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02-28-2019, 02:38 PM
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Join Date: May 2011
Location: Liberty, MO
Posts: 252
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Same thing
I had similar symptoms and it was due to a faulty EXP Bus that was intermittent. It drove me crazy for almost a year. I blamed every single other electrical connection in the plane before we figured it out. Now, with breaker switches, it all works.
Good luck. These kind of things make you lose confidence in airworthiness and certainly take the fun out of it.
John
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02-28-2019, 08:07 PM
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Join Date: Mar 2013
Location: Houston,MS
Posts: 63
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AeroElecric
Jonathan. The Aero book will be a great start on getting your system as you want. If the design of your wiring is well thought out you should never be without power to whatever you want to call the buss, with what ever you feel is most important. If designed properly that diode failing could have been overcome by a single flip of a switch.
__________________
RV-4 flying
F1 Rocket
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02-28-2019, 08:26 PM
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Join Date: Jul 2013
Location: US
Posts: 2,251
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Quote:
Originally Posted by Carl Froehlich
Sorry but disagree. All designs should be examined for the result of any component be it a switch, relay, terminal or equipment failure. If the result is not acceptable for the mission, then the builder needs to address the design. In this case a single failure resulted in the loss of all avionics. The cause of the failure is not the focus. Everything you put in your airplane can fail, design to mitigate such failures if you cannot live with the result.
For a day VFR airplane less rigor is required.
Carl
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Agreed. So something about *this* design allowed a Single Point Failure at the diode which took everything out. But I don't think the Z-whatever design from Nuckolls has that flaw...failure of the diode wouldn't cause the system-wide failure. I could be wrong, but if my understanding is right, diode failure would simply result in inability to isolate and power the E-buss.
I did a full FTA on my system, to ensure that no single failure could leave me without sufficient capability in IMC to get down safely, as you note. Given the backup batteries for primary and redundant EFIS, plus an E-buss wired basically as per the Z drawing (specific items on E-buss chosen to mitigate an alternator failure), I ended up with no SPFs that would result in a safety of flight issue...and no dual battery/dual alternator configuration.
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2019 Dues paid!
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02-28-2019, 08:45 PM
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Join Date: Feb 2018
Location: Prosser, WA
Posts: 107
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Quote:
Originally Posted by RV7A Flyer
I disagree. The *flight instruments* are most important (if you're in IMC), followed by the navigation. ATC will see you and get people out of your way, and you can deal with the lost comm later.
If you're VFR, navigate to the nearest airport and land.
Aviate
Navigate
Communicate
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I do have back up airspeed, artificial horizon, altimeter, turn and bank indicator, heading indicator in steam gauges and these continued to work and I am thankful and yes they are absolutely important/critical. I do find I really enjoy the EFIS and the navigation aspects and I do carry paper charts (good for blocking sun most of the time) in addition to Fore Flight on IPAD and Phone, so there was a Primary, secondary, and backup for navigation, but not for comms. I will address this issue and see about making it bullet proof!
Lots of ideas out there and my plane will be better in the near future! Yay
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N122EF RV7A
S40 Prosser Washington
=VAF Dues paid 2019=
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02-28-2019, 08:52 PM
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Join Date: May 2006
Location: Pocahontas MS
Posts: 3,884
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A handheld and convenient access to your external comm antenna cable would go a long way toward mitigating comm loss.
Even a handheld with its rubber ducky can work pretty well in an RV.
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03-01-2019, 08:39 AM
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Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,596
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Quote:
Originally Posted by RV7A Flyer
SNIP Given the backup batteries for primary and redundant EFIS, plus an E-buss wired basically as per the Z drawing (specific items on E-buss chosen to mitigate an alternator failure), I ended up with no SPFs that would result in a safety of flight issue...and no dual battery/dual alternator configuration.
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Agree - having a bunch of equipment specific backup batteries mitigates the single battery shortfall for IFR and seems to be is a popular approach for builders using Van?s wire kit and/or Knuckles? designs. I have not noticed a similar wide adoption of such backup batteries for communications or transponder.
I also note the fixation of alternator failure as the prime mitigation target falls short of all the other stuff that will bite you (like listed by the OP).
In my RVs I use two PC-625 batteries and a thoughtful power distribution scheme, and no backup batteries. I believe this provides for a more robust system and makes for a simpler, as light or lighter and more easly maintained install.
But as with all such things, builders should build as they want, not how people tell them to build.
Carl
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03-02-2019, 03:32 PM
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Join Date: Feb 2018
Location: Prosser, WA
Posts: 107
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Update from Original poster
I have replaced the Rectifier diode and put in a back up line on the load side, and now have 13.5v at idle on the ground. I have all my instruments and radios back, and it all appears to working as designed. Makes me think the rectifier has been slowly failing over the last 4 months and led to a possible unneeded replacement of the alternator (but also a good learning experience).
Best of all I feel much more confident diagnosing an electrical issue, have spare rectifiers and fuses. Now if the weather will just clear up!
Thanks you to all those who helped with their ideas.
__________________
N122EF RV7A
S40 Prosser Washington
=VAF Dues paid 2019=
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03-02-2019, 05:22 PM
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Join Date: May 2013
Location: Mount Vernon, Wa
Posts: 643
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Quote:
Originally Posted by Jonathan Alvord
I have replaced the Rectifier diode and put in a back up line on the load side, and now have 13.5v at idle on the ground. I have all my instruments and radios back, and it all appears to working as designed.....
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Did you mount the new diode package on a heat-sink?
__________________
Ken W.
Mount Vernon, WA
2020 VAF Supporter
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03-02-2019, 05:46 PM
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Join Date: May 2006
Location: Pocahontas MS
Posts: 3,884
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My vfr rv4 shows ~14.4v at idle, right after cranking, using a Denso 55A automotive alternator. 13.5v will take forever to charge a battery. (Edit) Sounds like you either have an alternator problem, or a measurement problem.
Last edited by rv7charlie : 03-02-2019 at 06:03 PM.
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