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Z-13/8 design and operating philosophy

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nuckolls.bob(at)cox.net
Guest

Posted: Sat Nov 22, 2008 8:33 am Post subject: Z-13/8 design and operating philosophy

 	  Quote: 	
		  >Hi Bob.  Love your book.


	


    Thank you. I'm pleased that you find it a good value.



 	  Quote: 	
		  >   On page 17-9 dealing with the SD-8 Alt, second column, second 

> paragraph.  I assume you would want to open the battery cont, 

> close the E-bus alt feed switch and close the SD-8alt control 

> relay (same as aux alt off/on swithch on Z-13 to on?)ONLY if the 

> main alt fails as mentioned in the next para?


	


    Yes. That was the original intent. E-bus alt feed is closed before

    you turn off the battery master for the purpose of load shedding

    during battery-only operations. To avoid having the e-bus go down

    during the changeover, you turn on alternate-feed first, battery

    master off next. SD-8 can go on at any time in the sequence.



    Now assuming that an SD-8 is installed, it may be brought on

    to support e-bus loads thus saving all the battery's stored

    energy to support approach to landing were the battery master

    is turned back on and other equipment items are added to

    the system loads.



 	  Quote: 	
		  >   Then will the SD-8 just be supplying pwr to charge the battery, 

> or will it directly be supplying pwr to the essential bus because 

> it is supplying more volts?


	


    It's a reasonable assumption that the battery was fully

    charged when the main alternator failed. There is no need

    for the SD-8 to "charge" the battery . . . it needs to support

    e-bus loads so as to NOT discharge the battery. As long as

    the SD-8 output remains above 12.7 volts or so, the battery

    will not contribute to operation of e-bus loads . . . i.e.

    is held in reserve.



 	  Quote: 	
		  >  Someone told me he flies around with his SD-8 aux alt switch on 

> all the time so there will never be a situation where there is no 

> missing pwr to the field to get it to work.  I don't think that is 

> the correct way is it? With the SD-8, is it best to assume the 

> endurance bus should not exceed about 7 amps (just under the ?


	


    He doesn't understand the equipment installed aboard

    his aircraft and has not crafted a Plan-A/Plan-B

    operating protocol based on understanding.



    His concerns for keeping the SD-8 "alive" are unfounded.

    First, the SD8 doesn't have an externally excited field.

    Second, assuming he has an active notification of low

    voltage (LV warning light) then the changeover from

    Plan-A to Plan-B after main alternator failure is

    a no-big-rush deal. The battery is sitting there

    substantially topped off and will run things nicely

    for some time . . . he could finish unwrapping his

    stick of gum and properly stow the wrapper before

    making the change.



    The SD-8 can be loaded to as much as 10A at cruise

    rpm without sagging below the 12.8 volt levels that

    begins to load the battery. There are no hard and fast

    "rules" about operations with the SD-8. Back before

    we installed SD-8's on a handy, vacated vacuum pump

    pad we sized AND MAINTAINED  batteries for the purpose

    of supporting e-bus loads to meet design goals.



    If the builder's design goals call for battery-only

    endurance to be equal to fuel endurance, then the

    options for battery-only ops were constrained

    by trade-offs for battery size versus endurance

    loads.



    Once a second engine driven power source is added,

    one may use ALL the capability of this source

    without taxing the battery. However, let us

    assume that endurance loads need to be 12 amps.

    Okay, 10A from the SD-8 and 2A from the battery.

    This formula for achieving comfortable termination

    of flight is still quite attractive.



    You make your own rules based on load analysis and design

    goals for operating YOUR CHOICE of endurance mode accessories

    and planning on how you'll supply that energy.



 	  Quote: 	
		  >   And finally, what is the best way to tie in dual LSEs and the 

> SD-8 together?  Thank you very much.  David Buntin


	


    Run each ignition from the battery bus on it's

    own fuse. Run only one ignition during endurance

    mode operations.



    Bob . . .

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longg(at)pjm.com
Guest

Posted: Sat Nov 22, 2008 9:48 am Post subject: Z-13/8 design and operating philosophy

Bob,



Thanks for updating our thinking. I too am going through this

installation.



Just to re-iterate the flow..



Low voltage condition or other on primary alt, so...



1. Switch main DC Power from Alt to Bat.

2. Shed un-necessary load.

2. Close the Alt E-Bus Feed switch.

2. Switch main DC Power from Bat to Off.

2. Switch on the Aux Alt SD-8 (After storing gum wrappers).

4. Fly to a safe place.

Thanks



--

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nuckolls.bob(at)cox.net
Guest

Posted: Sun Nov 23, 2008 1:38 pm Post subject: Z-13/8 design and operating philosophy

At 11:37 AM 11/22/2008, you wrote:

 	  Quote: 	
		  



Bob,



Thanks for updating our thinking. I too am going through this

installation.



Just to re-iterate the flow..



Low voltage condition or other on primary alt, so...



1. Switch main DC Power from Alt to Bat.

2. Shed un-necessary load.

2. Close the Alt E-Bus Feed switch.

2. Switch main DC Power from Bat to Off.

2. Switch on the Aux Alt SD-8 (After storing gum wrappers).

4. Fly to a safe place.


	




    That works. Just keep in mind that the whole idea

    behind artfully maintained batteries and second

    engine driven power sources is so that a "safe"

    place is also a comfortable, convenient place for

    effecting repairs to your machine. Further, all

    the goodies on the panel cannot offer the

    be-there-when-you-need-it utility of the stuff

    in your flight bag.



    Bob . . .



[quote]Thanks



--

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