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Static RPM

JohnF

Well Known Member
I am fairly sure I am correct about this, but other inputs would be appreciated.

I had static WOT RPM at first trial setting at 5,200 +
Next trial setting gave steady RPM increase until 4,200, then added throttle began to show a reduction in RPM.

Another trial setting gave pretty much the same thing.

Time constraints made me stop; tomorrow I will try more. I suspect the reduction in RPM after 4,200 with added throttle was due to fairly heavy over pitch setting. You agree?
 
That's right

I think you need to reduce pitch a bit. I did three settings and plotted static RPM vs. Blade angle (measured with the forum's handy attachment and a digital level) then picked the setting for 4900 rpm and got 4930. I think I need to reduce pitch setting a bit since I couldn't get to 5500 in level flight but it sure climbs nice!

Wayne 143WM/120241
 
I agree, Wayne. Tried this morning to reduce pitch, but cannot move the blades enough to change things. I have a total movement latitude of one space between the marks on the indicator on the prop mount. I am going to remove the prop and check the restructer plate because something is not right. My first rpm trial was 5,200 and able to go more. Now I can't get over 4,200 and then more throttle reduces rpm..I suspect something is not right with the plate because I should be able to move the indicators more than one space.
 
Prop Adjustment

John are you using a digital level to make your adjustments?

John
RV12 N1212K
 
static rpm

Yes, I have a digital level and the angle mount that (I think it was) Tony's idea posted earlier...its not the sameness of the two blades that I think is the problem, it is that I cannot move the angle enough...I should be able to have a range or blade rotation as shown on the marks on the mount of more than one space...the fact that my first run gave over 5,200 rpm with more throttle yet to be used, and now can't get over 4,200 before rpm reduction with throttle advance tells me something isn't right and I am pulling the prop to inspect the restrictor plate...I should be able to move the blades a lot more.
 
Yes, I have a digital level and the angle mount that (I think it was) Tony's idea posted earlier...its not the sameness of the two blades that I think is the problem, it is that I cannot move the angle enough...I should be able to have a range or blade rotation as shown on the marks on the mount of more than one space...the fact that my first run gave over 5,200 rpm with more throttle yet to be used, and now can't get over 4,200 before rpm reduction with throttle advance tells me something isn't right and I am pulling the prop to inspect the restrictor plate...I should be able to move the blades a lot more.

John,
It only takes a small movement of the blade angle to get major change in static RPM. My prop only allows about one space on the hub for adjustment, similar to yours. Please reread Scott's recommendation to change prop pitch by only 0.3° in post #15 in this thread: http://www.vansairforce.com/community/showthread.php?t=59682&page=2
Also, recommend reading the RVator article on adjusting the prop:
http://www.vansaircraft.com/RVator/2010/3-2010-RVator.pdf
in that article Scott says that a change of only 0.2°-0.3° makes a measureable change in aircraft performance. Based on that article, if you move the blades to full maximum pitch, and come back 0.3° per step, using the digital level fixture you should come close to ideal.
I doubt if there is anything wrong with your propeller. ;)

Tony
 
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I haven't run my engine yet, so....

.... I probably don't know what I am talking about, but - how could more throttle possibly reduce RPM? And how could that possibly have anything to do with the prop?

This sounds like some other problem to me - throttle linkages, carb syncronization, etc.
 
static rpm

I don't know; carb sync was done with as Carbmate and was dead on at idle
(1800) at the most sensitive setting on the carbmate, and also at max rpm which at the time was 5200 rpm. Nothing on the linkage was changed, and my first run with the prop gave over 5,200 with throttle yet remaining. I moved the prop to a flatter angle and since then can't get anywhere near 5,000; the wierd thing is that rpm max'es at aroiund 4200 and then more throttle shows as reduction in rpm. I am going to pull the prop to remove any doubt that the restrictor plate is not properly in place and more or less start over. I will also recheck throttle linkages although I doubt there's any problem there, but who knows?
 
Check fuel flow

how could more throttle possibly reduce RPM?
If the prop adjustment does not fix the low RPM, the fuel pressure and flow rate should be checked. A RPM drop with more throttle could mean that there is a restriction in the amount of fuel reaching the engine. Once the engine reaches maximum RPM with available fuel, opening the throttle more creates a leaner mixture, thus causing lower RPM.
Joe
 
static rpm

Joe, your input re fuel quantity makes sense, but I see in my notes that I was showing 4.8 psi fuel pressure at the time, tho' pressure and amount of fuel delivered might be different. I will look into this tho. thanks
 
I think my guess was correct as to why I saw a reduction in rpm after a certain amount of throttle was input; the prop was overpitched and at the upper limit of the engine's ability to keep things spinning it just reduced rpm due to overloading the engine...anyway that is the way I see it.

I started over this morning..put the prop at finest pitch, ran it, keep reducing the pitch in small increments, and checking it. I finally settled on 5,100 rpm at max because I fly from a 7,500-ft airport, and density altitudes are typically 8 to 9 thousand and I feel a bit better starting out with what amounts to a 'climb' setting. I can refine it was I gain experience with this setting.
 
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Digital Tach

I always use a digital tach when I first set up a prop and a new engine. They are cheap at Aircraft Spruce (about $50). Just don't forget to take the gearbox reduction into account.
 
My max static is around 4135 rpm & mine acts the same I checked my blade angle with a prop protractor & the blades are pitched at 24 degrees. I am wondering if anyone has the ideal pitch angle in degrees. I think if I had the right degrees it might save me a lot of time. I would like to try thae degree method first if one of you could give me a starting degree.
Thanks in advance

RV12 waiting for the inspector
RV-7A 350 hrs
 
Because there are so many variables when taking the pitch measurement, supplying an angle is impossible. Hope you are using a digital level and not the plastic dial type prop protractor which is useless.

Use one of the mounts as shown in a number of previous posts for your digital level. Ensure the blade is parallel to the ground. Use a stick or piece of PVC, and put a mark on it to ensure when you rotate the blade, the opposite blade tip is the same distance from the ground. Place the digital level on the blade. Find the midpoint by rotating the blade pitch from stop to stop (max pitch to min pitch). Rotate the prop half a revolution and place the digital level in the same exact position on the opposite blade. Ensure each is pitched the same.

The midpoint is a good starting point. From there make tiny adjustments to both blades (0.2 deg) until you get a static RPM of 4950-5000.
 
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Here is an article I wrote a while back on ground adjustable props. It is on the Rotax website.

http://www.rotax-owner.com/rotax-blog/item/9-understanding-the-ground-adjustable-prop

Marty is right. 4135 static is too low. I have tested many props 2&3 blade and the pitch angles all vary and even the static rpms. Set it up around 4850 +/- static at WOT on the ground. Static is for nothing more than to get you in the ballpark so using a specific angle from one plane to another is no better. The aircraft then needs to fly to get your prop fine tuned for your specific flying. Once you set the static go fly. Go to your average altitude and go WOT for 30-45 seconds. A fairly good WOT rpm is around 5600-5650. This can vary some depending on your own personal needs in the flight performance envelope.
 
Stan,
Do exactly as Marty and Roger suggest. Make miniscual changes between test runs. Use the digital level as a guide, but do not try to use it to obtain a specific angle. When you get close to the static RPM you are looking for, use the level to get the two blades as close to the same angle as possible, for smoothest operation.

One more tip. After you have the prop set up the way you want it, get a dynamic balance done. On my plane this made a huge difference in vibration level.

Let us know how it goes.

John
 
Hi Stan,

Once you test fly it and get an rpm and if you let me know what it is I can give you a pretty good estimate of how may degrees to subtract to flatten the pitch and you may only have to make one adjustment. I have reset well over a hundred LSA and experimental prop pitch setups in the last few years mainly from MFG's because they tend to over pitch the prop and end up with a loss of over all performance and over stresses the engine. These guys with engines of June 2006 or earlier that have max WOT rpms less than 5500
(i.e. 5000-5300) are looking the crack cases. That's one of the reasons for that service bulletin years ago and why those cases can't qualify for the 2000 TBO. Over pitching can and does cause harm. The newer cases are a little stronger due to a design change. If one of the older cases crack it is usually right on top about mid engine just off the center line. Oil doesn't gush out, but does seep or ooze out.

If you need any help just give me a call. The RV12 is a really good performer with the proper rpm.
 
Hi Stan,

Once you test fly it and get an rpm and if you let me know what it is I can give you a pretty good estimate of how may degrees to subtract to flatten the pitch and you may only have to make one adjustment. I have reset well over a hundred LSA and experimental prop pitch setups in the last few years mainly from MFG's because they tend to over pitch the prop and end up with a loss of over all performance and over stresses the engine. These guys with engines of June 2006 or earlier that have max WOT rpms less than 5500
(i.e. 5000-5300) are looking the crack cases. That's one of the reasons for that service bulletin years ago and why those cases can't qualify for the 2000 TBO. Over pitching can and does cause harm. The newer cases are a little stronger due to a design change. If one of the older cases crack it is usually right on top about mid engine just off the center line. Oil doesn't gush out, but does seep or ooze out.

If you need any help just give me a call. The RV12 is a really good performer with the proper rpm.

Roger for technique adjusting prop angle, can one use two 1x4? sticks taped together on the front and back of a blade to make those small prop angle changes easier/smoother with a little leverage?

Best,
Doug in IL
Former CTSW owner
 
Hi Stan,

Once you test fly it and get an rpm and if you let me know what it is I can give you a pretty good estimate of how may degrees to subtract to flatten the pitch and you may only have to make one adjustment. I have reset well over a hundred LSA and experimental prop pitch setups in the last few years mainly from MFG's because they tend to over pitch the prop and end up with a loss of over all performance and over stresses the engine. These guys with engines of June 2006 or earlier that have max WOT rpms less than 5500
(i.e. 5000-5300) are looking the crack cases. That's one of the reasons for that service bulletin years ago and why those cases can't qualify for the 2000 TBO. Over pitching can and does cause harm. The newer cases are a little stronger due to a design change. If one of the older cases crack it is usually right on top about mid engine just off the center line. Oil doesn't gush out, but does seep or ooze out.

If you need any help just give me a call. The RV12 is a really good performer with the proper rpm.

I agree with Roger that many are over pitching their prop - Vans is no exception. There have been posts from the Vans folks in this forum that make the claim that the recommended pitch for the 12 won't harm the engine which is incorrect. WOT level flight of 5650 is optimum and SL912-016 describes the types of environments that can lead to engine failure. The 12 suffers from several precursors. Rotax developed these parameters from experience.
 
I agree with Roger that many are over pitching their prop - Vans is no exception. There have been posts from the Vans folks in this forum that make the claim that the recommended pitch for the 12 won't harm the engine which is incorrect. WOT level flight of 5650 is optimum and SL912-016 describes the types of environments that can lead to engine failure. The 12 suffers from several precursors. Rotax developed these parameters from experience.

Sorry for sounding simple here. As an overthinker/underdoer, I find it real difficult to smoothly and consistently obtain the VANS desired prop pitch setting just by loosening bolts and hand twisting blades . My idea to gain leverage is to loosen bolts juuuust enough to barely move blades, then retighten/snug-up/torque bolts without effecting the desired blade angle......seems a little leverage is called for to achieve satisfactory results on a consistent basis. I haven't checked my own idea (tape a lever to the blade to more precisely adjust it within specs/tolerances). Just wanted to see what tips or tricks others in the forum may have learned to achieve best results....Any thoughts out there???
 
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Sorry for sounding simple here. As an overthinker/underdoer, I find it real difficult to smoothly and consistently obtain the VANS desired prop pitch setting just by loosening bolts and hand twisting blades . My idea to gain leverage is to loosen bolts juuuust enough to barely move blades, then retighten/snug-up/torque bolts without effecting the desired blade angle......seems a little leverage is called for to achieve satisfactory results on a consistent basis. I haven't checked my own idea (tape a lever to the blade to more precisely adjust it within specs/tolerances). Just wanted to see what tips or tricks others in the forum may have learned to achieve best results....Any thoughts out there???

In the shop at Van's we use a tool made of plywood that is about 3 ' long.
It hooks on the blade and provides additional leverage for making small blade movements while setting the pitch.
You do need to be careful because the blades are hollow so you could do damage if the blade camp bolts were still too tight. When using a tool like this, the blade should move with very little force. If not, the clamp bolts are still too tight.

Regarding Van's recommended pitch being too course......
It actually matches up with what Roger (past poster in this thread) and other shops (such as Lockwood Aviation) use.
Additionally, during Aero Friedrichshafen (a large aviation trade show in Germany that is heavily attended by Rotax personnel) this past spring, Van's had a face to face sit down meeting with some of the Rotax staff (including the head engineers for the 912 engine program).
The chart in their documentation, and how Van's engine RPM during climb compares to the chart was one of the topics discussed. In a nut shell the engineers said that the climb RPM's typical on an RV-12 using the general pitch recommendations made by Van's, are not a concern to them.
 
I agree with Roger that many are over pitching their prop - Vans is no exception. There have been posts from the Vans folks in this forum that make the claim that the recommended pitch for the 12 won't harm the engine which is incorrect. WOT level flight of 5650 is optimum and SL912-016 describes the types of environments that can lead to engine failure. The 12 suffers from several precursors. Rotax developed these parameters from experience.

Stating a WOT at level flight RPM without stating an altitude is leaving an import piece of info out that is relevant to proper propeller pitch.
 
In the shop at Van's we use a tool made of plywood that is about 3 ' long.
It hooks on the blade and provides additional leverage for making small blade movements while setting the pitch.
You do need to be careful because the blades are hollow so you could do damage if the blade camp bolts were still too tight. When using a tool like this, the blade should move with very little force. If not, the clamp bolts are still too tight.

Regarding Van's recommended pitch being too course......
It actually matches up with what Roger (past poster in this thread) and other shops (such as Lockwood Aviation) use.
Additionally, during Aero Friedrichshafen (a large aviation trade show in Germany that is heavily attended by Rotax personnel) this past spring, Van's had a face to face sit down meeting with some of the Rotax staff (including the head engineers for the 912 engine program).
The chart in their documentation, and how Van's engine RPM during climb compares to the chart was one of the topics discussed. In a nut shell the engineers said that the climb RPM's typical on an RV-12 using the general pitch recommendations made by Van's, are not a concern to them.

WOW, that is good to know! Any chance of a photo? Suggestion, how more capable/effecient would owner/maintainers be if our special tool kits contained one of those 3" thingy miJobs which kinda goes, hand in hand, with VAN's blade angle measurement fixture....Another hot seller for the store. Or, maybe just a photo of VAN's stick and a trip to local hardware store to fabricate something...is best?

Lastly, is my following interpretation of your last sentence above correct? "The ROTAX RPM response factors in related Manifold Pressure: Therefore it is no concern if prop pitch configurations and RPM indicate 27.6 and higher (ie;29.5) MAP at WOT RPM (49-5100) on take-off/climb to cruise. Any DA. Hope this question is accurate...

Very Respectfully,
Doug
 
I believe 4900 is logging the engine in climb.

Need ~ 5200 RPM when climbing ~ 1000 fpm at 1000 MSL on a standard day.
 
I believe 4900 is logging the engine in climb.

Need ~ 5200 RPM when climbing ~ 1000 fpm at 1000 MSL on a standard day.

I guess I got carried away with my limited ability to determine if average WOT/Take off/climb rpm ~5000 rpm and manifold pressure ~ 29.5 is ok?

Then at altitude rpm range 5200 to 5500 at 26.5-27.5 manifold pressure.

So, high manifold pressure on take off and climb then normal after reaching cruise rpm 5200-5500 rpm. Is that OK?
 
I have been struggling lately trying to get my prop pitch adj. to achieve those RPM ranges I noted from past threads. WOT in level flight was giving me 5720 so I had been inching in the pitch about .2 at a time, but see little to no change. What I am shooting for is 5500-5650.

I had actually constructed a similar device as previously mentioned using a 1x6 board, about 36" long. I cut a hole in the upper portion that was close to the shape of the prop blade and lined the opening with felt for padding. I use it as a lever to move the blade while keeping the bolts fairly snug. I also find the pitch and matching the pitch on both blades is tough. However, it is still difficult to hold a pitch point. Even with the bolts "snug" when the prop is moved the pitch can change. When I torque the bolts the pitch changes. During my last conversation with Sensenich when I would mention how difficult the prop is to set the pitch and hold the pitch while torqueing I was told "yes it is."

I am going to do a few more tests to try and achieve something close to 5650 at WOT, and if I can not get the prop to hold the pitch I'm torqued to I will be sending the hub to Sensenich for inspection/verification of proper milling/clamping specs.
I
 
I have been struggling lately trying to get my prop pitch adj. to achieve those RPM ranges I noted from past threads. WOT in level flight was giving me 5720 so I had been inching in the pitch about .2 at a time, but see little to no change. What I am shooting for is 5500-5650.

I had actually constructed a similar device as previously mentioned using a 1x6 board, about 36" long. I cut a hole in the upper portion that was close to the shape of the prop blade and lined the opening with felt for padding. I use it as a lever to move the blade while keeping the bolts fairly snug. I also find the pitch and matching the pitch on both blades is tough. However, it is still difficult to hold a pitch point. Even with the bolts "snug" when the prop is moved the pitch can change. When I torque the bolts the pitch changes. During my last conversation with Sensenich when I would mention how difficult the prop is to set the pitch and hold the pitch while torqueing I was told "yes it is."

I am going to do a few more tests to try and achieve something close to 5650 at WOT, and if I can not get the prop to hold the pitch I'm torqued to I will be sending the hub to Sensenich for inspection/verification of proper milling/clamping specs.
I

Double dang!!
All thread tips considered, can anyone please tell me if 29.5 MAP/5100 RPM WOT at takeoff and climb-out is acceptable based on the Van?s Rotax discussion Scott referred to?
Thank you!
Doug
 
I have been struggling lately trying to get my prop pitch adj. to achieve those RPM ranges I noted from past threads. WOT in level flight was giving me 5720 so I had been inching in the pitch about .2 at a time, but see little to no change. What I am shooting for is 5500-5650.

I had actually constructed a similar device as previously mentioned using a 1x6 board, about 36" long. I cut a hole in the upper portion that was close to the shape of the prop blade and lined the opening with felt for padding. I use it as a lever to move the blade while keeping the bolts fairly snug. I also find the pitch and matching the pitch on both blades is tough. However, it is still difficult to hold a pitch point. Even with the bolts "snug" when the prop is moved the pitch can change. When I torque the bolts the pitch changes. During my last conversation with Sensenich when I would mention how difficult the prop is to set the pitch and hold the pitch while torqueing I was told "yes it is."

I am going to do a few more tests to try and achieve something close to 5650 at WOT, and if I can not get the prop to hold the pitch I'm torqued to I will be sending the hub to Sensenich for inspection/verification of proper milling/clamping specs.
I

Are you using Vans TOOL-00002 Prop Pitch Bracket per SECTION 47: SPINNER & PROPELLER Page 47-07? I find this tool very easy to use with excellent accuracy and repeatability. Follow instructions exactly using a high quality digital level for the blades and and high quality bubble level on the hub. My blades are set to 0.1 degree and engine is extremely smooth in cruise. It shouldn't take more than 30 minutes to set blade pitch...
 
Thanks for the reply Jim. I use a digital level with a fixture attach to the level I made based on an article titled, Pitch Perfect. The fixture firmly attaches to the level and is in the shape of a T. The horizontal of the T has a lip to guide me on the trailing edge, and the vertical of the T is shaped pretty well to the contour of the prop.

I did use another level to level the prop each I rotated the prop but after a conversation with Sensenich the tech felt the prop needed to be level but using a level each time was a bit much. I use a reference mark each rotation to get the prop in the correct spot to check the pitch angle.
 
Thanks for the reply Jim. I use a digital level with a fixture attach to the level I made based on an article titled, Pitch Perfect. The fixture firmly attaches to the level and is in the shape of a T. The horizontal of the T has a lip to guide me on the trailing edge, and the vertical of the T is shaped pretty well to the contour of the prop.

I did use another level to level the prop each I rotated the prop but after a conversation with Sensenich the tech felt the prop needed to be level but using a level each time was a bit much. I use a reference mark each rotation to get the prop in the correct spot to check the pitch angle.

Thanks all, and yes I use the vans bracket but I was thinking a lever for fine tuning is useful. Fellas any thoughts to my question on post 27? Thanks again!!
 
Doug my take on your post 27 is MP is not a good measure for prop pitch but RPM will be. There are a number of variables with MP with field elevation for instance.
There are a couple of articles from Rotax users in several aircraft, and plenty of RV12 experience to draw from. I took this info way back and use it ti try and set my prop pitch.
Prop settings
Static 4900-5100
Take off 4850-5000
WOT level 5500-5650

Use these number as you want. My problem has been WOT going to 5720 and trying to get enough pitch to move closer to 5650. It?s been tough.
 
Thanks for the reply Jim. I use a digital level with a fixture attach to the level I made based on an article titled, Pitch Perfect. The fixture firmly attaches to the level and is in the shape of a T. The horizontal of the T has a lip to guide me on the trailing edge, and the vertical of the T is shaped pretty well to the contour of the prop.

I did use another level to level the prop each I rotated the prop but after a conversation with Sensenich the tech felt the prop needed to be level but using a level each time was a bit much. I use a reference mark each rotation to get the prop in the correct spot to check the pitch angle.

Your call, but I'd said not good enough. Prop hub must be leveled each time a blade pitch is measured. Also recheck cabin longeron level each time blade is moved - plane moves when engine is turned by hand. You need an extremely repeatable fixture to measure blade angle. I strongly advise purchase of the tool mentioned from Vans.
 
Doug my take on your post 27 is MP is not a good measure for prop pitch but RPM will be. There are a number of variables with MP with field elevation for instance.
There are a couple of articles from Rotax users in several aircraft, and plenty of RV12 experience to draw from. I took this info way back and use it ti try and set my prop pitch.
Prop settings
Static 4900-5100
Take off 4850-5000
WOT level 5500-5650

Use these number as you want. My problem has been WOT going to 5720 and trying to get enough pitch to move closer to 5650. It’s been tough.

Thank you Pat, useful! And just guessing, is it possible your hub is original version and prone to slippage even after torqueing? I replaced mine with Revision B hub which has better clamping, but doesn't escape the newest Prop SB...
 
I recently gave the serial to Sensenich and Don was okay with it as it ends with a C. He did however offer to check it if I wanted to take the entire hub off and ship it back.
I told him I was going to try a few more time to get it set properly but if it still was moving I would be shipping it to him. He seemed concerned I didn?t have the pitch cylinder in the middle seated properly.
The last time I reassembled, did a static run, I was seeing only 4500 RPM. Then the SB came out so it?s coming back apart anyway.
 
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