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  #11  
Old 04-04-2018, 07:54 AM
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rmartingt rmartingt is offline
 
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Originally Posted by Carl Froehlich View Post
Exactly correct. Design for continued IFR flight after a fault with no pilot immediate action.
That's what I'm going for with Mod 3. I'd have to go wire-by-wire to confirm but I think it should be tolerant of any one failure without killing the engine. We could take that down the rabbit hole of auto-switching for fuel pumps and ECU control but that might be taking it too far--I'd rather just run both pumps for takeoff and landing, and I don't think automatic ECU switching is really feasible. So I'd just have to live with that one--it's a much less likely failure mode anyway.

The emergency power feed is a second line of redundancy giving me a way to kill everything else and still have power to the engine. Or, if for some reason I lost both alternators it would let me easily maximize time on batteries. For the cost of a switch and some wire, it's cheap insurance.
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  #12  
Old 04-04-2018, 09:48 AM
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Originally Posted by rmartingt View Post
That's what I'm going for with Mod 3.
Let's see some architecture.

BTW, let's not focus on IFR. The issue here is keeping the engine running without interruption....anytime, anywhere.

The best system would not require a type certificate check ride to fly safely. It would have a master switch, two ON-OFF switches for the ignitions, and a fuel pump switch...the same as any light airplane, familiar to all.

I think we're creating our own future safety crisis with endless variations on complex electrical systems. A few years down the road, not even the builder will remember how it is wired. The second owner ain't got a snowball's chance. God help anyone who borrows the airplane.
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  #13  
Old 04-04-2018, 10:52 AM
Electrogunner Electrogunner is offline
 
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KISS

Sometimes simple can be reliable too.

The last thing you want to think about in an actual emergency is ... Oh I need to toggle this switch before this one because.... I have a cross feed that could back feed a fault.

Just saying. My opinion
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  #14  
Old 04-04-2018, 11:06 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by DanH View Post
Let's see some architecture.

BTW, let's not focus on IFR. The issue here is keeping the engine running without interruption....anytime, anywhere.

The best system would not require a type certificate check ride to fly safely. It would have a master switch, two ON-OFF switches for the ignitions, and a fuel pump switch...the same as any light airplane, familiar to all.

I think we're creating our own future safety crisis with endless variations on complex electrical systems. A few years down the road, not even the builder will remember how it is wired. The second owner ain't got a snowball's chance. God help anyone who borrows the airplane.
Dan,

There is merit in your position. I offer however that we should not consider every builder/pilot unable to learn and understand how their aircraft systems work. Perhaps I'm too old school. In my first life I was never allowed to touch a valve or switch before I could draw the system, explain how it worked, and list all immediate actions in the event of a casualty.

We are way passed steam gauges and vacuum pumps. For any IFR airplane there are just too many better options than a 1960 Cessna single split master switch. For those who fly only VFR, no issue.

As a side issue, I have found no data to show that the new full electronic engine management system create more power or are more efficient than one running pMags and a well balanced standard fuel injection system. I've seen some special case applications that may or may not provide some gain in the margins, but for 99% of us the cost and risk of these installs would seem to override this approach. I'm open for anyone to provide the performance data that proves me wrong.

Carl
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  #15  
Old 04-04-2018, 12:10 PM
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DanH DanH is offline
 
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Originally Posted by Carl Froehlich View Post
I offer however that we should not consider every builder/pilot unable to learn and understand how their aircraft systems work.
After all, 90% of us are above average.

Quote:
there are just too many better options than a 1960 Cessna single split master switch.
Really good architecture for EFI/EI power doesn't have anything to do with the master switch. Master on, off, or broken, the engine should continue to run.

Quote:
As a side issue, I have found no data to show that the new full electronic engine management system create more power or are more efficient than one running pMags and a well balanced standard fuel injection system.
Let's not go there and ruin Bob's thread.
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Last edited by DanH : 04-04-2018 at 12:16 PM.
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  #16  
Old 04-04-2018, 12:25 PM
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rmartingt rmartingt is offline
 
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Quote:
Originally Posted by DanH View Post
Let's see some architecture.
See my link above: https://drive.google.com/file/d/0Bzc...w?usp=drivesdk

Actual wiring diagrams are still in work.

Quote:
Originally Posted by DanH View Post
BTW, let's not focus on IFR. The issue here is keeping the engine running without interruption....anytime, anywhere.
Right. Though one could argue that you should have an engine system that you'd trust for IFR, whether you intend to fly it or not.

Quote:
Originally Posted by DanH View Post
The best system would not require a type certificate check ride to fly safely. It would have a master switch, two ON-OFF switches for the ignitions, and a fuel pump switch...the same as any light airplane, familiar to all.
Who says that "just like any light airplane" is the best way to do it? Or is that just "that's how we've always done it" and therefore we should keep doing it whether it's really the best idea or not?


Quote:
Originally Posted by DanH View Post
I think we're creating our own future safety crisis with endless variations on complex electrical systems. A few years down the road, not even the builder will remember how it is wired. The second owner ain't got a snowball's chance. God help anyone who borrows the airplane.
Anyone who jumps into any airplane without first learning the peculiarities of its systems is an idiot. Anyone who lets someone borrow their airplane (especially a homebuilt) without making sure that person understands the peculiarities of that airplane is also an idiot. Airplanes aren't cars, and "hop in and go" went out the window a long time ago. We preach all the time about getting transition training for airplanes, and about taking the time to learn your avionics before you fly with them; what makes transition training for the other systems any different? Nobody expects an average guy driving a steam Cherokee to hop into a glass-paneled RV without at least a few hours of transition; is "your engine works a differently now" an insurmountable obstacle?

In any case, is a "fancy" electrical system really that much more complicated compared to a traditional electrical system and a vacuum system operating together? Good markings and careful thought during the system design process should keep the operator's complication to a minimum. And good record-keeping (schematics and wire diagrams) will make design and maintenance a whole lot easier.


Quote:
Originally Posted by Carl Froehlich View Post
As a side issue, I have found no data to show that the new full electronic engine management system create more power or are more efficient than one running pMags and a well balanced standard fuel injection system. I've seen some special case applications that may or may not provide some gain in the margins, but for 99% of us the cost and risk of these installs would seem to override this approach. I'm open for anyone to provide the performance data that proves me wrong.
It's not always about raw performance.

The biggest attraction, for me, is to have what someone here once described: an engine that does what you tell it to do, without you having to re-tell it each time. It's the idea of not having to play flight engineer. It's the idea of doing away with hot-start techniques, vapor lock, manual leaning, carb ice, and swapping parts around to optimize performance. It's about a system that (to me, at least) is actually more intuitive, from a systems understanding point, and easier to optimize and operate than a mechanical injection or carb system and magnetos.

As an aside, I had the opportunity to sit with Dave Anders last week and learn about his airplane, including what the SDS system can do. Very fascinating discussion and it reinforced my decision to go EFI.


Maybe it's a generational thing. I never tuned engines or hot-rodded cars or motorcycles as a kid. I have never driven a car that didn't have electronic fuel injection. My first full-time job involved testing the most advanced civilian cockpit in the world (at least at the time) in the engineering sim. The first time I flew a glass cockpit airplane for real, I was showing the owner (a 767 captain) how to use various functions on his new Skyview despite never using it before or ever reading the manual. And now my day job involves troubleshooting and devising fixes for an entire range of aircraft, from older jets with cable-driven flight controls and mechanically-controlled engines, up to the latest full fly-by-wire jets with computerized doors.

I'm aware that going EFI and using a fancier electrical system brings with it additional responsibilities. I know it's different than "traditional" light airplanes. But I'd also opine that the electrical system and engine management of traditional light airplanes isn't exactly a goal to be aspired to, either.
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  #17  
Old 04-04-2018, 12:34 PM
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Mike S Mike S is offline
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Quote:
Originally Posted by DanH View Post
Let's see some architecture.
I cant help with "seeing" but I can do a quick description of what I had in the 10.

Dual batteries and dual alternators. Each battery fed by its own alternator ----big battery and big alternator, small battery and small alternator. Basically two parallel systems, but a cross feed Schottky diode to allow current to flow from the main or big system to the aux or small system. All electronics ----EFIS, radios, ignitions----directly fed from aux with back up via the diode. All other electrical loads fed directly from the main system. Your critical electrical loads suck current from either system, depending on which has the higher potential.

Quote:
Originally Posted by DanH View Post
The issue here is keeping the engine running without interruption....anytime, anywhere.
Well, at least as far as the ignition goes-----cant help dry tanks.

Quote:
Originally Posted by DanH View Post
The best system would not require a type certificate check ride to fly safely. It would have a master switch, two ON-OFF switches for the ignitions, and a fuel pump switch...the same as any light airplane, familiar to all.
Yep, what I described above---------as well as failure light on each charging circuit.

I only had one occasion to see the backup system in action------worked just as it should-----seamless transition.
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  #18  
Old 04-04-2018, 04:13 PM
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Ironflight Ironflight is offline
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Quote:
Originally Posted by DanH View Post
The best system would not require a type certificate check ride to fly safely. It would have a master switch, two ON-OFF switches for the ignitions, and a fuel pump switch...the same as any light airplane, familiar to all.

I think we're creating our own future safety crisis with endless variations on complex electrical systems. A few years down the road, not even the builder will remember how it is wired. The second owner ain't got a snowball's chance. God help anyone who borrows the airplane.
Iím definitely with Dan on this one. I fly a LOT of different airplanes - some kit company demonstrators, some personal homebuilts, and some ďone of a kindsĒ, and youíd be surprised how often the personal homebuilts have systems complex beyond their need. I also used to be responsible for operating one of the most complex human-carrying flying machines ever built, and itís electrical complexity was eye-watering. Today a similar ship would have automatic bus reconfiguration and do what was necessary to keep critical systems going without human intervention. And, in fact, the last spaceship I operated was built that way.

My own electrical designs follow this philosophy - if something bad happens electrically, diodes do what is necessary to keep power going to the right places - no human switch throwing is required as an initial response. I might have to step in to clean up systems after the initial failure response is complete - but if I donít, itís not critical. In an emergency, I want to aviate, navigate, and communicate (in that order), and not have to work a set of procedures I might or might not remember because they havenít been needed since the airplane was tested.

Remember, you lose half your IQ points in an unexpected emergency, no matter who you are. Donít make it harder than it needs to be.

Paul
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  #19  
Old 04-04-2018, 06:09 PM
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rmartingt rmartingt is offline
 
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Quote:
Originally Posted by Ironflight View Post
Iím definitely with Dan on this one. I fly a LOT of different airplanes - some kit company demonstrators, some personal homebuilts, and some ďone of a kindsĒ, and youíd be surprised how often the personal homebuilts have systems complex beyond their need. I also used to be responsible for operating one of the most complex human-carrying flying machines ever built, and itís electrical complexity was eye-watering. Today a similar ship would have automatic bus reconfiguration and do what was necessary to keep critical systems going without human intervention. And, in fact, the last spaceship I operated was built that way.

My own electrical designs follow this philosophy - if something bad happens electrically, diodes do what is necessary to keep power going to the right places - no human switch throwing is required as an initial response. I might have to step in to clean up systems after the initial failure response is complete - but if I donít, itís not critical. In an emergency, I want to aviate, navigate, and communicate (in that order), and not have to work a set of procedures I might or might not remember because they havenít been needed since the airplane was tested.

Remember, you lose half your IQ points in an unexpected emergency, no matter who you are. Donít make it harder than it needs to be.
But we aren't talking about space shuttle levels of complexity. We're talking two master switches instead of one, two fuel pump switches (one of which has to stay on) instead of one. I'm trying to keep switch-flipping to a minimum while still ensuring reliability. I guess if you really wanted to you could "hard wire" one of the fuel pumps so it runs any time power is on, but that's a lot of current to waste if you just want power on for a bit to do some avionics maintenance. I'll just remember to leave one of them on.

Going by my "Mod 3", for any single electrical power failure, supply to the engine bus would be uninterrupted as it's fed through diodes from both the primary and aux bus. The response, at the pilot's leisure, would be to flip the crossfeed switch and maybe load-shed nonessential equipment, depending on the failure. Same goes for avionics; the EFIS will have its own internal backup battery to hold the line if necessary. For a local VFR flight you probably wouldn't even have to mess with the crossfeed if you didn't want to--just come back and land.

The only two cases I can think of* where a single failure requires any immediate action are (a) the failure of a fuel pump, where the corrective action is the same as in a conventional system--turn on another fuel pump, and use both for takeoff and landing; and (b) the failure of the primary ECU (flip the secondary ECU switch). Considering the demonstrated reliability of the SDS ECU, that's something I can deal with.


The emergency feed is basically a backup to the backup. It's there if things really start going to pot, like losing both master contactors or both alternators. Or if I have some other failure where I want to kill everything else quickly but need to keep the engine going. It's a high-current switch that ties the engine bus (and nothing else) directly to the batteries. I suppose they could even come on at startup and stay on, if you wanted to operate that way, and the diodes would keep anything untoward from happening.


Has anyone besides majuro15 even looked at the last diagram I posted? Can I please get some useful, constructive feedback on what I've presented instead of "why aren't you going mechanical and mag" and "more than four switches is too complicated"? Maybe I confused things a bit resurrecting my old thread from last July, but still...
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  #20  
Old 04-04-2018, 06:43 PM
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Carl Froehlich Carl Froehlich is offline
 
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Originally Posted by rmartingt View Post
SNIP...

Has anyone besides majuro15 even looked at the last diagram I posted? Can I please get some useful, constructive feedback on what I've presented instead of "why aren't you going mechanical and mag" and "more than four switches is too complicated"? Maybe I confused things a bit resurrecting my old thread from last July, but still...
I did. Looking at that and your previous diagrams I assume the entire engine is running off the one engine buss, is that correct? Is it not possible to have half of the engine on each battery with separate feeds?

Carl
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