Hi Frans,
I mentioned the cross tube since you had mentioned the failure of a carb
and that both sides could be fed through the single carb and the"fat"
cross tube. Outside that scenario, there should normally be little flow
and resistive drop.
I am not sure what a cross tube does to "soften" the incoming air pulses.
The flow rate is mainly determined by the linear speed profile and the
fixed surface area of the downgoing piston with the major flow restriction
at the intake valve orifice. The extra compliance of the cross tube is
probably only a small increment to the supply through the carb unless
the butterfly is nearly closed.
Sadly there is no public detailed spec on the Rotax 9xx series, but I do
try to relate its operation from what I learned from Charles Taylor, John
Heywood,
and Will Pulkrabek's books.
For most pilots wanting to learn a bit more about their engines (I.e.,
Lycosaurus types), John Schwaner's Engineering Manual is great! Full
of easy to read facts, not conjecture or rumor from a very experienced A&P.
(www.sacskyranch.com)
--------
Ira N224XS
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