Jonathan,
I totally agree with all you say.
At 1,100 hours and 100 hours after changing my engine to the 912S, I fitted the
Airmaster propeller.
I immediately set the cruise pitch to 4700rpm through a connection with my
computer
and I have now done 1,100 hours with this setup and I am completely happy
with it.
I usually cruise at between 24 and 25 inches manifold pressure which gives a
lovely
smooth and quiet performance and opening up to 26 inches gives me 140 knots
cruise.
I have tested it fully loaded and found that I can leave it in cruise setting
and
climb at just over 500 fpm after take off, fully satisfying any LAA
requirements.
Dave Watts
G-BXDY Classic Monowheel 2,200 hours
> On 13 Oct 2015, at 20:19, jonathanmilbank <jdmilbank@yahoo.co.uk> wrote:
>
>
> 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.
>
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> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=447899#447899
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