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  #141  
Old 05-20-2018, 11:21 AM
scsmith scsmith is offline
 
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A slight thread drift (sorry) but a couple of Michael's points here are thought provoking. The idea of being a good maintainer, and the observation that wire bundles are generally very long-lived.

I had a very good friend who, before becoming a FO and captain for a major, worked as a mechanic for the same major, specializing in avionics and electrics. They had a 757 with chronic electrical shorting problems. After hours and hours of testing, he isolated it to a short stretch of wire bundle. When he unbundled it, he found some aluminum chips in the bundle that had fallen from above when some other mechanic drilled a hole in something. The aluminum chips had wiggled and vibrated into the bundle until they cut into the Tefzel and caused a short.

Lesson: Wire bundles can be damaged/affected by other maintenance activities.


Quote:
Originally Posted by Toobuilder View Post
These design excercises are a fine use of time, but lets not forget one simple axiom: You can't add "quality" after the fact.

In this application I see a bunch of angst and concern over what happens when a circuit fails... It would be nice to see that much concern going into the actual fabrication, installation and maintenance of the circuit in the first place. After all, a given battery, wire, and connectors should be MORE RELIABLE than (for example) the bolt holding the drive gear on the back of the crank on your next flight. If you doubt this, then you are not doing your job as a maintainer.

I know Ross has countless examples of "failed" components that are directly related to poor installation practices. In my time with the E-AB world I've seen some downright scary fabrication of critical systems so it appears we have a long way to go before we get it right. I've also spent 30+ years in military and commercial aviation and can say that "wiring" is highly reliable. Short of combat or other acute damage, wire bundles live long and happy lives. I'd suggest we start by ensuring to the best of our ability that the circuit you DO install does NOT fail. That means no chaffing, good grounds, strain relief, proper crimps, regular load testing of batteries, and no possibility of short circuits. Do this and the probability of relying on this yet to be determined "perfect" redundant architecture drops to the noise level.
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  #142  
Old 05-20-2018, 01:00 PM
bluskydreamin bluskydreamin is offline
 
Join Date: Oct 2015
Location: midwest
Posts: 61
Default Same but different...

Bob,

I am still building my -10 and have the following config:

SDSFI
Z-14 dual split buss with cross feed contactor.
60A B&C primary alternator.
BC410 secondary alternator.
2 - Odyssey 625s in the back.
1- Shorai 36Ah battery FWF mounted up high as an aux batt just for the engine buss should I need it. This battery only connects to the engine buss via a Honeywell 20A locking toggle switch. It will be charged / maintained in the hangar as needed between flights via a maintenance lead in the oil door recess.

I could connect the Shrorai to a charging circuit through a diode but have chosen not to. For the typical duration away from the nest it will hold the necessary charge. For anything longer, multi-day OSH, Bahamas, etc. maintenance top off is easy enough via cord or solar. Don't have to worry about overcharging OV Li issues on the running plane.

Is 5lbs worth the added safety net? Will I ever use it? In the -10 I'm not worried about an extra 5lbs hanging around for the piece of mind personally. If it gets to be an issue, I'll lay off the heavy IPAs and extra pizza every week.

The extra $$$ for the dedicated AUX engine battery is peanuts compared to what we put in the rest of the plane.

In normal mode the engine buss will be fed through a primary engine buss switch and diode by the 60 A buss. If I have smoke, the 2 battery masters go off, the aux engine buss switch connected to the aux batt goes on. The avionics to get on the ground have their own B/U batts. I land... NOW, just like I would in any other electrical FI config airplane to sort out why.

It's not automatic but its robust and I will drill the switch procedure at each run up.

"Red switches OFF - Yellow Switch UP!" for any engine power loss or smoke in the cockpit period....LAND!

As a comparison risk management process....When we skydive we expect a malfunction on every jump. The cut away / reserve deployment is mentally rehearsed before every exit regardless of skillset. It should be muscle memory. This rehearsed procedure has gotten me on the ground safely a couple of times when the main canopy did not deploy as it should have. Automatic activation devices can be used for auto reserve deployment if chosen. AADs are "problem solving automation" but can get you into another set of issue entirely if they deploy the reserve in "fringe malfunction" areas.

I view my EFI system in the same way personally. If there's a problem I will deal with it appropriately. Build the system as best you can with sound building practices and know the fault scenarios. The thought that I should build my experimental for anyone to fly and be fully "auto" is something that I personally do not put any weight to....but to each their own.

Quote:
Originally Posted by rocketman1988 View Post
"...Ok, so as a trained engineer/designer, what can you contribute to the discussion? How would you increase reliability, reduce risk, and simplify operation?..."

Those are fair questions. Since I am just beginning my electrical architecture, I am in the process of researching what I actually need, and what I want. I can't answer the "how" questions at this point. Since there appears that any kind of "standard" does not exist, I followed this thread looking for what others are considering and how it compares to those systems designed by people who actually have electrical architecture backgrounds.

After reading this thread, it seems far easier for people to reject other's designs than actually suggest a realistic solution. Realistic is the key word. It is a fine "thought exercise" to try and design a perfect system. In reality, regardless of the number of iterations tried, the perfect system will remain just out of reach. What it comes down to is what is acceptable to each builder. I will defer the "how" questions until I am farther into my design process.

Maybe someone out there who actually is flying with EFIS, EFII, dual batteries, and dual alternators would care to share their experience with their particular design. A discussion based on actual experience might be more helpful than trying to design a perfect system.
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  #143  
Old 05-20-2018, 01:49 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is online now
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
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Quote:
Originally Posted by bluskydreamin View Post
SNIP....

I am still building my -10 and have the following config:

SDSFI
Z-14 dual split buss with cross feed contactor.
60A B&C primary alternator.
BC410 secondary alternator.
2 - Odyssey 625s in the back.
1- Shorai 36Ah battery FWF mounted up high as an aux batt just for the engine buss should I need it. ...SNIP
.
Assuming you are careful in how you connect the two PC-625 batteries I offer that the extra Shorai battery is not needed, nor or the backup EFIS batteries.

Carl
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  #144  
Old 05-20-2018, 03:23 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
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Quote:
Originally Posted by Toobuilder View Post
These design excercises are a fine use of time, but lets not forget one simple axiom: You can't add "quality" after the fact.

In this application I see a bunch of angst and concern over what happens when a circuit fails... It would be nice to see that much concern going into the actual fabrication, installation and maintenance of the circuit in the first place. After all, a given battery, wire, and connectors should be MORE RELIABLE than (for example) the bolt holding the drive gear on the back of the crank on your next flight. If you doubt this, then you are not doing your job as a maintainer.

I know Ross has countless examples of "failed" components that are directly related to poor installation practices. In my time with the E-AB world I've seen some downright scary fabrication of critical systems so it appears we have a long way to go before we get it right. I've also spent 30+ years in military and commercial aviation and can say that "wiring" is highly reliable. Short of combat or other acute damage, wire bundles live long and happy lives. I'd suggest we start by ensuring to the best of our ability that the circuit you DO install does NOT fail. That means no chaffing, good grounds, strain relief, proper crimps, regular load testing of batteries, and no possibility of short circuits. Do this and the probability of relying on this yet to be determined "perfect" redundant architecture drops to the noise level.
Couldn't have said it much better. Keep the number of connections and components to a minimum (less components= less connections). We've covered in other threads how you should make connections, install strain relief and support wiring, keeping it away from high temps and chafing- vitally important with EFI and EI. You can't blame an ECU for "failing" when you don't feed it electrons through good power and ground connections.
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm



Last edited by rv6ejguy : 05-20-2018 at 03:38 PM.
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  #145  
Old 05-20-2018, 03:35 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
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Location: Calgary, Canada
Posts: 5,766
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Quote:
Originally Posted by bluskydreamin View Post
Bob,


1- Shorai 36Ah battery FWF mounted up high as an aux batt just for the engine buss should I need it. This battery only connects to the engine buss via a Honeywell 20A locking toggle switch. It will be charged / maintained in the hangar as needed between flights via a maintenance lead in the oil door recess.

I could connect the Shrorai to a charging circuit through a diode but have chosen not to. For the typical duration away from the nest it will hold the necessary charge. For anything longer, multi-day OSH, Bahamas, etc. maintenance top off is easy enough via cord or solar. Don't have to worry about overcharging OV Li issues on the running plane.


It's not automatic but its robust and I will drill the switch procedure at each run up.

"Red switches OFF - Yellow Switch UP!" for any engine power loss or smoke in the cockpit period....LAND!

I view my EFI system in the same way personally. If there's a problem I will deal with it appropriately. Build the system as best you can with sound building practices and know the fault scenarios. The thought that I should build my experimental for anyone to fly and be fully "auto" is something that I personally do not put any weight to....but to each their own.
My RV6A also has no alternator connection to the backup battery- just a 30 amp ATO fuse and toggle switch to the engine bus. I isolate that bus from the primary battery and alternator by turning off the master.

I also have all my backup switches labeled in yellow. They all go on if the engine stops so I don't need to search for them or think much. It's a trained response.

Nobody flies my plane without a good systems checkout as it's pretty different from most other RVs- turbocharged, electrically dependent, auto engine and variable pitch (not CS) prop. I hope nobody lends out their plane to people unless they understand the systems. That being said, the checkout can be a lot shorter if you don't have a complex electrical layout which requires a checklist to operate in an emergency.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #146  
Old 05-21-2018, 08:47 AM
DanH's Avatar
DanH DanH is offline
 
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Location: 08A
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Quote:
Originally Posted by rocketman1988 View Post
After reading this thread, it seems far easier for people to reject other's designs than actually suggest a realistic solution.
A sincere attempt to provide review, as most request, requires time and thought. And we've been discussing much of it for a long time. Didn't feel a great need to post architecture again, but...

Here's an oldie from a past discussion on developing architecture. It proposes independent dual systems as the best solution for electrically dependent engines (specifically, in that discussion, electronic ignition), but the idea of developing in logical order holds for any proposal.

Start with the basic concept, add charging and airframe power supply, then flesh out the system with required components. I've added the sketch on the right for this discussion, power for full EFI/EI, which in its current iteration requires bringing power to a single bus.



Quote:
Originally Posted by rv6ejguy View Post
Some of the people commenting have zero experience even flying EFI equipped engines so take that into consideration when reading what they have to say.
Ross, how might specific EFI flight experience aid discussion of basic power supply architecture?

Quote:
Originally Posted by rv6ejguy View Post
My RV6A also has no alternator connection to the backup battery- just a 30 amp ATO fuse and toggle switch to the engine bus. I isolate that bus from the primary battery and alternator by turning off the master.
That was a system add-on following an incident. You added it a long time ago. Views change. Would you use the same architecture if you were wiring the new airplane today? If so, why, in technical terms?
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  #147  
Old 05-21-2018, 11:35 AM
rocketman1988 rocketman1988 is offline
 
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Default Guys, Thank You...

Thank you to the numerous PMs and thread posts on currently flying systems and your experience with them.
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  #148  
Old 05-21-2018, 11:53 AM
Pukauma Pukauma is offline
 
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Much cleaner diagram(s), Dan. I have been considering running an AWG 6 "fat wire" to the switches for the EFI bus. According to Nuckolls he feels it does not require fusing. Eliminates another component and connections.

http://www.vansairforce.com/communit...uckolls&page=2

Any complaints with that?
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  #149  
Old 05-21-2018, 12:06 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by DanH View Post

Ross, how might specific EFI flight experience aid discussion of basic power supply architecture?

That was a system add-on following an incident. You added it a long time ago. Views change. Would you use the same architecture if you were wiring the new airplane today? If so, why, in technical terms?
I didn't say comments from people not flying EFI have no merit, just consider that their ideas have never flown. I personally always value your input and ideas as they are almost always well considered and you have wide experience in many fields. Some others here, not so much.

Actual working experience with any topic is a bonus in my view. For example, if someone has done a lot of nice composite work, they're far more qualified to give advice IMO compared to someone who has little or no experience on that subject- which is why you don't see me giving advice on that topic.

While a clean sheet design may work flawlessly, you don't know without some time on it. Lot's of folks think they have a great idea but have no experience using those circuits to know how well it works or if it's been reliable for a period of time. In this business, we consider that important and significant.

On my layout, I'd use it again with no changes because it's simple and it works. I need nothing more than that. I only offer what has worked for me and others to put forth ideas and make people think. I know most people have their own ideas for their aircraft. Their mission and experiences are likely different from mine and I get that. I am not the "know it all guy" on this topic. What I do have is feedback and ideas from hundreds of customers over many years who have been flying EFI. I've learned some useful things from this thread too which I'll distribute to out customers.

I've/ we've learned from my mistakes and others to improve system reliability. On other forum at the moment, the topic is how best to implement backup fuel and spark on an alternative engine. The sub topic was the details on two forced landings caused by crank sensor wires melting though from poor routing near exhaust systems. While obvious to most people, these 2 builders didn't consider their choices carefully enough and both planes were damaged as a result. We can learn from those mistakes and add special cautions and improved thermal resistance and shielding to those wires. You can't get feedback from someone who has never done something.

There are plenty of ways to approach and implement an electrical layout for your EFI aircraft (as we've seen on numerous threads here). No best way for everyone so I think people looking for a definitive layout that they should use may be disappointed. I would urge everyone reading this thread to take all the good ideas put forth and perhaps use them to improve your design.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm



Last edited by rv6ejguy : 05-21-2018 at 12:18 PM.
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  #150  
Old 05-21-2018, 02:26 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by Pukauma View Post
I have been considering running an AWG 6 "fat wire" to the switches for the EFI bus. According to Nuckolls he feels it does not require fusing.
True enough, but I would not select #6 for a 20 amp max load just to skip a fuse.
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