Bill Freeman wrote:

                     SNIP

  There is only one vent to receive ram pressure through a NACA
vent in the belly, this  is where NACA vents really function beautifully.

I like the idea put forth, to drill a vent hole to in the vent line, to
avoid ice build-up on the ram port.  I'm not sure if this would be necessary
with a NACA type vent.

How about some help on this.
Question.....are NACA vents immune to rain, ice, slush entering the opening
since the ramp SEEMS to only accept air to the pressure chamber/ramp
opening?

Jerry,

Please don't use only one vent line.  Cessna has tried this for years, and
even with
their super simple gravity feed systems (both)  they get very weird things
going on.  They
wound up having to put one-way valves between tank vent lines to keep fuel from
siphoning on an uneven ramp, and the systems still don't vent properly.  They
eventually gave up and put one vent per tank, fully independent.  I really
think this
is the best and safest way.   Liquids and gases, esp when the liquid can
turn into a
gas, do very unexpected things in complex piping systems and often not what we
would expect.  The C182 would not have a LEFT-RIGHT-BOTH-OFF selector if it
vented right, it would be ON-OFF like a C150, with ON being BOTH.

Paul,

Another "DO"

DO - Provide one independent fuel tank vent for each and every tank, and two is
much better.

The fuel vent  check valve (air in, no fuel out) stuck to its seat and my
C182 started running
rough over the wilds (really!) of Wyoming.  A quick switch of tanks made it
go away
instantly, but I was wondering what was going on.  Pretty soon it started to run
rough on that tank and I switched back and headed for the nearest airport.
On the ramp, I blew into the vent line and felt a discrete "POP" as the check
valve freed up.  It has a small hole in designed into it, but this was not
enough to keep
the engine running at cruise power.  The "Fuel Vent BJ" is a part of every
preflight
now on both the C182 and the Long EZ.  Recomended.

I usually have to switch tanks on the C182,  i.e.  run on the right tank
mostly due
to the uneven fuel flow which is caused by poor venting and fuel transferring
upstream and uphill due to the uneven venting.  Some experts say that you
can run 25 gallons out of the left tank of a C182 when flying on "both" (31
gallons
per tank) due to this extremely uneven fuel  transfer phenomenon which is due
to the interconnected venting system. Won't quit but gets pretty right wing
heavy.

For consideration  as a "DO" ---

How about recomending either a sump at each tank of about 1 quart capacity,
or dual fuel inlet fittings, esp important for very shallow tanks - which is
about
any aircraft wing tank.

The AOPA Piper Tri-Pacer project airplane crashed because the pilot was un-
familiar with that aircrafts propensity to unport a fuel inlet in their shallow
gravity feed fuel system.  The expert Piper folks know some trick that helps,
but let's learn from this.  As the fuel sloshes around in the tank, you should
be able to keep a 1 qt sump (with a   >1" diam inlet) full even in a prolonged
slip or skid with only a few gallons in the tank, assuming normal bouncing
around.  Altho, any time you are using the last few gallons, be aware of
keeping the ball centered.  This is less important with designs that have
a lot of dihedral.

Bill

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