Matronics Email Lists Forum Index Matronics Email Lists
BBS Forum Interface to the Matronics Email Lists
 
 Get Email Distribution Too!Get Email Distribution Too!    FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Double pole switch failure mode?

 
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> AeroElectric-List
View previous topic :: View next topic  
Author Message
nuckolls.bob(at)aeroelect
Guest





PostPosted: Thu Apr 19, 2018 7:45 am    Post subject: Double pole switch failure mode? Reply with quote

From: Mark and Kathleen Navratil <czechsix(at)msn.com>

To: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

Subject: Re: Double pole switch failure mode?



Bob, is http://www.aeroelectric.com/PPS/ACAD_Architecture_Dwgs/ where you keep the latest diagrams? Iím planning to use Z-14 for my RV-14 and want to make sure Iíve got the latest. I think it does almost everything I want as is, except I may replace the two battery buses with an essential bus fed by diodes from each battery and run the ignition & fuel injection off of that, so that the engine will run as long as at least one battery has juice left in it. I know that can also be accomplished with the cross-tie contactor, but donít want to have to add that switch to my engine failure checklistÖ



Thanks for making the diagrams available in CAD format, sure beats using whiteout and multiple photocopies of my original RV-8A diagram from 15 years ago!



-Mark


Your welcome . . .

Z-14 in an RV8? Sometimes I'm sorry that I ever published
that architecture. I may delete it from Rev 13. It was offered
for the very rare instances of larger airplanes like a Lancair IVP
with dual efis, a/c, etc . . .

Have you considered Z13/8? What's the failure mode effects
analysis that drives the decision toward Z-14? What engine
ignition combination are you using? What are your anticipated
endurance loads for sustained flight with a failed main
alternator? Under what conditions can you deduce a need
to depend solely on a battery for continued flight?

Keep in mind that the vast MAJORITY of bad days in the cockpit
have roots in the pilot's poor decisions. Only a tiny portion
of aviation mishaps are rooted in mechanical/electrical
failures and MOST of those would have been easily mitigated
with relatively minor changes in architecture and better
attention to preventative maintenance. Like treating
your battery with as much care and attention as you do
tires, fuel tanks and reports for icing along your route
of travel.

The RV8 is probably the highest cost/performance ratio
design in Van's two-seated product line. To burden
this airplane with the weight, expense and complexity
of a system like Z14 may be intellectually comforting
on some level but I suggest it offers no demonstrable
reduction in operational risks for your project.

One of my first Z13/8 builders invested the saved weight
and expense in his RV8 project by making improvements
to cabin heating comfort and adding an oxygen
system. The kinds of numbers he and his son enjoyed
in the use of this airplane were nothing short of
astounding.

Before we launch into a discussion about how to modify
Z-14, how about exploring the failure situations under
which Z13/8 would not meet practical design goals
for electrical difficulties en route?

Yes, the latest .dwg files are at https://goo.gl/dPKjRi



Bob . . .


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List
Back to top
czechsix



Joined: 22 Apr 2018
Posts: 2

PostPosted: Tue Apr 24, 2018 9:36 am    Post subject: Z-13 vs. Z-14 Reply with quote

Bob,
I'm interested in Z-14 for my RV-14A, not my RV-8A. I was just pointing out that back when I built my RV-8A I don't think the wiring diagrams were available in an editable format, so I used ink and whiteout. The -8A had single alternator and one PC680 main battery plus a small backup battery dedicated to one of the elec ignition systems. I only flew it VFR.
On the RV-14A, it will be full IFR cross country cruiser with all glass panel and I'm planning to use SDS electronic fuel injection and elec ignition. That's a lot of stuff riding on the electrical system, especially given that you need to have the high pressure elec fuel pump running at all times (no engine driven pump with EFI).
I want to fly the airplane to Alaska, Caribbean, etc...some areas that are far from home and sometimes pretty remote. Having been stuck for a few days on a cross country in my -8A due to a failed regulator, I'd prefer to have more redundancy on the -14A not just for safety but also so I can dispatch and get somewhere after a failure. The SD-8 is pretty marginal for going long distances in an airplane with electrically dependent fuel pump, engine control unit, injectors, ignition and the EFIS system even if you shed the second display and lights and transponder and such. The engine systems alone will use up most of the SD-8's capacity. Therefore I plan to use the 20-40A B&C 410-H as my second alternator on the vac pad (it isn't much different cost-wise from the SD-8, main downside is a couple more pounds).
Then there's the question of single vs dual batteries. I would like to take advantage of the weight savings of the EarthX battery, but I don't yet trust it 100%...obviously anything can fail (including a PC680), but EarthX has a lot of built-in smarts that I don't fully understand and among other things it can completely shut itself off if it isn't happy. With one battery, the importance of good maintenance goes up and replacement intervals get shorter (at least my philosophy is to replace a single battery every 3 years even if it is performing well). Furthermore with a single battery, the avionics and ECU/ignition system may reboot while cranking.
Adding a second battery addresses these concerns. The TCW backup battery could be a solution for the second battery, but it costs more than an EarthX battery and has more limited capacity.
So I'm thinking I'll use two EarthX batteries, each with their own alternator...two independent electrical systems with unlimited generating capacity. That alleviates my concerns about battery failure modes because it's extremely improbable for both to fail at the same time (I'll have them physically isolated). And I don't have to change them out every 3 years like I did on my PC680 in my RV-8A, I can pretty much run them until one of the dies or fails to crank (because the other one can get me where I want to go on that flight). Even though they are more expensive than a PC680, I think my long-term maintenance (replacement) cost will be about the same because I'll use them longer. Having two batteries keeps the display/EIS/ECU stuff from rebooting during engine start. And two EarthX batteries are still quite a bit lighter than one PC680. In fact, the all-up system weight of dual B&C alternators & regulators with dual EarthX batteries is almost exactly the same as a single Planepower alternator and PC680 that comes with the stock RV-14 kit...so it's break even with respect to weight.
So...that leads me to Z-14. It addresses all my requirements and concerns in a way that Z-13/8 does not. The main thing I'm trying to decide with Z-14 is where to connect all the engine related stuff. Most of the parts are dual redundant (ECUs, ignition coils, pumps) so I could split those up between the two respective battery buses. The one part that is not redundant is the injectors. So I was thinking about running the power for the injectors off a bus that is fed via diodes from each battery. The diodes would keep the two electrical systems isolated while allowing the engine to run as long as either battery is providing power.
Thanks,

-Mark


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List
Back to top
View user's profile Send private message
jluckey(at)pacbell.net
Guest





PostPosted: Tue Apr 24, 2018 8:35 pm    Post subject: Double pole switch failure mode? Reply with quote

Mark,
Many of the ideas you mention are included in this design I created several years ago. You would simply need to add a second alternator.

This design contains a lot of things I want in my RV7:
1. Automatic fail-over
2. No brown-out during cranking
3. Source isolation
4. Simple operation

It is in pure schematic format for easier electrical analysis, as opposed to a hybrid schematic/wiring diagram as are commonly seen on this forum.

It may give you some food for thought,
-Jeff

On Tuesday, April 24, 2018 10:51 AM, czechsix <czechsix(at)msn.com> wrote:



--> AeroElectric-List message posted by: "czechsix" <czechsix(at)msn.com (czechsix(at)msn.com)>

Bob,

I'm interested in Z-14 for my RV-14A, not my RV-8A. I was just pointing out that back when I built my RV-8A I don't think the wiring diagrams were available in an editable format, so I used ink and whiteout. The -8A had single alternator and one PC680 main battery plus a small backup battery dedicated to one of the elec ignition systems. I only flew it VFR.

On the RV-14A, it will be full IFR cross country cruiser with all glass panel and I'm planning to use SDS electronic fuel injection and elec ignition. That's a lot of stuff riding on the electrical system, especially given that you need to have the high pressure elec fuel pump running at all times (no engine driven pump with EFI).

I want to fly the airplane to Alaska, Caribbean, etc...some areas that are far from home and sometimes pretty remote. Having been stuck for a few days on a cross country in my -8A due to a failed regulator, I'd prefer to have more redundancy on the -14A not just for safety but also so I can dispatch and get somewhere after a failure. The SD-8 is pretty marginal for going long distances in an airplane with electrically dependent fuel pump, engine control unit, injectors, ignition and the EFIS system even if you shed the second display and lights and transponder and such. The engine systems alone will use up most of the SD-8's capacity. Therefore I plan to use the 20-40A B&C 410-H as my second alternator on the vac pad (it isn't much different cost-wise from the SD-8, main downside is a couple more pounds).

Then there's the question of single vs dual batteries. I would like to take advantage of the weight savings of the EarthX battery, but I don't yet trust it 100%...obviously anything can fail (including a PC680), but EarthX has a lot of built-in smarts that I don't fully understand and among other things it can completely shut itself off if it isn't happy. With one battery, the importance of good maintenance goes up and replacement intervals get shorter (at least my philosophy is to replace a single battery every 3 years even if it is performing well). Furthermore with a single battery, the avionics and ECU/ignition system may reboot while cranking.

Adding a second battery addresses these concerns.† The TCW backup battery could be a solution for the second battery, but it costs more than an EarthX battery and has more limited capacity.

So I'm thinking I'll use two EarthX batteries, each with their own alternator...two independent electrical systems with unlimited generating capacity. That alleviates my concerns about battery failure modes because it's extremely improbable for both to fail at the same time (I'll have them physically isolated). And I don't have to change them out every 3 years like I did on my PC680 in my RV-8A, I can pretty much run them until one of the dies or fails to crank (because the other one can get me where I want to go on that flight). Even though they are more expensive than a PC680, I think my long-term maintenance (replacement) cost will be about the same because I'll use them longer. Having two batteries keeps the display/EIS/ECU stuff from rebooting during engine start. And two EarthX batteries are still quite a bit lighter than one PC680. In fact, the all-up system weight of dual B&C alternators & regulators with dual EarthX batteries is almost exactly the same as a si!

ngle Planepower alternator and PC680 that comes with the stock RV-14 kit...so it's break even with respect to weight.

So...that leads me to Z-14. It addresses all my requirements and concerns in a way that Z-13/8 does not. The main thing I'm trying to decide with Z-14 is where to connect all the engine related stuff. Most of the parts are dual redundant (ECUs, ignition coils, pumps) so I could split those up between the two respective battery buses. The one part that is not redundant is the injectors. So I was thinking about running the power for the injectors off a bus that is fed via diodes from each battery. The diodes would keep the two electrical systems isolated while allowing the engine to run as long as either battery is providing power.

Thanks,

-Mark

Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=479518#479518



AeroElectric-List" target="_blank">http://www.matronics.com/Navigator?Aer - MATRONICS WEB FORUMS -
http://wiki.matronics.com[/url]

http://www.matronics.c=


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List



PowDist01b.pdf
 Description:

Download
 Filename:  PowDist01b.pdf
 Filesize:  43.18 KB
 Downloaded:  10 Time(s)

Back to top
czechsix



Joined: 22 Apr 2018
Posts: 2

PostPosted: Thu Apr 26, 2018 4:04 pm    Post subject: Re: Double pole switch failure mode? Reply with quote

Thanks Jeff. If a second alternator was added to your diagram, I think the main difference would be that you have a single main bus fed from each battery/alternator via diodes whereas Z-14 has an additional switch to manually close the Cross-Tie solenoid. That provides you with the 'automatic failover' you are describing. The main drawback is you can't crank the engine from either battery...not a safety issue, but most people sooner or later experience going to the hangar, getting out the airplane, and then it won't crank. It's nice to be able to use the second battery for cranking since you've got it installed anyway...

-Mark


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List
Back to top
View user's profile Send private message
nuckolls.bob(at)aeroelect
Guest





PostPosted: Thu Apr 26, 2018 4:39 pm    Post subject: Double pole switch failure mode? Reply with quote

Subject: Re: Double pole switch failure mode?
From: "czechsix" <czechsix(at)msn.com>
To: aeroelectric-list(at)matronics.com


--> AeroElectric-List message posted by: "czechsix" <czechsix(at)msn.com>


Bob,



I'm interested in Z-14 for my RV-14A, not my RV-8A. I was just pointing out that back when I built my RV-8A I don't think the wiring diagrams were available in an editable format, so I used ink and whiteout. The -8A had single alternator and one PC680 main battery plus a small backup battery dedicated to one of the elec ignition systems. I only flew it VFR.

Understand. Sorry 'bout that. Too many irons in
the fire . . .

On the RV-14A, it will be full IFR cross country cruiser with all glass panel and I'm planning to use SDS electronic fuel injection and elec ignition. That's a lot of stuff riding on the electrical system, especially given that you need to have the high pressure elec fuel pump running at all times (no engine driven pump with EFI).

Dual pumps?

<snip>

. . . Therefore I plan to use the 20-40A B&C 410-H as my second alternator on the vac pad (it isn't much different cost-wise from the SD-8, main downside is a couple more pounds).

Agreed.

Then there's the question of single vs dual batteries. I would like to take advantage of the weight savings of the EarthX battery, but I don't yet trust it 100%...obviously anything can fail (including a PC680), but EarthX has a lot of built-in smarts that I don't fully understand and among other things it can completely shut itself off if it isn't happy. With one battery, the importance of good maintenance goes up and replacement intervals get shorter (at least my philosophy is to replace a single battery every 3 years even if it is performing well). Furthermore with a single battery, the avionics and ECU/ignition system may reboot while cranking.

I think the EarthX products have paid their dues
in the marketplace. The electronics are modeled
after the Battery Management Systems in the PMA/
STC products from True Blue. I was reasonably
aware of the development of that product, even
got to witness some of the catastrophic failure
testing during my last tenure in TC aviation at
Textron.

The only time these batteries 'get unhappy'
is discharge below some lower threshold which
is to prevent battery destruction . . . it's
value below that which represents less than
5% state of charge . . . i..e pooped.

It also shuts down for high current drain
numbers that pose risk for battery destruction
but comfortably greater than cranking currents
expected on your airplane.

I would have no heartburn flying an EarthX . . . not
so much for lithium products with lesser battery
management systems.

Adding a second battery addresses these concerns. The TCW backup battery could be a solution for the second battery, but it costs more than an EarthX battery and has more limited capacity.

So I'm thinking I'll use two EarthX batteries, <snip> so it's break even with respect to weight.

Agreed. The aux battery could be smaller since
its critical duties are limited to mitigation
of brownout-reset issues.

So...that leads me to Z-14. It addresses all my requirements and concerns in a way that Z-13/8 does not. The main thing I'm trying to decide with Z-14 is where to connect all the engine related stuff. Most of the parts are dual redundant (ECUs, ignition coils, pumps) so I could split those up between the two respective battery buses. The one part that is not redundant is the injectors. So I was thinking about running the power for the injectors off a bus that is fed via diodes from each battery.

I don't see any value in diode isolated
dual feeders . . . the main bus already
has feeders from 4 energy sources. A few
years back, one of my builders split the
injector supplies such that each injector
had its own fuse. This offered fault isolation
that prevents a single fault from taking all
the injectors off line. His engine would
produce power to sustain flight while missing
the fuel flow of on injector.

I think you're on the right track. Sorry
for the light participation in this thread.





Bob . . .


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List
Back to top
Display posts from previous:   
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> AeroElectric-List All times are GMT - 8 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Powered by phpBB © 2001, 2005 phpBB Group