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  #1  
Old 11-20-2020, 05:28 PM
lon@carolon.net lon@carolon.net is offline
 
Join Date: Aug 2015
Location: Santa Monica, California
Posts: 159
Default Dynon Skyview HDX grounding/corrosion point

I'm hoping someone can tell me where a Dynon Skyview HDX dual-display system is grounded in a 2018 RV-12 ELSA powered by a Rotax 912ULS engine.

I'm asking because after a year and a half of trouble-free operation, my Dynon HDX has been failing on virtually every flight, sometimes in as little as three minutes after takeoff, other times after a half hour. When it fails, the left half of my displays blink "ADAHRS Fail" and then "Attitude Recovering"; and the moving map says "Position Unknown." Several times, my altimeter and airspeed indicator have failed too. The altimeter has shown me at 50,600 MSL or below sea level, when I'm actually at 3500 or 4500 feet. And the airspeed indicator has shown me as fast 205 kts and as slow as 30 kts.

Dynon has been as helpful as it can be. It tried to repair my original ADAHRS, and when that failed on the first post-repair flight, it sent me a replacement ADAHRS and when that failed it sent me a second replacement ADAHRS. It also replaced my GPS. When none of these steps worked, Dynon concluded that I must have a short in the system, somewhere. But Dynon couldn't tell me where to look, because Dynon isn't familiar with the wiring pattern on an RV-12.

I took the plane to a shop with an avionics specialist. They didn't find a short, but did replace my battery which they said was failing, but that didn't fix the problem.

Last week, Van's issued a Service Letter telling RV-12 owners to do a Dynamic Propeller Balance. Van's said that if the balance is not done, damage could be done to the plane, and that the EFIS and Pitot systems may fail. I thought the Service Letter finally identifed my problem, and I had a Dynamic Propeller Balance done yesterday. I test flew my plane this morning, and the Dynon failed yet again, just three minutes into the flight.

The latest suspect is corrosion, because my plane is at Santa Monica Airport, less than two miles from the ocean. Two separate pilots have pointed to corrosion as the likely culprit, one of them suggesting that the likely spot is where the Dynon system is grounded.

I didn't build the plane, so I didn't wire it, and I don't know where the Dynon system is grounded, or even how the system is wired. If anyone can tell me where to look for the ground point, or where else to look for corrosion, I'd be most thankful.
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Lon Sobel
Santa Monica, CA
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  #2  
Old 11-20-2020, 06:13 PM
David Paule David Paule is online now
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,653
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Lon, you can buy the plans for the RV-12 on an inexpensive thumb drive from Van's. And a number of the sections can be downloaded for free on the Van's support web site.

Dave
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  #3  
Old 11-20-2020, 06:37 PM
lon@carolon.net lon@carolon.net is offline
 
Join Date: Aug 2015
Location: Santa Monica, California
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Quote:
Originally Posted by David Paule View Post
Lon, you can buy the plans for the RV-12 on an inexpensive thumb drive from Van's. And a number of the sections can be downloaded for free on the Van's support web site.

Dave
Thanks Dave, I have the thumb drive and even the physical Kit Assembly Instructions. However, I can't find any pages that show where the Dynon Skyview HDXs are grounded, because the KAI is about building the plane, not about installing its avionics. The HDX installation manual doesn't show the RV-12 grounding point, because HDXs are installed in all kinds of planes. Unless I've simply overlooked the relevant pages, my issue has fallen in the crack between documentation for building an RV-12 and installing an HDX.
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  #4  
Old 11-20-2020, 06:49 PM
Bob Y Bob Y is offline
 
Join Date: Jul 2017
Location: Piedmont, SC
Posts: 204
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Per page 4-34 of the Skyview Installation Manual:

“To minimize the possibility of audio “humming”, a 16 AWG wire may optionally be
connected between the ground point for the intercom/audio panel/radio(s) and
SkyView display case(s). To attach the wire to the rear of the SkyView display, a 4-
40 x 3/16” long screw may be screwed into the threaded boss above the USB ports
on the back of the SkyView display.”

Page 4-14 shows the ground point on the rear of the HDX. I did install these during my build.

Hope this helps.
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  #5  
Old 11-20-2020, 08:44 PM
Mich48041 Mich48041 is offline
 
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Location: Riley TWP MI
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The failures are likely to be caused by a bad connection(s). I suggest that
you take every connection apart and inspect it, then put it back together.
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RV-12 Flying
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  #6  
Old 11-20-2020, 08:49 PM
lon@carolon.net lon@carolon.net is offline
 
Join Date: Aug 2015
Location: Santa Monica, California
Posts: 159
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Quote:
Originally Posted by Bob Y View Post
Per page 4-34 of the Skyview Installation Manual:

“To minimize the possibility of audio “humming”, a 16 AWG wire may optionally be
connected between the ground point for the intercom/audio panel/radio(s) and
SkyView display case(s). To attach the wire to the rear of the SkyView display, a 4-
40 x 3/16” long screw may be screwed into the threaded boss above the USB ports
on the back of the SkyView display.”

Page 4-14 shows the ground point on the rear of the HDX. I did install these during my build.

Hope this helps.
This may help, Bob. I'm not having humming, so I don't need to ground the intercom/audio panel/radio to the HDX. I'm wondering which part of the plane is the grounding point for the HDX system. Is it the battery terminal, or part of the chassis? What I need to look for is a loose or corroded ground connection between the HDX system and whatever the ground point for the HDX might be.

Thanks, Lon
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  #7  
Old 11-20-2020, 08:50 PM
lon@carolon.net lon@carolon.net is offline
 
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Location: Santa Monica, California
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Quote:
Originally Posted by Mich48041 View Post
The failures are likely to be caused by a bad connection(s). I suggest that
you take every connection apart and inspect it, then put it back together.
Thanks Joe. Will do.
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  #8  
Old 11-20-2020, 09:05 PM
12vaitor 12vaitor is offline
 
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Location: Panama City, FL
Posts: 153
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The electrical system schematics for the RV-12 can be found on the Van's Aircraft website. Pick the one applicable to your aircraft's baseline. I had an ANSI E size one printed at a local copy store with a large format printer so I could read it.

https://www.vansaircraft.com/downloa...SystemDiagrams

John Salak
RV-12 N896HS
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  #9  
Old 11-20-2020, 09:17 PM
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PaulvS PaulvS is offline
 
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Location: Western Australia
Posts: 527
Default Grounding

Typically there will be a main grounding point for instruments on the inside of the firewall behind the instrument panel. This will in turn be connected to the battery negative terminal and the engine case. There may be multiple ground connections for radio, HDX's, audio board, intercom etc.

Have you noticed what system voltage is being displayed on the HDX when the problems occur?

Another item to check is the fuses, if they are the automotive blade type then it is easy enough to remove/inspect/replace.

Good luck, it is a pity the avionics shop couldn't track it down.
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  #10  
Old 11-20-2020, 10:29 PM
lon@carolon.net lon@carolon.net is offline
 
Join Date: Aug 2015
Location: Santa Monica, California
Posts: 159
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Quote:
Originally Posted by PaulvS View Post
Typically there will be a main grounding point for instruments on the inside of the firewall behind the instrument panel. This will in turn be connected to the battery negative terminal and the engine case. There may be multiple ground connections for radio, HDX's, audio board, intercom etc.

Have you noticed what system voltage is being displayed on the HDX when the problems occur?

Another item to check is the fuses, if they are the automotive blade type then it is easy enough to remove/inspect/replace.

Good luck, it is a pity the avionics shop couldn't track it down.
Paul, Thanks. This is exactly the info I was looking for. I’ll look at those spots over the weekend. One of the failures occurred at 12.8 volts, but most occurred at 13.8 or 13.9 volts. There’s nothing significant about those voltages, is there?
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