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OK People - Electrical System Architecture

snoop9erdog

Well Known Member
Tell me what you think. After days of reading and researching for my RV9 for what I want my electrical to be in Mr. Reeves awesome sight I have come to the conclusion that there are three main camps of Electrical:

1. The Modern VPX ECB's - There was a VPX bash in this thread "To VPX or No VPX" where the majority of posters seemed to think the world was ending with the "all eggs in one basket" issue of failure modes (yet, ignoring Marks backup methods in case of box failure). The Glass panel integration of this box and circuit troubleshooting would be fantastic. It is expensive but seems convenient.

2. The Standard Wiring Method - Many advocated for the less expensive and proven CB's, Buss's, Fuses, etc. When reading Bob's awesome book you are introduced to basic bare bones 1950's wiring that evolves into applications of Essential Buss architecture. Much of this makes sense ...however.......there is a current thread talking about "to relay or just use a switch".....this opened up discussion about points of failure again that "don't kid yourself, relays and diodes and switches do fail".

Ok so, if due to the possibility of aforementioned potential failures + some others (alternator, etc.), people are equipping with essential buss's........isn't it a little hypocritical or ironic that many will jump on the bandwagon to discredit a VPX system with equivalent backups?

Afterall....stepping back and looking at the big picture of risk....isn't the big fan out front a big potential "single point of failure, all eggs in one basket" item? Which leads me to the third camp...

3. Bare bone architecture w/Modern Backup (Essential Backups are way outdated and not really practical for Glass Panels nowadays). In other words, all we/you need is to essentially go back to Van's supplied wiring diagrams and then utilize the backup batteries (4 hour endurance that will outlast vans standard tanks) for PFD, G5, carry an old Garmin pilot or equivalent GPS and a handheld comm for backup. Bingo??

However, I did see and like the concept of Ironflights electrical method of utilizing a small lightweight 5AH battery that is constantly charging and has all of his buss'e tied together by a multitude of diodes that enables a hands off approach to not having to remember any backup sequence in the heat of the moment. Just flip master batt with backup batt and leave it alone.

Conclusion and question:

The above is my observation, and after thinking about it, I'm leaning towards wiring my craft with a simple basic single buss system that utilizes the current modern unit/LRU designated backup batteries....and possibly using the IBBS or similar to backup ONLY the GTN, Autopilot, & Engine Instruments. KISS

The question is: Is that sufficient backup for a Basic IFR with Pmags machine?...or....would you go a step further and put those items on a completely separate backup fuse buss connected to a backup SD-8 coming off the battery (bypass the master contactor)? But then again.....now I'm back to an essential buss with diode connecting the system.

Given the modern day Glass panel setups and for the gents out there flying with experience on their panels, how would you approach it now if you had to do it all over again?


Sorry if too long but maybe it will help someone in the planning stage.

Thx for the input
 
Power distribution

Ed,

Send me your email address and I?ll provide my power distribution design. It has been flying in four RVs for years (soon to be five).

Carl
 
Bob N. has stated that the purpose of the Endurance Bus is not for redundancy, but rather to reduce pilot workload in case the alternator fails when IFR. But it still requires two switches to be operated: E-Bus on and Master off. With a little forethought and practice, the pilot could just as easily shut off 2 or 3 non-essential switches. Many modern avionics have a built-in backup battery. And modern LED lighting does not draw a large current. So loss of the alternator does not present an immediate emergency requiring prompt dumping of non-essential loads. Go ahead and finish your coffee before flipping switches. I think that simpler is better
 
Ed, Send me your email address and I?ll provide my power distribution design. It has been flying in four RVs for years (soon to be five). Carl

Carl, you say that every time someone asks about electrical systems. If you believe it to be as good as something from Nuckolls or Ausman, post it here for peer review.
 
Carl, you say that every time someone asks about electrical systems. If you believe it to be as good as something from Nuckolls or Ausman, post it here for peer review.

Yep - two considerations:
- Will require posting several Power Point slides. I?ll work on that.
- I?m more inclined to directly engage the interested builder, not to start a circular debate. I?ve gone over the design with people we know and respect and they see the value. Many others however get eyes glazed over and just kibitz and go down the ?that is not what I do? road.

In get back home later tonight and will send emails to those who have asked.

Carl
 
IFR redundancy

From a non-IFR pilot but wanting to set up a simple system that would work for IFR.

A very related question-

If I am planning on dual screen Dynon Skyviews and each one having its own dedicated back-up battery. So, do I need auxiliary, if it all fails, separate power source to a Garmin GTN625 (the GPS only version)?

I know the Dynon isn't legal for IFR, but would it get you home, or to the nearest safe airport, on it's own?

The answer would affect the back-ups I need to plan.

PS There is also a separate Garmin G5 with its own battery to help keep you level and straight.
 
Exactly

That's exactly the dillema I'm facing Gill.

I have the 625 purchased already and getting ready to add the G3x system with Garmin Autopilot for fully integrated system......with G5.

Worst case with a failed dark GTN navigator....I believe the back up batteries for the G5 and the panels along with a simple handheld GPS would get you safely headed (assuming weather awareness) away from low minimums.

Is that good enough....or make it more complex and add backup battery or alternator?

I would say for overall peace of mind.....yes a backup power source for the GTN to ultimately shoot an approach would be necessary. But what is the best method or most practical and simple for the backup source?

Another question then....if the modern backup batteries are being used as the redundancy method.... wouldn't before launch, you need to be able to verify/test the charge level of the backup batteries? Do these batteries allow that? Similar to mag check?
 
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Ed,

I am in same boat as you. Single G3x, G5, 625.

My goal is to KISS. One main bus, A TCW backup battery that will supply power for 4 components I deem essential (haven?t decided that yet), and a backup battery for the G5. Oh, and my Ipad w/ foreflight.

Like you said, we only got one engine, so...
 
That's exactly the dillema I'm facing Gill.

...

Another question then....if the modern backup batteries are being used as the redundancy method.... wouldn't before launch, you need to be able to verify/test the charge level of the backup batteries? Do these batteries allow that? Similar to mag check?

Don't know about the Garmins, but the Dynon Skyview back-up battery has a recommended cycle for using a self-test mode. It reminds you when the self-test is due and the self-test is also a capacity check.


And to expand on my previous question. Can you execute a GPS approach with the Skyview if you have the IFR database?
 
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I ended up using two batteries, with one reserved as a backup source (can also be cross-tied to the main buss). Once switched on (typically always on), it powers my G3X, minus the AP servos, and my EI. I then installed switches/relays to connect that power bus to the following (diodes used to prevent cross draining back to main bus):

430W
SL40
AP servos
transponder

This gives me flexibility to best manage power drain in various situations while IFR. I used the small form factor toggles installed in an upper corner of the panel, so it doesn't take up much space and away from most hand movement.

Larry

That's exactly the dillema I'm facing Gill.

I have the 625 purchased already and getting ready to add the G3x system with Garmin Autopilot for fully integrated system......with G5.

Worst case with a failed dark GTN navigator....I believe the back up batteries for the G5 and the panels along with a simple handheld GPS would get you safely headed (assuming weather awareness) away from low minimums.

Is that good enough....or make it more complex and add backup battery or alternator?

I would say for overall peace of mind.....yes a backup power source for the GTN to ultimately shoot an approach would be necessary. But what is the best method or most practical and simple for the backup source?

Another question then....if the modern backup batteries are being used as the redundancy method.... wouldn't before launch, you need to be able to verify/test the charge level of the backup batteries? Do these batteries allow that? Similar to mag check?
 
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Original poster wants IFR with Pmags so I would suggest:

Conventional wiring with fuses/circuit breakers and NO VPX.
30 amp backup alternator mounted on the vac pump drive which should be sufficient to power all avionics so no avionics load shedding or essential buss needed.
No backup battery needed especially if the screens have their own built in.
Individual switches on all avionics especially if using fuses behind the panel and NO avionics master.
An extra buss feed wire directly from the battery (+) to the buss with a fuse at the battery end and a toggle type CB on the panel which would be activated if there was a suspected master relay failure in flight.

Just my suggestions. I am sure many will not agree!!

Fin
9A IFR.
 
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Yep

Yep, many will disagree.

That?s ok though, as your opinion carries the same weight as everyone else?s.

Lots of different choices, no right or wrong answers...
 
I have redrawn Carl's electrical drawing to make it easier to understand. My apologies to Carl if there is an error(s). To simplify the drawing, I have left out many details like fuses and circuit breakers and relay control wiring and loads and etc. This is my interpretation of Carl's electrical system. It may be downloaded HERE.
enhance
 
Tell me what you think. After days of reading and researching for my RV9 for what I want my electrical to be in Mr. Reeves awesome sight I have come to the conclusion that there are three main camps of Electrical:

1. The Modern VPX ECB's - There was a VPX bash in this thread "To VPX or No VPX" where the majority of posters seemed to think the world was ending with the "all eggs in one basket" issue of failure modes (yet, ignoring Marks backup methods in case of box failure). The Glass panel integration of this box and circuit troubleshooting would be fantastic. It is expensive but seems convenient.

2. The Standard Wiring Method - Many advocated for the less expensive and proven CB's, Buss's, Fuses, etc. When reading Bob's awesome book you are introduced to basic bare bones 1950's wiring that evolves into applications of Essential Buss architecture. Much of this makes sense ...however.......there is a current thread talking about "to relay or just use a switch".....this opened up discussion about points of failure again that "don't kid yourself, relays and diodes and switches do fail".

Ok so, if due to the possibility of aforementioned potential failures + some others (alternator, etc.), people are equipping with essential buss's........isn't it a little hypocritical or ironic that many will jump on the bandwagon to discredit a VPX system with equivalent backups?

Afterall....stepping back and looking at the big picture of risk....isn't the big fan out front a big potential "single point of failure, all eggs in one basket" item? Which leads me to the third camp...

3. Bare bone architecture w/Modern Backup (Essential Backups are way outdated and not really practical for Glass Panels nowadays). In other words, all we/you need is to essentially go back to Van's supplied wiring diagrams and then utilize the backup batteries (4 hour endurance that will outlast vans standard tanks) for PFD, G5, carry an old Garmin pilot or equivalent GPS and a handheld comm for backup. Bingo??

However, I did see and like the concept of Ironflights electrical method of utilizing a small lightweight 5AH battery that is constantly charging and has all of his buss'e tied together by a multitude of diodes that enables a hands off approach to not having to remember any backup sequence in the heat of the moment. Just flip master batt with backup batt and leave it alone.

Conclusion and question:

The above is my observation, and after thinking about it, I'm leaning towards wiring my craft with a simple basic single buss system that utilizes the current modern unit/LRU designated backup batteries....and possibly using the IBBS or similar to backup ONLY the GTN, Autopilot, & Engine Instruments. KISS

The question is: Is that sufficient backup for a Basic IFR with Pmags machine?...or....would you go a step further and put those items on a completely separate backup fuse buss connected to a backup SD-8 coming off the battery (bypass the master contactor)? But then again.....now I'm back to an essential buss with diode connecting the system.

Given the modern day Glass panel setups and for the gents out there flying with experience on their panels, how would you approach it now if you had to do it all over again?


Sorry if too long but maybe it will help someone in the planning stage.

Thx for the input

Ed;
There is another option for wiring, with the simplicity of the VPX. I love the idea of the VPX, but it is overkill for me, and I am just not that comfortable with it, at least not yet.

Everybody likes to quote The Aeroconnection, and the wiring schematics included probably include something you and I should follow. But there is another part that almost everybody skips over.

In the beginning of the book, Mr Nuckols describes how state of the art in 12V electronics, is the modern car. Most aircraft wiring came out of the 1950's, or before.

So my choice is to follow a schematic from Aeroconnection, but implement it as "automotively" as I can. My 1st choice was just to use a fuze/relay panel from a car. But I couldn't figure out how to wire it to be able to shut things off. At least not yet.

A little shopping shows lots of other different options. I am using a fuze/relay panel from a company called Littlefuze. Eaton's "Bussman" sells similar products. The marine industry sells complete switch panels.

The unit I bought has 2 completely separate busses, is IP68 for waterproof and shockproof. It is everything I need other than a master relay, all in one.

It has 2 power posts for the power input, and one big ground. All the other connectors are Delphi (GM) water proof automotive connectors. It is sold as a SSV power distribution module, where SSV stands for "severe service vehicle". Construction and offroad type vehicles.

I have replaced far more switches in the last 40 years, than automotive relays.

That is my choice anyway.
 
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I don't like VPX (too much unknown hardware & software), but that's been done to death ...

I'm also not a great fan of multiple back-up batteries. First off if you will be relying on a/some back-up batteries to get you safely out of IMC should the alternator quit then it/they need capacity checking on a regular (annual or 6 month) basis. Devices from reputable manufacturers have an app to check capacity.

The batteries will fail at some point and will require replacement. That will be expensive ($200 is not unusual) and can involve dangerous goods shipping charges. All assuming the battery is still available. Therefore, back-up batteries will introduce a maintenance overhead.

Two alternators are often a cheaper option, possibly in the short term and certainly in the long term, when coupled with a well though through electrical architecture.

Pete
 
Hmmm... some interesting perspectives here.

Of interest, a backup battery doesn't need to be a complex, expensive part. Mine is a 7.5AH sealed lead acid battery commonly used in computer UPS (uninteruptable power supply) applications. Cost me about $35. It gets tested every time I start the airplane as it serves as my "brown out" battery.

I power my critical avionics from it (GNS navigator, primary and secondary EFIS and associated annunciators). On a regular basis I do software updates and tinkering with avionics and monitor the ESS battery voltage over time to get a feel for its capacity. If I see ESS battery voltage dropping more quickly than would be consistent with my desired backup time frame, the battery gets changed. Haven't had to do that yet, but I have a fresh battery on the shelf, just in case. At a cost less than a case of beer, keeping a spare handy is a simple and cheap solution.

While we are on this topic, keep in mind that AFS/Dynon has their Advanced Control Module which is available in either a fused or electronic circuit breaker configuration. I would pick this hands-down over a VPX.
 
I have redrawn Carl's electrical drawing to make it easier to understand. My apologies to Carl if there is an error(s). To simplify the drawing, I have left out many details like fuses and circuit breakers and relay control wiring and loads and etc.

That's smart Joe. The act of re-drawing anyone's proposed system promotes real understanding. I've found re-drawing and organizing and generally cleaning up my own drawings is a worthwhile thought exercise.

This one is fundamental architecture, a great place to start. Got another with development of detailed component wiring? The cool thing about that exercise is that you're actually building the wiring harness in a form of virtual reality...which makes it easy to build later, for real.
 
Thanks Dan,
No, I do not plan to make a detailed schematic of Carl's drawing. He has done that and makes it available if asked. There are lots of ways to wire an airplane. Some ways have an unrecognized design flaw. But most electrical architecture is not right or wrong, just different, a matter of personal preference. I prefer simple fuses and a single bus. Add a small backup battery for IFR or night.
 
I have redrawn Carl's electrical drawing to make it easier to understand. My apologies to Carl if there is an error(s). To simplify the drawing, I have left out many details like fuses and circuit breakers and relay control wiring and loads and etc. This is my interpretation of Carl's electrical system. It may be downloaded HERE.
enhance

Joe - nice job simplifying the PowerPoint slides to understand the functionality of the Three Buss design. I'll use it.

Thanks,
Carl
 
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