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Avionics Master

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gmvouga(at)hotmail.com
Guest

Posted: Mon May 14, 2007 6:29 pm Post subject: Avionics Master

All,



I'm working on my panel and I'm trying to decide if I should put an Avionics 

Master switch.  In my experience with rental planes this was nice to have 

since there was one switch to turn everything on or off during engine start 

or shutdown.



Is there any reason not to add this feature?  I'm planning an E-Bus and Main 

Bus configuration similar to the Z-13/8 design.



Thanks



_________________________________________________________________

Make every IM count. Download Messenger and join the i’m Initiative now. 

It’s free. http://im.live.com/messenger/im/home/?source=TAGHM_MAY07

nuckollsr(at)cox.net
Guest

Posted: Mon May 14, 2007 7:57 pm Post subject: Avionics Master

At 07:28 PM 5/14/2007 -0700, you wrote:



 	  Quote: 	
		  



All,



I'm working on my panel and I'm trying to decide if I should put an 

Avionics Master switch.  In my experience with rental planes this was nice 

to have since there was one switch to turn everything on or off during 

engine start or shutdown.



Is there any reason not to add this feature?  I'm planning an E-Bus and 

Main Bus configuration similar to the Z-13/8 design.


	


   Why "similar to"? What feature do you find missing

   or performance goal that has gone lacking. Goto



http://aeroelectric.com



   . . . and put 'avionics master' in the search box.

   After reviewing the discussions, help us out by

   citing where you perceive a return on investment for

   having the feature.

   Bob . . .



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

        ( "Physics is like sex: sure, it may   )

        ( give some practical results, but     )

        ( that's not why we do it."            )

        (                                      )

        (                 Richard P. Feynman   )

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

fvalarm(at)rapidnet.net
Guest

Posted: Mon May 14, 2007 8:19 pm Post subject: Avionics Master

Greg,



It's been discussed several times and as I recall, the reason to not do it

is a) theoretical single point of failure, and b) no real good reason to do

it.



Bevan

RV7A

Wiring and misc panel work



--

mwcreek(at)frontiernet.ne
Guest

Posted: Mon May 14, 2007 9:45 pm Post subject: Avionics Master

This is an excerpt from the GRT install manual referring to the use of an

avionics master (at least that is what I read into it).  Perhaps Bob can

clear this up as it is somewhat ambiguous.



Power Connections

The display units each include 2 isolated power input connections. This

allows redundant power sources, such as a main and secondary bus. The

display units consume approximately 1 amp, making even a small 3 Amp-Hour

gel cell a suitable emergency source.



The configuration of the power supplied to the display unit(s) is left to

the installer. Considerations such as the number of power buses, the desire

or not to supply one pieceof equipment with power from redundant buses

(which in theory allows the possibility of one device affecting both buses),

the configuration of the electrical system with respect to backup equipment,

and so on, may dictate the best configuration for a particular airplane.



No provision is included within the display units for a power switch. If a

power switch is desired for the EFIS, the +12V power should be controlled

with the switch (not ground). The display units include internal

thermally-activated fuses. This protects the equipment from internal

electrical faults. Power supplied to the EFIS must pass through a fuse or 4

circuit breaker or fuse. It should be sized to allow at least 1.5 amps per

display unit, with a maximum rating of 5 amps.



The AHRS and display units monitor all of their power inputs, and alarms are

available to annunciate the loss of any power source that was provided and

is expected to be working according to the "General Setup" menu.

The majority of the current flow into the display unit will occur on the bus

with thehighest voltage.



It is desirable to have the display units and AHRS off during the engine

start if all of the buses which power them are used for supplying power to

the engine starter. This maximizes the current available for the starter,

and may extend the life of the CCFL backlight in the display unit.

--

gmvouga(at)hotmail.com
Guest

Posted: Tue May 15, 2007 5:31 am Post subject: Avionics Master

Bob,

I wanted to use the LR-3 controller and the SD-8, but I didn't find a design 

that incorporated both.  So, my electrical system is kind of a combination 

of Z-12 and Z-13/8.  I started with the Z-12 and then removed the circuit 

with the SB-1/20A alternator.  Then I added the SD-8/regulator circuit from 

Z-13/8.

You are right about the search engine.  I actually hit send on my email and 

then instantly remembered that I should have checked the archives first.  Of 

course, I found that this subject has been discussed several times before.

My initial reasoning was to protect my "sensitive" avionics during power 

fluxuations during startup and shutdown.  It seams that modern avionics 

should not have this problem according to your comments in the past.  

However, I am using some experimental electronics that may or may not have 

gone through extensive testing for power fluxuations.  I agree that the 

manufacturers should have made their products robust enough, but did they?  

I'm not sure we can know for sure unless someone tests the units thoroughly 

either in the lab or just through normal use.

Greg

 	  Quote: 	
		  From: "Robert L. Nuckolls, III" <nuckollsr(at)cox.net>

Reply-To: aeroelectric-list(at)matronics.com

To: aeroelectric-list(at)matronics.com

Subject: Re: Avionics Master

Date: Mon, 14 May 2007 22:56:09 -0600

<nuckollsr(at)cox.net>

At 07:28 PM 5/14/2007 -0700, you wrote:

>

><gmvouga(at)hotmail.com>

>

>All,

>

>I'm working on my panel and I'm trying to decide if I should put an 

>Avionics Master switch.  In my experience with rental planes this was nice 

>to have since there was one switch to turn everything on or off during 

>engine start or shutdown.

>

>Is there any reason not to add this feature?  I'm planning an E-Bus and 

>Main Bus configuration similar to the Z-13/8 design.

   Why "similar to"? What feature do you find missing

   or performance goal that has gone lacking. Goto

http://aeroelectric.com

   . . . and put 'avionics master' in the search box.

   After reviewing the discussions, help us out by

   citing where you perceive a return on investment for

   having the feature.

   Bob . . .

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

        ( "Physics is like sex: sure, it may   )

        ( give some practical results, but     )

        ( that's not why we do it."            )

        (                                      )

        (                 Richard P. Feynman   )

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

_________________________________________________________________

Catch suspicious messages before you open them—with Windows Live Hotmail.

redeloach(at)fedex.com
Guest

Posted: Tue May 15, 2007 5:49 am Post subject: Avionics Master

Why can one not just use the "off/on" switch on each device ?

:}

---

mlas(at)cox.net
Guest

Posted: Tue May 15, 2007 6:27 am Post subject: Avionics Master

Check the $price$ of that on/off switch in the radio and how much it

cost to have it changed.  Then you will know why you don't want to use

them all the time.  The on/off switches on the radio seems to fail more

often then a standard toggle switch, especially on the Narco and king

radios.



Mike Larkin



--

mprather(at)spro.net
Guest

Posted: Tue May 15, 2007 7:00 am Post subject: Avionics Master

Do they fail from operations or age?

Matt-



[quote] 



 Check the $price$ of that on/off switch in the radio and how much it

 cost to have it changed.  Then you will know why you don't want to use

 them all the time.  The on/off switches on the radio seems to fail more

 often then a standard toggle switch, especially on the Narco and king

 radios.



 Mike Larkin



 --

rjquillin

Joined: 13 May 2007
Posts: 123
Location: KSEE

Posted: Tue May 15, 2007 7:12 am Post subject: Avionics Master

At 06:48 5/15/2007, you wrote:

 	  Quote: 	
		  Why can one not just use the "off/on" switch on each device ?

:}


	


There some are IM's that specify the piece of equipment is not to be 

energized during engine start, and is to be powered from the 

"avionics" bus and turned on post start.

Lack of a power switch is also common with remotely installed boxes, 

some with similar power source restrictions.



One panel mounted instrument that immediately comes to mind is the 

JPI EDM series engine monitors.

There is no "off/on" switch on this device.



Ron Q.

john(at)ballofshame.com
Guest

Posted: Tue May 15, 2007 7:34 am Post subject: Avionics Master

I'm guessing they mostly fail from lack of use.  I often wonder if ANY

switch installed in the real world has ever made it to the rated # of

cycles achieved in the manufacturer'ss accelerated life testing.



-John

www.ballofshame.com



[quote] 

 <mprather(at)spro.net>



 Do they fail from operations or age?

 Matt-



> 

>

> Check the $price$ of that on/off switch in the radio and how much it

> cost to have it changed.  Then you will know why you don't want to use

> them all the time.  The on/off switches on the radio seems to fail more

> often then a standard toggle switch, especially on the Narco and king

> radios.

>

> Mike Larkin

>

> --

redeloach(at)fedex.com
Guest

Posted: Tue May 15, 2007 8:24 am Post subject: Avionics Master

Thanks to all who responded!



red  :}  (My initials but in this case, Rookie in Early Development)

---

nuckollsr(at)cox.net
Guest

Posted: Tue May 15, 2007 10:14 am Post subject: Avionics Master

At 08:32 AM 5/15/2007 -0700, you wrote:



 	  Quote: 	
		  



I'm guessing they mostly fail from lack of use.  I often wonder if ANY

switch installed in the real world has ever made it to the rated # of

cycles achieved in the manufacturer's accelerated life testing.


	




   Probably not. Lab tests never duplicate the combination of

   stresses that over time (not operating cycles) will bring the

   switch to it's knees.



   Switches regularly used are happier/healthier and longer

   lived than switches that sit for long periods of time unused.

   I've replaced more switches that succumbed to under-use

   than from wear-out.



    Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Tue May 15, 2007 10:26 am Post subject: Avionics Master

At 06:30 AM 5/15/2007 -0700, you wrote:



 	  Quote: 	
		  



Bob,



I wanted to use the LR-3 controller and the SD-8, but I didn't find a 

design that incorporated both.  So, my electrical system is kind of a 

combination of Z-12 and Z-13/8.  I started with the Z-12 and then removed 

the circuit with the SB-1/20A alternator.  Then I added the SD-8/regulator 

circuit from Z-13/8.


	




 	  Quote: 	
		  You are right about the search engine.  I actually hit send on my email 

and then instantly remembered that I should have checked the archives 

first.  Of course, I found that this subject has been discussed several 

times before.



My initial reasoning was to protect my "sensitive" avionics during power 

fluxuations during startup and shutdown.  It seams that modern avionics 

should not have this problem according to your comments in the past.

However, I am using some experimental electronics that may or may not have 

gone through extensive testing for power fluxuations.  I agree that the 

manufacturers should have made their products robust enough, but did they?


	


   Call them up and ask them. The aura that surrounds the

   avionics master switch and the mythology that birthed the

   thing will never go away unless responsibly skeptic

   consumers drive it away.



   The "spikes" from starter motors don't exist. Spikes from

   starter contactors do exist but they eat up starter push buttons

   and do not propagate out onto the system.



 	  Quote: 	
		  I'm not sure we can know for sure unless someone tests the units 

thoroughly either in the lab or just through normal use.


	


   The guy who designed the thing should KNOW what stresses

   his product will stand. Further, if there are stresses that

   his product will not stand, he should know how big they are

   and exactly where they come from. There's no excuse for

   levying a requirement on the installation of a product without

   being able to support that requirement with the "numbers" and

   simple ideas that support them.



   Call them up. Point them to articles on the website and ask

   them where they're wrong. If you don't get good (understandable)

   answers, get the folks names and phone numbers and let me call

   them.



   Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Tue May 15, 2007 10:28 am Post subject: Avionics Master

At 06:30 AM 5/15/2007 -0700, you wrote:



 	  Quote: 	
		  



Bob,



I wanted to use the LR-3 controller and the SD-8, but I didn't find a 

design that incorporated both.  So, my electrical system is kind of a 

combination of Z-12 and Z-13/8.  I started with the Z-12 and then removed 

the circuit with the SB-1/20A alternator.  Then I added the SD-8/regulator 

circuit from Z-13/8.


	


   Keep in mind that the z-figures are for ARCHITECTURE and

   do not necessarily drive combinations of hardware. For example,

   A figure Z-13 could use an internally regulated main alternator,

   an externally regulated with any regulator.



   Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Tue May 15, 2007 10:34 am Post subject: Avionics Master

At 10:43 PM 5/14/2007 -0700, you wrote:



 	  Quote: 	
		  

<mwcreek(at)frontiernet.net>

This is an excerpt from the GRT install manual referring to the use of an

avionics master (at least that is what I read into it).  Perhaps Bob can

clear this up as it is somewhat ambiguous.



Power Connections

The display units each include 2 isolated power input connections. This

allows redundant power sources, such as a main and secondary bus. The

display units consume approximately 1 amp, making even a small 3 Amp-Hour

gel cell a suitable emergency source.



The configuration of the power supplied to the display unit(s) is left to

the installer. Considerations such as the number of power buses, the desire

or not to supply one pieceof equipment with power from redundant buses

(which in theory allows the possibility of one device affecting both buses),

the configuration of the electrical system with respect to backup equipment,

and so on, may dictate the best configuration for a particular airplane.



No provision is included within the display units for a power switch. If a

power switch is desired for the EFIS, the +12V power should be controlled

with the switch (not ground). The display units include internal

thermally-activated fuses. This protects the equipment from internal

electrical faults. Power supplied to the EFIS must pass through a fuse or 4

circuit breaker or fuse. It should be sized to allow at least 1.5 amps per

display unit, with a maximum rating of 5 amps.



The AHRS and display units monitor all of their power inputs, and alarms are

available to annunciate the loss of any power source that was provided and

is expected to be working according to the "General Setup" menu.

The majority of the current flow into the display unit will occur on the bus

with thehighest voltage.



It is desirable to have the display units and AHRS off during the engine

start if all of the buses which power them are used for supplying power to

the engine starter. This maximizes the current available for the starter,

and may extend the life of the CCFL backlight in the display unit.


	




   I'm skeptical of the "extended life" claim. However, any of the

   z-figures offers dual feed busses. The e-bus is a dual feed bus

   and addresses the reliability idea that might have driven any

   form of "dual power input" scheme built into the equipment. If

   the need to have the stuff powered off during cranking is real,

   then one could install a normal feed switch in series with the

   normal feedpath isolation diode.



   Call them up and ask them which DO-160 power input protocols

   are beyond their ability to tolerate. As with other cases,

   if you don't get understandable answers, find out who I need

   to talk to and I'll go find out what's really going on.



   Bob . . .

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