Dear Forum Member,
I little while back I requested feedback from the group regarding performance
numbers
monowheel users are achieving (and I got one Tri's) and I promised to provide
results from such study. I do thank those that provide data, and although
the data was a bit scarce and riddled with a little too much variability to
provide a conclusion regarding monowheel performance, I will share the end
result
of my effort to get reasonable performance from my airplane.
First let me say: please, let me beg that we don't sidetrack the conversation on
a discussion about operation of the 912ULS at lower RPMs again. That discussion
resulted on very important info from Rotax coming to light that supports
operation
in the regimes discussed here (if proper fuel is used) but that conclusion
has been reached on the previous thread.
So my conclusion: the monowheel can indeed achieve operational performance with
a simple ground adjustable (GA) prop that will stamp a huge grin in your face
worthy of all the Europa marketing hoopla :D and without the need to install
a CS prop. Of course, you can achieve even better performance with the CS prop
but not all of us can afford one of those props (and besides, I don't want to
install one until I am reasonably sure I am not going to ground loop my mono).
I went from a meager 110 KTAS @ 23"/5200RPM cruise speed to consistent 135 KTAS
with just changing the prop (to another GA prop, which prop revealed later).
I have been flying the prop for a couple of weeks, including a couple of
x-countries,
and this speed is achieved at 23"/5200RPM 4500' (at 3000' I get around
133 KTAS at 24"/5200RPM) and T.O at 5200RPM with climb a little over
1500fpm@75KIAS.
Today conditions in the ground were 25C/30.02"/hg. I was fairly light
today with 10 gallons of fuel, me (164lbs), 20 lb ballast in copilot seat and
empty weight of around 780lbs. My airplane doesn't have the speed fairings.
A few days back I did a few GPS runs at WOT and was getting around 145 KTAS at
something like 5600-5700RPM
True airspeed was calculated using a three leg GPS cloverleaf run and the NTPS
GPS_PEC spreadsheet for calculations.
Although not an objective observation, I think the takeoff run is a little
longer
with this new prop. But it is still short (next time will pay more attention).
Although the RPM is steady at 5200RPM during the TO roll and initial climb,
the prop loads up quickly during acceleration to 75 kts. But once at 75 kts
the climb is so brisk that by the time I was a little past the end of our 4000'
runway I had to level off at around 900' (class C on top of my field). Simply
stunning. On cruise climb I power back to around 4800 RPM which gives me around
25-26"/hg and still get around 1000fpm climb.
Although haven't really pushed to the limits of Florida temps, my oil and CHT
temps
remain OK, 210+ for CHT and oil tends to run lower at around 195.
So what prop did I use: I found a used DUC Swirl 68.1" Inconel three blade I got
---From a friend. According to him, it didn't do much for him on his LSA but
what
a difference is this prop making in my Europa.
So I am not making the claim that you don't need a CS prop. On the contrary,
that
would make the airplane even better and truly extract it's true performance.
But again, for those of us that can't afford it, this is a viable option. As
JohnFrance indicated to me (he gets similar performance with an EProp), the use
of these modern GA props does require a bit of understanding of how they work
as they do get this performance with some compromises. In my case the compromise
is that the prop will load up in cruise climb and run at lower RPM. But
once you accelerate to cruise speed the RPMs go up.
But heck, I am happy right now. On my last short x-country I had some tailwind
and during descent I was showing around 155 knots GS. I know, that is cheating
but it was sweet. My friends in their RVs took off maybe 5 minutes after me and
I landed before them. Now they don't make fun of my Europa anymore.
Now, If I could only get this grin out of my face.... :)
Best Regards,
Chris
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