Today's Message Index:
----------------------
1. 08:38 AM - Re: Cruise speed data for Monowheel with 912ULS (n7188u)
2. 09:29 AM - Re: Re: Cruise speed data for Monowheel with 912ULS (Pete)
3. 10:22 AM - Populated Instrument Module weight (rparigoris)
4. 12:13 PM - Re: Cruise speed data for Monowheel with 912ULS (n7188u)
5. 12:16 PM - CKT exhaust header tube needed, please. (JonathanMilbank)
6. 12:53 PM - Re: Populated Instrument Module weight (n7188u)
7. 01:23 PM - Re: Re: Rotax 912ULS Low Fuel Pressure (Jeffrey Williams)
8. 01:27 PM - Re: Populated Instrument Module weight (D McFadyean)
9. 01:42 PM - Re: Re: Rotax 912ULS Low Fuel Pressure (Pete Zut)
10. 03:24 PM - Re: Re: Cruise speed data for Monowheel with 912ULS (Pete)
11. 03:26 PM - Re: Re: Cruise speed data for Monowheel with 912ULS (Pete)
12. 04:20 PM - Re: Cruise speed data for Monowheel with 912ULS (Griffo)
13. 06:58 PM - Re: CKT exhaust header tube needed, please. (Bud Yerly)
14. 07:52 PM - Re: Re: Cruise speed data for Monowheel with 912ULS (Bud Yerly)
15. 08:06 PM - Re: Cruise speed data for Monowheel with 912ULS (Peter pender)
16. 09:10 PM - Re: Cruise speed data for Monowheel with 912ULS (Griffo)
17. 09:15 PM - Re: Cruise speed data for Monowheel with 912ULS (n7188u)
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Subject: | Re: Cruise speed data for Monowheel with 912ULS |
First let me apologize to the group for trying to dig so deep into this subject.
I am by no means an expert but I have been around a bit. However, my goal is
to learn and as an Engineer I do tend to overthink stuff a little (good thing
when you design life critical medical devices :) ).
Griffo, this subject is so complex, and open to so much debate that yes, what you
mention is valid, but a few items beg to be clarified as to ensure we are comparing
apples to apples.
First, RPM alone is not enough to determine the power output of an engine (although
you mention speed which could be used as the additional parameter but I prefer
not to due to variability). You need a way to determine that the pitch in
your prop is set correctly to start with (and hence the engine is developing
the desired power). A common way to "communicate" this to aircraft builders is
through the "static RPM" parameter. But, although a good starting point for
first flight, the final outcome is so dependent on the prop design that the parameter
alone is not enough to properly set a ground adjustable prop.
And yes, the "art" of adjusting a fixed pitch prop will always depend on the preference
of the user so is there really a "right" answer?, certainly not. Keep
in mind though that the Europa, as well as my LongEZ, ire aircrafts designed
for speed so it is my goal to maximize speed and still retain acceptable TO performance.
Also, the engine operates most of the time in cruise regime, so to
achieve descent efficiency it is desirable to operate at power/RPM settings that
avoids "chocking" the engine with low throttle settings.
The consensus I found in the Rotax-Owners forums that made most sense to me is
to adjust the prop pitch so that you get 5800 RPM WOT in the air at level flight
(of course this would be altitude and temp dependent). Then check RPM on takeoff
to make sure it will still provide acceptable takeoff and climb performance.
If you set your prop with that specific baseline then yes the MAP info is
unnecessary for comparison purposes but only if everyone does it that way (unlikely).
BTW, I have spoken to CTLS owners in my field and they agree that 4900 to 5000
RPM on initial climb is customary. As soon as you go to cruise climb speeds that
number goes up significantly. If you don't do that the cruise performance will
be dismal. They still get impressive TO performance and keep in mind that
you are operating at that lower RPM high torque regime for a very short period
of time. My LongEZ gives me only 2200 RPM on initial rollout (totally unacceptable
per Rutan) but goes up to 2500 by the time I am rotating. On cruise I have
to live with 2700 with my throttle lever at around 1/4 open (100 RPM less than
redline) which is not great. So is the nature of the beast. In the LongEZ
I play with altitude to achieve optimal RPM. Yes, altitude is my VP control :)
But that works on a prop that is slightly overpitched.
Right now , on my Europa, I am getting around 5300 RPM/80 knts @ WOT on climb but
WOT at level flight still exceeds 5800 RPM. At cruise, I checked today, I am
at 5200 RPM/22" MAP at 3000' but only truing 115 ktas. I think based on this
I still need more pitch. BTW, Bud Yerly told me my airplane will be slow since
I still don't have my final shiny coat of paint. I believe him.
Of course I can keep tweaking the blade angle until I reach a good compromise (and
ultimately that will be the process) but with just a little feedback from
the group I can then compare the performance of my airplane to other folks flying
the Europa out there.
Best Regards,
Chris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=501478#501478
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Subject: | Re: Cruise speed data for Monowheel with 912ULS |
Fwiw, my mono classic with the short but wide warpdrive has the same expected issue:
If set to keep it above 5300 static and in the climb (to reduce gearbox/spline
abuse), then my cruise is also slow. To get good cruise, I end up pitching
to around 5000 static.... which isnt good for the gearbox. My Classic
really needs a CS prop to be able to get book cruise numbers. Once I have it
back in the air (2 months maybe), Ill get some fresh numbers to share.
Cheers,
PeteZ
> On Apr 23, 2021, at 11:45 AM, n7188u <chmgarb@gmail.com> wrote:
>
>
> First let me apologize to the group for trying to dig so deep into this subject.
I am by no means an expert but I have been around a bit. However, my goal
is to learn and as an Engineer I do tend to overthink stuff a little (good thing
when you design life critical medical devices :) ).
>
> Griffo, this subject is so complex, and open to so much debate that yes, what
you mention is valid, but a few items beg to be clarified as to ensure we are
comparing apples to apples.
>
> First, RPM alone is not enough to determine the power output of an engine (although
you mention speed which could be used as the additional parameter but I
prefer not to due to variability). You need a way to determine that the pitch
in your prop is set correctly to start with (and hence the engine is developing
the desired power). A common way to "communicate" this to aircraft builders
is through the "static RPM" parameter. But, although a good starting point for
first flight, the final outcome is so dependent on the prop design that the
parameter alone is not enough to properly set a ground adjustable prop.
>
> And yes, the "art" of adjusting a fixed pitch prop will always depend on the
preference of the user so is there really a "right" answer?, certainly not. Keep
in mind though that the Europa, as well as my LongEZ, ire aircrafts designed
for speed so it is my goal to maximize speed and still retain acceptable TO
performance. Also, the engine operates most of the time in cruise regime, so to
achieve descent efficiency it is desirable to operate at power/RPM settings
that avoids "chocking" the engine with low throttle settings.
>
> The consensus I found in the Rotax-Owners forums that made most sense to me is
to adjust the prop pitch so that you get 5800 RPM WOT in the air at level flight
(of course this would be altitude and temp dependent). Then check RPM on
takeoff to make sure it will still provide acceptable takeoff and climb performance.
If you set your prop with that specific baseline then yes the MAP info
is unnecessary for comparison purposes but only if everyone does it that way (unlikely).
>
> BTW, I have spoken to CTLS owners in my field and they agree that 4900 to 5000
RPM on initial climb is customary. As soon as you go to cruise climb speeds
that number goes up significantly. If you don't do that the cruise performance
will be dismal. They still get impressive TO performance and keep in mind that
you are operating at that lower RPM high torque regime for a very short period
of time. My LongEZ gives me only 2200 RPM on initial rollout (totally unacceptable
per Rutan) but goes up to 2500 by the time I am rotating. On cruise I
have to live with 2700 with my throttle lever at around 1/4 open (100 RPM less
than redline) which is not great. So is the nature of the beast. In the LongEZ
I play with altitude to achieve optimal RPM. Yes, altitude is my VP control
:) But that works on a prop that is slightly overpitched.
>
> Right now , on my Europa, I am getting around 5300 RPM/80 knts @ WOT on climb
but WOT at level flight still exceeds 5800 RPM. At cruise, I checked today, I
am at 5200 RPM/22" MAP at 3000' but only truing 115 ktas. I think based on this
I still need more pitch. BTW, Bud Yerly told me my airplane will be slow since
I still don't have my final shiny coat of paint. I believe him.
>
> Of course I can keep tweaking the blade angle until I reach a good compromise
(and ultimately that will be the process) but with just a little feedback from
the group I can then compare the performance of my airplane to other folks flying
the Europa out there.
>
> Best Regards,
> Chris
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=501478#501478
>
>
>
>
>
>
>
>
>
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Subject: | Populated Instrument Module weight |
Hi Group
Curiosity question: Whats the weight of your Populated Instrument Module, and what
do you have in it?
I know some have went on a weight reduction mission, before and after results would
be of interest.
Thx. Ron P.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=501480#501480
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Subject: | Re: Cruise speed data for Monowheel with 912ULS |
Thanks PeteZ and I think we are starting to get a great conversation going.
First: I don't think you should fixate on the static RPM number, it's meaningless
as long as the TO performance is acceptable and you are not overloading the
engine during climb. See the blurb I added at the end of this posting regarding
the CTLS. They call in their manual that once RPM reaches 4800 during TO roll
power is acceptable for takeoff.
Second: I am using a Woodcomp Klassic prop that came out of a Sport Cruiser (same
engine I have). I have the maintenance manual for that airplane and it calls
for max. 5,000 100 rpm ground static RPM. The CTLS people I talk to confirmed
today they climb at 4900-5000 RPM all the time. So lets really see in what
context the 5200 RPM recommendation from Rotax comes from (which I am sure is
important but is that for continuous operation).
BTW, as I was writing this I thought of looking at the CTLS operator manual. Very
interesting. RPM during initial TO roll is called to be 4800-5000 RPM. Climb
RPM 4800-4900. Prop is set to 5500 RPM at WOT in level flight and 4800 RPM recommended
for cruise. WOT static RPM 4900. This is from Flight Design USA web
site.
As the owner of a LongEZ I quickly learned that TO performance must be compromised
in order to achieve the speed potential of the airplane (which is still hard
to do). So yes, my takeoff run is longer than if I had finer pitch in the prop
but it must be done to keep the RPM at bay during cruise (I would have to
bring the throttle to idle to not overspeed the prop on that airplane). Yes, the
Europa is that kind of airplane that really needs a constant speed prop but
if you don't have one it is not the end of the world. At least me, I don't have
the $10K needed to put one on mine.
BTW, if your thing is to fly from short unimproved runways then of course set your
prop for that environment.
Best,
Chris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=501481#501481
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Subject: | CKT exhaust header tube needed, please. |
Today while approaching to land and after landing, the engine sounded quite a lot
different. After removing the cowls, the header tube for right rear #3 cylinder
was seen to have cracked circumferentially completely around. Rather than
weld the two parts back together and end up finding further cracking due to the
weld, I'd rather just replace the tube with one that is whole.
The carburettors are maintained well balanced with a CarbMate electronic balancer
and the Airmaster propeller runs nice and smooth as well. This crack has appeared
after more than 4 years in service, so I'm not dissatisfied.
Thanks,
Jonathan
G-EIKY Classic tri-gear
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=501482#501482
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Subject: | Re: Populated Instrument Module weight |
Ron,
When I pull my panel off for transponder install in the next couple of weeks I
will let you know what mine is. I have a bunch of old school stuff so doubt it
will be very light but who knows (or that it would be appealing to many pilots
out there). The transponder I'm sure will add a lot percentage wise.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=501483#501483
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Subject: | Re: Rotax 912ULS Low Fuel Pressure |
This has caused me to think a bit.
The Europa builder=99s manual shows the fuel going from the fuel
selector to the electric fuel pump and then to the engine=99s
mechanical fuel pump. Is that how it is set up?
If so, does the fuel get pulled through the electric fuel pump by the
mechanical fuel pump when the electrical fuel pump is turned off? That
seems like it would cause variation at that point.
Various aircraft builder=99s books from the EAA show a parallel
system for low-wing aircraft. Those diagrams make sense to me. In other
words, they show the fuel being provided by a parallel fuel system, with
fuel lines going from the fuel selector to both 1) the electric fuel
pump and then to the carb, and 2) to the engine=99s mechanical
fuel pump and to the carb.
That way, if the mechanical pump quits, the electrical pump doesn=99
t have to try to push fuel though the mechanical one to get to the carb.
And, the mechanical pump doesn=99t have to pull fuel through the
electric fuel pump if the electric fuel pump is off or it quits.
Which way should this be set up, and and if you think it=99s the
way shown in the Europa builder=99s manual, why?
Jeff Williams
Builder A157
> On Apr 22, 2021, at 10:19 PM, Griffo <scangriffin@bigpond.com.au>
wrote:
>
<scangriffin@bigpond.com.au>
>
> Hi Dave,
>
> Hi,
>
> It=C3=A2=C2=C2=99s good that you are taking precautions to avoid
having the electric (boost/back up) pump mask/hide a failed mechanical
fuel pump.
> However, I would question the merit of leaving your electric pump on
at all times, as I would expect a pump, so operated, to become a service
item replaced at ?? hours of operation (as the mechanical pump has a
recommended service life).
> I only use my electric pump =C3=A2=C2=C2=93 prior to engine start
(off for start) to check fuel pressure/availability. On again, for
take-off. Off when safe height above terrain achieved. On again, when
downwind for landing.
> Your engine will run perfectly without the need for the electric pump,
which should only be used when you have a mechanical fuel pump failure,
at critical times, when fuel starvation is not a good option.
>
> --------
> 46
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=501476#501476
>
>
>
>
>
>
>
>
>
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Subject: | Re: Populated Instrument Module weight |
20lbs with txpndr and radio. No horizon, no DI. Analogue.
Duncan McF.
> On 23 April 2021 at 18:21 rparigoris <rparigor@hotmail.com> wrote:
>
>
>
> Hi Group
> Curiosity question: Whats the weight of your Populated Instrument Module, and
what do you have in it?
> I know some have went on a weight reduction mission, before and after results
would be of interest.
> Thx. Ron P.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=501480#501480
>
>
>
>
>
>
>
>
>
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Subject: | Re: Rotax 912ULS Low Fuel Pressure |
Fwiw, mine was pulling through the elec fuel pump, but I have re-hosed it
and now added an andair checkvalve in parallel with the pump. Common
practice, and removes any fuel pump restriction.
Will be interesting to see if that change reduces the drop.
Cheers
PeteZ
On Fri., Apr. 23, 2021, 4:30 p.m. Jeffrey Williams, <
jeffwill55@sbcglobal.net> wrote:
> This has caused me to think a bit.
>
> The Europa builder=99s manual shows the fuel going from the fuel se
lector to
> the electric fuel pump and then to the engine=99s mechanical fuel p
ump. Is
> that how it is set up?
>
> If so, does the fuel get pulled through the electric fuel pump by the
> mechanical fuel pump when the electrical fuel pump is turned off? That
> seems like it would cause variation at that point.
>
> Various aircraft builder=99s books from the EAA show a parallel sys
tem for
> low-wing aircraft. Those diagrams make sense to me. In other words, they
> show the fuel being provided by a parallel fuel system, with fuel lines
> going from the fuel selector to both 1) the electric fuel pump and then t
o
> the carb, *and * 2) to the engine=99s mechanical fuel pump and to t
he carb.
>
> That way, if the mechanical pump quits, the electrical pump doesn
=99t have
> to try to push fuel though the mechanical one to get to the carb. And, th
e
> mechanical pump doesn=99t have to pull fuel through the electric fu
el pump if
> the electric fuel pump is off or it quits.
>
> Which way *should* this be set up, and and if you think it=99s the
way
> shown in the Europa builder=99s manual, why?
>
> Jeff Williams
> Builder A157
>
>
> On Apr 22, 2021, at 10:19 PM, Griffo <scangriffin@bigpond.com.au> wrote:
>
>
> Hi Dave,
>
> Hi,
>
> It=C3=A2=82=AC=84=A2s good that you are taking precautions to avoid
having the electric
> (boost/back up) pump mask/hide a failed mechanical fuel pump.
> However, I would question the merit of leaving your electric pump on at
> all times, as I would expect a pump, so operated, to become a service ite
m
> replaced at ?? hours of operation (as the mechanical pump has a recommend
ed
> service life).
> I only use my electric pump =C3=A2=82=AC=9C prior to engine star
t (off for start) to
> check fuel pressure/availability. On again, for take-off. Off when safe
> height above terrain achieved. On again, when downwind for landing.
> Your engine will run perfectly without the need for the electric pump,
> which should only be used when you have a mechanical fuel pump failure, a
t
> critical times, when fuel starvation is not a good option.
>
> --------
> 46
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=501476#501476
>
>
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|
Subject: | Re: Cruise speed data for Monowheel with 912ULS |
Wow that is low. Our local authorized Rotax service guy would shake his head,
and show me the chewed customer splined shafts he has on his shelf.
:-)
Petez
> On Apr 23, 2021, at 3:22 PM, n7188u <chmgarb@gmail.com> wrote:
>
>
> Thanks PeteZ and I think we are starting to get a great conversation going.
>
> First: I don't think you should fixate on the static RPM number, it's meaningless
as long as the TO performance is acceptable and you are not overloading the
engine during climb. See the blurb I added at the end of this posting regarding
the CTLS. They call in their manual that once RPM reaches 4800 during TO
roll power is acceptable for takeoff.
>
> Second: I am using a Woodcomp Klassic prop that came out of a Sport Cruiser (same
engine I have). I have the maintenance manual for that airplane and it calls
for max. 5,000 100 rpm ground static RPM. The CTLS people I talk to confirmed
today they climb at 4900-5000 RPM all the time. So lets really see in what
context the 5200 RPM recommendation from Rotax comes from (which I am sure is
important but is that for continuous operation).
>
> BTW, as I was writing this I thought of looking at the CTLS operator manual.
Very interesting. RPM during initial TO roll is called to be 4800-5000 RPM. Climb
RPM 4800-4900. Prop is set to 5500 RPM at WOT in level flight and 4800 RPM
recommended for cruise. WOT static RPM 4900. This is from Flight Design USA web
site.
>
> As the owner of a LongEZ I quickly learned that TO performance must be compromised
in order to achieve the speed potential of the airplane (which is still
hard to do). So yes, my takeoff run is longer than if I had finer pitch in the
prop but it must be done to keep the RPM at bay during cruise (I would have to
bring the throttle to idle to not overspeed the prop on that airplane). Yes,
the Europa is that kind of airplane that really needs a constant speed prop but
if you don't have one it is not the end of the world. At least me, I don't
have the $10K needed to put one on mine.
>
> BTW, if your thing is to fly from short unimproved runways then of course set
your prop for that environment.
>
> Best,
> Chris
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=501481#501481
>
>
>
>
>
>
>
>
>
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|
Subject: | Re: Cruise speed data for Monowheel with 912ULS |
Forget to ask: 80? or high compression 100hp? (Might be less of an issue on the
80)
> On Apr 23, 2021, at 3:22 PM, n7188u <chmgarb@gmail.com> wrote:
>
>
> Thanks PeteZ and I think we are starting to get a great conversation going.
>
> First: I don't think you should fixate on the static RPM number, it's meaningless
as long as the TO performance is acceptable and you are not overloading the
engine during climb. See the blurb I added at the end of this posting regarding
the CTLS. They call in their manual that once RPM reaches 4800 during TO
roll power is acceptable for takeoff.
>
> Second: I am using a Woodcomp Klassic prop that came out of a Sport Cruiser (same
engine I have). I have the maintenance manual for that airplane and it calls
for max. 5,000 100 rpm ground static RPM. The CTLS people I talk to confirmed
today they climb at 4900-5000 RPM all the time. So lets really see in what
context the 5200 RPM recommendation from Rotax comes from (which I am sure is
important but is that for continuous operation).
>
> BTW, as I was writing this I thought of looking at the CTLS operator manual.
Very interesting. RPM during initial TO roll is called to be 4800-5000 RPM. Climb
RPM 4800-4900. Prop is set to 5500 RPM at WOT in level flight and 4800 RPM
recommended for cruise. WOT static RPM 4900. This is from Flight Design USA web
site.
>
> As the owner of a LongEZ I quickly learned that TO performance must be compromised
in order to achieve the speed potential of the airplane (which is still
hard to do). So yes, my takeoff run is longer than if I had finer pitch in the
prop but it must be done to keep the RPM at bay during cruise (I would have to
bring the throttle to idle to not overspeed the prop on that airplane). Yes,
the Europa is that kind of airplane that really needs a constant speed prop but
if you don't have one it is not the end of the world. At least me, I don't
have the $10K needed to put one on mine.
>
> BTW, if your thing is to fly from short unimproved runways then of course set
your prop for that environment.
>
> Best,
> Chris
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=501481#501481
>
>
>
>
>
>
>
>
>
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Subject: | Re: Cruise speed data for Monowheel with 912ULS |
Word of caution;
Its my opinion that airframe/propeller manufacturers want to optimise sales (particularly
in the highly competitive sport aircraft market). They will happily
compromise engine servile life to do this.
On the other hand, engine manufactures (Rotax) want to preserve the service life
of the engine and will set perimeters that have a good chance of achieving this.
Again, in my opinion, the (Rotax) engine operating perimeters should transcend
anything being put out by the airframe or propeller manufacturers.
Follow the Rotax recommendations for static and max rpm time limits. Set your engine
to work between these limits and you wont go far wrong. If this does not
meet your operational requirements - invest in an in flight adjustable propeller.
--------
46
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=501489#501489
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Subject: | CKT exhaust header tube needed, please. |
If you have an older CKT there were some weld issues.
The 912S is a rougher engine and the exhaust system will shake. If the crack was
near the spring attachment it is a weld problem.
Another issue is drilling of EGT holes. Stress risers happen.
If the muffler is hitting the frame the down tube can be stressed in bending and
crack.
Wrong kinds of springs can be a problem also, but the springs break before the
tube normally.
Sometimes we just don't know. Contact Robin at CKT. They will take care of you.
Best Regards,
Bud Yerly
-----Original Message-----
From: owner-europa-list-server@matronics.com <owner-europa-list-server@matronics.com>
On Behalf Of JonathanMilbank
Sent: Friday, April 23, 2021 3:17 PM
Subject: Europa-List: CKT exhaust header tube needed, please.
Today while approaching to land and after landing, the engine sounded quite a lot
different. After removing the cowls, the header tube for right rear #3 cylinder
was seen to have cracked circumferentially completely around. Rather than
weld the two parts back together and end up finding further cracking due to the
weld, I'd rather just replace the tube with one that is whole.
The carburettors are maintained well balanced with a CarbMate electronic balancer
and the Airmaster propeller runs nice and smooth as well. This crack has appeared
after more than 4 years in service, so I'm not dissatisfied.
Thanks,
Jonathan
G-EIKY Classic tri-gear
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Subject: | Re: Cruise speed data for Monowheel with 912ULS |
Guys,
The main problem with playing with pitch on the propeller is one never wants to
overload or lug the engine on takeoff.
See Rotax SL 912-16R1 which states to set WOT for takeoff no lower than 5200 on
the 912 and 912S/914 with specified fuel octanes.
Reason is detonation. If you run high quality gas 5200 Static WOT pretty much
assures you that detonation is unlikely.
Since detonation is destructive and at 5000 RPM can't be detected by ear easily
and the engine has no knock sensor, it is probably a good idea not to lug the
engine down below that.
Aircraft manufacturers are interesting.
To tout the top speed of an aircraft a fixed pitch is set to 4000 for WOT takeoff.
Needless to say one can check the Rotax Operational charts and that is at
the limit of the propellers capability and frankly beyond the edge of possible
detonation, but at 7500 feet MSL the cruise speed is decent so it is put in
the brochure.
For takeoff distance, the aircraft manufacturer sets 5650 and gets spectacularly
short takeoffs. Of course, immediately after liftoff the engine is at 5800
RPM and the throttle is ripped back to prevent an overspeed.
Manufacturers are interested in airplane sales. You will not get the exact performance
of the book normally.
It is prudent to set 5200 for auto gas operations especially where octane ratings
may be suspect.
In test flying to get the best from your aircraft the test pilot must fly boring
short flights at differing prop settings to get the best all around prop setting.
For me that was 5000 RPM on AvGas WOT Static. I got 5500 at 90 Kts climb, 5000
at cruise at 134Kts. In a 900 pound APS or empty wt. trigear.
Clean composite aircraft will run out of prop with a fixed pitch almost all the
time. You will have to live with reducing the power to maintain 5000 RPM for
cruise or run around like the LSAs at higher RPMs trying to get somewhere.
Performance testing requires repetitive tests at specific RPM, MP, FF, Altitude
and weight. Make a spreadsheet and note the prop pitch for the test, fuel type,
WOT static indications, TO roll, Climb speed to get 5500 exactly, and log
the RPM, Throttle position, MP, FF, at each cruise altitude. Land and tweak the
prop and go fly again compensating for the altitude change as the temp changes
to maintain roughly the same density. SPREADSHEETS TELL THE STORY!
Don't go cheap on fuel.
I have tested an 80 HP KR at 4000 RPM WOT on AvGas and the takeoff was less than
spectacular. Over a 1000 foot takeoff roll. Float in the landing was so bad
shutting the engine off is preferred on a hot day. 10,000 foot speed was quite
impressive. If I recall that little KR2 went nearly 138 Knots on a fixed Warp
Drive tapered blade. (Cold day!) Never did that again. Most of that planes
life was done at 5000 RPM WOT Static. Speed dropped only about 10 knots but
you could get off the ground in 800 feet and land on a 3000 foot runway and
turn off at mid field without shutting off the engine.
I prefer to spend the bucks and install a constant speed prop on composite aircraft.
You get the best takeoff distance, climb rate and best cruise your engine
can provide.
I still don't do Max Continuous at altitude with the 914. I stick with my charts
and look for the best range, max endurance, or time to destination I can get.
My little Europa responds. On 912S equipped aircraft, fuel flow does not
decrease with altitude above roughly 3500 MSL. So, either a leaning kit is needed
or at WOT your gas milage tends to sag, so setting the throttle slightly
back and or adding a leaning kit increases performance and range slightly.
On a 912S ram air is not normally a good idea. It tends to lean the engine excessively
rather than add MP. The typical Bing is designed to suck air, that is
why the Bing 64 on the 914 has all those gimmicks to keep the mixture right.
Go get some data on your plane. But don't blow the engine doing it. It's expensive
and time consuming.
Best Regards,
Bud Yerly
-----Original Message-----
From: owner-europa-list-server@matronics.com <owner-europa-list-server@matronics.com>
On Behalf Of n7188u
Sent: Friday, April 23, 2021 11:38 AM
Subject: Europa-List: Re: Cruise speed data for Monowheel with 912ULS
First let me apologize to the group for trying to dig so deep into this subject.
I am by no means an expert but I have been around a bit. However, my goal is
to learn and as an Engineer I do tend to overthink stuff a little (good thing
when you design life critical medical devices :) ).
Griffo, this subject is so complex, and open to so much debate that yes, what you
mention is valid, but a few items beg to be clarified as to ensure we are comparing
apples to apples.
First, RPM alone is not enough to determine the power output of an engine (although
you mention speed which could be used as the additional parameter but I prefer
not to due to variability). You need a way to determine that the pitch in
your prop is set correctly to start with (and hence the engine is developing
the desired power). A common way to "communicate" this to aircraft builders is
through the "static RPM" parameter. But, although a good starting point for
first flight, the final outcome is so dependent on the prop design that the parameter
alone is not enough to properly set a ground adjustable prop.
And yes, the "art" of adjusting a fixed pitch prop will always depend on the preference
of the user so is there really a "right" answer?, certainly not. Keep
in mind though that the Europa, as well as my LongEZ, ire aircrafts designed
for speed so it is my goal to maximize speed and still retain acceptable TO performance.
Also, the engine operates most of the time in cruise regime, so to
achieve descent efficiency it is desirable to operate at power/RPM settings that
avoids "chocking" the engine with low throttle settings.
The consensus I found in the Rotax-Owners forums that made most sense to me is
to adjust the prop pitch so that you get 5800 RPM WOT in the air at level flight
(of course this would be altitude and temp dependent). Then check RPM on takeoff
to make sure it will still provide acceptable takeoff and climb performance.
If you set your prop with that specific baseline then yes the MAP info is
unnecessary for comparison purposes but only if everyone does it that way (unlikely).
BTW, I have spoken to CTLS owners in my field and they agree that 4900 to 5000
RPM on initial climb is customary. As soon as you go to cruise climb speeds that
number goes up significantly. If you don't do that the cruise performance will
be dismal. They still get impressive TO performance and keep in mind that
you are operating at that lower RPM high torque regime for a very short period
of time. My LongEZ gives me only 2200 RPM on initial rollout (totally unacceptable
per Rutan) but goes up to 2500 by the time I am rotating. On cruise I have
to live with 2700 with my throttle lever at around 1/4 open (100 RPM less than
redline) which is not great. So is the nature of the beast. In the LongEZ
I play with altitude to achieve optimal RPM. Yes, altitude is my VP control :)
But that works on a prop that is slightly overpitched.
Right now , on my Europa, I am getting around 5300 RPM/80 knts @ WOT on climb but
WOT at level flight still exceeds 5800 RPM. At cruise, I checked today, I am
at 5200 RPM/22" MAP at 3000' but only truing 115 ktas. I think based on this
I still need more pitch. BTW, Bud Yerly told me my airplane will be slow since
I still don't have my final shiny coat of paint. I believe him.
Of course I can keep tweaking the blade angle until I reach a good compromise (and
ultimately that will be the process) but with just a little feedback from
the group I can then compare the performance of my airplane to other folks flying
the Europa out there.
Best Regards,
Chris
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Subject: | Re: Cruise speed data for Monowheel with 912ULS |
Hi Chris,
The SL that I referred Griffo to back in your other post states the you should
have 5200 rpm min at take off WOT. It doesn't say what part of TO. It also doesn't
mention any thing about static revs in regard prop pitch. They now have a
sort of power chart as well but once again, pretty vague.
Pete is probably correct that it doesn't help the gearbox but I think the main
reason is to protect the crankshaft. That SL came out after a crash where an aircraft
with an inflight adjustable prop had been operated for some time at too
low revs for the MAP.
Prior to that most people tried for 4900 to 5000 at TO for a bit of cruise performance
and I'm sure a lot of people still do.
It's really what ever people feel comfortable with.
Cheers Peter
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Subject: | Re: Cruise speed data for Monowheel with 912ULS |
Hi Peter,
If you have 5200 rpm STATIC, you will get that as soon as you open your throttle,
to start the TO run. The rpm will climb as you accelerate, moving up into the
5 min max operating range. If your aircraft/engine is climbing into the no
go zone, raise the nose/steepen the climb to control the rpm within safe limits.
As you say, its what "people feel comfortable with" unfortunately the engine
may not be so comfortable with this arrangement, resulting in problems "down the
track".
--------
46
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Subject: | Re: Cruise speed data for Monowheel with 912ULS |
I did continue my research (learning was after all the intent of this posting)
and found a Rotax SL-912-016 which does state that WOT operation during takeoff
should not result in an RPM lower than 5200 RPM. In light of this new factual
information I will say please do follow this recommendation.
But I will say this openly: I didn't buy a certified airplane, instead I choose
to build an experimental Europa and, at least in the US, that means that it is
my responsibility to determine what are the operational parameters that will
result in safe operation but also in the performance I expected to achieve from
this aircraft. Google "LongEZ N295JF" (Race 25) and I think you will understand
where I come from.
Sadly, we do live in a litigious society and having open discussions in public
forums regarding the essence of what experimental aviation is about is dangerous
business so I will desist right now from doing that. I will share any factual
info I find such as the one presented above or in the previous postings but
it is up to each individual to decide what to do with that info. Really sad.
But I still would be interested in receiving information regarding RPM/MAP and
speed for your 912 ULS monowheel as originally intended.
And PeteZ, both the CTLS and the Sport Cruiser are equipped with he 100 HP ULS
engine.
Best Regards,
Chris Martin
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