REFLECTOR: Oil lines and ground wire.

[Scott Derrick]

I posted the following question on the aero-electric list

--> AeroElectric-List message posted by: "Scott Derrick" <scott at tnstaafl.net>
>
>
>Hows your feeling about using 1/2" copper oil lines from my engine to the
>nose cooler as a ground return?

The consensus of %100 of the folks who replied was that it was not only a bad idea but my plane would be a disaster waiting to happen.  Stories of arcing and the resulting conflagration from an oil fed fire abounded. I was somewhat taken aback, as I thought it was a good idea if implemented correctly.

I then asked Bob Knuckles(of Aero-Electric fame) who monitors the list to comment.  His reply follows..


>From Bob:

   It's not a "new" idea. I had some long-ez builders using an aluminum
   vacuum line as a ground return about 15 years ago. It would be interesting
   to see how many are still flying with that arrangement and what prompted
   any changes.

   I think the risks are low IF integrity of the electrical connections
   are high. This means sweat soldered, large area joints that would
   assure both mechanical and electrical integrity of the conduit.

   The drawing at

http://www.aeroelectric.com/Pictures//Conduit_Gnd.pdf

   illustrates some techniques suggested for getting high currents onto and
   off of a copper conduit ground system. Similar techniques would apply
   whether you ran wires or hot oil down the conduit.

   Of course, the run of copper between electrical connections would have
   to be similarly robust in terms of fluid tightness and electrical integrity.
   Standard copper tube fittings sweat soldered together should do the job.

   There are probably a trainload of prohibitions with foundations running
   the gammut of regulatory mandates to sky-is-falling hysteria. But if you
   can bolt a wing on correctly, one should be able to build a run of 
copper that
   has similar integrity for electrons and hydrocarbons.

   Bob . . .