Could these problems be exacerbated by exceeding the maximum propeller
mass-inertia limit recommended by Rotax? In the case of the 912 this was
6000 kg-cm squared.
Does anyone know what the current recommended limits are for the 912S and
the 914, and how commonly-used propellers such as Warp Drive compare to
them?
Mike
Europa Club Safety Officer
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com]On Behalf Of Ami McFadyean
Subject: Re: Europa-List: Rotax starting - 912S
<ami@mcfadyean.freeserve.co.uk>
That being so, the 'shaking and banging' is likely caused by the low
frequency primary resonance (torsional and/or blade-flap) that is inevitably
present below normal cranking speeds. In the absence of any damping, the
forces produced by resonance will build-up towards infinity. The crank and
gearbox get hit with similar forces too; its just that the sprag is the weak
link in the chain (and, if it's any consolation, cheaper than a new crank!).
However, damping of resonance is provided by the friction clutch in the
gearbox; hence Rotax's insistence that this be maintained at the upper
limit. Also anything that accelerates the cranking engine quickly through
and clear of the resonant band should help (i.e. powerful battery, good
contacts, high torque motor). We have to hope that it is the 'shaking and
banging' ONLY that causes the problem, not the loads of normal starting.
Last Summer, there was a certain 912S CT that was regularly shaking the
carburettors out of the mounting sockets on start up, possibly exacerbated
by the big floppy 2-blade prop it had.
Duncan McF.
----- Original Message -----
From: "P.A.D.Clarke" <paddyclarke@lineone.net>
Subject: Re: Europa-List: Rotax starting - 912S
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