

    convenience component without adding to the utility/

    enjoyment of flying the airplane.

 	  Quote: 	
		  You need to protect your avionics equipment per the manufacturer

recommendation. I think GRT's are about 3 amps. Remember, you are

protecting the wire in front of the device as well as the devices. If

you are pushing 20A through a wire rated for 3A on your GRT, you've got

something backwards. Remember, step it down before you deliver. Don't

introduce parts and complexity with relay's unless you really need them.

Half of the stuff in my panel is pulling less than 3 amps, even the

strobe lights.


	


    Agreed. When we're considering the design goals for

    a TC system, the first rule is MEET ALL PERFORMANCE

    GOALS consistent with MINIMIZED WEIGHT, VOLUME, and

    PARTS COUNT. The latter three criteria generally go

    hand-in-hand with MINIMIZED COST OF OWNERSHIP.

 	  Quote: 	
		  Life is easy, keep it simple. You don't need 3 batteries to be safe. You

do need to give lots of TLC to the one or two batteries you do have and

change them regularly. Don't wait for problems to arise before deciding

you should beef up your system to overcome poor maintenance on your

part.


	


    Exactly!  EVERY flight plagued with a tense if not

    unhappy outcome happens for some combination of three

    reasons: (1) Lack of understanding that gives rise to (2) poor

    selection/attainment of design goals and/or (3) failure

    to maintain performance consistent with those goals.



    If you don't understand what you're doing and why you're

    doing it, then "adding more goodies for the purpose of

    adding safety" is at best a tax on cost of ownership;

    at worst a sad disappointment. The simplest, lightest,

    easiest to understand flight system with well considered

    Plan-A/Plan-B and maintenance will never be root cause

    of a bad termination of flight.



    Very few TC aircraft are blessed with such attention

    to detail for reasons that are clear. As both designer,

    builder, owner and operator of your OBAM aircraft, you're

    offered an opportunity that exceedingly few of our

    Spam-Can flying brothers will enjoy.



    But if it were easy, everybody would be doing it.



    Bob . . .

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bcondrey

Joined: 03 Apr 2006
Posts: 580

Posted: Sat Jan 31, 2009 1:28 pm Post subject: Re: Bob Nuckolls's Z-14 with dual Lightspeed iii and SD-8

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.  



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.



Bob

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