G-IANI wrote:
> Ideally the return pipe should be a single piece from end to end. So the
> high risk of leakage is at the end connections (the pipe being severed mid
> cockpit is, even in an accident, possible but very unlikely if properly
> routed).
I see your reasoning. But why then should we have the possibility to
close the main fuel line TO the engine? If it is a 912(S) it should also
be of one piece, and the end at the engine is also higher than the tank.
Reasoning should be consequent: if there is a fuel close off valve, all
exits from the tank should be closed.
Furthermore, I doubt that the fuel line will remain intact by a serious
crash landing. There has been at least one occasion (I know off) where
the front of the airplane broke off, taking the engine with it.
Occupants survived without injuries. Aluminium pipes will break in such
a situation, and rubber lines will tear apart. In case of a 914, the
entire fuel tank will drain via the broken return line.
> By fitting a one way valve, this suggests that the unwanted flow is coming
> from the tank. The engine end (with the restrictor in it) is higher than the
> tank so fuel would not flow from the line if disconnected.
Only if properly "disconnected". In a crash, it is highly doubtful that
the line will be disconnected at the very end, and remain higher than
the tank.
Given the fact that a one way valve will not add significant weight,
maintenance, or failure points, I think it is a worthwile safety feature.
Frans
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