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  #261  
Old 06-22-2018, 12:31 PM
rv7charlie rv7charlie is offline
 
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So, where can we view the schematic? Or at least, the wiring diagram?
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  #262  
Old 06-22-2018, 02:48 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by rcpaisley View Post
System32 harnesses have fusible links in the harness on all 12v supply wires.
Each injector and each coil pack power lead is individually protected.
The breaker requirement does not change. If a coil pack were to short out, it would pop its fusible link and not affect anything else. If an injector power lead were to short out, it would pop the fusible link for only that one injector.
The fusible links are located in the engine side circular connector backshell.
Robert
Thank you Robert. A tidy solution; my compliments sir.
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  #263  
Old 06-19-2019, 05:59 AM
TASEsq TASEsq is offline
 
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Location: Melbourne, Australia
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Quote:
Originally Posted by rmartingt View Post
So I'm getting closer to being able to start my systems installation and hoping to make some progress on my electrical diagram while I'm laid up next week. I've been looking over some thoughts on electrical systems and trying to figure out how best to go about providing reliable power to an SDS EFI system on an IFR-equipped aircraft.
So Bob (OP),

For those like me coming to this and reading through it over a long evening, with itís twists and turns, waiting for the ending...

What did you decide?

Would you be able to share your final architecture with us?
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  #264  
Old 06-19-2019, 10:33 AM
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rmartingt rmartingt is offline
 
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Originally Posted by TASEsq View Post
So Bob (OP),

For those like me coming to this and reading through it over a long evening, with itís twists and turns, waiting for the ending...

What did you decide?

Would you be able to share your final architecture with us?
Iíve settled on a system pretty much the same as the one in this post:
http://www.vansairforce.com/communit...&postcount=123


My remaining decision is whether to use relays/contactors for the engine bus, or go directly through high-current switches. Iím not sure if I like the idea of having all the engine power running up to a pair of switches on the panel and then back forward even if it is protected with high-current fuses. Iím planning an automotive relay for my pitot heat which would be the other high-current item.

The part of me that says ďsimpleĒ says just use the switch; it just goes against what Iíd normally do for bus control.

Been working on the actual wire diagrams and think Iíve figured out the supplied wiring for the SDS system from the documentation. But Iím using prep and paint of interior components to stall and delay having to buy more parts right now.
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  #265  
Old 06-19-2019, 12:00 PM
tims88 tims88 is offline
 
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I don't remember there being much, if any, discussion about possible failures downstream of an engine bus. On the Aeroelectric website, Bob has some videos discussing an accident where he points out that a failure downstream of the engine bus can blow the fuses on both paths to the engine bus (although it sounds like this was determined to not be the cause of the accident).

The videos can be found here if anyone is interested: http://www.aeroelectric.com/Referenc...eb2008_LA-IVp/
The 3rd video is where he shows this happen but all of the videos have good information in them.

Perhaps proper component selection can prevent this but I figured it was worth mentioning.
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  #266  
Old 06-20-2019, 07:34 AM
unitink72 unitink72 is offline
 
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Originally Posted by tims88 View Post
Bob has some videos discussing an accident where he points out that a failure downstream of the engine bus can blow the fuses on both paths to the engine bus
I do recall reading about an accident like that he analyzed in depth. If its the one I recall, the builder had put fuses on the feeds of both sides of the engine bus. They were the same size as the individual circuit breakers. So if there was a short to ground failure on any part of the engine bus, it would blow one fuse followed quickly by the other.

He made it through phase 1 with no issues then crashed on one of his first flights with passengers.

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Last edited by unitink72 : 06-20-2019 at 07:40 AM. Reason: add image
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  #267  
Old 06-20-2019, 08:18 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by unitink72 View Post
I do recall reading about an accident like that he analyzed in depth. If its the one I recall, the builder had put fuses on the feeds of both sides of the engine bus. They were the same size as the individual circuit breakers. So if there was a short to ground failure on any part of the engine bus, it would blow one fuse followed quickly by the other.

He made it through phase 1 with no issues then crashed on one of his first flights with passengers.

It scares me that a DAR or FSDO inspector signed off on an airplane with such a glaring failure waiting to happen.

Lesson learned (again) - if you must have an electrically dependent engine you better know what you are doing. Do not just copy what looks pretty on paper and repeat other peoples mistakes.

Carl
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  #268  
Old 06-20-2019, 09:34 AM
AdamB AdamB is offline
 
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Quote:
Originally Posted by unitink72 View Post
I do recall reading about an accident like that he analyzed in depth. If its the one I recall, the builder had put fuses on the feeds of both sides of the engine bus. They were the same size as the individual circuit breakers. So if there was a short to ground failure on any part of the engine bus, it would blow one fuse followed quickly by the other.

He made it through phase 1 with no issues then crashed on one of his first flights with passengers.

Correct.
It has to do with the blow time differences between fuses and breakers.

The breakers are slow when compared to fuses. So when you have breakers protecting the ignitions, a fault on either one of them caused both the upstream fuses to blow prior to the breakers ever popping which resulted in loss of power to the ignition bus.
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  #269  
Old 06-20-2019, 10:23 AM
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Walt Walt is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
It scares me that a DAR or FSDO inspector signed off on an airplane with such a glaring failure waiting to happen.

Lesson learned (again) - if you must have an electrically dependent engine you better know what you are doing. Do not just copy what looks pretty on paper and repeat other peoples mistakes.

Carl
Do you really expect an FAA guy or DAR to analyze your system architecture? If you do, you're in serious trouble.

This also brings up another point, if the builder of a aircraft with an elaborate electrical system, electrically dependent engine, electronic ignition, fuel injection etc. ever sells the plane or isn't around to take care of it.. you may have a bit of trouble finding someone to maintain it or help fix it.
(if you don't think this stuff fails you haven't been around very long)

When you build one of these complex birds you're pretty much on your own.
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Last edited by Walt : 06-20-2019 at 10:35 AM.
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  #270  
Old 06-20-2019, 10:40 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by Walt View Post
Do you really expect an FAA guy or DAR to analyze your system architecture? If you do, you're in serious trouble.
No - I do not rely on a DAR or FSDO inspector and I would not expect either to do a detailed analysis. I would however expect that an inspector (or any trusted agent) doing a cursory glance at a power diagram having fuses/breakers in parallel to a load should have alarm bells going off in his head.

I say again - if you must have an electrically dependent engine you better know what you are doing.

Carl
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