Fuel system -- a possible solution
Re the recent e-mail by Richard Meredith-Hardy pointing out the fuel supply
problems, and his solutions to the problem. While cutting an inspection hole
in the top of the tank may be the ideal answer, for those of us who have
already fitted the tank and bonded the cockpit module into the fuselage and do
not relish cutting a large chunk out of the area between the headrests (assuming
it could in fact be done without removing the tank completely) may I suggest a
possible solution that we are considering:-
1) Remove the vent pipe from its tank outlet fitting and attach it to a small
threaded pipe fitted to the aluminum fuel filler just under the mounting flange
( Drill and tap and secure with redux) . Lead this pipe downwards through the
bottom of the fuselage to a suitable high pressure area underneath. This would
provide a new vent for the tank with no possibility of siphoning the fuel out of
the tank. If the pipe, near the bottom of its downward path, went through a
larger diameter catch tank (say 2" dia) then any water drawn up into the vent
would be collected in the catch tank and not drawn up into the fuel tank. Any
water collected in the catch tank would drain out automatically after every
flight.
2) Remove the aluminum vent pipe outlet fitting from the tank and attach a
small diameter aluminum or copper tube (car brake pipe?) about 2ft long to the
tank side of this fitting (a push fit into the inside dia of the outlet &
secured with redux). This pipe can then be bent into a suitable curve that
would enable the fitting to be replaced through the 3/4 " hole in the tank and
allow the new tube on the inside of the tank to touch the bottom of the tank.
(Or use a flexible tube inside the tank with a weight on the end of it forming
a
"Flop" tube)
3) Lead a plastic tube from this adapted vent outlet, via a "T" piece, to a
liquid manometer mounted where the old fuel sight gauge was fitted and vented
back to a "T" piece on the new vent line. By attaching a small rubber
"pumper" (as used by doctors to pump up blood pressure measurement devices) to
the "T" piece on the tank /manometer pipe run you can blow bubbles through the
new "DIP" tube in the tank and the pressure required to do so is measured by the
manometer sight tube and is therefor proportional to the level of fuel in the
tank!! In fact, if there were no leaks in the pumper line, you would only have
to do this at the start of a flight and the gauge would show a correct reading
during fuel burn and during climb. It would only have to be given another
"pump" during decent if you wanted to check the fuel contents. This method
is immune to false readings with pitch changes as there is only air in the pipe
connecting the tank to gauge and not liquid as in the normal europa
arrangement. The only problem I can foresee (unless anyone knows better) is
that with any negative G maneuvers the liquid in a simple manometer could be
displaced into the feed pipes but, with a more complicated design of manometer
with different diameters of tubes in each leg (which I have developed), this can
be avoided.
How can I put a PCX file of the design up on to this forum for those interested?
4) The only problem not addressed is the removal of debris from inside the
tank but by fitting a gauze strainer on the tank filler (similar to that fitted
to Land Rover Vehicles) then most of the large chunks can be avoided in the
first place.
Ted
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