Jos, Dan, and all,
The discussion of the fuel system is an academical-discussion, but
nevertheless, I will give you more ideas to think about.
First of all, don't think that the pumps in SERIES are only helpful at high
altitudes. Stable fuel-pressure is fine at lower altitudes as well. At the
critical phase of flight
-Take Off - the volume of one pump is more as enough. In this phase of
operation, a higher pressure (or in other words, a stable pressure) is the
important thing. Does one of you checked the fuel-flow of the "Pierburg"
fuel pump? At full power (5800 RPM) the fuel flow of the 914 is ~33l/h.
Have a look at www.msi-motor-service.com and learn more about this pump. In
PARALLEL there is so much fuel going back to the tank. In case of an
pump-failure when operating in SERIES, the second pump works - in this phase
of flight - in the same way as when in PARALLEL. Don't are the fuel pumps on
the 912 (mechanical-electrical) in SERIES, as well? What do you think is the
reason for that? Does one of you would start a discussion on that? I don't
think so. Pierburg fuel-pumps are developed for car- and stationary engines,
not for aircraft-engines. At the beginning of manufacture of the 914 engine,
Rotax take the drawings of Pierburg. Does one of you know, that the original
design of the 914 runs with the mechanical pump, as we can see on the 912
engine? I think the real problem of the 914 fuel pump-design is the
dependence on electricity. What happens in case of an serious
electricity-problem? Then the flight becomes s i l e n t. In this situation,
God gives you a meadow under your wings! The dependence on electricity is
the real and only problem of the 914 fuel system, not the PARALLEL -or
SERIES- design.
Let me know, what you are thinking about this problem.
Regards,
Gottfried
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