My Airmaster gives 5000 rpm when set to Auto and Cruise. I've been using this
excellent
propeller hub for over 15 years and had it first inspected, then modified
for the wider blades after fitting a 100hp engine. I've never seen anything
written which states that you can't set the coarse pitch stop for less than
5000 in manual cruise.
My Rotax 912ULS isn't fitted with a turbo and therefore can't be "over-boosted"
no matter how low the rpm. The only sensible constraint I was given about
setting
the coarse stop, was to ensure that if stuck at the coarse limit for some
reason, then in the event of having to go around late on final approach, the
aircraft should still be able to climb safely at low rpm with full throttle,
flaps
down and heavily laden. This is easily done at low airfield elevations, with
the coarse pitch stop set to allow 4700 rpm in my normal 115 - 120 kt cruise.
I can't see the point of being allowed to cruise fast using lots of power while
not being allowed to enjoy the benefit of a quieter engine running at lower,
quieter rpm. It doesn't make sense when considering that this touring aircraft
should be set up to benefit from quieter engine operations to afford the
occupants
a more restful flight and also safer due to reduced noise distraction.
For many years I have cruised far and wide at around 120 knots with the rpm set
manually to around 4700 with no ill effects. The reduction in noise generated
by taking the rpm 300 lower is very agreeable.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=447899#447899
|