REFLECTOR: Grounding Point

Al Gietzen ALVentures at cox.net
Fri Dec 3 11:15:53 CST 2004


Subject: RE: REFLECTOR: Grounding Point

 

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..............

Sounds right to me; but I wouldn't necessarily count on the surface of fuel
flowing from the nozzle, I'd lke another path.

 

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. 

Agreed.  And probably you touching the strake and the fuel cap ring, before
the cap is open, while holding the nozzle, or direct touching by the nozzle,
will neutralize the problem as long as there is a connection from the
cap/ring to the fuel surface by chain, cable or screen. 

 

I guess some things to keep in mind are that static charge is a surface
phenomenon; that low humidity (very dry or very cold air) is more conducive
to static buildup; and that there is only a certain air/fuel ratio that is
conducive to combustion; so it is generally in a small zone near the opening
to the tank that is at issue.

 

Al

 

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