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Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Mon May 09, 2022 11:45 am Post subject: Too many Circuit breakers....

On Mon, May 9, 2022 at 2:29 PM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:



 	  Quote: 	
		     	  Quote: 	
		  These days, with EFIS equipment, it's more about inconvenience than load shedding. Some EFIS products take 2-3 minutes to boot and self-calibrate,Ã‚ and I've seen them 'lock up' during engine start. If they reboot due to brownout at engine start, that 3 minutes feels like half the planned flight time. Ã‚Â  If they lock up, then you typically have to power down the whole panel to get them to restart.Ã‚ 	


 Â  If I were qualifying an electro-whizzy for TC

 Â  aircraft, DO160 power input tests have to demonstrate

 Â  timely fault free recovery under various

 Â  power input conditions. I would not be able to

 Â  put such devices on a TC aircraft.

	
I'll bet you couldn't sell a $100,000 certified EFIS array for $5,000 (or under $2K on the used market, either. 

I doubt that any of the newer exp models have the same 'lockup' issues, but it can happen with some of the near-prehistoric ones (pre-turn of the century). But once up and running, they're about as solid as the $100,000 certified models.Â 

Many homebuilt a/c could never pass FAA certification either, but they perform their missions better than any certified a/c. We play the cards we're dealt (or can afford to purchase).Â 

Charlie

_________________
Charlie

cluros(at)gmail.com
Guest

Posted: Mon May 09, 2022 1:00 pm Post subject: Too many Circuit breakers....

One of the rockets I fly has a current production GRT which has to be left off for engine start or it goes dark and locks up. Once the engine starts we quickly turn it on and check that the red idiot light is out. If itâ€™s not then we donâ€™t know what the problem is but since oil pressure is a possibility I would just shut it down. Not ideal.



 	  Quote: 	
		  On May 9, 2022, at 13:46, Charlie England <ceengland7(at)gmail.com> wrote:



ï»¿



On Mon, May 9, 2022 at 2:29 PM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:



 	  Quote: 	
		     	  Quote: 	
		  These days, with EFIS equipment, it's more about inconvenience than load shedding. Some EFIS products take 2-3 minutes to boot and self-calibrate,Ã‚ and I've seen them 'lock up' during engine start. If they reboot due to brownout at engine start, that 3 minutes feels like half the planned flight time. Ã‚  If they lock up, then you typically have to power down the whole panel to get them to restart.Ã‚ 	


   If I were qualifying an electro-whizzy for TC

   aircraft, DO160 power input tests have to demonstrate

   timely fault free recovery under various

   power input conditions. I would not be able to

   put such devices on a TC aircraft.

	
I'll bet you couldn't sell a $100,000 certified EFIS array for $5,000 (or under $2K on the used market, either. 

I doubt that any of the newer exp models have the same 'lockup' issues, but it can happen with some of the near-prehistoric ones (pre-turn of the century). But once up and running, they're about as solid as the $100,000 certified models. 

Many homebuilt a/c could never pass FAA certification either, but they perform their missions better than any certified a/c. We play the cards we're dealt (or can afford to purchase). 

Charlie

Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Mon May 09, 2022 3:56 pm Post subject: Too many Circuit breakers....

snipped

 	  Quote: 	
		   Charlie, What's your brown-out booster look like?



 Getting real close! Thanks!



 Andy

Sorry for the delay in answering this. There are lots of options out 
	


there. I picked one that had both a low enough input voltage, and plenty 

of 'headroom' on the higher voltage end, simply for better survivability.



This is the one I used (with a few spares for future projects):

 Â https://smile.amazon.com/gp/product/B07XG323G8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1



I set it up on the bench with an adjustable bench supply to maintain 

around 11V with an 8V supply voltage (the little blue block with a slot 

head screw is the adjustment). The old GRT EFIS had multiple 

diode-isolated power inputs, so I simply tapped the EFIS' primary power 

wire & ground to power the boost converter, and fed the converter's 

output to one of the spare power inputs on the EFIS. They're pretty 

small (~1" x 2.5") so I just drilled some ventilation holes in a plastic 

prescription bottle & used it for a case. the whole affair was basically 

just a bulge in the harness going to the EFIS.



On the particular units I received, the output ground is common to the 

input ground, so I only needed one output connection to the EFIS. Note 

that some boost converters may actually isolate the grounds, so you need 

to check for that, and also check to be sure that tying them together 

(via the ground in the plane and the EFIS) won't be an issue for the 

converter.



Also note that this particular unit is limited to 3 amps. It will 

probably handle most single EFIS units, but I wouldn't think powering 

more than one with it would be a good idea. On the other hand, you do 

get extras for other stuff. 





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Charlie

andymeyer

Joined: 31 Mar 2015
Posts: 54
Location: SW MI

Posted: Tue May 10, 2022 8:04 pm Post subject: Re: Too many Circuit breakers....

Drew this up in upverter.com... Not the best for schematics, but I think this gets the idea across. Pinouts of devices aren't defined here.  Fuse Blocks are the above recommended fuse blocks.



The AV30E needs at most 2 amps. (attitude indicator)

The Engine Monitor needs at most 1 amp.

The IFD GNS side - max 7.5 amps, but it's got diode OR'd inputs on the GNS side. 

IFD Comm side doesn't have dual inputs for some reason. Might diode OR those externally - needs 10 amps.



If no to the diodes, what bridge rectifier is recommended?



Those are the 3 things I need to get somewhere if things go bad. Master relay craps out, etc... 



Not sure if this link will get you to the source drawing, but it might... https://upverter.com/design/meyerkc135/62568e2b082ab4c7/aircraftarchitecture/



Plan is to replace the PC680 and the backup battery every 3 years. 



Trying to keep it simple. Looking at what I currently have, I've got little protection from the dark and stormy, though I can (with conservative weather planning) get somewhere on one mag and the AV30 (backup battery). I'm loosing the mag for the second ignition.

1344TDraft.png

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed May 11, 2022 8:53 am Post subject: Too many Circuit breakers....

At 11:04 PM 5/10/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "andymeyer" <meyerkc135(at)gmail.com>



 Drew this up in upverter.com... Not the best for schematics, but I think this gets the idea across. Pinouts of devices aren't defined here.  Fuse Blocks are the above recommended fuse blocks. 	


   What engine are you planning?



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

andymeyer

Joined: 31 Mar 2015
Posts: 54
Location: SW MI

Posted: Wed May 11, 2022 9:53 am Post subject: Re: Too many Circuit breakers....

Bob,



It's an O-235 C1C with 8.5:1 pistons and dual Lightspeed Plasma III's. Carbureted... No vacuum system or mags. She's flying right now (with 1 mag, 1 Plasma III), but our ramp shuts down for 10 weeks so I'll be doing this upgrade then.



My diagram is somewhat derived from the Z11 (might be an older version since it still had the AEC9001-1 in it - I bought your book years ago...



Engine monitor is an ~30 channel system with 2 ARM Cortex-M7's (one in the instrument, one back by the engine) and a 3.5inch touchscreen... Should have put dual independent power inputs on it. Maybe on my next rev of the PCBA. 



Andy

Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Wed May 11, 2022 12:29 pm Post subject: Too many Circuit breakers....

On 5/11/2022 12:53 PM, andymeyer wrote:

     

      	  Quote: 	
		          	  Quote: 	
		  --> AeroElectric-List message posted by: "andymeyer" <meyerkc135(at)gmail.com> (meyerkc135(at)gmail.com)



Bob,



It's an O-235 C1C with 8.5:1 pistons and dual Lightspeed Plasma III's. Carbureted... No vacuum system or mags. She's flying right now (with 1 mag, 1 Plasma III), but our ramp shuts down for 10 weeks so I'll be doing this upgrade then.



My diagram is somewhat derived from the Z11 (might be an older version since it still had the AEC9001-1 in it - I bought your book years ago...



Engine monitor is an ~30 channel system with 2 ARM Cortex-M7's (one in the instrument, one back by the engine) and a 3.5inch touchscreen... Should have put dual independent power inputs on it. Maybe on my next rev of the PCBA. 



Andy

	
     	
     The monitor sounds really nice. Are you gonna Bogart the     design, or share?

     

     

     Charlie

       	 		 			 				 			 		 		 			

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Charlie

andymeyer

Joined: 31 Mar 2015
Posts: 54
Location: SW MI

Posted: Wed May 11, 2022 6:04 pm Post subject: Re: Too many Circuit breakers....

Charlie,



Starting a new topic on the engine monitor...



Andy

Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Wed May 11, 2022 6:11 pm Post subject: Too many Circuit breakers....

On 5/11/2022 9:04 PM, andymeyer wrote:

 	  Quote: 	
		   



 Charlie,



 Starting a new topic on the engine monitor...



 Andy

Sounds good!
	




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Charlie

nuckolls.bob(at)aeroelect
Guest

Posted: Thu May 12, 2022 5:51 pm Post subject: Too many Circuit breakers....

At 12:53 PM 5/11/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "andymeyer" <meyerkc135(at)gmail.com>



 Bob,



 It's an O-235 C1C with 8.5:1 pistons and dual Lightspeed Plasma III's. Carbureted... No vacuum system or mags. She's flying right now (with 1 mag, 1 Plasma III), but our ramp shuts down for 10 weeks so I'll be doing this upgrade then.



 My diagram is somewhat derived from the Z11 (might be an older version since it still had the AEC9001-1 in it - I bought your book years ago... 	


   Why no second alternator on the vacuum pump pad?



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

andymeyer

Joined: 31 Mar 2015
Posts: 54
Location: SW MI

Posted: Thu May 12, 2022 6:08 pm Post subject: Re: Too many Circuit breakers....

Bob,



The SD-8 concerns me 'cause if I lose the electric system, I lose the engine which means I won't get enough power out of the SD8 (low RPM) to run the ignitions to restart. 



Got an option that makes sense, or can you talk me into the SD8?



I still wonder about master switch failure - I think I have that covered in my design above. Engine, monitoring, attitude and GPS.



Andy

david(at)carter.net
Guest

Posted: Fri May 13, 2022 3:17 am Post subject: Too many Circuit breakers....

Why not base the design on Bob's Z-101? Seems that you are recreating the wheel. Â 

http://forums.matronics.com/viewtopic.php?p=498198&highlight=&sid=b64f62254568037b48c88b877d06b539



On Thu, May 12, 2022 at 10:09 PM andymeyer <meyerkc135(at)gmail.com (meyerkc135(at)gmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "andymeyer" <meyerkc135(at)gmail.com (meyerkc135(at)gmail.com)>

 

 Bob,

 

 The SD-8 concerns me 'cause if I lose the electric system, I lose the engine which means I won't get enough power out of the SD8 (low RPM) to run the ignitions to restart. 

 

 Got an option that makes sense, or can you talk me into the SD8?

 

 I still wonder about master switch failure - I think I have that covered in my design above. Engine, monitoring, attitude and GPS.

 

 Andy

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=506749#506749

 

 

 

 

 

 

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  -

 Electric-List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

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  FORUMS -

 eferrer" target="_blank">http://forums.matronics.com

 ===========

 WIKI -

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 Â  Â  Â  Â  Â  -Matt Dralle, List Admin.

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david(at)carter.net (david(at)carter.net)

nuckolls.bob(at)aeroelect
Guest

Posted: Fri May 13, 2022 8:56 am Post subject: Too many Circuit breakers....

At 09:08 PM 5/12/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "andymeyer" <meyerkc135(at)gmail.com>



 Bob,



 The SD-8 concerns me 'cause if I lose the electric system, I lose the engine which means I

 won't get enough power out of the SD8 (low RPM) to run the ignitions to restart. 	


    What is the condition(s) that would cause

    you to 'loose' the electrical system?

    This is what FMEA is all about. Go through

    a thought exercise that considers 'what if'

    for any single failure . . . switch broke . . .

    wire falls off terminal . . . pump gets

    asthma . . . regulator quits . . . etc. ect.



    The process is pretty simple:



    First deduce the ways in which the part

    can fail.



        Terminal falls off, regulator goes

        silent, regulator goes wild, bulb

        burns out, handle falls out of switch,

        contactor sticks closed, etc. etc.



    How will you become aware that the failure

    has occurred?



        Something quits working . . . something

        wildly mis-behaves . . .



    Is the failure pre-flight detectable?



       Yes? Make sure it's on your checklist.



       No?  What are your periodic inspection plans

       for assessing that system's airworthiness?



    How does this failure affect the probable

    outcome of your flight?



        The vast majority of failures on airplanes

        are no big deal . . . FBOs make their

        living fixing no big deals . . . well . . .

        it's usually a big deal to the wallet but

        at lease your airplane isn't bent.



    If koss of that feature poses risk to your

    maintaining order in the cockpit, what are your

    plan-b protocols for dealing with the failure?



 

        Check out the PowerPoint slides for my

        weekend seminars at:



  http://aeroelectric.com/Reference_Docs/Seminar_PP_Slides/



        . . . in particular, the packet on Failure

        Tolerance 



        Page 10 illustrates my personal plan-b

        as an airplane renter . . . with the whole

        panel gone dark, it was my plan-b to get

        to where I was originally headed.



        Those slides speak to a constellation of

        architectures tailored to the builder's

        design goals and project features.



    ARCHITECTURE and judicious accessories scattered

    about the system should be your refinement of

    the plan-b protocols based on your FMEA.



    Do you have a copy of the 'Connection? If

    not, you can download it . . .



  http://www.aeroelectric.com/Books/Connection/AEC12A_PDF.zip



    Appendix Z in the bound book is NOT the latest

    configuration for all drawings. See



  https://tinyurl.com/y26qe4y9



    for the latest iterations. As others have noted,

    take particular not of Z101. This architecture

    is a kind of melting pot of drawing refinement

    and discussions here on the List over the past

    30 years or so.



    It's a tinker-toy/leggo approach to system architecture

    decisions . . . pick and choose which bus structures

    make sense for your project. But note that even

    with a FULL UP, nearly bullet-proof system, all

    features and functions are managed with but three

    switches and one breaker.



    I would strongly encourage using that orphaned

    vacuum pump pad for something exceedingly useful

    with a very low cost of ownership compared to

    adding ANY standby batteries to your system . . . 

    you DO plan to maintain an airworthy main battery . . .

    no?



  	  Quote: 	
		  I still wonder about master switch failure - I think I have that covered in my design above. Engine, monitoring, attitude and GPS. 	


    Sift thru the functionality of features in

    Z101 . . . suppose the battery contactor

    DOES open. How will you know it happened and

    what's the protocol for managing the event?



    All this may seem like a LOT of work . . . yeah . . .

    you're right. But in 50 years of reading dark-n-stormy-

    night stories in the aviation rags I've yet to

    encounter a pilot who demonstrated an understanding

    of the function and limitations of his ship's

    electrical system.



    If he HAD understood better, he probably would have

    not experienced the SURVIVABLE event that allowed

    him to write the story.



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Fri May 13, 2022 12:41 pm Post subject: Too many Circuit breakers....

On 5/12/2022 9:08 PM, andymeyer wrote:

 	  Quote: 	
		   



 Bob,



 The SD-8 concerns me 'cause if I lose the electric system, I lose the engine which means I won't get enough power out of the SD8 (low RPM) to run the ignitions to restart.



 Got an option that makes sense, or can you talk me into the SD8?



 I still wonder about master switch failure - I think I have that covered in my design above. Engine, monitoring, attitude and GPS.



 Andy

I'mÂ  not following the question. The alternator(s) are not participants 
	


in starting the engine. Any electronic ignition is operating on the 

battery until the engine is running and spinning the alternator fast 

enough to generate current.



I think Bob was asking, why not run a backup alternator instead of a 

backup battery. Assuming ~2 amps draw per ignition, you'd get around an 

hour of operation from the ignition battery, but a backup alternator 

lasts through fuel exhaustion.



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Charlie

andymeyer

Joined: 31 Mar 2015
Posts: 54
Location: SW MI

Posted: Fri May 13, 2022 6:49 pm Post subject: Re: Too many Circuit breakers....

David,

Yes - looked at the Z101 - wasn't in my old book - or at least I missed it. Modifying it to use the rectifier to support the E bus.



Bob,

The failure that comes to mind is the master switch opens or shorts and pops the fuse link for some reason (failed connection, failed relay, etc...) EBus solves this - gets me on the ground with an attitude, engine monitoring and GPS.

Alternator failure, regulator failure, OV trip, etc... that won't recover - EBus gets me on the ground.

Battery failure - very low risk, but my AV30 stays alive and the second ignition battery keeps the fan spinning.

EBus is checkable by flipping it on before the master...

I've walked through most of the failures... I didn't pull out my old Douglas FMEA forms or calculated Risk Probability Severity numbers, but I ran through most of the things going wrong, how to detect, and what to do about it. Any I'm forgetting that would take this architecture down?



I'm thinking the only things I need on the essential bus are the AV30E, the GPS, and Engine monitor - a very paltry load. 



I've looked at the pad mount alternators - I'm just really tight to the firewall in my Long EZ. BandC oil filter adapter required a recess in the firewall to fit. A 5aH battery will get me ~an hour of flight time on a single ignition if needed. Considering a 12aH LiFePo battery, and monitor it frequently...

nuckolls.bob(at)aeroelect
Guest

Posted: Fri May 13, 2022 6:54 pm Post subject: Too many Circuit breakers....

 	  Quote: 	
		    	  Quote: 	
		  Andy 	
 I'mÂ  not following the question. The alternator(s) are not participants in starting the engine. Any electronic ignition is operating on the battery until the engine is running and spinning the alternator fast enough to generate current.



 I think Bob was asking, why not run a backup alternator instead of a backup battery. Assuming ~2 amps draw per ignition, you'd get around an hour of operation from the ignition battery, but a backup alternator lasts through fuel exhaustion. 	


    Yeah . . . 



    Just for grins, let's test the utility of Z101 for

    your project.  See:



  https://tinyurl.com/y3yyjjqp



    Let's make this a List exercise to go over the

    possibilities. If you were to use the

    cited drawing as is, what loads would you

    assign to each bus?



    Will you need brownout boosting? Are

    you interested in being able to fire up

    some radios in pre-flight? Let's get

    all your proposed electro-whizzies

    lit up on some bus.



    Then let's see what might be eliminated

    for simplicity/cost without sacrificing

    untility.



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

nuckolls.bob(at)aeroelect
Guest

Posted: Sat May 14, 2022 8:49 am Post subject: Too many Circuit breakers....

At 09:49 PM 5/13/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "andymeyer" <meyerkc135(at)gmail.com>



 David,

 Yes - looked at the Z101 - wasn't in my old book - or at least I missed it. Modifying it to use the rectifier to support the E bus.



 Bob,

 The failure that comes to mind is the master switch opens or shorts and pops the fuse link for some reason (failed connection, failed relay, etc...) EBus solves this - gets me on the ground with an attitude, engine monitoring and GPS.

 Alternator failure, regulator failure, OV trip, etc... that won't recover - EBus gets me on the ground.

 Battery failure - very low risk . . . 	


    But can you make it zero?



  	  Quote: 	
		  . . . but my AV30 stays alive and the second ignition battery keeps the fan spinning. 	


  . . . yup . . . those are all FMEA bullet points

  each presenting its own cause/effect/probability

  factors.



  Very well . . . sounds like you have a plan.

  Please include ALL batteries in your periodic

  airworthiness verification protocol.



  Fly comfortably



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

andymeyer

Joined: 31 Mar 2015
Posts: 54
Location: SW MI

Posted: Sat May 14, 2022 9:56 am Post subject: Re: Too many Circuit breakers....

Bob,



Thanks! I've got other builders watching our learnings here closely so... 



I added the appropriate loads to where they need to go. 

Main bus: (breaker size)

Pitot: 20A

Lighting: 10A

Boost pump: 5A

Starter Relay



Avionics Bus is:  

Garmin stuff is 15 A  (incl Audio panel)

AXP 322 + Stratux = 5A

ELT 1A



E Bus:

AV30E - 2A

Engine Monitor - 2A

IFD - 17.5A (GPX+Comm)



No need for brown-out boosting if I put the Avionics master in, Yes, if I don't. The Garmin items that I'd want brownout protection on all have internal diode or'd inputs so I can put the brownout booster on power #2 and it'll keep it awake. Same with the Avidyne IFD. AV30 will stay awake with it's internal battery. Engine monitor runs down to ~4.5 volts on the input. Okay, you just talked me into brownout boosting - booster + a few wires - simple. (Fuse to the booster, then do I also fuse each output line of the booster?



I modified the diagram to two versions - one dual alternator, one dual battery. 

I was wondering why all of the relays - can we not get good switches to handle these loads, or is the relay + small switch + connections(7) more reliable than a higher power switch + connections (2) ?

Dual Alt Preflight:

Pre-flight... EBus on - check that the AV30 wakes up. Master on, EBus off.

Run up... Eng Bus Alt feed on, Master off - make sure engine keeps running. But, everything else goes dark for this check???

Aux Alt to middle position, master off, make sure things don't go dark, check voltage, Aux alt up, check voltage rise (>13, but need higher RPM with SD8), aux alt to middle, Main alt on, Aux alt off, recheck voltage > 13.0



Annually, load test battery.



Major electrical failure: (failed master, shorted master bus, loose wire to master...)

Everything goes dark and quiet except battery bus and AV30.

Aux Alt on. E Bus wakes up and starts powering up. 

Mixture - cut-off. Eng Aux bus on. Mixture rich. Things get noisy again.



\n

Dual Batt pre-flight:

Pre-flight... EBus on - check that the AV30 wakes up. Master on, EBus off.

Run-up... Ignition - test #2 on both normal and standby power.



Annually, load test both batteries.



Major electrical failure:

Everything goes dark except battery bus and AV30.

EBus alt on, IFD comes back up. monitor voltage on main battery. AV30, IFD and engine monitoring remains.

When main battery is < 6V, then move ignition #2 to middle position - #2 battery. 5Ah, ~2 hours of flight time with AV30 battery and engine monitoring. Engine monitoring dies around 4.5 volts.[/b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat May 14, 2022 10:22 am Post subject: Too many Circuit breakers....

At 12:56 PM 5/14/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "andymeyer" <meyerkc135(at)gmail.com>



 Bob,



 Thanks! I've got other builders watching our learnings here closely so... 



 I added the appropriate loads to where they need to go. 

 Main bus: (breaker size)

 Pitot: 20A

 Lighting: 10A

 Boost pump: 5A

 Starter Relay



 Avionics Bus is:  

 Garmin stuff is 15 A  (incl Audio panel)

 AXP 322 + Stratux = 5A

 ELT 1A



 E Bus:

 AV30E - 2A

 Engine Monitor - 2A

 IFD - 17.5A (GPX+Comm) 	


   <snip>



   Very well. I'll let you guys 'fill in the blanks'.



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

user9253

Joined: 28 Mar 2008
Posts: 1922
Location: Riley TWP Michigan

Posted: Sat May 14, 2022 12:18 pm Post subject: Re: Too many Circuit breakers....

If the battery contactor fails open, everything will NOT go dark.  You probably won't even know that that it failed because the aircraft electrical system is normally powered by the alternator.  You might notice some voltage instability, but won't know the cause.  The voltage regulator might be failing.

 One reason for using a relay is to handle current that is greater than the switch ampacity.  Another reason for using relays is for remote control.  The pilot should have the ability to shut off all electrical power as close to the source as possible.  Suppose the plane makes a forced landing that results in leaking fuel.  The pilot might not be able to exit the aircraft due to aircraft damage or pilot injuries.  If the electricity is shut off at the source, there is  less chance of sparking wires igniting fuel.  Why not wire your plane per Z-101?  I has passed peer review.  Z-101 does not have an avionics switch to fail.

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Joe Gores

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