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E-Buss and Master Switches

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david.nelson(at)pobox.com
Guest

Posted: Sun Aug 16, 2009 7:34 am Post subject: E-Buss and Master Switches

Hi Bob,



I'm going over the finer details of a design based largely upon Z-11.  Why 

wouldn't one, for normal ops, have both the E-Buss and Master in the 'On' 

position?



My reasoning being:



- In the event of some electrical problems, you only have to contend with 

switching off one switch rather than remembering to turn the E-buss 'On' 

followed by turning the Master 'Off'.



- If the problem persists, we aren't in any different position than if we 

turned on the E-Buss followed by turning off the Master.



Am I missing something fundamental here or was I always assuming that the 

E-Buss was always originally 'Off' during normal ops?



Thank you,

 	 /\/elson

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jay(at)horriblehyde.com
Guest

Posted: Sun Aug 16, 2009 9:23 am Post subject: E-Buss and Master Switches

Hi there David,



I had to write a procedure on how to use a system that I wired to one of the

Z diagrams and then it became clear why one does not want to leave the e-bus

alt feed on.  In the event of a fault, smoke, what have you, the first thing

that you want to do is isloate the power sources from the fault as fast as

possible- hence the DC master; once its off only the short fat wire between

the battery and your solenoid is live (and the E-bus alt to the switch

wire).  So, unless the fault is right there (usually unlikely), then you

have removed the power that is driving the fault.  In a mag equipped

aircraft the engine should still run and in an all electric aircraft the ECU

and fuel pumps should have directly connected wires that bypass the DC

master.  If you still have smoke and trouble then you know that you are now

seriously in the dwang, as the fault is somewhere in those, non-isolatable,

wires.

However, if switching the DC master off clears the fault you can now switch

the E-bus alt feed on and see what happens; then maybe switch off a few

circuits on the main bus; switch the DC master back on, etc.  This is

assuming that landing is not a luxury that you are presently afforded- such

as if you are crossing the Atlantic and you're 10 hours into a 22 hour

flight... 



If you can land, better to figure the problem out on the ground of course,

using just the E-bus to get you down.



Jay



--

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Aug 16, 2009 10:37 am Post subject: E-Buss and Master Switches

At 10:30 AM 8/16/2009, you wrote:

 	  Quote: 	
		  

Hi Bob,



I'm going over the finer details of a design based largely upon 

Z-11.  Why wouldn't one, for normal ops, have both the E-Buss and 

Master in the 'On' position?


	


   Could, but not necessary. Doesn't hurt. But you DO

   want to pre-flight test the dual power path philosophy

   for the e-bus.



 	  Quote: 	
		  My reasoning being:



- In the event of some electrical problems, you only have to contend 

with switching off one switch rather than remembering to turn the 

E-buss 'On' followed by turning the Master 'Off'.


	


   Remember? It's recommended that you have a checklist

   for shutdown. It's also recommended that you consider

   an ergonomic arrangement of switches wherein ship's

   DC power controls are grouped. Leaving the airplane

   should be preceded by placing all switches down (OFF).



 	  Quote: 	
		  - If the problem persists, we aren't in any different position than 

if we turned on the E-Buss followed by turning off the Master.



Am I missing something fundamental here or was I always assuming 

that the E-Buss was always originally 'Off' during normal ops?


	


   That was the original design philosophy. But failure

   mode effects analysis for the system's design included

   consideration of risk for having the switch ON under

   any flight conditions. Wired as shown, you may operate

   it with any philosophy you choose.

        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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david.nelson(at)pobox.com
Guest

Posted: Sun Aug 16, 2009 11:45 am Post subject: E-Buss and Master Switches

Hi Jay,



I certainly understand your reasoning for the below and I had a similar 

argument in my head.  But then this scenario popped up in my head.  Currently, 

I'm only VFR rated but plan to go for the IFR ticket within a couple of years 

of project completion.  I imagined flying in the soup and would I want to reset 

all my avionics and wait for them to reinitialize?  I'll be honest, I don't how 

long it will take for my equipment to re-initialize while flying - I'll add it 

as a 'todo' item for further investigation.



Ugh - this is making my head hurt. To me, I guess what it comes down to is that 

we must architect our systems for fault tolorance, know how the systems are 

designed and how they work, understand the associated risks and trade-offs, and 

train for emergencies.  Thanks to Bob, we can thank him for the 1st three.



 	 /\/elson



On Sun, 16 Aug 2009, Jay Hyde wrote:



[quote] 

 Hi there David,



 I had to write a procedure on how to use a system that I wired to one of the

 Z diagrams and then it became clear why one does not want to leave the e-bus

 alt feed on.  In the event of a fault, smoke, what have you, the first thing

 that you want to do is isloate the power sources from the fault as fast as

 possible- hence the DC master; once its off only the short fat wire between

 the battery and your solenoid is live (and the E-bus alt to the switch

 wire).  So, unless the fault is right there (usually unlikely), then you

 have removed the power that is driving the fault.  In a mag equipped

 aircraft the engine should still run and in an all electric aircraft the ECU

 and fuel pumps should have directly connected wires that bypass the DC

 master.  If you still have smoke and trouble then you know that you are now

 seriously in the dwang, as the fault is somewhere in those, non-isolatable,

 wires.

 However, if switching the DC master off clears the fault you can now switch

 the E-bus alt feed on and see what happens; then maybe switch off a few

 circuits on the main bus; switch the DC master back on, etc.  This is

 assuming that landing is not a luxury that you are presently afforded- such

 as if you are crossing the Atlantic and you're 10 hours into a 22 hour

 flight... 



 If you can land, better to figure the problem out on the ground of course,

 using just the E-bus to get you down.



 Jay



 --

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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david.nelson(at)pobox.com
Guest

Posted: Sun Aug 16, 2009 12:12 pm Post subject: E-Buss and Master Switches

Hi Bob,



100% agree that the pre-flight checklist should involve toggling both swithches 

to ensure proper operation.  That should be item regardless of normal ops.



I'm giving an awful lot of thought to switch placement and overall cockpit 

ergonomics. Being my 1st time, I'm learning that it is not as easy as a task as 

I had thought it would be....and I am making progress.



 	 /\/elson



On Sun, 16 Aug 2009, Robert L. Nuckolls, III wrote:



 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>



 At 10:30 AM 8/16/2009, you wrote:

> 

> <david.nelson(at)pobox.com>

> 

> 

> Hi Bob,

> 

> I'm going over the finer details of a design based largely upon Z-11.  Why 

> wouldn't one, for normal ops, have both the E-Buss and Master in the 'On' 

> position?



  Could, but not necessary. Doesn't hurt. But you DO

  want to pre-flight test the dual power path philosophy

  for the e-bus.



> My reasoning being:

> 

> - In the event of some electrical problems, you only have to contend with 

> switching off one switch rather than remembering to turn the E-buss 'On' 

> followed by turning the Master 'Off'.



  Remember? It's recommended that you have a checklist

  for shutdown. It's also recommended that you consider

  an ergonomic arrangement of switches wherein ship's

  DC power controls are grouped. Leaving the airplane

  should be preceded by placing all switches down (OFF).



> - If the problem persists, we aren't in any different position than if we 

> turned on the E-Buss followed by turning off the Master.

> 

> Am I missing something fundamental here or was I always assuming that the 

> E-Buss was always originally 'Off' during normal ops?



  That was the original design philosophy. But failure

  mode effects analysis for the system's design included

  consideration of risk for having the switch ON under

  any flight conditions. Wired as shown, you may operate

  it with any philosophy you choose.

       Bob . . .



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

       ( . . .  a long habit of not thinking   )

       ( a thing wrong, gives it a superficial )

       ( appearance of being right . . .       )

       (                                       )

       (                  -Thomas Paine 1776-  )

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

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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jay(at)horriblehyde.com
Guest

Posted: Sun Aug 16, 2009 12:54 pm Post subject: E-Buss and Master Switches

Hey David,



I kinda agree... re waiting for stuff to reset; I suppose that the best is

exactly what we are arming ourselves with right here- a pretty good

understanding of exactly how our sytems work.



As an aside, the MGL EFIS systems that I am using a lot now have the option

(as many others also do) of their own standby and backup battery ( a little

isty bitsy thing) that keeps them all running when you switch off the DC

master- sort of like an airborne UPS you might say; so the reset doesn't

really happen   I hope...  



Jay



--

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Aug 16, 2009 1:24 pm Post subject: E-Buss and Master Switches

At 02:56 PM 8/16/2009, you wrote:

 	  Quote: 	
		  

Hi Bob,



100% agree that the pre-flight checklist should involve toggling 

both swithches to ensure proper operation.  That should be item 

regardless of normal ops.



I'm giving an awful lot of thought to switch placement and overall 

cockpit ergonomics. Being my 1st time, I'm learning that it is not 

as easy as a task as I had thought it would be....and I am making progress.


	


   Add this drawing to your sources of ideas . . .



http://www.aeroelectric.com/PPS/Switch_Panels/Switches.pdf

   In several variations I've suggested an ordering of

   switches that groups function and mitigates the

   effects of mistakenly grabbing an adjacent switch.

   Operating the wrong switch is high on the list

   of concerns for some builders.



   Here I've built the switch strings where the

   least used are at the far left and most used

   at far right with power distribution and control

   in the middle. You may have other design goals in

   mind but these drawings may offer a place to start.

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Aug 16, 2009 1:37 pm Post subject: E-Buss and Master Switches

 	  Quote: 	
		  I imagined flying in the soup and would I want to reset all my 

avionics and wait for them to reinitialize?  I'll be honest, I don't 

how long it will take for my equipment to re-initialize while flying 

- I'll add it as a 'todo' item for further investigation.


	


   I forgot another item from your posting.



   If it's ever necessary to force any piece of equipment

   to re-boot, it's ill-advised to initiate it with any

   part of the power distribution system that affects more

   than one piece of equipment. Any such processes are

   best accomplished on one piece at a time with controls

   unique to that piece of equipment and then perhaps only

   if you really need that piece of equipment for

   comfortable completion of that flight.



   More than one dark-n-stormy night story advanced to

   higher levels of interest and intrigue as pilot

   attempts to diagnose/fix some problem by manipulation

   that serves only distracted him or made other things

   happen that worsened the situation.



 	  Quote: 	
		  Ugh - this is making my head hurt. To me, I guess what it comes down 

to is that we must architect our systems for fault tolorance, know 

how the systems are designed and how they work, understand the 

associated risks and trade-offs, and train for emergencies.  Thanks 

to Bob, we can thank him for the 1st three.


	


   It shouldn't be painful. It's called failure mode effects

   analysis and generally takes a LONG time to do a good

   job. Not that it's difficult . . . but new possibilities

   or combinations arise with thought, time and conversation with

   others. I'm pretty sure that every FMEA report I've submitted

   was considered by others "complete" and suitable for

   publication. Personally, I've considered them perhaps

   99 percent complete while keeping an eye out for new

   ideas.  Don't rush it.  The thing that's nice about the

   airplanes we build here is that the last 1% item can be

   accommodated in a timely manner and at our convenience.

   The TC airplane guys HAD to call the work 100% complete

   because any changes after certification was a horribly

   protracted process.

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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david.nelson(at)pobox.com
Guest

Posted: Sun Aug 16, 2009 2:12 pm Post subject: E-Buss and Master Switches

Hi Jay,



"Airborne UPS" - haha - I like that.  I had been resistant to using the 

internal battery option of the AFS unit. Instead opting for a small aux 

battery. I've recently changed my mind on that front as it somewhat simplyflied 

my panel and wiring while still maintaining the goal of being able to power up 

the EFIS before engine startup.  After that, everthing else can get turned on.



 	 /\/elson

On Sun, 16 Aug 2009, Jay Hyde wrote:



[quote] 

 Hey David,



 I kinda agree... re waiting for stuff to reset; I suppose that the best is

 exactly what we are arming ourselves with right here- a pretty good

 understanding of exactly how our sytems work.



 As an aside, the MGL EFIS systems that I am using a lot now have the option

 (as many others also do) of their own standby and backup battery ( a little

 isty bitsy thing) that keeps them all running when you switch off the DC

 master- sort of like an airborne UPS you might say; so the reset doesn't

 really happen   I hope...  



 Jay



 --

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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