I am going to be controversial ! I can't resist it.
I don't think Europas go as fast as some people say. Most Europa pilots
I know claim top speeds for a 912 Europa around 135 kts which is what I
have seen for myself and that's pretty fast for an 80 hp aircraft with
what has to be said is a very sensible landing speed. As you know I sell
the Arplast VP prop and I get some good feed back from my customers. To
have a 75% cruise speed of 135 kts there is an implication that the top
speed of said aircraft is 149 kts. That's just using a very simple
theory that aircraft speed follows a cube of the power. I know Kim Prout
has done lots of things to his A/C and he does achieve fantastic figures
but for most Europa owners I don't think you're going to get fantastic
cruise performance by fitting a VP prop (and that's from someone who
sells more VP props to UK Europas than anyone else currently). You will
get a fantastic improvement in take off performance because the full
power of the engine can be realised and you may choose to drop cruise
RPM by a marked amount but don't mistake RPM for power. If it takes 60
hp to drag a Europa along at given speed then that does not change.
You're not going to change tractive power by more than few % by fitting
different propellers. I have been selling props for almost 10 years and
the differences we see are usually around 3% to 5%. To increase the top
speed of a Europa from say 135 to 150 kts would take an improvement in
blade efficiency from say 0.75% to 100% that's an improvement of 33%
which just isn't going to happen unless your base propeller was a piece
of 4 x 2.
Furthermore - from my Rotax 912 manual 10 litres per hour equates to 33
hp or around 41% power. From a cruise speed of 120 kts that would imply
a top speed of 162 kts which I find hard to believe.
Below is a table of speed and power for a 149 kt A/C based on cube law.
149 100%
146 95%
144 90%
141 85%
138 80%
135 75%
132 70%
129 65%
126 60%
122 55%
118 50%
114 45%
110 40%
105 35%
100 30%
94 25%
87 20%
I am ready to be proved wrong.
Jerry
LTS@avnet.co.uk
http://www.avnet.co.uk/touchdown
----- Original Message -----
From: Tony Krzyzewski <tonyk@kaon.co.nz>
Subject: RE: Inflight Variable Pitch Props
> >>> Congratulations to the owners of these Europa aircraft. They are
quite
> >>> obviously created from totally different materials from mine ! I'm
> certainly
> >>> jealous.
>
> The NZ aircraft is a not so special 912 powered Classic Europa by the
name
> of ZK-UBD without the go faster kit. Before we put the Airmaster CS
prop
> onto the aircraft we could only achieve 105 knots indicated at 65%
cruise -
> or we could achieve 133 knots indicated and not get off the ground
without
> using every bit of available runway.
>
> When I won the navigation contest on Saturday I did the entire run at
75%
> power, 135knots true at 1000feet agl.
>
> I very much suspect that Kevin's 914 powered Europa is tidier in
finish than
> UBD!
>
>
> Tony
>
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