REFLECTOR: Grounding Point

[Richard Riley]

We went around and round on this topic on one of the canard mailing lists a 
few months ago.  Following all the suggestions, I talked with a fuel system 
designer at the Very Large Aerospace Company where I work and came up with 
the following for my plane...

The fuel cap ring is attached to a coarse brass screen, shaped in a tube, 
that goes from the fuel cap ring to bottom of the tank.  It is attached by 
a brass ball chain to the fuel drain, and to a brass bolt in the outboard 
fuel bulkhead.  That bolt is then attached by a wire to the engine, and 
therefor to the exhaust pipes.

Most of the static charge in refueling is created by the fuel falling from 
the nozzle to the surface of fuel in the tank.  The brass screens strips 
that away.  No matter what the level of the fuel, it's pierced by the chain 
going to the fuel drain.  And then the whole thing is electrically bonded 
to the engine block.  If the fuel truck attaches the ground strap to the 
exhaust pipe, all the potential is equalized.


At 09:21 AM 10/24/04, Al Gietzen wrote:
>I guess there are different views on this, but I see little relation (as 
>in maybe "none") between grounding the exhaust pipe, and refueling 
>safety.  The static charge buildup is between the nozzle and the fuel 
>(surface); or the nozzle and the potential existing static charge on the 
>surface of the strake due air friction.  So have a metal chain or cable 
>from the cap ring hanging into the fuel, and keep the nozzle against the 
>ring; and, if you have just landed, wipe the surface of the strake with a 
>damp cloth before contacting the nozzle to the ring.
>
>Anyway, that's my take; but I've been wrong once before in my lifeJ.
>
>Al
>Subject: REFLECTOR: Grounding Point
>
>I didn't find a direct reference in the archives, so I was still wondering 
>if the exhaust pipes is an adequate grounding point when refueling?  I 
>always assumed it was but I'd hate this to be a FireBall Falacy.
>
>Chuck
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