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Individual Circuit Breakers vs Electronic Circuit Breaker System

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Where I stand at this point

Well it's been a very informative discussion and I thank you all for your views.

First, let me say that Vertical Power calls their VP-X system an "Electronic Circuit Breaker System", which I will shorten to ECBS. And so when I use the term ECBS I include all of the brands out there, and I mean systems similar to the VP-X.

Coming into this, I knew that ECBS are expensive - multiple thousands. However I didn't have enough info to decide whether the systems give you enough advantage to make the expenditure worth it. Oftentimes, expensive boxes are worth the investment. But, again, in the case of ECBS I was too ignorant to be able to make the decision. Hence this thread.

Some time in the future I'll take on the re-wiring and/or panel upgrade of my airplane. The attributes I'm looking for when thinking about upgrading strongly include:

1) Maintainability/accessibility - I'd prefer to be able to access the devices
while seated in the front seat. I'd like to avoid contorting myself under the
panel.

2) Reliability.

I had to make a change to the CB's in the right hand "wing" of the instrument panel and it was pure torture. Not accessible. Any new panel design or re-wiring effort will include moving those CB's....OR installing some ECBS.

So i was initially attracted to the ECBS concept. All wires run to one spot. I have to say that I erroneously thought that, somehow, an ECBS system would result in simpler wiring. I also liked the fact that you could observe status of various circuits.

After reading everyone's comments I can see that one way or another - fuse block, CB bank, ECBS, you still have to run the same wires to some connection.

Given what I've read, I'm going to either stick with CB's or move to a fuse block.

The only reason I'm considering a fuse block is that it's smaller so it takes up less space, and is more easily swung out of the way but swung out for access.

However I tend to lean towards CB's.

One option I'm considering is mounting a block of CBs much like Walt's arrangement in post #42, but on a hinged door so that it swings out from the panel.

Anyway that's where I stand now and, again, I thank everyone for taking the time to post their views.
 
One option I'm considering is mounting a block of CBs much like Walt's arrangement in post #42, but on a hinged door so that it swings out from the panel.

Another option is just a variation of the idea you've mentioned above. Mount the CB's on a sub-panel which screws to the face of the main frame of the instrument panel. Wire the CB's such that you have a large enough service loop to allow the sub-panel to be unfastened from the main panel and laid out face-down on your knees so you can work on it. This will cost you an extra foot or more of wire for each circuit but SO worth it when it comes time to work on the power circuits. The same advice would apply to a fuse block installation.

Also, with fuse blocks, be aware that some fuse blocks suffer from poor retention of the "clips" into which the fuses are inserted. This means that inserting a fuse can cause those clips to back out -the harder you push, the further they back out until they touch the metal to which the fuse block is mounted. Then the real fun begins! For those who wish to go with fuse blocks always suggest installation of an insulator between the block and the metal panel to which it is mounted.
 
Another option is just a variation of the idea you've mentioned above. Mount the CB's on a sub-panel which screws to the face of the main frame of the instrument panel. Wire the CB's such that you have a large enough service loop to allow the sub-panel to be unfastened from the main panel and laid out face-down on your knees so you can work on it. This will cost you an extra foot or more of wire for each circuit but SO worth it when it comes time to work on the power circuits. The same advice would apply to a fuse block installation.

Yes that occurred to me to just screw a CB block sub-panel to the main panel.
Simpler to install - 4 screws holding the sub panel onto the main panel - and the longer service loops makes access to the back side of the CB's much more convenient. Also, possibly less main panel space would be taken with some nutplates as opposed to the hinge leaf.

Drawback is, as you say, longer service loops. I wouldn't care about the cost of extra wire. My only concern would be the wires of the much larger service loops for 25-odd CBs taking up a lot of space behind the panel. And I'd have to come up with a method of supporting those loops when flying acro, and yet a quick release of those supports when I need to pull the panel.

With the hinged door, I would have to have a service loop as well (said door held to the panel with a 2-3 screws on the edge opposite the vertical hinge line). But the door service loop could be smaller than the one necessary for the screwed on panel.

Thanks for the info on fuse block failure modes. To be honest I think that my using fuse blocks has a very low probability. But it's good to know this.
 
I have a question about a concept, and am wrestling with this issue at this time as well. Is there merit to a train of thought to have traditional circuit breakers, for the absolutely mission critical items, (essentially whatever needed to keep the big fan up front turning), and say power to a Garmin G5, and then route everything else through the ECBS solution?

Is that a way to have one’s cake and eat it too? (Less real estate for CB’s on the panel, but the few there, are critical ones, not prone to risk of the mystery box failure, but then you get all the benefits of the ECBS for the vast majority of everything else.)

Thanks,
Lance
 
I have a question about a concept, and am wrestling with this issue at this time as well. Is there merit to a train of thought to have traditional circuit breakers, for the absolutely mission critical items, (essentially whatever needed to keep the big fan up front turning), and say power to a Garmin G5, and then route everything else through the ECBS solution?

Is that a way to have one’s cake and eat it too? (Less real estate for CB’s on the panel, but the few there, are critical ones, not prone to risk of the mystery box failure, but then you get all the benefits of the ECBS for the vast majority of everything else.)

Thanks,
Lance

Yes, that's how I'm wiring mine and how many people I've seen deal with EFI systems. For an RV-10 for example, if you try to put EFI onto your ECB solution with the typical avionics you'll run out of circuits before you get everything into the box, so that's issue 1. I also don't quite care about reconfiguring the engine components, unlike cabin electronics which may be replaced or moved around at a more accelerated schedule, so the benefits of the ECB solution isn't really all there for those devices. My plan is to have an E-bus with fuses to handle the engine electronics, and everything else will go onto a VP-X type solution.
 
I have a question about a concept, and am wrestling with this issue at this time as well. Is there merit to a train of thought to have traditional circuit breakers, for the absolutely mission critical items, (essentially whatever needed to keep the big fan up front turning), and say power to a Garmin G5, and then route everything else through the ECBS solution?

Is that a way to have one’s cake and eat it too? (Less real estate for CB’s on the panel, but the few there, are critical ones, not prone to risk of the mystery box failure, but then you get all the benefits of the ECBS for the vast majority of everything else.)

Thanks,
Lance

Yes, that is what I did with mine. I have the engine critical items on an essential bus and everything else on the VPX...and yes, you will run out of circuits on the VPX in a full IFR RV-10 if you try and put everything on the VPX...
 
ECB or not?

Yes, that is what I did with mine. I have the engine critical items on an essential bus and everything else on the VPX...and yes, you will run out of circuits on the VPX in a full IFR RV-10 if you try and put everything on the VPX...

I find it hard to believe this is an optimized solution that balances electrical system availability, redundancy, reliability, weight, cost, maintainability, system reconfigurability and functionality for a single engine IFR airplane. The probability of a common mode event that results in concurrent loss of power to multiple system functions has to be significantly higher than a comparable electrical system based on individual circuit breakers or fuses. If you have an essential buss with fuses of circuit breakers then you clearly understand the common mode problem and potential single point failure that would worry me with a VPX system. I understand the desire to have the latest all singing and dancing whiz bang piece of kit that is easy to install and wire up that replaces something as mundane as a bunch of thermal circuit breakers. When I see data that quantifies in real number what level of protection against loss of more than one circuit function due to internal failures ( predicted or measured) is available from any of the current ECB offerings (VPX etc.) and the MTBF of the system overall and that it is in the same ballpark as a simple circuit breaker system then I might be more inclined to trade some panel real estate for much higher cost, weight and added functionality ( which I may not be able or want to use). Until that time I will probably continue to put the VPX into the category of an expensive solution looking for a problem that doesnt exist but does potentially create problems of its own making.
KT
 
I have golden rule on design: Never add software stuff, when analog will work. JMHO

This rule is hardly "golden". Maybe "silver"? JMHO.

You're ruling out cell phones (use landline... oh wait the phone carriers themselves have been using software switching for years, guess you'd better stick to operator assisted calls), computers (use an abacus), modern TV's (whatever you can still get with rabbit ears), internet (use the library), etc.

Perhaps you just meant for flying. In which case you're ruling out glass panel and EFB, both are, by now, more reliable than the analog equivalent.

-c
 
I find it hard to believe this is an optimized solution that balances electrical system availability, redundancy, reliability, weight, cost, maintainability, system reconfigurability and functionality for a single engine IFR airplan ... I understand the desire to have the latest all singing and dancing whiz bang piece of kit that is easy to install and wire up that replaces something as mundane as a bunch of thermal circuit breakers ...
KT

we read the same but took away different things.
I thought @keitht meant he acknowledges the potential pitfalls, which is why he's protecting his essential circuits with traditional breaker/fuse. For the the non-essential stuff he's opting for the convenience that "whiz bang" has to offer.

Others have pointed out that every wire has 2 ends, etc... as if that means systems like VP-X offer no real convenience. I disagree.

In addition to convenience there's value in standardization and componentization (is that a word?). Any shop can look at a VP-X based system and tell at a glance whether it's put together correctly. If something's wrong, then it's the unit at either end or the wiring harness. No one needs to trace spaghetti.

An obscure example: Saville Row standardized how men's suits are put together. I can have a suit cut in Istanbul, sewn in Hong Kong and fitted in SF. But every thread has 2 ends one might say... then you're missing the point.

-c
 
In addition to convenience there's value in standardization and componentization (is that a word?). Any shop can look at a VP-X based system and tell at a glance whether it's put together correctly. If something's wrong, then it's the unit at either end or the wiring harness. No one needs to trace spaghetti.

I can't believe you would think any shop could look at a sealed red box with wires coming out of it that requires a computer with serial port to program and tell at a glance if something is wrong. I think you may have meant to say traditional bus bar, breakers and wires are super easy for any shop to look at and tell if there is something amiss at a glance. Nothing more straight forward to troubleshoot in my book than that. I office and work at an aircraft service facility and participate in what goes on in the shop on a daily basis. You have to keep it simple (KISS).

I think that there is another factor when it comes to threads like these where we have the equivalent of the one-hump camel guys arguing with the two-hump camel guys as to which is "best". In the end they both get you to the oasis and watering hole.

I think it wise for everyone reading this thread to realize that you will see a disproportionate amount of chatter online when something fails because that is what triggers discussion. Meanwhile there may be hundreds or thousands of perfectly happy customers who never have trouble with a product and just go on flying pleased as punch with their product and have to reason to go search or post about it. If a product has a 95% satisfaction rate and only 3% of the remaining 5% go online to tell their stories of woe, then it can make the product look worse that it truly is. In my example we were disappointed that a cheap USB charge cable could whack the whole VPX system down. But we didn't replace it with a legacy electrical bus. We still think it's functional enough and reliable enough (without any more cheap charge cords) to keep it in the bird. Although we have become guarded about the installation and look at it as more delicate than advertised. In retrospect we probably should isolate the USB power port with a dedicated feed and inline fuse bypassing the VPX module to mitigate a known risk. In the final analysis we would be hesitant to go with any type ECB system for a new build in the foreseeable future.
 
we read the same but took away different things.
I thought @keitht meant he acknowledges the potential pitfalls, which is why he's protecting his essential circuits with traditional breaker/fuse. For the the non-essential stuff he's opting for the convenience that "whiz bang" has to offer.

Others have pointed out that every wire has 2 ends, etc... as if that means systems like VP-X offer no real convenience. I disagree.

In addition to convenience there's value in standardization and componentization (is that a word?). Any shop can look at a VP-X based system and tell at a glance whether it's put together correctly. If something's wrong, then it's the unit at either end or the wiring harness. No one needs to trace spaghetti.

An obscure example: Saville Row standardized how men's suits are put together. I can have a suit cut in Istanbul, sewn in Hong Kong and fitted in SF. But every thread has 2 ends one might say... then you're missing the point.

-c

Not sure what international suit manufacturing has to do with aeronautical systems engineering or the price of butter - but maybe those of us that spent the evening at 40,000 ft have it figured out. Clearly a VPX electrical system solution is front and center in your thinking.

KT
 
Others have pointed out that every wire has 2 ends, etc... as if that means systems like VP-X offer no real convenience. I disagree.

In addition to convenience......

-c

Would you list the conveniences that an ECBS system like VPX provides? To me that's one of the important factors in deciding whether or not to spend the money on such a system, and one of the things I hoped to learn in starting this discussion.

Thanks
 
I find it hard to believe this is an optimized solution that balances electrical system availability, redundancy, reliability, weight, cost, maintainability, system reconfigurability and functionality for a single engine IFR airplane. The probability of a common mode event that results in concurrent loss of power to multiple system functions has to be significantly higher than a comparable electrical system based on individual circuit breakers or fuses. If you have an essential buss with fuses of circuit breakers then you clearly understand the common mode problem and potential single point failure that would worry me with a VPX system. I understand the desire to have the latest all singing and dancing whiz bang piece of kit that is easy to install and wire up that replaces something as mundane as a bunch of thermal circuit breakers. When I see data that quantifies in real number what level of protection against loss of more than one circuit function due to internal failures ( predicted or measured) is available from any of the current ECB offerings (VPX etc.) and the MTBF of the system overall and that it is in the same ballpark as a simple circuit breaker system then I might be more inclined to trade some panel real estate for much higher cost, weight and added functionality ( which I may not be able or want to use). Until that time I will probably continue to put the VPX into the category of an expensive solution looking for a problem that doesnt exist but does potentially create problems of its own making.
KT

...and THAT is your OPINION, to which you are entitled. It is your build, I respect your design choices.

I am entitled to mine, as well...unfortunately, there are many, many people on this board that feel that their OPINION of how things should be done is the only way that works, is safe, is reliable, is _________...and they tend not to respect others design choices...

It comes down to risk and risk mitigation. Everyone has their own level of acceptable risk; some are ok with one in a million odds and others are searching for that ever elusive "perfect" system (hint: it doesn't exist).

It seems as if this board is descending into "My way or the highway"...and it is a shame...
 
...and THAT is your OPINION, to which you are entitled. It is your build, I respect your design choices.

............
It seems as if this board is descending into "My way or the highway"...and it is a shame...

I don't really see that happening here. I think people are merely stating their decision and why they chose it.

No one has said, "....and if you do otherwise you are wrong (or a fool or an idiot etc)."

I know that early on, some people wrote that they started the popcorn machine. But I think that the conversation, here, has been fairly congenial and instructive.

I think the popcorn got stale.
 
But I think that the conversation, here, has been fairly congenial and instructive.

I completely agree. I find it is usually the person who complains the most about "opinions" is one to have the most hardened one. In my case I only pointed out the facts of a failure mode we experienced, followed by a quick personal opinion based on that experience. Cooled by pointing out that like most anything we deal with in society, there are always more complaints than atta-boys as there are lots of happy customers who are likely to never feel the need to report in.
 
... Cooled by pointing out that like most anything we deal with in society, there are always more complaints than atta-boys as there are lots of happy customers who are likely to never feel the need to report in.
Humans are very susceptible to "negativity bias" (https://en.wikipedia.org/wiki/Negativity_bias) and that might be what we are seeing here. As you wrote, more people report issues than report correct operation:

"I just crossed 100 hours, and my VPX is still working perfectly!" -Said by almost nobody

It's normal that we report issues and don't report when things are working great. As the recipients of these (mostly negative) reports, we might want to keep in mind our natural tendency to store them in our memories with a greater weight than they probably deserve.

Same with things like airliner crashes - which as we all know are very rare - the 5 o'clock news does not say "There were 150 thousand successful airline flights globally today!"
 
...and THAT is your OPINION, to which you are entitled. It is your build, I respect your design choices.

I am entitled to mine, as well...unfortunately, there are many, many people on this board that feel that their OPINION of how things should be done is the only way that works, is safe, is reliable, is _________...and they tend not to respect others design choices...

It comes down to risk and risk mitigation. Everyone has their own level of acceptable risk; some are ok with one in a million odds and others are searching for that ever elusive "perfect" system (hint: it doesn't exist).

It seems as if this board is descending into "My way or the highway"...and it is a shame...

No need to shout- just trying to understand the compromises you considered in the design of the system you implemented. I am making an assumption you did postulate some design number for the system you chose and not just read the VPX sales literature - maybe I was wrong to make that assumption given the emotional nature of your reply. If we can stay above the fray I really would be interested in your thought process for making the design decision- I am sure I could learn something.
 
really?

"...I find it hard to believe this is an optimized solution that balances electrical system availability, redundancy, reliability, weight, cost, maintainability, system reconfigurability and functionality for a single engine IFR airplane..."

I think that statement says it all. You are firmly in the camp of "It isn't my way" and there would be nothing that I, or anyone else could say to sway your opinion...(not shouting)...nor would I try. I can only say what I have done, and how it is working for me. If you do not agree with my design choices, that is fine; It really doesn't matter to me as I built my airplane how I wanted and based on my level of risk aversion. I am sure you did the same. You, however, do not see me questioning your design decisions, though...
 
"...I find it hard to believe this is an optimized solution that balances electrical system availability, redundancy, reliability, weight, cost, maintainability, system reconfigurability and functionality for a single engine IFR airplane..."

I think that statement says it all. You are firmly in the camp of "It isn't my way" and there would be nothing that I, or anyone else could say to sway your opinion...(not shouting)...nor would I try.

You, however, do not see me questioning your design decisions, though...

Actually all he said was that he found it hard to believe. Not impossible to believe...hard to believe. He did not say his mind could never be changed.

He didn't question anyone's design decision with that statement.

He stated his opinion.
 
Trying something new (for me, anyway): responding to multiple posts in a single reply. Here goes...

I can't believe you would think any shop could look at a sealed red box with wires coming out of it that requires a computer with serial port to program and tell at a glance if something is wrong.
That's not what I meant. I don't expect to debug a blackbox. I expect it to be simple to verify the connections between the EFIS and the ECB (i.e., integrity of the harness) and isolate the problem to the EFIS or the ECB then rely on the manufacturers to provide the fix thereafter.

Your example with the bad USB cable indicates VP not fully standing behind their product. That is a concern.

I think you may have meant to say traditional bus bar, breakers and wires are super easy for any shop to look at and tell if there is something amiss at a glance.
On the contrary, the few times I looked at wiring behind instrument panels I'm usually presented with a complete mess of wires and cables. But I agree that bus bars and breakers themselves are super staightforward.


I think that there is another factor when it comes to threads like these where we have the equivalent of the one-hump camel guys arguing with the two-hump camel guys as to which is "best". In the end they both get you to the oasis and watering hole.
Agreed. I like the philosophy of ECB over the simplicity of busbars and breakers. That's a personal preference. I do not in any way mean to indicate that I endorse the VP-X product, though I would like to see these types of products continue to mature.


Not sure what international suit manufacturing has to do with aeronautical systems engineering or the price of butter
It is admittedly an obscure reference.

...but maybe those of us that spent the evening at 40,000 ft have it figured out.
Not sure what 40,000 ft has to do with this discussion. Are you suggesting those of us who routinely fly below 12,000 are more accepting of avionics failures?

Clearly a VPX electrical system solution is front and center in your thinking.
Again, I am not tied to the VP-X product. I like the concept and would like to see it continue to grow.

Would you list the conveniences that an ECBS system like VPX provides?
Without being specific to VPX (which I admitted have no direct experience with) I just like the concept of connecting controllers (e.g., knobs and switches) and devices (e.g., lights and EFIS) to a blackbox and then assigning the functions via software. The wiring is therefore simplified. For me, personally, doing the complex part (I.e., assigning the function) via software feels more convenient. If, say, the switch assigned to nav lights goes bad, I can "borrow" the beacon switch to control the nav lights and default beacon with the master switch. This can be done without touching any wiring.
I don't know whether and how well VP-X delivers on this promise... But it's a direction I prefer.

-c
 
Actually

Actually all he said was that he found it hard to believe. Not impossible to believe...hard to believe. He did not say his mind could never be changed.

He didn't question anyone's design decision with that statement.

He stated his opinion.

Actually, the statement itself is questioning the design decision, but whatever…

Build what you want, want what you build…
 
Design decisions

Bob,
Writing a response in capitals is considered shouting. I am currently helping another builder wire his project which includes a VPX and the associated PCU module so I have a little familiarity with the VPX system, the work that is necessary to wire it into the system and the firmware programing to assign the switches to the functions and set the monitoring parameters. I haven't got to associating the switch functions with features like flap control etc. but it seems pretty straightforward to do. I feel pretty confident that I could draw a system block diagram of the inner workings of the VPX and make an educated guess at likely component ballpark failure rates. Nowhere have I found any published numbers from Ashtronics or other sources - which is not surprising since it is not TSO’d or any other approval but only recommended for experimental aircraft use by the manufacturer. In all probability if the hardware was designed to meet DO254 and the software designed to meet DO178 B for flight critical systems the manufacturer would have included that information in the sales brochure. So my point is that if you use this equipment you have to make your own best guess as to the integrity of the design and the design standards employed. They may be OK but without confirmation by credible data you are very much on your own. Conversely circuit breakers and fuses have a lot of well documented failure rate and performance data. Trading reliability and availability for functionality appears to me to be the key attraction but maybe you see it differently - I was just trying to make sure I hadn't missed something.

KT
 
...and

"...Writing a response in capitals is considered shouting..."

Or, in context, emphasizing...example: HEY, GET OVER HERE vs Hey, get over HERE. Anyway, my capitalization of OPINION was meant to be an emphasis, not shouting. There is very little tone to this type of media...

"... I could draw a system block diagram of the inner workings of the VPX and make an educated guess at likely component ballpark failure rates..."

That is great, how do those component failure rates compare to other comment rates within the design? What order of magnitude do think it is? Now compare that to every other part on the aircraft. Again, it comes down to risk aversion.A good example might be the Challenger EAB; it has had a few accidents due to strut mount bracket failure causing a folded wing. People have decided not to fly this model aircraft because of it, while completely disregarding the rest of it's near 40 year history. That's OK, they are more risk averse than the people who continue to fly it...but the same type of conversation takes place. One person's opinion is supposed to carry more weight than the next...

"...In all probability if the hardware was designed to meet DO254 and the software designed to meet DO178 B for flight critical systems the manufacturer would have included that information in the sales brochure..."

If you really wanted to know, maybe try and call Chad at Astronics. He has always returned my calls, and he knows the product.

"...So my point is that if you use this equipment you have to make your own best guess as to the integrity of the design and the design standards employed. They may be OK but without confirmation by credible data you are very much on your own..."

Kind of like the whole experimental aviation hobby? Walk up and down the rows at Oshkosh and talk to folks. There are a large number of people who are "...on their own..." with portions of their build, and they are OK with it. If that's not you thing, fine but not everyone shares you opinion.

"...Conversely circuit breakers and fuses have a lot of well documented failure rate and performance data. Trading reliability and availability for functionality appears to me to be the key attraction but maybe you see it differently - I was just trying to make sure I hadn't missed something..."

Not arguing the data on c/b and fuses. Use them, if you want...I also used some. I guess my overall point is that we are not building a certified aircraft. Choices must be made and everyone will have different choices. Some of those choices will put you "on your own", and you will need to be accepting of that fact...but being on your own doesn't necessarily make it wrong. Had Van himself not gone "on his own" by modifying that first aircraft, we wouldn't even be having this discussion. Take that as an example; no, not everyone has his background...but some do.
 
and ………….. more

Bob,
So lets cut to the chase……… I am not bashing the VPX, PPS or any other Ashtronics product just wondering why you would implement an essential bus with circuit breakers and fuses. The VPX pro system has two processors and separation of output switches, power supplies and other functions assigned to each processor
It is essentially two sport VPX systems in one box - if I read the literature correctly, and it has 30 switched outputs - should be more than enough for any single engine IFR aircraft. There is still the possibility of common mode generic design problems (software, firmware, hardware) resulting in loss of all functions but with well written requirements, thorough comprehensive testing those risks can be minimized. So why, if you are so confident of the basic integrity and system availability of the VPX, would you put circuit breakers in the essential bus powered distribution pathways.
I can think of a number of reasons why you did that but rather than make a wild guess I would prefer to get your version.

KT
 
VPX, Circuit breakers and fuses

We have an RV-7A with VPX-Pro and it has been completely reliable so far - three years and about 250 hours of service. We do have CB's for the alternator field and pMags, plus a small fuse block for high load but non-critical systems like seat heat.

We are also building an electrically dependent RV-10. The VPX Pro does not have enough circuits for a fully IFR equipped airplane, nor does it have 20 amp circuits needed for an air conditioning system. It would be tough to find enough panel space to do CB's only.

Dual bus, alternators and batteries plus a cross tie breaker intended only for use during engine start. We have a combination of the VPX Pro, conventional CB's plus a couple of fuse blocks.

The SDS computers, fuel pumps, and coil packs are each on separate hot battery busses protected by CB's. Injector power is normally half from each hot battery bus, but can be switched to all on one or the other. The VPX system can die completely and we still should have fully redundant power for the engine, along with the G3X system, engine instruments (from an IBBS), and a G5 with it's own backup battery.

Probably overkill, but most of my experience is from Part 121 flying and I used to be a Boeing and Lockheed engineer. It's my first electrically dependent light airplane and it's what makes me comfortable.
 
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Bob,
So lets cut to the chase……… I am not bashing the VPX, PPS or any other Ashtronics product just wondering why you would implement an essential bus with circuit breakers and fuses. The VPX pro system has two processors and separation of output switches, power supplies and other functions assigned to each processor
It is essentially two sport VPX systems in one box - if I read the literature correctly, and it has 30 switched outputs - should be more than enough for any single engine IFR aircraft. There is still the possibility of common mode generic design problems (software, firmware, hardware) resulting in loss of all functions but with well written requirements, thorough comprehensive testing those risks can be minimized. So why, if you are so confident of the basic integrity and system availability of the VPX, would you put circuit breakers in the essential bus powered distribution pathways.
I can think of a number of reasons why you did that but rather than make a wild guess I would prefer to get your version.

KT

Actually, there are 25 general purpose circuits plus a few that are specific function such as the starter, alternator field, and a couple others. There are 10 switch inputs. It is entirely possible to run out of circuits in an IFR single engine aircraft, especially if functionality like wig wag lights are used, which requires 2 circuits + a switched circuit.

My backbone electrical system is fairly close to the Z-14, and also uses some of Carl F's ideas. Basically it is a dual battery, dual alternator, split bus with a crosstie. While the VPX will allow two alternators, only one can be active at a time. I am actually running both alternators all the time, so in normal ops, I have two independent electrical systems as the crosstie is open. One side powers the VPX, the other is primarily for the electrically dependent engine items; these items are connected with traditional C/B's...a diode bridge is incorporated as well.

Using traditional breakers for the small number of circuits was convenient and cost effective; more so than a second VPX. Pretty simple, really...

Are there some features and functionality changes that I would like to see in a future VPX? Definitely. I will not hesitate using the VPX for any future projects...
 
Apples and oranges?

I am interested in whether products like the VPX should be properly considered as “systems” or devices. If the cross feed relay fails in a Z-14 design, has the Z-14 system failed? Nope. But many posts seem to assume a failure of the entire VPX, every function, as it’s likely failure mode (vs the limited failure of the wig-wag relay, or even the failure of one full “channel” of the VPX). What is the expected failure mode(s) of the VPX? IDK, and I haven’t seen this discussed. But it would seem to matter to someone trying to evaluate the two approaches.
 
Sam,

I don't know about expectations. All I know is that our single-event VPX failure was a total "device" or "system" failure (pick your term). All or nothing, symantics aside. Phone charging cord unplugged, everything normal. Phone charge cord plugged in, the VPX and associated circuit wiring disappear. Virtually removed from the aircraft. No lights, flight deck, avionics, wigwag, trim or anything else utilizing the VPX ECBS. We still use the same original ECBS unit today. Shorted charge cord was cut up and discarded to ensure no dumpster divers tried to use it. Take that as only one data point or blip.
 
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Sam,

I don't know about expectations. All I know is that our single-event VPX failure was a total "device" or "system" failure (pick your term). All or nothing, symantics aside. Phone charging cord unplugged, everything normal. Phone charge cord plugged in, the VPX and associated circuit wiring disappear. Virtually removed from the aircraft. No lights, flight deck, avionics, wigwag, trim or anything else utilizing the VPX ECBS. We still use the same original ECBS unit today. Shorted charge cord was cut up and discarded to ensure no dumpster divers tried to use it. Take that as only one data point or blip.
Even if this is the only failure of all the units that have shipped and they had shipped, say10,000 units then that represent a failure rate of 10E-4 per hr which is far from acceptable for the consequences of this type of failure by at least 3 orders of magnitude. I would be surprised if this is the only shipped unit to have experience a failure with these consequences so the failure rate for total system loss of power control is likely worse - maybe an order of magnitude worse. If the electrical system failure rate in an all or mostly all electric airplane is significantly worse than the power plant then something is seriously out of balance
KT
 
Even if this is the only failure of all the units that have shipped and they had shipped, say10,000 units then that represent a failure rate of 10E-4 per hr which is far from acceptable for the consequences of this type of failure by at least 3 orders of magnitude. I would be surprised if this is the only shipped unit to have experience a failure with these consequences so the failure rate for total system loss of power control is likely worse - maybe an order of magnitude worse. If the electrical system failure rate in an all or mostly all electric airplane is significantly worse than the power plant then something is seriously out of balance
KT

Your math assumes each unit only flies 1 hour.
Also in risk assessment you need to start with a baseline, then assess whether the “additional” risk is acceptable. Suppose (using your numbers) its 10E-4 additional risk over a baseline risk of 10E-2 (my made up number)... then would you still say it’s unacceptable?
Some might... to each his own.
Nevertheless I find all too often people make up numbers out of thin air then try to “deduce” a result as if those made up numbers lend credence. It achieves the exact opposite, IMHO.
 
Sam,

I don't know about expectations. All I know is that our single-event VPX failure was a total "device" or "system" failure (pick your term). All or nothing, symantics aside. Phone charging cord unplugged, everything normal. Phone charge cord plugged in, the VPX and associated circuit wiring disappear. Virtually removed from the aircraft. No lights, flight deck, avionics, wigwag, trim or anything else utilizing the VPX ECBS. We still use the same original ECBS unit today. Shorted charge cord was cut up and discarded to ensure no dumpster divers tried to use it. Take that as only one data point or blip.

I think USB has only 4 leads + ground. So per what you say if you short a specific one of those 4 to ground then VPX disappears from your system. I assume this wouldn’t happen if you unplug USB from your VPX. So either your USB wiring is faulty (easy to check) or VP should be on the hook to render a diagnosis and remedy.
I assume you’ve done all this, but you haven’t really shared VP’s response.

You’ve treated the symptom by cutting up that faulty cable, but the gremlin is still in your system. E.g., if you were to plug in a faulty USB devise that shorted the connection from the device end, you’d end up in the same place... or am I completely misunderstanding?

-c
 
Your math assumes each unit only flies 1 hour.
Also in risk assessment you need to start with a baseline, then assess whether the “additional” risk is acceptable. Suppose (using your numbers) its 10E-4 additional risk over a baseline risk of 10E-2 (my made up number)... then would you still say it’s unacceptable?
Some might... to each his own.
Nevertheless I find all too often people make up numbers out of thin air then try to “deduce” a result as if those made up numbers lend credence. It achieves the exact opposite, IMHO.

Taking your comments a bit out of order. Lets consider acceptable risk.

If you fly on a commercial flight your expectation is that taking a one hour flight is not going to significantly shorten your life expectancy. Assuming you expect to live to 80 years old that works out at 700,800 hrs so lets round that up 1,000,000 hrs and say that the chances of having a serious life changing event by taking the flight is 1:100.
So the chances of that event occurring on a per hour basis is the reciprocal of that number 10E-8. So in the big airplane world all major systems have a basic design requirement to meet a 10E-9 failure rate for loss of function and any failure that has a catastrophic effect. When all the system effects are combined the number needs to be better than 10E-8 and over the last 20 years that has generally held true and commercial air travel has been remarkably safe. For us flying our single engine, single string flight controls, single generator electrical systems aircraft we have no choice but to accept a much lower level of safety when we consider single point failures and the level of cost,weight and complexity it would take to mitigate those issues. So although we have single point failures, we (at least most of us) do everything in our control to avoid the consequences of failures in those single point areas. Accepting a failure rate of loss of function of 10E-6 in a single string system requires very careful design, analysis, testing, maintenance and modification which is why we (those of us that really care about these numbers) are using aircraft engines that have a legacy back the the 1930's and represent the most reliable power plants available (not the cheapest, nor the most fuel efficient). Looking at the number of those engines flying, the number of hours flown, the failure rate for failures resulting in a significant event the failure rate is somewhere in the region of 10E-6 to
10E-7 failures per flight hour.

Turning to electronics and electrical systems.

Getting to a 10E-6 failure rate with single string analog avionics electronics is possible with careful design, good thermal management and quality component selection. It is much harder to meet those numbers with digital electronics where component complexity is increased, feature size is smaller and the issues of software design and the probability of unintended features in the system operation place greater demands on systems engineering, testing, qualification, validation and revalidation following modifications or updates.
It is very easy to overlook the level of systems engineering needed to write acceptable design requirements that will specify the characteristics of the architecture needed to meet specific failure modes and effects that are inherent in any digital system implementation. In our particular case is it a single string processor with simple switch outputs or is it a dual self checking pair of processors with smart switches or is it a bunch of simple state machines with smart switches in a distributed architecture that is required?
It all depends on how the requirements are written and where the designers accept the compromises. At least for me, loss of all outputs resulting from the first apparent failure is not acceptable and if I can't be certain that isn't going to occur I have no interest in considering such a system when the alternative has less perceived functionality but has proven verifiable data confirming the absence of total loss of function on a first failure. If you consider the graph of probability of the event on one axis and the severity of consequences on the other axis then it is easy to see that how to draw the line between between acceptable and unacceptable. For each of us that line is going to be in a different place depending on our own risk /reward tolerance and past life experiences.

KT
 
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... For each of us that line is going to be in a different place depending on our own risk /reward tolerance and past life experiences.

KT

I don't follow... but that's ok. As you say it's a personal choice, and I agree. So if your logic works for you, then great.
But from his posts I gather @jliltd didn't suffer a "significant failure event", which based on the context of your post I'm assuming you meant accident, injury, or death.

But if I'm misunderstanding you, and that you in fact have baseline statistics of system failures in GA fleet that did NOT result in accidents, then I'm all ears.
 
...and

"...For each of us that line is going to be in a different place depending on our own risk /reward tolerance and past life experiences..."

It means we all have different levels of risk aversion...

Build what you want, want what you build.

...and always realize that the perfect aircraft has never, and will never, be built.

Some people follow "what has always been done" and other lead the way in expanding the envelope...each person must decide for themselves...
 
Taking your comments a bit out of order. Lets consider acceptable risk.

If you fly on a commercial flight your expectation is that taking a one hour flight is not going to significantly shorten your life expectancy. Assuming you expect to live to 80 years old that works out at 700,800 hrs so lets round that up 1,000,000 hrs and say that the chances of having a serious life changing event by taking the flight is 1:100.
So the chances of that event occurring on a per hour basis is the reciprocal of that number 10E-8. So in the big airplane world all major systems have a basic design requirement to meet a 10E-9 failure rate for loss of function and any failure that has a catastrophic effect. When all the system effects are combined the number needs to be better than 10E-8 and over the last 20 years that has generally held true and commercial air travel has been remarkably safe. For us flying our single engine, single string flight controls, single generator electrical systems aircraft we have no choice but to accept a much lower level of safety when we consider single point failures and the level of cost,weight and complexity it would take to mitigate those issues. So although we have single point failures, we (at least most of us) do everything in our control to avoid the consequences of failures in those single point areas. Accepting a failure rate of loss of function of 10E-6 in a single string system requires very careful design, analysis, testing, maintenance and modification which is why we (those of us that really care about these numbers) are using aircraft engines that have a legacy back the the 1930's and represent the most reliable power plants available (not the cheapest, nor the most fuel efficient). Looking at the number of those engines flying, the number of hours flown, the failure rate for failures resulting in a significant event the failure rate is somewhere in the region of 10E-6 to
10E-7 failures per flight hour.

Turning to electronics and electrical systems.

Getting to a 10E-6 failure rate with single string analog avionics electronics is possible with careful design, good thermal management and quality component selection. It is much harder to meet those numbers with digital electronics where component complexity is increased, feature size is smaller and the issues of software design and the probability of unintended features in the system operation place greater demands on systems engineering, testing, qualification, validation and revalidation following modifications or updates.
It is very easy to overlook the level of systems engineering needed to write acceptable design requirements that will specify the characteristics of the architecture needed to meet specific failure modes and effects that are inherent in any digital system implementation. In our particular case is it a single string processor with simple switch outputs or is it a dual self checking pair of processors with smart switches or is it a bunch of simple state machines with smart switches in a distributed architecture that is required?
It all depends on how the requirements are written and where the designers accept the compromises. At least for me, loss of all outputs resulting from the first apparent failure is not acceptable and if I can't be certain that isn't going to occur I have no interest in considering such a system when the alternative has less perceived functionality but has proven verifiable data confirming the absence of total loss of function on a first failure. If you consider the graph of probability of the event on one axis and the severity of consequences on the other axis then it is easy to see that how to draw the line between between acceptable and unacceptable. For each of us that line is going to be in a different place depending on our own risk /reward tolerance and past life experiences.

KT
Thanks Keith, that was a pleasure to read. Very interesting see in numbers how this kind of risk is evaluated.
 
.........and the issues of software design and the probability of unintended features in the system operation place greater demands on systems engineering, testing, qualification, validation and revalidation following modifications or updates.

KT

The use of software in the systems especially complicates things. Just think of the bugs that are found on operating systems after they are released...and then the bugs that appeared in the updates which were fixed by later updates.

I'm a career software engineer and I know how hard it is to think of everything when designing software. It's not easy. Neither is thorough testing. To think of every possible eventuality is difficult and to test all the ones you can think of can take enormous amounts of time. I've worked on systems where we never ran out of ideas of things to test - but you had to stop somewhere.
 
Perhaps a good poll would be who has had in flight mechanical vs in flight electrical problems. I would be interested which is more likely.
 
The use of software in the systems especially complicates things. Just think of the bugs that are found on operating systems after they are released...and then the bugs that appeared in the updates which were fixed by later updates.

I'm a career software engineer and I know how hard it is to think of everything when designing software. It's not easy. Neither is thorough testing. To think of every possible eventuality is difficult and to test all the ones you can think of can take enormous amounts of time. I've worked on systems where we never ran out of ideas of things to test - but you had to stop somewhere.

To wit (from the Homebuilt forum regarding a G3X installation):


"Jul 4, 2021

..........................
edit: None of these problems existed prior to my most recent update of the operating software. I have also lost my fuel flow data, in gph."
 
Let's start with Vertical Power VP-X costs $1700 to $2400 (plus wiring kit). It is cool, interfaces with EFIS systems, and can monitor and control the electrical system from EFIS I gather (never used one). Even if you add up all the cost of a standard electrical system (they call "old way") it is significantly less cost, despite their exaggerated comparison cost chart they use in their promotional material. We can debate cost but in my experience the VP-X would be significantly more expensive than fuses/CB's and switches. If it fails, it is not like replacing a fuse, a CB or a switch. VP-X has "extras" but I don't think that justifies cost for me; your mileage may vary.

Even with Vert Power VP-X you still need:
  • Panel switches, including master, mag and starter
  • Trim switch(es), on panel or stick
  • Flap switch, on panel or stick
  • Battery Contactor
  • Starter Contactor
  • VP-X Wiring Harness or Connector-Only Kit, ($300 to $700)

The Vert Power VP-X boasts other functions besides just circuit switching and protection. Some of these things are not needed or redundant at least for my application.
  • Pitch trim motor controller........................... (Covered w/ Rocker switch included with MAC trim motor)
  • Roll trim motor controller ............................(Not Required)
  • Reversible flap motor control with braking .....(Covered w/ high current double pole double throw momentary toggle center off switch)
  • Flap position sensor input ............................(Covered w/ looking out the canopy at flaps)
  • Trim position sensor inputs ..........................(Covered w/ Indicator included with MAC elevator trim) ​
  • Flap and trim switch input ...........................(Covered w/ special mechanical switches as stated above)
  • Switch inputs .............................................(Covered w/ Standard big chunky satisfying mechanical toggle switches)
  • Aux battery voltage measurement ................ (Covered w/ my GRT EIS)
  • Starter annunciator .....................................(Covered - Push start, prop turning = annunciation)
  • Main power input from battery contactor ........(Not Required)
  • RS-232 interface to EFIS ..............................(Not Required)
  • Ethernet interface to PC (..............................(Not Required)

What you need with a typical RV is a handful or two of lower current circuits (with switch and circuit/wire protection CB/fuse) and a few higher current circuits. Total circuits may be 12-18 current protected circuits. Keep in mind you can have more than one load on a single CB or fuse, as long as all wires have current capacity greater than the CB/fuse rating. Remember you are protecting the wiring not the load. Like your house there are many outlets and/or lights on one CB. You don't need a CB or fuse for every little item, but some items do deserve or require their own CB or fuse.

Fuses are light, simple and cheap. The down side might be not inflight replaceable. The up side is blowing a fuse is rare, BUT you should not have anything critical on fuses you can't keep flying without, unless you have spare and can access the fuse box. Also you need a tool to pull and replace the fuse typically. The generic fuse boxes you can buy for cars or boats are pretty easy to wire.

CB's are reliable, gives visual indication of trip and can be easily reset. One might ask should you reset a tripped CB inflight? The answer might be no, wait until you get on ground and can check reason for trip. CB's cost more then a car/boat fuse box and fuses. CB's weigh a tad more. Bus bar on CB's is a no brainer. A copper strip with holes. The cross sectional area of the strip (at the hole) has enough area to carry a lot of current. There are aerospace quality CB bus bars as shown in previous post in this thread. The BUS BAR can be divide, high current loads on one bus bar and lower current items on parallel bus bar.

I have mostly CB's (because they look cool :D and I had them), supplemented with fuses and fusible link (Bussman High AMP Fuse). I have under $500 (more with inflation) in my core electrical distribution with discrete switches and circuit current protection (CB's & Fuses). I prefer discrete mechanical components vs proprietary semi conductor software system I can't service. The monitoring of electrical components and system is by individual indication or GRT EIS (alternator load/voltage). I have OV indication and Aux bus automatic isolation.

Bottom Line - The Vert Power VP-X is overkill for my needs, costs more, and I understand and can repair my electrical system with off the shelf parts.

PLEASE DO NOT QUOTE THIS IN FULL IF YOU REPLY:D
 
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Let's start with Vertical Power VP-X costs $1700 to $2400 (plus wiring kit). It is cool, interfaces with EFIS systems, and can monitor and control the electrical system from EFIS I gather (never used one). Even if you add up all the cost of a standard electrical system (they call "old way") it is significantly less cost, despite their exaggerated comparison cost chart they use in their promotional material. We can debate cost but in my experience the VP-X would be significantly more expensive than fuses/CB's and switches. If it fails, it is not like replacing a fuse, a CB or a switch. VP-X has "extras" but I don't think that justifies cost for me; your mileage may vary.
ETC.......

This post is so exquisitely right on! Approaches like the VPX are in a bin I call "Just because there is something you can do doesn't mean you should". It also fits into what I call "TechnoPopulism", exuberance for something that is technology based simply due to an implicit but untrue assumption that technology automatically=good/progress, and accepting what someone (the sales/advertising side) has told them because it "seems and feels" right, but would fail honest scrutiny.

Experience in the software world is that even for well tested software the residual fault density averages around 3 or 4 faults per thousand lines of code. I don't know how much code is in a VPX like box, but I can imagine it is well over 1000 lines of code. And the fact is that something like jliltd's shorted USB cable managed to find one of those faults, bringing the full electrical system down. Ironically, this is exactly the kind of thing the box should have simply protected against - tripped just that shorted output!
 
I'll toss in my $.02 which won't be worth that by the time others read this:

Most everybody I've seen that uses a microcontroller enabled switchbox wouldn't dream of using this for a fuel injection controller or electric ignition. Basically they don't want to add a small microcontroller and software as a dependency to keep the windmill turning.

Now, I'd argue that flight instruments in VFR conditions are less important that the engine, but just as important in IFR conditions. So, logically, unless you are absolutely certain that you will never find yourself in IMC, you wouldn't want your instruments terminated on it either.

Once you eliminate the critical stuff, then all you have left is a very expensive controller box that can drive your trim (assuming you don't view that as critical) or your lights.

Reading that a super noisy usb brick can hose the CPU tells me that there isn't nearly enough isolation between the power source and CPU. There are standards for this: https://do160.org/power-input/ and if everything else in the airplane worked, then it's very likely that the VPX isn't up to the same standards.

In my airplane, I put in standard automotive blade fuses. They are super reliable, available everywhere, and you can get illuminated or resettable models. I was able to find a fuse block that looks nice enough to be mounted on my panel with a clear cover that goes over it. It takes up less space than the breakers would have.

Works for me....
 
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I think this looks reasonable enough to use auto fuses and still give me the features of seeing if something failed.
 

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VPX

"...Most everybody I've seen that uses a microcontroller enabled switchbox wouldn't dream of using this for a fuel injection controller or electric ignition. Basically they don't want to add a small microcontroller and software as a dependency to keep the windmill turning..."

...Now you are including everyone that is using electronic ignition and electronic fuel injection...can you guess what an ECU is?

So I guess there a bunch of us out there that are really in trouble because not only are we using the VPX (oh, the horror), we are also flying behind one brand or another EFII systems...and doing it IFR...OMG.

See, everyone has an opinion...
 
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"...Most everybody I've seen that uses a microcontroller enabled switchbox wouldn't dream of using this for a fuel injection controller or electric ignition. Basically they don't want to add a small microcontroller and software as a dependency to keep the windmill turning..."

...Now you are including everyone that is using electronic ignition and electronic fuel injection...can you guess what an ECU is?

So I guess there a bunch of us out there that are really in trouble because not only are we using the VPX (oh, the horror), we are also flying behind one brand or another EFII systems...and doing it IFR...OMG.

...right?! Like me. 2x PMags, 2x HDX, GTN650xi, hard IFR to LPV minimums, all on a VPX with 6+ years and 1300+ trouble-free hours except for 2 episodes of electrical components acting up...and the VPX caught the problems (one short circuit, one runaway flap motor). The VPX closed the circuits, ID'd the problems, allowed me to troubleshoot and fix the problems and reactivate the systems, both times in IFR. I love my VPX.

Look, I think this entire thread has been a POSITIVE example of how VAF can bring out detailed and well-considered and -supported discussions. Plenty of pros, plenty of cons, all by VAFers who really and seriously seem to know their stuff. I contend that the OP has plenty to consider, and I believe it the thread just about run its course.

However, before putting the thread to bed, I offer the opportunity for final thoughts.
 
...Now you are including everyone that is using electronic ignition and electronic fuel injection...can you guess what an ECU is?

So I guess there a bunch of us out there that are really in trouble because not only are we using the VPX (oh, the horror), we are also flying behind one brand or another EFII systems...and doing it IFR...OMG.

See, everyone has an opinion...

I think you missed my point... I'm talking about compounding risk with one microcontroller depending on another and the fact that EFI and EI vendors that I've seen specifically recommend against powering their units with a VPX.

Also, consider that not all microcontroller implementations are created equal. If an EFI box was subject to failure due to electrical noise, I'd be just as skeptical.

If you had a ford/dodge/chevy/toyota that wouldn't start with a cheap USB brick installed, you'd fault the truck, not the brick... right?
 
I think you missed my point... I'm talking about compounding risk with one microcontroller depending on another and the fact that EFI and EI vendors that I've seen specifically recommend against powering their units with a VPX.

A very important consideration.
 
... all on a VPX with 6+ years and 1300+ trouble-free hours except for 2 episodes of electrical components acting up...and the VPX caught the problems (one short circuit, one runaway flap motor). The VPX closed the circuits, ID'd the problems, allowed me to troubleshoot and fix the problems and reactivate the systems, both times in IFR.

Scroll, tell us about those episodes. What happened, and how was the use of a VPX better than another form of circuit protection?

For example, that short circuit. What was that circuit driving? How did the VPX help you ID and troubleshoot? Same for the flap motor. Why was it running away, and how did a VPX help fix it? Be specific please.

I contend that the OP has plenty to consider, and I believe it the thread just about run its course.
However, before putting the thread to bed, I offer the opportunity for final thoughts.

Careful now. I detect a bit of RCS ;)
 
...

"...Look, I think this entire thread has been a POSITIVE example of how VAF can bring out detailed and well-considered and -supported discussions..."

...and it also brings out the, "...I don't see why you didn't do it my way..." discussions, as well...
 
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