Fergus,
>Can we discuss the pros and cons of pumped
>fuel to the selector versus pumps following it?
Some thoughts:
o If the pumps come before the selector then you will need to fit stop
valves in the lines to the pump (or drain the tank before doing any
maintenance such as pump replacement or changing pump filters).
o Placing of pumps aft (below baggage bay) allows reasonably easy
access and will help with CofG. (It also allows the gascolator to be at the
lowest point of the system which a number of people who have contributed to
the fuel system debate have mentioned as important. Personally, I don't
follow their logic: if all of the fuel going to the engine passes through
the gascolator, it will be able to perform its function of separating water
and foreign matter no matter at what height it is mounted.)
o I have 3/8 aluminium lines routed from the tank outlets forward to
the selector (mounted in the standard position), then aft to pump and
gascolator, then forward to a firewall bulkhead connection. There is room to
spare for this configuration as the aluminium lines take up much less space
and can be routed much more neatly than hose.
o Not sure I follow your argument about two routes for pumped fuel.
The routes are going to have to come together somewhere and, unless you
start adding weight and complexity in the form of NR valves, you are still
going to have a single point of failure. A single 3/8 line has heaps of
capacity for any engine which could safely be fitted into a Europa. If you
are worried about pump redundancy, you could fit a dual pump arrangement
like the one illustrated on Tony K's web site. Don't forget the KISS
principle.
o Also don't think I share your views on the need for hose couplings
which contribute more weight and more sources of failure. The structure is
actually quite stiff once things are bonded together and there seems to be
no way that relative movement could flex a line anywhere remotely close to
its yield point (even noting someone's recent and a bit over-the-top
description of the fuel tank as a "plastic bag"). Of course, you need to
route the lines sensibly and give them reasonable lengths for flexing
between any points (e.g. tank and selector) where there may be any relative
moement.
Best regards,
Nick Hammond
XS Monowheel 418
-----Original Message-----
Subject: Fuel routings
Cheers:
I am STILL routing fuel lines in my separated cockpit - due to
difficulty in adopting 3/8inch alum. lines to the design for my diesel.
First consideration is whether to run the outlets rearward to
pumps etc., then forward to the fuel selector valve which is on the bottom,
just behind the 'mudguard' -- or to run the outlets forward to the selector
then to pumps and forward to engine compartment. Reason for dilemma is that
the heavy engine can well dictate rear position of pumps etc. for CofG
reasons.
Second consideration is that engine pump will require steady
supply, as diesel injector demands ample and uninterrupted supply of air-
and water-free flow, and excess return to tank. I am keen to provide two
routes of pumped fuel to the engine (takeoff gangload, and enroute
lowpressure for whatever reason).
Third is minor, really, - the aircraft seems flexible rearwards
and the alum fuel lines are not, so hose couplings need to intercede.
My main query is: Can we discuss the pros and cons of pumped
fuel to the selector versus pumps following it? Your thoughts will be given
a warm welcome, and thanks,
Happy Landings
Ferg A064
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