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Date: Wed, 20 Jun 2007 09:25:49 -0400
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Subject: Re: L235 wingtank vents
From: "bob mackey" <n103md@yahoo.com>
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Terrance writes:
> The wing tanks each have two vent outlets.  One I have traced
> to to top of the tank near the gascap.  The other outlet at the
> root also vents into the wing tank, as confirmed by pressure buildup,
> with cap, outlet and other vent plugged.
> I can't find any indication in the builders book of where in the fuel
> tank this vent might originate .. i.e. up high, or possibly down low,
> perhaps to serve as part of a sight-gage outlet.

The cap, outboard vent, and inboard outlet are standard equipment.
The inboard vent is a bonus. Could have been for a sight gauge,
a fuel return, or to connect to the header tank vent line.

Do you know what engine the initial builder intended to use?
Automotive conversions or fuel systems with regulated fuel pressure
might have a fuel return line. Is the fuel selector valve installed?
Does it have some extra ports that might be for return lines?

A sight gauge could be installed on the back of the nose gear tunnel
where it would be low enough and still visible to the pilot. The stock
fuel system effectively has such a sight gauge in the clear vinyl
tubing specified between the fuel transfer pump and the header tank.
i.e. no extra tubes necessary if you plumb from the wing tank's outlet
to the header tank's vent.

The extra line could also be for the inert gas purge...

-bob mackey
 L235/320 #30