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How reliable is reliable

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nuckollsr(at)cox.net
Guest

Posted: Sat Mar 17, 2007 2:52 pm Post subject: How reliable is reliable

At 05:10 PM 3/16/2007 -0700, you wrote:



 	  Quote: 	
		  



Out of curiosity Bob, would you then mainly advocate z-14 for new designs 

with a 20A alternator.  In the past it seems you have suggested z-14 over 

z-12 for people in the planning stages (correct me if I'm wrong).  Maybe a 

z-14 that uses the second bus as a smaller main alt. out e-bus, not used 

for starting...smaller battery...



In what instance would you use z-12 over z-14 with a 20A alternator? Save 

a little $ and #?



-Ryan (In the pondering stage)


	


To my way of thinking, perhaps 1-2% of all OBAM aircraft

under construction will be used in ways that justify a

Z-14 installation. Here's a post I made in 2005 to a similar

question:



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

At 08:46 PM 2/9/2005 +0100, you wrote:



<snip>



 	  Quote: 	
		  Thank you for your thoughtful reply. The 2 batt/2 alt setup (Z11) did get me

excited but the type of flying (very occasional dusk VFR, no IFR, over water

at times) plus a common sensical KISS principle to govern decisions may

dampen my enthusiasm for Z11.


	


   Let's try to put some things into perspective. There are tons

   of dark-n-stormy night stories wherein alternators and batteries

   are star performers in the role of villain. Given the proven

   reliability of modern automotive alternators . . . in particular

   the converted Nipon Denso products from B&C . . . probability

   of alternator failure is a small fraction of what we've come to

   expect from certified iron. Combine this with the very robust,

   sealed lead-acid batteries -AND- a truly meaningful preventative

   maintenance plan and we've beat the worst worries into submission.



   If one simply installs Van's a-la C-172 wiring with a modern

   alternator and well maintained RG battery, probability of

   having to take a staring role in a dark-n-stormy night play

   due to electrical systems issues is very low.



   By taking advantage of variations on a theme described in the

   z-figures, one can push those probabilities still lower. In

   10+  years of suggesting builders consider the e-bus, I've

   had only one reader write and tell me the e-bus turned an

   alternator failure into a ho-hum event. However, I've had

   perhaps a half dozen people write and thank me for the OVM-14

   crowbar ov module. Far more folks have experienced an ov

   condition that forced alternator shutdown than simple

   alternator failure. I don't recall the numbers of ov

   experiences that benefited from an e-bus installation after

   the alternator was shut off. Even if the builder did not

   have an e-bus, keeping a well maintained RG battery on

   board goes a long way to saving the day.

 	  Quote: 	
		  In the final analysis, I think it all boils down to whether I want full

electronic ignition, partial, or all mags.


	


  If you go electronic ignition, consider at least one p-mag

  which does not depend on electrical system for operation.

 	  Quote: 	
		  I am finishing the wings which means that I have a long way to go - you'll

see my posts as the situation evolves.


	


   I have a client with enough funds to strive for the

   "ultimate" system which may include dual efis, dual

   electronic ignition, dual autopilots . . . For the

   moment, I'm still trying to justify ruling out

   a Figure Z-13/8 installation thus saving about a 23

   pound penalty for going with Z-14.



   Reliability doesn't have to be heavy or expensive . . .

   just well considered. Since the e-mag/p-mag guys

   came along, reliability is getting easier, lighter

   and less expensive all the time.

------------------ end of quotation -------------------------



   If I owned a certified machine, I would endeavor to

   (1) add ACTIVE NOTIFICATION OF LOW VOLTAGE. (2)

   install and MAINTAIN an RG battery. (3) Modify

   the architecture to turn the avionics bus into an

   E-BUS. (4) When an if the stock alternator craps,

   I'd get a modern automotive adaptation in place.



   These simple changes alone would elevate the spam

   can's SYSTEM reliability by a quantum jump. Implementation

   of an e-bus/bat-maintenance protocol makes the vast

   majority of demonstrated concerns go away. Virtually

   every dark-n-stormy night story I've read that concerned

   electrical systems would never had been written had

   the owner-operators of the subject airplanes availed

   themselves of the knowledge and understanding offered

   to you here on this List.



   Now, if you don't plan to have a vacuum system then

   the vacuum pump pad is open and you'll be many watt-hours

   ahead in planning for alternator failure by adding the

   SD-8 and perhaps even downsizing the battery for a wash

   in weight.



   Z-13/8 is an exceedingly robust system that should

   handle everything you or I would want to do at

   reliability levels that far exceed those of the

   certified ships that we're ALREADY using do do the

   same kinds of flights.



   Now, Z-12 and Z-14 have some appeal but I'd recommend

   Z-12 only as an upgrade to an existing Z-11 or spam-can

   clone and Z-14 for ships like a Lancair IVP with full-up

   dual IFR panels.



   Obviously, if you have the $time$ and don't mind the

   weight, you can pile on as many backups to backups that

   suits your worry levels . . . but I'll suggest that

   Z-13/8 is the value leader in return for reliability

   with the lowest investment in $time$ and loss of

   payload.



   It would cost more dollars and talented manpower than

   you or I are willing to expend to put numbers on the

   relative reliability of Z-13/8 vs Z-14 for the various

   operating scenarios. But it's my considered judgement

   that Z-14 is overkill for most of the OBAM aircraft

   under construction.



   Bob . . .

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ryan42

Joined: 06 Jul 2006
Posts: 14

Posted: Sun Mar 18, 2007 5:20 pm Post subject: Re: How reliable is reliable

 	  Quote: 	
		  Z-13/8 is an exceedingly robust system that should 

handle everything you or I would want to do at 

reliability levels that far exceed those of the 

certified ships that we're ALREADY using do do the 

same kinds of flights. 



Now, Z-12 and Z-14 have some appeal but I'd recommend 

Z-12 only as an upgrade to an existing Z-11 or spam-can 

clone and Z-14 for ships like a Lancair IVP with full-up 

dual IFR panels. 



Obviously, if you have the $time$ and don't mind the 

weight, you can pile on as many backups to backups that 

suits your worry levels . . . but I'll suggest that 

Z-13/8 is the value leader in return for reliability 

with the lowest investment in $time$ and loss of 

payload. 



It would cost more dollars and talented manpower than 

you or I are willing to expend to put numbers on the 

relative reliability of Z-13/8 vs Z-14 for the various 

operating scenarios. But it's my considered judgement 

that Z-14 is overkill for most of the OBAM aircraft 

under construction. 	




That sounds entirely reasonable.  It just seems that by removing the z-13/20 drawing (which I have no problem with), IF the airplane meets the kind of requirements and worry levels to warrent a backup 20 amp alternator, it sounds like you suggest z-14 over z-12 for new ships?

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nuckollsr(at)cox.net
Guest

Posted: Sun Mar 18, 2007 7:49 pm Post subject: How reliable is reliable

At 06:20 PM 3/18/2007 -0700, you wrote:



 	  Quote: 	
		  

 > Z-13/8 is an exceedingly robust system that should

 > handle everything you or I would want to do at

 > reliability levels that far exceed those of the

 > certified ships that we're ALREADY using do do the

 > same kinds of flights.

 >

 > Now, Z-12 and Z-14 have some appeal but I'd recommend

 > Z-12 only as an upgrade to an existing Z-11 or spam-can

 > clone and Z-14 for ships like a Lancair IVP with full-up

 > dual IFR panels.

 >

 > Obviously, if you have the $time$ and don't mind the

 > weight, you can pile on as many backups to backups that

 > suits your worry levels . . . but I'll suggest that

 > Z-13/8 is the value leader in return for reliability

 > with the lowest investment in $time$ and loss of

 > payload.

 >

 > It would cost more dollars and talented manpower than

 > you or I are willing to expend to put numbers on the

 > relative reliability of Z-13/8 vs Z-14 for the various

 > operating scenarios. But it's my considered judgement

 > that Z-14 is overkill for most of the OBAM aircraft

 > under construction.

That sounds entirely reasonable.  It just seems that by removing the 

z-13/20 drawing (which I have no problem with), IF the airplane meets the 

kind of requirements and worry levels to warrent a backup 20 amp 

alternator, it sounds like you suggest z-14 over z-12 for new ships?


	




    Depends on the airplane and the missions. If you're

    building a long-legged, $200,000 cross country rocket

    and you intend to spend hours crossing weather fronts,

    then something like Z-14 (along with a second pilot

    in the right seat) is the uptown way to go.



    If you have an as-purchased airplane wired ah-la C172/

    A-36 and you'd like to go all-electric with minimal

    changes to the system, then Z-12 is an option to consider.



    If you're starting from scratch and intend to use your

    airplane like 95% of your brothers use their airplanes,

    then I'm betting that Z-13/8 has a high probability of

    meeting your mission requirements at a minimum of

    cost and weight.



    Bob . . .



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

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

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

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