The vent needs to be forward facing in order that that the tank and fuel
supply benefit from a small amount of pressurisation. This is equivalent to
only 2' head of fuel at 150mph, but enough to overcome the head losses
between the bottom of the tank and the inlet to the backup fuel pump, so is
significant given that pumps have little ability to suck and any suction is
bad for inhibiting vapour locking.
Who knows what the pressure in the tank will be if the vent is otherwise
sited below the fus. aft of the cockpit.
Certainly, if the aft-positioned fuel cap is left off a Europa during flight
then there is enough suction in the area of the open filler and therefore
the tank be able to pull all of the fuel out of the sight gauge.
Could be quite an interesting challenge to prevent an underside
forward-facing vent from blocking!
Duncan Mcf.
----- Original Message -----
From: "Fergus Kyle" <VE3LVO@rac.ca>
Subject: Europa-List: It's not easy when you're stupid
>
> Cheers,
> Clear as my mind can be (at times) it has recently rebelled over a
> simple paradox involving vents. I plan a bellyside outlet for the
> suction-block bottle in the fuel vent department.
> I note also the remarks of several regarding mud and crud along
the
> belly due to various manoeuvres, planned and otherwise, during landing and
> takeoff. As a monowheel manipulator, I cannot get the shape of the (say)
> 1/4inch [6mm] diameter vent sitting out in the slipstream whether the tip
> should be hacked off at 90deg (hipress?), or scarfed at 45deg (top or
botm?)
> or tapered horizontally or whatever.
> Having had trouble explaining oak leaves and mud on the bottom of
> several Harvards in earlier days, I can't seem to correlate the vision
with
> a mudfree vent for my Europa. Your considered opinions, severally and
> separately, would hopefully disarm this quandary. Secondarily of course it
> may prompt a vicious and viral debate which could destroy the site for
> weeks.
> Shamelessly,
> Ferg
> A064
>
>
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