Ken Jantz wrote:

In reading over Ed's vivid account I could feel the sense of panic I'm
sure he did.  I haven't seen the earlier posts describing gas
container, but plastic compounds are the worst for generating static
charges, but being non-conductors of electricity, they don't drain it
off, they just continue to build until the potential difference is
great enough for a nearby conductor to attract the charge, generating
the spark. For that reason, only metals should be used around highly
flammable materials like gasoline.

To test this, generate a static charge on your body by scuffling
across a carpet, petting the cat, or however works for you.  Touch the
plastic part (only) of a swith or outlet plate.  If the theory works
(!) you will not get a static discharge until you move close to the
plate screws.  If the system is properly grounded you'll get your
static shock when the potential on your body is attracted to the metal
parts of the system. But the challenge in a fueling operation is not
to insulate (the plastic), but to provide a conductive path to ground
(the metal).

If you have a mobile fuel truck at your airport, watch their
procedures for fueling.  If they are doing it correctly, they will
ground the aircraft with a ground wire from the grounded truck, then
open the filler cap, insert the nozzle, and hold the metal fuel nozzle
against a metal part of the filler cap until fueling is complete.  The
fueling hose is either carbon based or has a grounding wire molded
into it to conduct static charges to the actual ground point.  Any
static built up by the aircraft is grounded (drained off) when first
hooked to the truck, and any that may be generated during fueling is
drained off through the closed loop grounding system before it can
discarge (spark) to some other ground.

Even with a metal can and rotary pump (especially one of those little
plastic jobbies), there is no closed circuit unless a metal part of
the aircraft is grounded (above the tires, rubber is an electrical
insulator) and the feed hose is appropriately grounded.  You can wrap
an insulated (18 to 16 gage) wire around the outside of the hose and
solidly attach it to the metal gas can and the metal hose tip (to bare
metal, there must be no paint film between any connection) to close
that grounding loop.

Composite aircraft should be grounded from the metal fuel filler ring
directly to ground.  If you are building a composite, it would be wise
to assure a groundable aircraft, particularly if the ribs, spars, and
fuselage structure are of metal.

Sounds like a lot of trouble, but so is putting out flash fires, if
you are so lucky as to do so.

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