In the Katana I suspect high revs are not an option but more a necessity.
The 912 may like high revs but it feels a lot nicer when not revved high.
Reference VP props there is the option to run at high engine speed and low
throttle setting or low engine speed and high throttle setting. I think
somewhere in between will be shown to be the best option.
Don't confuse drop in rpm with drop in fuel consumption. In my experience
speed and fuel consumption follow a close line. There may be some small
benefit in running the prop with the best pitch and therefor efficiency but
a drop in engine speed of say 20% is unlikely to produce a consumption
improvement of even a quarter of that figure.
I ran my own R912 for the first time this weekend. I have fitted a fuel flow
version of the EIS to my aircraft and will be preparing a detailed report of
pitch ( or rpm ) versus fuel consumption for a range of aircraft speeds. I
would be interested to see any similar information on the 912.
Jerry
Flying Hi - Wish I was
jerry@flyinghi.demon.co.uk
http://www.avnet.co.uk/touchdown
-----Original Message-----
From: Tennant@t-online.de <Tennant@t-online.de>
Date: 16 February 1999 08:32
Subject: katana performance
>In the search for more details on the rotax performance with a variable
pitch
>prop I have borowed the Diamond Aviation Katana handbook.
>
>Diamont have done a lot of testing on the 912 and there are a lot of
details of
>engine output, manifold pressure and fuel consumption at various power
settings
>and altitudes for the 912.
>
>Some of the numbers are surprising e.g. It is recomended not to run the
engine
>below 4300 rpm to avoid accelerated wear. The normal cruise RPM is advised
as
>5450 RPM (prop 2400). For fast cruise use 5450 RPM and open the throttle to
the
>maximum manifold pressure for that altitude, then reduce the manifold
pressure
>by 0,7 inch!
>
>I was nervous running my engine above 5000 RPM before I read this handbook
but
>it seems that the 912 is extremely robust and loves these revs.
>
>It makes good reading for all of you with variable pitch props.
>
>Best regards
>
>Barry Tennant
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