The prop discussion for the 80 horse is a good reminder of mistakes I've ma
de.
The Rotax 912 is a great engine. Low on power and torque, but reliable and
light and as Creighton would say "it'll run on cat pee" although I wouldn
't recommend it as it is hard to collect! 87 RON Octane or regular gas is
all it needs, but it does like higher octane premium gas. Even ethanol tha
t is not older than say a month is OK provided you can get it started.
Matching a prop to it is not difficult but can be costly if one forgets tha
t the engine and prop are the powerplant and the prop is a torque converter
of sorts.
For a fixed pitch Warp Drive, the 80 HP can only easily drive a 62 inch tap
er 3 blade Warp.
At Custom Flight, we tried the wide chord Warp 3 blade at 64 inch and the e
ngine could not pull the prop. (Same issue on the 80HP Jab and VWs. Longe
r is not better.)
The 62 inch range prop does not appreciably affect speed, in fact it is abo
ut a wash with most props. If you want to go faster, prop length is not te
rribly critical from 62-67 inches. If you want initial takeoff acceleratio
n longer is better, but soon after liftoff, the prop unloads and frankly th
e plane is sluggish and cruise speed is lost.
Even by lowering the pitch for the 64 inch wide chord Warp, we found we cou
ld get 5000 RPM but the low pitch on the prop resulted in terrible accelera
tion and disappointing cruise.
So, the Warp taper blade set to a pitch that will yield 5000 RPM at WOT wit
h premium gasoline was used for years as a good all around prop for the 80H
P engine. That was about 17-18 degrees depending on cowl inlet MP, engine
compression and fuel octane.
If you lower the octane of your fuel to 87 RON (regular grade) Rotax recomm
ends setting the pitch to achieve 5200 static RPM at WOT to preclude detona
tion.
That pitch from experience is between 17 and 19 degrees at a manifold press
ure of 26 to 28 inches for most prop brands. If I recall (remember I have
CRS aka, can't remember s__t), on a cold air plenum XS style cowl I found
a touch over 17.5 degrees is about all I could get for 5200 static WOT comf
ortably on regular gas. Most of my testing was done using 100LL so the eng
ine octane was not an issue.
Performance with the Airmaster tapered Warp Drive AP332 required the tapere
d blade for the stock 912 operations. By setting the fine pitch adjustment
to 5200 at WOT then locking it in manual mode was an acceptable takeoff an
d climb setting but speed at cruise was tolerable at about 125-127 KTAS at
5000-7500 feet and with the constant speed set to cruise setting of 5000, a
nd near WOT we got about 134 KTAS. Takeoff using the 5700 WOT was very com
fortable with the Airmaster and Warp Drive taper blade on the 80 HP Rotax 9
12.
Cold air intake, engine condition, and of course altitude and leaning are a
ll factors that affect the fixed pitch prop performance. If you look into
new propeller swept tip and narrow chord designs you can get a bit of a boo
st over the rather simple Warp, but not much. In testing at Airmaster we f
ound the blade difference in speed of the various brands was about 3 knots
on most light sport aircraft. The cleaner the airframe design of the aircr
aft, the more twist you need in a propeller. Sensenich has a great three b
lade ground adjustable for the 912S (100HP) and in testing was a game chang
er for that engine. The CT guys love it o the 912S. I never tested one on
an 80HP Europa. What I found was the newer blades with modest twist like
the Whirlwind and Sensenich blades have a lot less residual thrust in the f
lare than the Warp Drive or the Wide Chord Sensenich. For the fixed pitch
Warp Drive, I'm afraid that the residual thrust in the mono or trigear is n
oticeable when landing. If setting a prop for cruise, I lower the idle RPM
to 1600 to try to reduce the float but that affects idle during start and
taxi to takeoff due to gearbox and of course carb balance roughness. Just
cracked.
As for basic prop maintenance, please do a check at least annually (I do a
25 hour check) on your aircraft to not only service the engine, and check c
ompressions and balance of the carbs, but also check the torque of your pro
p and do a thorough check of prop blade fixation torque on all ground adjus
table and constant speed propellers.
Even just using your digital level (or cell phone level) with each blade at
the same position ( I use horizontal and cut a piece of wood to set the pr
op tip at the same spot but a level will do also) to the horizon will tell
you if you are having blade creep. These blades today are tough, but over
time glass compresses and moves so the prudent owner operator/maintainer wi
ll do a proper check as part of an annual condition inspection IAW the prop
manufacturers checklist. At a minimum, during the 5 year inspection, fix
the prop dings, repaint if necessary (properly do your coats evenly), and b
alance the prop to assure the blade angle, all torques and balance are with
in tolerance. I like to pull the prop, hang it from a string (as described
in my paper on prop balancing) and get a good static balance. You can=92t
dynamically balance a prop without it being very close statically balanced
.
Best Regards,
Bud Yerly
-----Original Message-----
From: owner-europa-list-server@matronics.com <owner-europa-list-server@matr
onics.com> On Behalf Of arwel pritchard
Sent: Sunday, January 22, 2023 5:49 AM
Subject: Europa-List: Warp Drive Propeller Diameter
m.ltd.uk<mailto:arwel.pritchard@powercom.ltd.uk>>
Good morning,
I have recently checked the pitch on my warp drive prop and as a result
found that one blade was significantly different from the other two.
I have re-pitched and it seems to run a lot smoother.
Looking in the manual, it suggests a 17 deg pitch for a 912ul (62" prop)
and a 19 deg pitch for a 912ULS (64") prop.
I have a 912 ULS but its fitted with a 62" prop. I have pitched it to 18
deg for now.
Question, is having a smaller prop on the ULS a disadvantage and why was
a 64" prop specified for the ULS over a 62" one?
Thanks
Arwel G-BYPM
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