ground cables

[mvidalr]

Hello guys,

Silly question:
I'm about to install the Stall Warner vane assembly. It is basically the first electrical item in the build that requires direct ground connection to the structure of the airplane.

Step 7 found in OP46-04 says "NOTE: Make sure to remove primer or paint that would prevent the ring terminal from making a ground connection to the mount bracket. [....] Attach the Ground Wire to the N.O. (Normally open) terminal on the ES E22-50K Micro Switch".

It is pretty straightforward, but my silly question is: because this part has to make solid ground, is it advisable to also leave the line of rivets that attaches the VA-195G (or VA-195G) Mount Bracket flange to the inside of the Leading Edge skin without primer so that metal-to-metal contact is achieved?

This because I've primed every single rib, including both sides of the flanges and all of the inside faces of the skins in the whole project so far (empennage and wings), thus they basically make primer-to-primer contact.

Am I overthinking this, or do I better start scraping some primer off before closing the wings?

Will this same principle also apply for NAV lights, strobes (specially strobes to avoid noise), landing/taxi lights, antenna, etc. in the future?
Or do the rivets make full metal-to-metal contact when they are set?

what say you?

thanks

[mvidalr]

help still appreciated

[wirejock]

+1
I'm there too. Would be nice to know.
I haven't visited Monterrey in a long time. Is it still pretty?

[Scott Hersha]

Miguel,
I believe the stall warning bracket rivets to the rib flange, right? You shouldn't have to worry about making a solid conductive connection with the many rivets that attach the ribs to the skin, spar, etc., and then all of it riveted together. If you question conductivity, measure the resistance between the electrical mount location and anywhere else on the wing structure using your volt/ohm meter. If you're still concerned, you could mount a ground strap from the rib in question to the spar web, but probably not necessary.

[mvidalr]

Originally Posted by wirejock

I haven't visited Monterrey in a long time. Is it still pretty?

Hello Larry,

From what I've read in other posts, it is recommended to have metal-to-metal ground connections. I'm still looking for a clearer answer however, as most of them are fuzzy (some tell you it doesn't matter, some say that squeezed rivets make enough contact, some others claim the contrary). So I've picked up my deburrind drill to work while I wait for an answer.

Monterrey is still pretty, but never as pretty as Austin, or Colorado.
I have flown to KAUS, KASE and KDEN many times before in my last job as a pilot. I miss that
When was the last time you visited Monterrey?
We had some rough times with crime rates going up and up for a couple of years, but it all seems to have dissipated (now there are other states such as Tamaulipas and Michoacan that have seen a recent growth in violence rates and organized crime), so it feels quiet and safe again. The city seems to be back on track.

[krw5927]

If you absolutely have to ground something and it's important, AC 43.13 shows you how to build a proper ground stud.

That being said, I too primed internal structure and rivet lines in my wing leading edges. I tested the stall warn switch and it grounded just fine through the rivets, so for me that particular device needs no other attention. It doesn't pass any significant current either.

For high current devices like landing lights, and all my avionics, and pretty much everything else in the plane, I ran dedicated grounds from a forest of tabs ground block.

Test it for yourself and convince yourself whether you need additional grounding measures or not.

[mvidalr]

Thanks guys,

I have decided ground locally and scrap off specific primer spots in the structure (probably around a male and its corresponding female dimple) to guarantee a solid ground conductive connection at any given point in the wing structure.

I love this forum.
Happy weekend

[Jesse]

I don't remember exactly where I heard this, but the force of a swelling rivet as it is squeezed or bucked will way more than override the primer that keeps metal from contacting metal between parts. My experience agrees with this. If I am ringing out wiring, I usually just pick any spot on the airframe that has a nutplate because it us riveted to the structure. I have yet to find one that wasn't solidly grounded. I'd recommend a #6 nutplate to screw a ring terminal into for your local ground.

[wirejock]

Miguel
I plan to test with my ohmmeter because I prime everything. Even nut plates. At that point I will decide. I think you could just run a drill bit in a few holes and the rivets would bond the parts and make the conductivity without scraping primer off.

I haven't been there since the early 80s. It was very nice then. I do love Estes Park though.