Tony,
One more thought on matching the 914 with a fixed propeller.
All advice given by our learned companions is true. I thought I'd throw
a couple of numbers I have seen for your decision process.
In accomplishing the initial flight test of the LSA version of the
Europa, I flew 12AY with two fixed pitch props attached to my 914
Trigear with Classic Wings and XS Fuselage mods...
Keep in mind propeller theory is a bit of a zen art as each airframe,
engine, turbo system, fuel injected vs carburated, etc. greatly affect
the performance as does the blade width, length, twist taper and
flexibility. Many times you are comparing apples and oranges. This
prop with this engine works great to one guy and is disgusting to
another. The prop twist and taper of one custom fixed pitch prop on a
trigear is no problem, and in the event of a ground loop in a mono, a
very costly mishap. In selecting a prop, the strength of a prop should
never be compromised and its ability to absorb abrasion from rain, grass
and dirt must be considered in the choices as well as cost and insurance
coverage for a prop strike. As all things in an airplane, compromises
must be made..
I have tested 64 inch Sensenich ground adjustable two blade and the Warp
Drive 64 inch three blade ground adjustable propellers.
Both were adjusted to work by minute pitch adjustments. I tweaked until
the whole engine/prop combination could be repeatable, dependable, and
acceptable to my standards. These standards are: it can't allow the
engine to overheat (ground or air), or over speed, or over boost in any
normal operation, give a minimum climb of 700 FPM fully loaded at 75
KIAS at full power, cruise at least 120 KIAS at sea level, and climb at
max continuous to 10,000 feet (7500 minimum) in 20 minutes or about 500
FPM average.
For testing here at my shop it have found the following:
Set the pitch so as to get 5200 RPM static at 40 inches of Manifold
Pressure (38 if you have the older 914). This drops your power
available from 115 HP to about 100 HP. This is a recommendation by
Rotax and prevents over boosting and eventual damage. It also is a good
all round start for a pitch setting. For the newer 914 engine, that is
about 21 degrees (20.5 for the old 914) prop pitch at the tip of the
Warp Drive.
Takeoff allows the prop to unload while accelerating to about 5500 RPM
while at 38 inches and gets you away from the ground quickly at 75 KIAS.
Once airborne and above 1000 MSL in a 75 KIAS Climb, begin pulling the
throttle back to 100% (out of turbo), the RPM drops disgustingly to
about 5000 at 34 inches MP. This greatly reduces the climb, read as
dropping the nose a lot. However if the climb speed is increased to 90
KIAS the RPM comes up to about 5300, the MP pressure stays close to the
mid 30s and the rate of climb is tolerable and the transition from the
75 to 90 with throttle retard seem natural.
Climb to 7500 MSL is reasonable at approximately 700 fpm with one on
board and a bit labored at 500 average loaded.
Cruise at 5500 MSL tops at about 122 KTAS at 5000 RPM and 31 inches.
Max at 5500 RPM and about 35 inches only goes up to about 127.
I am working from memory here on Sunday morning so the numbers are ish.
I have found with a basic Airmaster AP 332, climb after takeoff is about
1400 FPM, Climb at max continuous starts at 1000 FPM and drops to 4-500
FPM at 10000 MSL. Climbs above 10,000 with the Airmaster start to drop
off using the narrow chord Warp Drive blades. Cruise is up from 120 ish
to 135 ish at 7500 MSL. Airmaster has now completed and is selling a
reverse or Beta with the AP332 for sea planes. Much was done to keep
this mod safe and full proof. So for you guys that must have
everything, (sea or ski operations), beta is now available. Use with
much care.
My experience has shown me that the 914 needs a constant speed prop with
automatic adjustment (rather than variable pitch) to be properly used
and give the full potential of the engine. The constant speed prop eases
cockpit workload in high cockpit task operations (takeoff and land),
provide a safety margin to prevent over speed, or over boost
possibilities in go around or spirited flight situations, improves
cruise speed and fuel mileage, and reduces the thrust for short field
operations when coming into a short field fully loaded.
That said, based on the repair rates of new low time mono pilots and
propeller tip damage I have experienced as an Airmaster dealer, a fixed
pitch prop used during the initial flight test and learning phase is not
a bad decision. It saves initial cost to the mono guys until they are
comfortable with the landing characteristics, techniques, etc. It also
gives a spare prop for the eventual tip strike or other maintenance
action after upgrading to a constant speed. Use care for the CG shift
and engine/gearbox/oil system changes during a prop swap.
My further testing of the Airmaster two and three blade has been cut
short by LSA testing and damage from Sun n Fun taking forever to fix
with the backlog of customers in my shop and the painters (customers
come first). My apologies to all, but circumstances have delayed any
further fixed pitch testing.... Jabiru engine testing with various
propellers has been curtailed also, until we can get the Jabiru 3300 in
an airplane that will stay cool enough throughout the performance
envelope to allow a full test profile.
Regards to All,
Bud Yerly
Europa Tech Support
Custom Flight Creations, Inc.
www.customflightcreations.com<http://www.customflightcreations.com/>
(813) 653-4989
----- Original Message -----
From: Tony Renshaw<mailto:tonyrenshaw268@gmail.com>
To: europa-list@matronics.com<mailto:europa-list@matronics.com>
Sent: Saturday, August 27, 2011 10:50 PM
Subject: Re: Europa-List: 914 Prop Question,,,,,,,,Thanks for the
responses
<tonyrenshaw268@gmail.com<mailto:tonyrenshaw268@gmail.com>>
Thanks to all that replied regarding the negatives of a Fixed Pitch
prop on a 914. It was more a revision of knowledge than a serious
desire, but Bob Catto is a very impressive fellow and it got me
thinking. As for better abilities in gliding and stopping re pitch
settings and other good advice, I am now the wiser.
Reg
Tony Renshaw
On 28/08/2011, at 7:12 AM, David Joyce wrote:
<davidjoyce@doctors.org.uk<mailto:davidjoyce@doctors.org.uk>>
>
> Tony, One benefit of a VP prop that I don't believe has been
mentioned but which reference to ground looping brings to mind is that
in fine pitch the slowing down effect of the idling prop is very
noticeably greater than in coarse pitch. If you are trying to glide
somewhere and the prop pitch change system still works, fine pitch is a
great asset whereas to stop in a short distance you definitely want it
in fine. On T/Off fine pitch also takes you very quickl;y through the
dodgy steering phase if you have a mono. Clearly a fixed pitch prop is
going to miss out somewhat on both counts. So I guess you are less
likely to lose control on the ground and end up ground looping if you
have a VP/CS prop.
> Incidentally have you looked at the list of flying planes
on the Europa Club website where engines & props are listed for pretty
much every flying Europa?
> Regards, David Joyce, G-XSDJ
>
>
>
>
http://www.matronics.com/Navigator?Europa-List<http://www.matronics.com/N
avigator?Europa-List>
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