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Fuel tank grounding is something we ought to take very seriously -
particularly with our non-conductive glass airplanes. It is the fuel
vapor that is prone to ignite (often explosively if in a closed
space like the unfilled volume of a tank). When you're filling a tank,
there's a lot of fuel vapor being flushed out of the filler opening,
right past the nozzle, where a spark from the fuel or filler ring to
the nozzle (which is grounded) can spoil your whole day. If the inside
of the tank is electrically isolated from ground, the flow of fuel as
it swirls around inside during filling can generate a static charge
(high voltage) with a high enough potential to force a discharge
(otherwise known as a spark) to a convenient ground. Since the nozzle
is grounded, any static build-up on the fuel as it flows through the
hose is dissipated to zero at the nozzle lip but from there on in,
the gas should enter a container which is also returned to the same
ground level. The method listed in the last post sounds like a good
way to do it, but only as long as your internal tank ground is
attached to whatever you hook the ground cable to at the gas pump or
truck.

Another way to be sure your fuel is groundable is by filling
the tanks with the aluminum mesh called "Explosafe", and running several bare aluminum wires throughout the mesh, with one connected
to the filler ring. Then via a wire from each tank to your ground
point. A test with an ohmmeter from the filler ring to where you
connect the ground cable (mine's the exhaust pipe, since the engine
is grounded) should show almost zero ohms. The stuff is also a good
anti-slosh agent and it's supposed to squelch a vapor explosion as
well. I have heard a single complaint that Explosafe can hold water
in it's mesh - but I've never seen a hint of a problem in over 460
hours, while flying to and from many varied climates. At the very
least, if you don't have any sort of tank grounding, and you're all
closed out, then when you fill up, stick the end of the nozzle into
the tank so at least the tip is always in contact with the fuel. Not
the best but better than nothing.

If any one is looking for filters for the hydro system, check out the
Norman Ultraporous Filter Co. in Bridgeview, IL (708-430-4000). They
make stainless filters that are rated to 6000 psi, with a range of
filter media from 2 to 200 microns. Their filters are serviceable
and come with a wide variety of fittings. A way to solve the bi-
directinal flow problem if you absolutely must have a filter in your
hydro system is to use two filter units with a properly rated
(pressure) check valve in series with each one. Plumb the pair into
your system so that one handles the flow out of the pump on gear up,
and the other one filters the flow in the opposite direction. I don't
have a filter in mine but I've used this technique in other places
many times - mainly because it's simple.

To Bob Chesley - Dang! I'm going to miss your move to my favorite
airport on the 14th. I'm leaving for Hawaii for 10 days on the
13th and won't be back until the 23rd. Since Camarillo is my home
away from home, and I have a lot of Lancair friends there, I will
definitely get by when I return and look you up.

Putting "sound-proofing" stuff in your two seater does little but add
unnecessary weight. You've got to wear a good quality head-set all
the time in one anyway so why bother? Fly behind a Lycoming without
a muffler for very long without a head-set and you won't be passing
the AME's whisper test anyway, so what's in an airplane or not will
cease to have meaning to you (no medical). To put it bluntly, you're
going to go deaf - I have seen the results. My dog has quite a few
hours in the right seat of N235SP and I really think he's ignoring
me more lately than ever before (I haven't found a head-set to fit
Schnauzers up to now). Bottom line? Save the weight.

Cheers,

Dan Schaefer
N235SP


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