Connecting "bonding" clamp to exhaust pipe during refueling - apparently not a good idea

wanttaja said:
I've taken my Fly Baby to full-service fuel maybe three times in the nearly 30 years I've owned it. Each time, the line person has clipped the ground to the non-rusty, non-painted, shiny steel tie down ring in the wing.

Had to break the news to them that the steel ring was bolted to non-conductive spruce.....

Ron Wanttaja
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Everything is conductive with enough voltage

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flyingron said:
Amusingly, nearly every line guy who goes to ground my plane puts the clamp on the nosegear centering tab. I have to point out to them that that is a piece of (non-conductive) bakelite.
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How many of them have ever heard the term "bakelite" before?
 
morleyz said:
Correct me if I'm wrong (I'm not an electrician nor an electrical engineer), but I didn't think the purpose of the bonding wire is to ground or remove static electricity, but rather to bond the systems (the aircraft and the fuel pump) so they are at the same potential so the static electricity that builds up from the fuel moving through the host, etc. doesn't discharge in the form of a spark. If there is no difference in electrical potential, there is no discharge.
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Basically correct, but the difference in potential prior to bonding can cause a spark as the bonding clamp is brought close to the airframe. The plane can have a significant static charge, largely thanks to that spinning fan out front. It's not only about charge due to fuel flow.

Ever get a shock from a car door in cold, dry weather? Same idea.
 
Half Fast said:
Basically correct, but the difference in potential prior to bonding can cause a spark as the bonding clamp is brought close to the airframe. The plane can have a significant static charge, largely thanks to that spinning fan out front. It's not only about charge due to fuel flow.

Ever get a shock from a car door in cold, dry weather? Same idea.
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Yes, due to human movement. That’s precisely why you’re not supposed to get in and out of your car during fueling. Most pumps have labels advising about it.
 
Half Fast said:
Basically correct, but the difference in potential prior to bonding can cause a spark as the bonding clamp is brought close to the airframe. The plane can have a significant static charge, largely thanks to that spinning fan out front. It's not only about charge due to fuel flow.

Ever get a shock from a car door in cold, dry weather? Same idea.
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That makes sense. I was only thinking of it in context of where there is risk of fuel ignition.
 
morleyz said:
That makes sense. I was only thinking of it in context of where there is risk of fuel ignition.
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Right, and we mitigate that risk by choosing a safe location to make the attachment, which is why I discouraged using the fuel cap chain up thread.
 
Had a fuel truck drive off with the grounding, clamp still attached, the cable flipped around wrapped around the gear and completely ripped my carbon fiber wheel fairing off that was a few AMU’s. Had a line guy heading towards my stacks on my Meridian with a grounding clamp. Yelled from across the ramp nooooooo!!!! Two issues there. Those stacks are ceramic coated, thus nonconductive, and they are crazy expensive to repair/replace. Always best to watch refueling if you can, not always practical.
 
The premise of this discussion (the youtube video about exhaust stack) is based on some misconceptions. One of those being that you would use an ohmmeter to determine the suitability of a static discharge point. The accepted standard is anything less than one megohm but static potential is not really the same thing as your general electrical stuff which is why you can get a shock from wearing a polyester shirt or why you would connect a ground strap to what you would consider a non-conductive plastic Jerry can.
 
wanttaja said:
With my aircraft being made out of wood, my best options are the exhaust, propeller, or carburetor. The latter is usually a bit oilly, don't like putting an alligator clamp on an aluminum prop, so....

Ron Wanttaja
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Ron, I have a glass plane. Always thought the grounding has to be to the gas tank. In my case it can't be so I use the cable from the cap that is in the fuel. Others use the exhaust which, to my mind, does absolutely nothing.
 
Goofy said:
Ron, I have a glass plane. Always thought the grounding has to be to the gas tank. In my case it can't be so I use the cable from the cap that is in the fuel. Others use the exhaust which, to my mind, does absolutely nothing.
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Did you build your plane? Many composite aircraft have conductive mesh and static wicks embedded for lightning protection.
 
Goofy said:
Ron, I have a glass plane. Always thought the grounding has to be to the gas tank. In my case it can't be so I use the cable from the cap that is in the fuel. Others use the exhaust which, to my mind, does absolutely nothing.
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The problem there is the connection of the ground strap to the cable. How far from the tank opening is the place you attach to? Too close, and a spark as the ground strap is connected might ignite the fuel vapors.

My fuel tank is right behind the firewall. I've been assuming it's connected to the engine ground (and hence to the exhaust), but now that I think about it, I should check.....

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Ron Wanttaja
 
Goofy said:
Ron, I have a glass plane. Always thought the grounding has to be to the gas tank. In my case it can't be so I use the cable from the cap that is in the fuel. Others use the exhaust which, to my mind, does absolutely nothing.
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What do you fly? A glass plane should have someplace specific to ground to like I mentioned for the DA40 above.
 
Stewartb said:
I keep the nozzle in hand as I climb up on the tires and cowl step. I presume all that must equalize it pretty well as I’ve never seen or been able to create a static spark in 30 years of doing it. I’m much more careful when wearing static-producing clothes like nylon winter jackets and gloves. With those I can feel the static discharge when I touch the plane with bare skin.
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I have a funny story about that... I work on Diesel Generators. We had a battery charger over charging at a customer facility. It was over 3 months by the time we got repair approval and parts. So on the coldest day in February I sent Marc out to replace the charger and batteries. It was really cold, long underwear cold. The batteries had been overcharging for several months. When he put a wrench to the negative battery cable, BOOM! the wrench sparked and the batteries exploded covering him in battery acid! They stripped him naked in 20°F weather and hosed him off, then sent him to the hospital in an ambulance to be checked out.

Marc was an experienced mechanic in aviation, trucks, tractors, and generators. He was older than me and had a temper. I got a call from the customer first telling me what happened. So I got in the truck and headed down to pick him up. When I got call from him I'm telling you I got an EARFULL!!! He was mad at me, mad at the job, and mad at the customer for stripping him naked in the cold... but mostly he was mad at himself for not recognizing the potential danger.

We had a service contract at the hospital, by the time I got there
he was sitting in the power plant office drinking coffee telling all his buddies about all the ordeal. It took me nearly an hour to get him out of there!! What a day!!

Marc and I worked together for 15 years. 2 years ago he died of cancer. I miss him every day. RIP Marc.
 
Ed Haywood said:
Did you build your plane? Many composite aircraft have conductive mesh and static wicks embedded for lightning protection.
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I haven't heard of anyone who has built a composite plane that installed mesh or static wicks. Although I'm sure there are some.

When I was building, it would have added about $5,000 to the cost of the airplane. So I ran a wire from my fuel cap rings to the ground block on the firewall.
 
Stewartb said:
Keep vapors in the tank and they can’t burn since the concentration is too rich. That’s why gas station nozzles have those rubber bras.
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They are not there for fire prevention.

They are mandated by EPA to capture the fuel vapors to reduce hydrocarbon emissions.

At least locally in NE Maryland, they are not longer used.
 
Over on Mooney Space, a bunch of people checked the continuity between the exhaust and the fuel filler. Some were not electrically connected, but most were.

So this video is a person extrapolating their ONE airplane to the whole fleet.
 
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