REFLECTOR: Grounding Point

[John Dibble]

After the previous round of discussion, I've been trying to understand
this ground issue.  I've noticed as the weather gets colder and drier
that I infrequently get a shock.  It seems that for the shock to happen
I need to first rub something and then touch something that is GROUNDED,
like a water faucet.  So it seems to me that an electrically insulated
fiberglass tank is actually a good deal and why do we want to provide a
ground where a static charge can discharge??
Also I think it is unlikely that flowing fuel can develop a charge.
>From what I remember about boundary layer theory, the fuel molecules
adjacent the hose/nozzle "stick" to the hose/nozzle surface and do not
move.  There is a gradual transition of fluid velocity between the
hose/nozzle surface and the bulk of the fluid flow.  So there is little
opportunity for the fuel to "rub" against the hose/nozzle surface and
develop a charge.
I think the safety screen is the best idea.  Where can I get or make
one?

John

Alex Balic wrote:

> Hey Al,I don't think that there is too much charge differential
> building up during actual fueling operations, I would think that when
> the fuel is flowing the charge could pass freely from the tank to the
> nozzle via the surface of the fuel and thereby keep the potential at
> or near zero- I will check up on this though..............I believe
> that the problem is that a spark occurs between the fuel nozzle and
> the aluminum cap, or between the nozzle and the skin in the vicinity
> of the cap when the two are brought into close contact just prior to
> fueling- assuming that the aircraft is not "grounded" to the fueling
> point.  There can be a lot of charge differential between the aircraft
> and the fuel truck due to many different reasons, and I am just trying
> to figure out the best way to make the differential zero before the
> fuel cap is opened, and/or placing the brass safety screen in the
> filler neck to prevent fire from entering the tank.  Like I said in a
> prior post I got severely jolted once re-fueling from a ground based
> pump station because I had the ground clip in one hand and touched the
> spam can I had just finished flying with the other- a mistake I will
> not repeat- and if I had fuel on my hand at the time I am pretty sure
> it would have ignited...About the chain- I was referring to the design
> that has the ball chain attached to the fuel drain line and it rolls
> around in the bottom of the tank- a chain that makes it into the fuel
> and attaches to the cap would certainly make more sense- and I think
> that touching the fuel ring with the nozzle before opening the cap
> would help as well.Alex
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