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  #31  
Old 10-25-2018, 05:10 PM
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Sam Buchanan Sam Buchanan is offline
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Default Where should the fuel rig be grounded?

The question for which I haven't seen the answer is "where should the ground wire be attached on the fueling rig?"

Does static need to be discharged at the pump or at the nozzle where gasoline enters the aircraft tank? It seems to me grounding should occur at the nozzle to eliminate static buildup as gasoline flows through the delivery hose post-pump. Is having the grounding cable at the pump leaving part of the system unprotected?
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  #32  
Old 10-25-2018, 07:15 PM
rv7charlie rv7charlie is offline
 
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Before anything else, I should say that a good friend of mine actually had a fuel fire while fueling his -6A from cans. He was fortunate; it did no damage. He had fire around the filler neck (quickly extinguished by dropping the cap into the fill neck), and a small fire on the ground due to spilling some of the can's contents as he recoiled from the fire. He will no longer fuel his plane except from an airport pump.

With that out of the way...

If I'm not mistaken, commercial pump hoses are bonded from nozzle to pump. Having said that, I suspect that if you fail to attach the ground line to the plane, and hold the nozzle over/in the fill neck without actually touching the neck, you could still get static buildup. I think this because it's my understanding that the fuel's flow through the hose can generate static charge buildup, similar to rubbing your shoes on carpet.

Having said all that, I'm pretty sure that plastic gas cans are impregnated with enough conductive material to bleed off any static charge, as long as they are in contact with ground or the source/destination of the fuel. And if you can believe the Gubmnt, metal is no help. See the last sentence in the 2nd paragraph. Also note the recommended procedure to minimize risk while transferring fuel in either direction.
https://www.cdc.gov/niosh/docs/98-111/default.html

Last, IIRC, the reason I was told to hook up the ground lead before getting the hose at the fuel farm was because the plane itself has the potential (pardon the pun) to build up a static charge in flight (think static wicks on high/fast planes), and there's a risk it could retain that charge as you approach it with the grounded fuel hose.

I continue to fuel from plastic gas cans; I just try to incorporate whatever new info I learn as time goes by.

Charlie

edit: Should have added: Touching the can to something metal on the plane before opening either fuel container should dissipate any static charge differences between the fuel and the plane.

Last edited by rv7charlie : 10-25-2018 at 07:35 PM.
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  #33  
Old 10-25-2018, 09:53 PM
RFSchaller RFSchaller is offline
 
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Any static spark would occur at the first contact point. If the component that makes that contact is grounded to any part of the airframe it should be at the same electric potential so know spark would occur. So it doesnít matter where you pick on the airframe to connect the ground wire as long as itís not insulated from the airframe. In practical terms that means donít pick a painted or nonconductive surface, but exhaust pipes, unpainted tiedown rings or unpainted nosewheel forks are good choices. The other end should have a conducting path to the fuel nozzle.
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  #34  
Old 10-25-2018, 10:00 PM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by Sam Buchanan View Post
The question for which I haven't seen the answer is "where should the ground wire be attached on the fueling rig?"

Does static need to be discharged at the pump or at the nozzle where gasoline enters the aircraft tank? It seems to me grounding should occur at the nozzle to eliminate static buildup as gasoline flows through the delivery hose post-pump. Is having the grounding cable at the pump leaving part of the system unprotected?
I was not as clear as I should have been. By "fueling rig", I'm referring to the ones that have appeared in this thread with either electric or hand-crank pumps. The aircraft end of a grounding scheme should obviously be connected to a conductive surface, but where should we connect the other end of a ground cable. To the plastic can, or a probe in the fuel, or the pump, or at the nozzle? Is it sufficient to have a conductive nozzle that is in contact with the metallic aircraft tank?

I am inclined to think the metallic nozzle would bleed off any charge created by movement of fuel in the system, but am wondering if I am overlooking something.
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