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local grounding for wingtip lights

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airlincoln(at)sbcglobal.n
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Posted: Sun Oct 26, 2008 9:42 am Post subject: local grounding for wingtip lights

Can't find this specifically addressed in Aeroelectric connection, but I think I have it figured out -- comments please.  Here's the situation:



RV-7, each wingtip has LED position light (22AWG), strobe light (18AWG shielded) and 75W landing light (14AWG due to length of wire run).  I think I read somewhere that you should NOT ground the shielding of the strobe wires at the wingtip, only at the power supply.  The position lights and landing lights will have two different size crimped ring terminals running from each of their ground wires, so I need to have a #6 nutplate/screw to ground the position lights to the outboard wing rib, and a #8 nutplate/screw to ground the landing lights to the outboard wing rib.  Since I don't know what material the ring terminals are made out of (I don't think they're aluminum), once I bottle brush the two locations where the grounding will occur, I need a cadmium washer between the rib and the ring terminal to avoid corrosion.  I was also planning on coating all components with vaseline before installation.  Have I got this all correct or am I over-thinking? 

 Comments/suggestions please.  



Jim Lincoln

RV-7A wings



DO NOT ARCHIVE

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peter(at)sportingaero.com
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Posted: Sun Oct 26, 2008 11:06 am Post subject: local grounding for wingtip lights

In my view you're over thinking! I would put the same size ring terminal

on the end of all the wires, say #10. Then see AC43.13-1B pages 11-76 to

11-78 and take your choice. Terminals are usually copper. If you coat

everything in vaseline before installation it probably won't work.

Install dry, if you have to apply vaseline do it once everything is

screwed up (perhaps only worthwhile if you live in a very damp maritime

environment). Does the earth for the strobe go back down the shielded

cable? Yes, don't earth the shield at the wing tip. I'm sure others will

have differing views!

Peter



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rv-9a-online(at)telus.net
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Posted: Sun Oct 26, 2008 11:21 am Post subject: local grounding for wingtip lights

Hi Jim. AC43-13 covers this in some detail.  My copy is at the hangar, so I

can't quote from it directly.  The sequence and material of the washers,

lock washers and terminals is covered precisely.  My recollection is for a

nutplate mount: cadmium plated bolt, cadmium plated lockwasher, cadmium

plated washer, terminal (tinned), aluminum alloy washer, substrate.



I actually drilled a hole in my spar (don't panic, it was cleared by the

factory) for the ground point.  Although the rib is probably fine, I just

wanted a lower resistance path.  I used dielectric grease rather than

Vaseline.



You can always crimp on new ring terminals with the same hole diameters and

use a single point for grounding if you want.



You are correct about the strobe shield, don't ground it at the wingtip.



Vern

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