I finally had time to go out on a nice day and do some speed
tests with a new Catto 3 bladed composite fixed pitch prop on my
Subaru EA81 powered Europa Classic monowheel.
Its been nothing but rain, thunderstorms and wind for a
month in the afternoons. Yesterday we got baseball size hail in
places! I had a flight a week ago Sunday - first flight with the Catto
prop and it was a hot day. 92 degrees at 10 in the morning and DA
was already 8470 ft! Field elev is 5090 ft. I had to wait behind four
other planes so that didn't help my engine temps just prior to takeoff.
Takeoff roll was noticeably longer than the WD and after popping off, I
held it under 50 ft for a while and slowly retracted the flaps as
it built up speed. Once 80 mph attained then started to climb
steeply. Climb rate settled on 1200 fpm for the first fifteen
hundred feet or so and then I climbed a little less steeply. Once
up to altitude, I leveled off and noticed oil temps were getting
high, around 240 degrees F. I started to get worried and slowed
down to hopefully drop oil temps. After about 10 minutes, temp
came down to about 225 and I started a speed run. Unfortunately,
my GPS had not locked on since takeoff. My ASI reads way low at
any kind of speed so that is of no use but wound it out to just under
redline (5600 rpm) and it seemed faster but I really couldn't tell without
a GPS. I decided to go back and land, pull the cowl and check
everything over. Nothing was wrong but I decided to do a mod on my oil
cooler setup and add an exit duct for the oil cooler. Before, the hot
air just emptied inside the cowl. This mod took a week and I also
added a duct to hopefully cool the alternator better.
Today was supposed to be fairly cool, 73 F and there was no
wind. DA was 6740, much better than the other day. Climb was even
better (1350) and oil temps were down. At 7600 ft I started a
speed run. It takes some time to build up speed. I trim it down ,
then let speed build up but then have to trim it down some more as
the plane starts climbing at 800 fpm. I have to do this several
times until the plane does not want to climb, then carefully watch
the VSI while tweaking the throttle and leaning the mixture for
best power. The faster the Europa goes, the more sensitive the
elevator is and is fairly difficult to get a smooth consistent run
without diving or climbing, especially if there are any bumps. The
air was very smooth so I got some good runs. 168 mph one way and
172 the other (no fudging or diving to gain speed first). I only
did two runs but I will do more next time. I did not try the new
cowl flap arrangement that allows me to partially block off the
cooling flow (and drag) at speed. I will try that next time.
Basically I feel I have gained a solid 20 mph over the best WD
performance. This was after tweaking and tweaking the WD until I
didn't think I could get any more out of it. Also, the best climb
I could get from the WD at the highest speed setting was 900 fpm in
the summer and 1100 fpm in the winter. The Catto was supremely
smooth. With the WD, it seemed as though blade flex would cause
some rude and rough reactions at times, particularly when it was hot.
I wanted to see what speeds I would get at 75% power, and
throttled back to 5000 rpm. Speeds settled around 150-155 mph.
This was better than my top speed before, so I am very happy. Fuel
burn at 5000 rpm was showing 5.3 gal/hr but I haven't calibrated
the fuel computer yet, so that may not be accurate. WOT fuel burn
showed 6.2 gph. Fuel burn at 4000 rpm was about 4 gph.
Tomorrow I will install the Speed fairing kit and then do another
test. I am really liking the Catto right now but there is a noticeably
longer
takeoff roll but I didn't think it was excessive, maybe 800 ft, up from
maybe 600 ft before at my elevation with no wind. I only fly from a 4700 ft
paved runway, so taking off of grass with a passenger on a hot day could
possibly get interesting!
One small negative with the Catto is that he will only make a SAE2 (maybe
SAE1
as well, I'm not sure) pattern, so I had to make an adapter to convert from
the
Rotax 4 inch pattern to SAE2 (4 3/4"). I don't see why a similiar prop
wouldn't help the Rotax 912/914 just as much. For me, I like the Catto far
better
than the NSI CAP 140 cockpit adjustable prop that I originally had on the
plane,
although takeoff roll was shorter with the NSI/WD setup.
Glenn Crowder
Golden, Colorado
USA
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