Earth bonding of fuel tanks

[Robert Lees]

You know when refuelling, you use a little wire that you clamp to the exhaust pipe (or wherever) to provide earth bonding?

How should earthing continuity be maintained to the fuselage and wing tanks? Should I provide an earthing strap to ensure that any static build-up is prevented?

Rob

[paulp]

grounding

Howdy Lee,

When I did the tanks on my conversion, I brazed a bonding strap the the fus. and then attached same to the tanks with soft solder and then used epoxy over the solder and the strap.

Worked great.

[Robert Lees]

Thanks, Paul, did that need a 337 (variance to the original design?)

[paulp]

variance

Lee,
I asked the same question and was advised that this was an extension of the bonding strap from the fus. to the wing butt and as such wasn't considered to be a variance. I already had one strap in place and the AI said that since I was adding an additional aux tank it should be the same as the existing tank.

[crispy critter]

Hey guys,
Unless you already have the wings apart it is easy to ground the wing tanks just by hooking your ground wire to sump drain or if you don't like that idea you can always open the door and hook it to the on/off valve.

[Richard Boyer]

I just went out and looked at my wing tank. My tank has an aluminum line going from the tank to the fuel valve to the main tank. So it is grounded or earthed. Then I decided to prove it. So, I walked all the way out to the hangar (in the back yard about 15 feet from the house) and pulled out my fancy multimeter and put it in the "ohms" mode. I touched the fuel line coming down from the tank, and then touched ground and it showed that there is a definite connection.

[farnorthflyer]

For Paulp:
In your reply, you mentioned adding an aux (wing?) tank.
I am considering doing that, but under the impression that new field approval rules will make it difficult. Was yours by field approval, or STC (I can't find an STC for the mod).

[paulp]

aux tank

Farnorthflyer:

Howdy, howdy.

The Harar STC(formerly Gilberti conversion) is for the mod to a BC12-D-4-85 with a 1380lb GTW or to the Model 19 with a 1575 GTOW. The model 19 calls for and allows the installation of an aux wing tank. It requires new fuel lines(5/16 id), valves and a most unique venting system. Since the addition of the tank is approved under the STC, the 337 showing the conversion will cover it. When you purchase the STC, you will rec. the drawings, parts lists and the actual STC with the aircraft SN & N# which stipulates that the STC is only for this aircraft and that the STC must remain with the paperwork.

Hope that this answers your ?

[AlvinMcIver]

On page 21 of the March 2003 edition of Light Plane Maintenance is an article entitled Fueling Safety, including instructions on making a grounding cable set. I made one and ground the tank, the funnel, and the gas can when I am loading my own.
Grounding the tank is the easy one as I just clip one of the three leads on the filler spout of the tank. For the funnel and gas can, both of which are plastic, I purchased a package of two metal washing machine filter socks, placed one in the funnel and soldered a copper line to the metal sock and ran the copper line up to and around the tab on the filter. I put the second metal sock over the spout of the gas can and secured it with a snap tie. I then connect the other two grounding leads, one to the copper winding on the tab of the funnel and the other to the sock on the spout of the gas can with the main line connected to a ground such that everything is grounded as the gas is poured from the gas can, through the funnel, into the tank, or at least that is what the article seems to suggest.
When I am fueling from the fuel truck (I never let the line guys fuel the plane because of their tendency to over flow the wing tanks as well as the main tank), I have them run the grounding strap to the exhaust. Given the conversation, however, I think I will check to make sure that that grounds the tanks as I had new motor mounts put in at last annual and there was some issue with the motor not being grounded with the airframe any more.

[paulp]

grounding-engine

Alan,

Howdy. I highly recommend running a ground cable from the engine to an engine mount and from there to the fus. frame. I had some problems with radio noise until I completed the aforementioned. It made all of the difference in the world.

[AlvinMcIver]

Thanks for the suggestion - not only for the fueling but also for the radio noise. The static in my handheld with an external antenna is bad, but since I am hard of hearing in the upper ranges and really love to fly, I can put up with it. Since my wife is neither hard of hearing nor in love with flying, she can't put up with it. I'll try the full monty of complete grounding and see if it makes a difference. Thanks again.

[Richard Boyer]

Earth Bonding = Tree Hugging???

[paulp]

Tree hugging

You will be happy to be able to hug a tree after the first time the static discharge hits the 100LL!