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Dead Horses don't die...

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Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Tue Oct 24, 2006 6:39 pm Post subject: Dead Horses don't die...

Apologies to belabor these two points, but another builder I know is dead-set on the ol' Cessna Split Master switch and a separate Avionics master.  As a long-time Nuckollhead, my plane is faithfully a Z-11, and electrically all runs, all hits, no errors.  My protestations have come to naught despite my best explanations.  

  

 The Avionics Master won't die because so many radio makers still insist on them by inclusion in installation schematics and threats of no warranty coverage if not used.  (I know this was true of Jicroair when I installed mine, and I have requests out to GRT, Trutrak and Garmin for clarification)  I suppose one could feed avionics by connecting a separate fuse block to the normal supply side of the e-bus through an "Avionics Master Switch" and accept the single-point failure potential.  

  

 On the split master side, I could propose using the switch, provided crowbar protection and low-voltage monitor/annunciation are employed.

  

 In order to offer guidance, I have searched the A-list archives & AeroElectric Connection website for supporting documentation and found Bob's article on Avionics Masters, but not the critical arguments I have seen for the past six or seven years supporting avoidance of the split master.  Can someone please point to specific references?

  

 Sorry for the broad request, but I am trying to spread the gospel here!

  

 Mark Phillips RV-6A with 366 hours of happy electrons...

  [quote][b]

_________________
From The PossumWorks...

nuckollsr(at)cox.net
Guest

Posted: Thu Oct 26, 2006 6:37 pm Post subject: Dead Horses don't die...

At 11:06 PM 10/22/2006 -0400, you wrote:



 	  Quote: 	
		  Apologies to belabor these two points, but another builder I know is 

dead-set on the ol' Cessna Split Master switch and a separate Avionics 

master.  As a long-time Nuckollhead, my plane is faithfully a Z-11, and 

electrically all runs, all hits, no errors.  My protestations have come to 

naught despite my best explanations.



The Avionics Master won't die because so many radio makers still insist on 

them by inclusion in installation schematics and threats of no warranty 

coverage if not used.  (I know this was true of Microair when I installed 

mine, and I have requests out to GRT, Trutrak and Garmin for 

clarification)  I suppose one could feed avionics by connecting a separate 

fuse block to the normal supply side of the e-bus through an "Avionics 

Master Switch" and accept the single-point failure potential.


	


   Not necessary. Run your "critical" items from the e-bus and

   put a switch in series with the e-bus normal feed path diode

   and call it the "avionics master switch". I will write to

   Trutrak and Garmin and inquire as to any special knowledge

   they have for the evils that lurk on the bus which are held

   at bay by the avionics master switch. Anyone laying any bets?

   When I wrote the article on avionics master switches over

   10 years ago, it had to be noticed by about 130,000 aviation

   types all over the world. NOT ONE individual contacted me

   to explain where I was wrong or even to complain about

   going against tradition.



   I know that Microair did not do their homework and build

   power handling circuitry that was NOT DO-160 qualifiable

   (20v for 1 S, 40v for 100 mS). That's why I stopped handling

   them . . . they knew their limitations and in spite of

   offers of free help, they elected to drive on as-is.



   But that still begs the question:



   Assume a radio IS vulnerable to start-up transients,

   where is it written that it's better to have ONE switch

   turn off all vulnerable radios as opposed to turning each

   vulnerable radio off with its own power switch? Just because

   there's only ONE switch to 'remember' doesn't make it any

   more likely to be operated at the right times. Failures to

   observe checklists have been demonstrated innumerable times.

   So if you can follow a checklist, turn off devices for which

   there are concerns. If you can't follow a checklist, then

   no number of switches installed anywhere will be a 100%

   prophylactic against gremlins that go spark in the dark.



 	  Quote: 	
		  

On the split master side, I could propose using the switch, provided 

crowbar protection and low-voltage monitor/annunciation are employed.



In order to offer guidance, I have searched the A-list archives & 

AeroElectric Connection website for supporting documentation and found 

Bob's article on Avionics Masters, but not the critical arguments I have 

seen for the past six or seven years supporting avoidance of the split 

master.  Can someone please point to specific references?


	


   There is nothing functionally wrong with the split-rocker

   switch. It was cleverly conceived when aviation decided to

   eliminate the possiblity of leaving an alternator on-line

   without also having a battery . . . but being able to run

   the battery by itself too.



   The S700-2-10 shown in most of the Z-figure master switches

   duplicates the split rocker functionality: OFF/BATTERY/BAT+ALT

   The split rocker has been elevated to a position of sainthood.

   I've seen all manner of toggle and rocker switch installations

   on OBAM aircraft where that infernal split-rocker has been

   enshrined in a place of prominence on the panel . . . even tho

   it doesn't look like any of the other switches.



   The point is, if you can purchase the progressive transfer,

   ON-ON-ON functionality in the switch style of your choice, then

   you need not genuflect before the alter of split-rocker switches

   from the certified world. The 2-10 switching protocols do the same

   thing in what ever style switch you choose.



   Bob . . .

Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Thu Oct 26, 2006 7:22 pm Post subject: Dead Horses don't die...

In a message dated 10/26/2006 9:42:25 PM Central Daylight Time, nuckollsr(at)cox.net writes:

  	  Quote: 	
		  Anyone laying any bets? 	


 >>>>>>>>>>>>>>>>>>>>>>>>>>>>

  

 Here's response from GRT- not sure I unnerstand it, tho- I have heard that main complaint is that voltage sag whilst firing up the Lycosaur will cause Horizons to re-boot.  Doesn't seem like a big problem since by the time you get to run-up all is back to normal. Original request below their response- GRT sez:

  

 "EIS on during engine start is correct, the EFIS system should be off during engine start.  The EFIS system has 3 power bus inputs so you could connect DU-1 input 1 to your Endurance bus and input 2 to your Main bus.  You would connect DU-2 input 1 to your main bus and input 2 to your Endurance bus.  Input 3 on both units could go to a small back up battery.  Your AHRS inputs would be the same as DU-1.  There are many ways to go on this."

  

  

 [quote] ---

_________________
From The PossumWorks...

bicyclop(at)pacbell.net
Guest

Posted: Fri Oct 27, 2006 12:20 am Post subject: Dead Horses don't die...

Our RV was wired something like this when we got it - with a switch

labeled "E-Bus" but which I thought of as an avionics master because the

radios wouldn't come on without it even with the master on. In fact it

was a switch/breaker. When I recently remade the panel, that same

switch/breaker fell apart in my hands while I was removing it from the

old panel. A single point of failure which, fortunately, failed on the

ground. There was an alternate feed switch, so I guess the switch

failure wouldn't have been a horrible thing in flight, but none the

less, I didn't include it in the new version of the panel. I figure that

it can't hurt to exercise all the radio switches regularly anyway so we

switch them off after each flight.



We do have a couple of items that don't like being on during engine

cranking. One is a Dynon D-10 which browns out and sometimes doesn't

come back so we've put an item in our checklist to pull its breaker

before start. The other is a Trio autopilot which the installation

instructions state not to subject to the reduced voltage of cranking so

we switch it on after startup. Some stuff is still out there that need

some kind of protection to avoid problems.



Pax,



Ed Holyoke




<nuckollsr(at)cox.net>



I suppose one could feed avionics by connecting a separate 

 	  Quote: 	
		  fuse block to the normal supply side of the e-bus through an "Avionics 

Master Switch" and accept the single-point failure potential.


	


   Not necessary. Run your "critical" items from the e-bus and

   put a switch in series with the e-bus normal feed path diode

   and call it the "avionics master switch".

khorton01(at)rogers.com
Guest

Posted: Fri Oct 27, 2006 1:31 am Post subject: Dead Horses don't die...

On 26 Oct 2006, at 22:34, Robert L. Nuckolls, III wrote:



 	  Quote: 	
		   

 <nuckollsr(at)cox.net>



   I know that Microair did not do their homework and build

   power handling circuitry that was NOT DO-160 qualifiable

   (20v for 1 S, 40v for 100 mS). That's why I stopped handling

   them . . . they knew their limitations and in spite of

   offers of free help, they elected to drive on as-is.




	


I've got a Microair com in my not-yet-flying aircraft.  I don't have  

an avionics master.  What sorts of problems can I anticipate due to  

the power handling issues?  Do I need to have the radio OFF during  

start up and shut down?



Kevin Horton         RV-8 (finishing kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

khorton01(at)rogers.com
Guest

Posted: Fri Oct 27, 2006 1:39 am Post subject: Dead Horses don't die...

On 26 Oct 2006, at 23:21, Fiveonepw(at)aol.com wrote:



[quote] And here is response from Garmin- again, original request below:



 "Garmin recommends that these units no be power up during engine  

 start to

 prevent voltage spike damage. "

 George Koelsch

 Garmin International

 Aviation Field Service Engineer

 george.koelsch(at)garmin.com

 913-397-8200



 --

Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Fri Oct 27, 2006 4:02 am Post subject: Dead Horses don't die...

In a message dated 10/27/2006 4:35:56 AM Central Daylight Time, khorton01(at)rogers.com writes:

  	  Quote: 	
		  What sorts of problems can I anticipate due to  

the power handling issues?  Do I need to have the radio OFF during  

start up and shut down? 	


 >>>>>>>>>

 "Radios ON/OFF" are checklist items for me- haven't seen any negative effects from radio yet when "OFF" item missed, but T2000 xpndr does seem to behave oddly if left on at shutdown.  "No Comm" errors, turning itself on before Master shut off, difficult to turn on (occasionally requires several attemps holding power button in) but otherwise seems to work fairly well.

  

 My 760 transmits very well, but reception from maybe 20% of other aircraft (ATC and unicoms always come in well) typically with older radios, is garbled in varying degrees and on rare occasions almost non-existent.  Haven't been able to resolve yet- curious if others experience this.  Close formation reception is often garbled- added resistor to antenna line as discussed here some time ago (thanks Bob!) helped quite a bit, but will upsize resistor at next opportunity & see if improves...

  

 Mark Phillips -6A, 360 hours

  [quote][b]

_________________
From The PossumWorks...

ceengland(at)bellsouth.ne
Guest

Posted: Mon Oct 30, 2006 5:57 pm Post subject: Dead Horses don't die...

Kevin Horton wrote:

 	  Quote: 	

 <khorton01(at)rogers.com>

 On 26 Oct 2006, at 22:34, Robert L. Nuckolls, III wrote:

> 

> <nuckollsr(at)cox.net>

>

>   I know that Microair did not do their homework and build

>   power handling circuitry that was NOT DO-160 qualifiable

>   (20v for 1 S, 40v for 100 mS). That's why I stopped handling

>   them . . . they knew their limitations and in spite of

>   offers of free help, they elected to drive on as-is.

>

 I've got a Microair com in my not-yet-flying aircraft.  I don't have  

 an avionics master.  What sorts of problems can I anticipate due to  

 the power handling issues?  Do I need to have the radio OFF during  

 start up and shut down?

 Kevin Horton         RV-8 (finishing kit)

 Ottawa, Canada

 http://www.kilohotel.com/rv8 

I'm flying a 15 year old -4 that I've owned for 3 1/2 years. It's got a 

dirt simple electrical system with a Microair comm that I never turn 

off. I'm not proud of it, but there...I've admitted it. No problems so far.

Charlie

nuckollsr(at)cox.net
Guest

Posted: Tue Oct 31, 2006 5:48 am Post subject: Dead Horses don't die...

<nuckollsr(at)cox.net>



   I know that Microair did not do their homework and build

   power handling circuitry that was NOT DO-160 qualifiable

   (20v for 1 S, 40v for 100 mS). That's why I stopped handling

   them . . . they knew their limitations and in spite of

   offers of free help, they elected to drive on as-is.

I've got a Microair com in my not-yet-flying aircraft.  I don't have

an avionics master.  What sorts of problems can I anticipate due to

the power handling issues?  Do I need to have the radio OFF during

start up and shut down?



Kevin

I'm flying a 15 year old -4 that I've owned for 3 1/2 years.

It's got a dirt simple electrical system with a Microair

comm that I never turned off. I'm not proud of it, but

there...I've admitted it. No problems so far. . .



Charlie



     And there's no particular reason to expect problems.

     The fact that MicroAir products have successfully survived

     all these years in hundreds if not thousands of airplanes

     is largely due to the fact that the dreaded and much touted

     startup spikes simply don't exist. The DO-160 rationale

     for transient withstand has to do with ability to survive

     the abnormal conditions of alternator runaway and/or

     alternator load-dump transients.



     Very few folks experience such events but if they do,

     it's while things are expected to be operating normally

     and the radio is ON. No amount of avionics master switches

     or observance of checklists will provide protection

     from these events. This is why the industry recommends

     designing and testing to those qualities.



     If I were to exercise the-best-we-know-how-to-do in

     the purposeful installation of sub-standard accessories,

     I suppose we could fabricate some sore of protected

     power conditioning system that would provide voltage

     limiting friendly to our relatively fragile purchases.

     But as many, many users have noted, the risk are low

     and adding such features to the system as Band-Aids

     is not good engineering.



     Don't loose any sleep over your MicroAir accessories.



        Bob . . .

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

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

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

nuckollsr(at)cox.net
Guest

Posted: Wed Nov 01, 2006 6:47 am Post subject: Dead Horses don't die...

At 08:00 AM 10/27/2006 -0400, you wrote:



 	  Quote: 	
		  In a message dated 10/27/2006 4:35:56 AM Central Daylight Time, 

khorton01(at)rogers.com writes:

What sorts of problems can I anticipate due to

the power handling issues?  Do I need to have the radio OFF during

start up and shut down?



 >>>>>>>>>

"Radios ON/OFF" are checklist items for me- haven't seen any negative 

effects from radio yet when "OFF" item missed, but T2000 xpndr does seem 

to behave oddly if left on at shutdown.  "No Comm" errors, turning itself 

on before Master shut off, difficult to turn on (occasionally requires 

several attemps holding power button in) but otherwise seems to work 

fairly well.



My 760 transmits very well, but reception from maybe 20% of other aircraft 

(ATC and unicoms always come in well) typically with older radios, is 

garbled in varying degrees and on rare occasions almost 

non-existent.  Haven't been able to resolve yet- curious if others 

experience this.


	


    Hmmm. . .  it would be really interesting to bench check

    some of these "problem" radios. I think I'll put a nice

    signal generator in my letter to Santa Claus.



 	  Quote: 	
		     Close formation reception is often garbled- added resistor to antenna 

 line as discussed here some time ago (thanks Bob!) helped quite a bit, 

 but will upsize resistor at next opportunity & see if improves...


	


    Let us know what size resistor you ultimately find adequate.

    Thanks!



    Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Wed Nov 01, 2006 6:50 am Post subject: Dead Horses don't die...

Inquiry:

I have on order from an avionics installer a GNS430, SL30 and

GTX327- I wish to avoid a separate avionics bus and plan to power these 

from my

endurance bus fuseblock, which is hot whenever the master contactor is on per

Bob Nuckolls' AeroElectric Connection system architecture.  Is this

acceptable or must I make sure these units are not powered up during engine

start?



 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>



   Interesting.  The installation manuals for the GNS-430 and the

   GTX-327 claim DO-160 Category A qualification for voltage spikes (I

   don't have an SL-30 Installation manual to look at).  Are they saying

   that they don't trust their test results, or that they didn't really

   do the test?  Or that they think the real world might be worse than

   the DO-160 requirements?



   Kevin Horton         RV-8 (finishing kit)

   Ottawa, Canada

     Funny you should ask. I've asked it dozens of

     times over the years of various promulgators of

     avionics master switches . . . I've yet to received

     a reasoned reply.

        Bob . . .

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

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

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

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