Possibly needing prop adjustment

[Marco01]

Just back from the Mt Blanc trip: 17426 feet at the GPS altitude! OAT -5° (only): was never able to reach this altitude with 22,5° pitch. Removing 2,5° has helped, even if I can't explain why... Flaps were set at 0° since it helps to get few hundred additional feet.

[FastEddieB]

[IrishAl]

Rotax is absolutely vemonant that rpms at WOT be at least 5500+ and especially adamant to stay away from WOT settings down around 5100-5300. This is taught in all Rotax schoolls, it's in bulletins. 

 

That couldn't be more definitive - thanks.

[Jacques]

Just back from the Mt Blanc trip: 17426 feet at the GPS altitude! OAT -5° (only): was never able to reach this altitude with 22,5° pitch. Removing 2,5° has helped,

Marco01

 

where exactly do you have the 20° ?

 

I assume it is 20° from the centerhub

 

asking because I have to reajust my Neuform for the 100hp (from the 80 )

 

merci

[IrishAl]

The common misunderstanding was that we needed to choose between cruise speed and climb rate.  Looking at the performance chart I could see that power for both good climb and best speed would require a flatter pitch.

 

CT, would you care to unpack that a bit?

[Tom Baker]

I am flying with the factory set pitch and get the performance indicated in the POH.  And I am not flying at sea level.  Chasing prop pitch to gain a little more torque and RPM is a dog chasing it's tail.  It's a fixed pitch prop and you will just be redoing it for winter versus summer, and if you fly at altitude versus sea level.

 

Roger is a mechanic with a LOT of expertise and the tools and time to play the game.  The rest of us should not try to fix what isn't broken.

Did your airplane come out of the container with the propeller installed? The CTLS that I have seen fresh out of the container had the propellers and rudders removed. At the very least Lone Mountain should have checked and set your propeller during the assembly process.

 

The CTSW were enough shorter that they could ship with their propellers installed.

[Ed Cesnalis]

The common misunderstanding was that we needed to choose between cruise speed and climb rate.  Looking at the performance chart I could see that power for both good climb and best speed would require a flatter pitch.

 

 

CT, would you care to unpack that a bit?

 

First of all I knew the answer, I knew that a 'race' prop = a 'climb' prop and that optimizing for speed and climb were the same things.  We also know that optimizing for climb vs cruise/speed is also a matter of using the 5,800RPM 5MIN limitation or the 5,500RPM Continuous limitation. This is where any compromise between speed and climb exists, either speed or climb needs to utilize all available power.

 

It is already the common knowledge in this thread that the legacy was for a coarse pitch limiting max RPM to less than 5,300.

 

Look at the performance graph, the original factory pitch setting that limitted my RPM to < 5,300 also limited my available horse power to ~90.  A flatter pitch is required to either go faster or climb faster

 

For years and perhaps into this day people have posted that they want to adjust [flatten] their pitch so that they can go faster and that they realize it will cost them some climb [not true - climb is enhanced]

 

[Anticept]

As long as it is known that there is a "too flat" too! Generally climb and acceleration are better on the flat side of what I will term "prop efficiency zone", and cruise is better on the coarser side. Go beyond these and you loose them all!

[Ed Cesnalis]

Too flat is generally governed by the 5,500' limitation.

[Doug G.]

100H. You do not have a fixed pitch prop.

[Anticept]

Too flat is generally governed by the 5,500' limitation.

 

I meant in general of all propellers. And it's 5,800

[gbigs]

Did your airplane come out of the container with the propeller installed? The CTLS that I have seen fresh out of the container had the propellers and rudders removed. At the very least Lone Mountain should have checked and set your propeller during the assembly process.

 

The CTSW were enough shorter that they could ship with their propellers installed.

 

What did Lone Mountain set your prop to? 

[gbigs]

First of all I knew the answer, I knew that a 'race' prop = a 'climb' prop and that optimizing for speed and climb were the same things.  We also know that optimizing for climb vs cruise/speed is also a matter of using the 5,800RPM 5MIN limitation or the 5,500RPM Continuous limitation. This is where any compromise between speed and climb exists, either speed or climb needs to utilize all available power.

 

It is already the common knowledge in this thread that the legacy was for a coarse pitch limiting max RPM to less than 5,300.

 

Look at the performance graph, the original factory pitch setting that limitted my RPM to < 5,300 also limited my available horse power to ~90.  A flatter pitch is required to either go faster or climb faster

 

For years and perhaps into this day people have posted that they want to adjust [flatten] their pitch so that they can go faster and that they realize it will cost them some climb [not true - climb is enhanced]

 

Capture.GIF

 

5500 also has a 5 minute limit.

[gbigs]

100H. You do not have a fixed pitch prop.

 

Yes it is.  It cannot be changed in flight.  It's ground changeable but only one setting done on the ground.  That amounts to a fixed pitch prop in flight.  No need to mince words.

 

Those playing around with their prop pitch are kidding themselves.   Since you can't change it in flight, whatever pitch you choose to reset or leave set is only optimal for part of the flight at best.

[FlyingMonkey]

5500 also has a 5 minute limit.

Maybe on your 912iS, I don't know, but not on the 912ULS. Maximum continuous is 5500rpm. You can run the engine at that rpm all day long.

[Roger Lee]

Both are continuous at 5500 rpm. In reality it can do more than 5500 rpm continuous. (Safety margins and liability)

[gbigs]

Both are continuous at 5500 rpm. In reality it can do more than 5500 rpm continuous. (Safety margins and liability)

I give you the Tach Table from 2.3.2 CTLS POH dated: 12-Nov-11

 

The Yellow Arc range (5 minutes) is 5500-5800

The Redline is 5800

[FlyingMonkey]

I give you the Tach Table from 2.3.2 CTLS POH dated: 12-Nov-11

 

The Yellow Arc range (5 minutes) is 5500-5800

The Redline is 5800

 

Um...yes.  Yellow arc 5500-5800.  Green arc 1800-5500.  Why did you leave out that 5500rpm is also in the green arc?  That means 5500 is both the end of the normal range and the beginning of the yellow arc.  If it makes you feel better, run continuously at 5499rpm.  But I bet it would be fine at 5501rpm too.  

 

Oh wait, you can't run continuously at 5499-5501rpm anyway, because your prop is too coarse...

[Runtoeat]

Mike, thanks for the links.  This is interesting.

[Ed Cesnalis]

I meant in general of all propellers. And it's 5,800

 

Its your choice, I like 5,500 for a max so I can cruise WOT.  5,800 does little for me, I can already climb really well its cruise speed that I (and most) want to optimize.

[Ed Cesnalis]

Yes it is.  It cannot be changed in flight.  It's ground changeable but only one setting done on the ground.  That amounts to a fixed pitch prop in flight.  No need to mince words.

 

Those playing around with their prop pitch are kidding themselves.   Since you can't change it in flight, whatever pitch you choose to reset or leave set is only optimal for part of the flight at best.

 

If you leave the coarse "factory" setting you cannot access full rated power. (take off or continuous you pick)

 

Granted you cannot optimize for sea level too but optimization at low altitudes provides little except a touch better economy.

[Tom Baker]

What did Lone Mountain set your prop to?

I have someone with more experience work on my airplane.

 

My airplane didn't come from Lone Mountain, but I did pick it up at the distributor who has delivered most CT's in the USA. I have been around two different distributors with ne CTLS fresh out of the container. All of them were shipped with the prop removed. If the prop was removed then the pitch needed to be checked and likely set.

[Tom Baker]

Those playing around with their prop pitch are kidding themselves.   Since you can't change it in flight, whatever pitch you choose to reset or leave set is only optimal for part of the flight at best.

People are not playing around with prop pitch like you are insinuating. They are trying to get it set right, and then they leave it alone. If your pitch is set right then good for you. For those that are not set right adjustment is in order.

[gbigs]

I have someone with more experience work on my airplane.

 

My airplane didn't come from Lone Mountain, but I did pick it up at the distributor who has delivered most CT's in the USA. I have been around two different distributors with ne CTLS fresh out of the container. All of them were shipped with the prop removed. If the prop was removed then the pitch needed to be checked and likely set.

 

What is your prop set to?  Are you flying at sea level most of the time?

[gbigs]

People are not playing around with prop pitch like you are insinuating. They are trying to get it set right, and then they leave it alone. If your pitch is set right then good for you. For those that are not set right adjustment is in order.

 

My point is a simple one.  Since the prop is fixed in flight ANY setting is static for all density altitudes for all flights made at that setting.  I contend there is no such thing as 'set right'.   Diddling with the prop pitch may allow you to tweek for a given density altitude but the gain is so small that risking doing it wrong outweigh leaving it at the factory setting.