I don't know about Rotaxes specifically and I only have experience with
geared Pratt & Whitney R1830s and 985s and Lyco GO480s but it was
important to keep positive thrust at all times on descent and approach
to keep the gears from chattering and fretting. I think this could be
good practice with the Rotax as well.
The practice was to keep descent (low) RPM until short final at which
point the props were put full forward to be ready in the event of a
go-around.
The RPM was kept down in descent in order that a low amount of thrust
was maintained at enough manifold pressure to prevent gearbox chatter.
As I remember we held 1500 prop RPM.
The P&Ws had combinations of Manifold Pressures and prop RPMs which were
not allowed which is apparently not the case with Rotaxes, but I can't
believe the clutch pack is only for start and shut down transients.
I'm still at least a couple of years away from flying so I'm curious how
others operate their engines.
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