Prop installation

OK, I'm officially lost. Page 47-03 has a "Warning: Before continuing, read the documentation concerning propeller installation included with your propeller and engine." My propeller contained no instructions, or any other printed material of any sort. There was a clear plastic envelop on the outside of the prop box that was sized like I'd expect for papers, but it had been cut open and was empty. I couldn't find anything relevant in the engine documentation.

I checked the Sensenich website and did find documentation for a Rotax ground adjustable prop ("Composite Aircraft 2 Blade Rotax/Jabiru Instructions-old style pitch cylinder") that looked pretty close to the one I have but it refers to a "Pitch Adjustment Cylinder" which was not included with my prop. Van's Figure 2 on 47-03 does not show a pitch adjustment cylinder so I'm not sure I got the correct documentation. The prop package did include a wood jig that fits the prop that I can put a level on to measure and adjust pitch and this:



which looks like it might be a pitch tool (#3 tool?) but I have no clue how to use it.

47-03 also says to pitch the prop using the #3 tool but I can't find any indication of what the pitch should be. There are a number of threads on VAF concerning pitch setting but they all seem to deal with fine adjustment and assume an initial setting that's close to correct.

Seems like I'm missing something.

tomkk said:

OK, I'm officially lost. Page 47-03 has a "Warning: Before continuing, read the documentation concerning propeller installation included with your propeller and engine." My propeller contained no instructions, or any other printed material of any sort. There was a clear plastic envelop on the outside of the prop box that was sized like I'd expect for papers, but it had been cut open and was empty. I couldn't find anything relevant in the engine documentation.

Seems like I'm missing something.

Click to expand...

Yes, you are missing the documentation that was supposed to be in the box. It is usually just laying in the bottom, in the area where the propeller blades are.
The clear pouch on the outside is only for shipping documentation (to Van's).

The document you need can be found HERE

It should clear up the confusion.

Thanks, Scott. I just took a quick look at that doc and you're right, that's exactly what I needed. A quick question. That doc say's "Unless specified by the aircraft manufacturer, use pitch setting 4 to start." My pitch gauge is marked with a 2 and a 3. Where's a good starting place? Thanks again.

tomkk said:

Thanks, Scott. I just took a quick look at that doc and you're right, that's exactly what I needed. A quick question. That doc say's "Unless specified by the aircraft manufacturer, use pitch setting 4 to start." My pitch gauge is marked with a 2 and a 3. Where's a good starting place? Thanks again.

Click to expand...

It seems that recently someone at Sensenich decided to only supply one of the three pin tools for RV-12 builders since two of the three will never be used.

I am pretty sure that #4 would have been the closest to optimal as far as a starting point goes. #3 will be the closest to #4 so use that. It will likely be a bit under pitched, but you can check after you get your engine running. If you WOT static RPM on the ground is not much over 5000 you can use that setting for a first flight.

Keep in mind that adjusting using the pins will sometimes only get the blade angles within .2 - .3 degrees of each other. For optimal performance and smoothness you need to match the pitch of both blades (preferable within .1 degrees of each other) using some type of precision measuring device.

Feeling kinda short changed...

I have one of the "older models" so no pitch tool for me. When I saw the picture I had the brief feeling that a new tool was on the way!..

PilotBrent said:

I have one of the "older models" so no pitch tool for me. When I saw the picture I had the brief feeling that a new tool was on the way!..

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I wouldn't consider the new style better.... just different.
I don't find it to be any more precise. I think they primarily change because the new style is what had to be used on the three blade prop, so they just made them the same.

rvbuilder2002 said:

It seems that recently someone at Sensenich decided to only supply one of the three pin tools for RV-12 builders since two of the three will never be used.

I am pretty sure that #4 would have been the closest to optimal as far as a starting point goes. #3 will be the closest to #4 so use that. It will likely be a bit under pitched, but you can check after you get your engine running. If you WOT static RPM on the ground is not much over 5000 you can use that setting for a first flight.

Keep in mind that adjusting using the pins will sometimes only get the blade angles within .2 - .3 degrees of each other. For optimal performance and smoothness you need to match the pitch of both blades (preferable within .1 degrees of each other) using some type of precision measuring device.

Click to expand...

Thanks. Do we know what angles the #3 & #4 are supposed to set? If the best way is to use a digital level with a fixture anyway, I can do that after initially setting with the tool if I have an idea what angle we're initially shooting for.

tomkk said:

Thanks. Do we know what angles the #3 & #4 are supposed to set? If the best way is to use a digital level with a fixture anyway, I can do that after initially setting with the tool if I have an idea what angle we're initially shooting for.

Click to expand...

Sorry, I can't help you with that.
We do not use the Sensenich supplied airfoil gauge so any number I give you will not correlate to what you would be measuring.

tomkk said:

Thanks. Do we know what angles the #3 & #4 are supposed to set? If the best way is to use a digital level with a fixture anyway, I can do that after initially setting with the tool if I have an idea what angle we're initially shooting for.

Click to expand...

I have the same tool - you won't really be able to use it because the hubs are set up for the older white cone - I guess you can have a couple of people hold the props while you push in the black hub....you can't mount the bolts because the tool holes will be covered up by the forward spinner bulkhead....which hadn't been changed for me....i gave up and bought a harbor freight digital protractor and constructed the tool as previously mentioned to measure and match pitch.

Use your static RPM to get the best number....

NB....small changes of 00.5 of a degree will change RPM 100-200 or so. I ended up at
~ 5050 static....all my climb and cruise numbers were per the book.

The #3 pin is closest, but you will need to fine tune by hand. Sensenich told me the pin idea looked great on paper and great advertising, but they prefer to set the final setting by hand. It is far more accurate. You can use a digital 12" torpedo level, a digital prop pitch tool (that you can find on Aircraft Spruce) or just a standard bubble level protractor for setting prop pitch. Even with just the bubble level protractor you should easlly get to 1/10 degree accuracy. Shoot for around 4950-500 rpm at take off and around 5600-5650 for wide open throttle at your AVERAGE altitude. This is not usually pattern altitude.

So, Loki & Cactus, what angle did you find gave you the correct static RPM? Just trying to find an initial setting to get me in the ballpark.

Don't get too concerned with the inital pitch setting - after your initial runs, you will be tweaking it a time or two to achieve Van's stated static/preflight RPMs, and then tweaking it again a time or two after flying it. I set my initial pitch near the limit of the fine pitch stops - better for the new engine to be using a fine pitch as opposed to a coarse pitch. Use a bracket/electronic level to set both blades to the same relative pitch.

Yeah actually, now that I think about it, an absolute angle doesn't mean much. Measuring the angle with a digital level makes it a function of the deck angle among other things. It looks like the initial suggestion of using the #3 pitch tool and adjusting from there based on static RPM is the best approach.

Hi Tom,

You are correct that the angle everyone may see would be a tad different depending on how the deck is the plane sits on and the way the plane sits all by itself. The #3 pin puts you close. Then fly it and see what final adjustment needs to be made from an actual flight scenario. Adjusting the prop takes about 30-45 min. Depending on your experience level.

BTW, the pitch adjustment limits built into the Sensenich props made specifically for the RV-12 are pretty restrictive - maybe a couple of degrees max? However it is amazing how much RPM change one can see with the slightest change in pitch angle (@ tenths of a degree). That is why use of a bracket/electronic level is so useful. You will not be able to consistently determine actual pitch angle values since every measurement scenario will be different. When I want to change my pitch a tad (say @ 0.2 degrees more pitch), I first check the current setting (and set level to "0" reference), increase the pitch by 0.2 degrees, and then transfer that reference setting to the other blade. Works well for me.

DHeal said:

You will not be able to consistently determine actual pitch angle values since every measurement scenario will be different. . Works

Click to expand...

In our shop, we make all prop pitch measurements with the digital level zero referenced to the canopy rail on the fuselage. Then it never matters what attitude the airplane is sitting at (unlevel ground, etc. )

Tom, start midrange. Use the digital level with fixture. Make the prop horizontal. I attached a dowel vertically to a chair, positioned it next to the prop tip, and marked the dowel. Measure one blade at the extremes of its adjusting range and note the degrees you see. Then set it at the middle. Then (IMPORTANT!) ROTATE THE PROP 180deg so the other blade is in the same position as the first, next to the dowel mark. Adjust it to the same angle as the first. Check both again for equality. Then torque it down and do the test run up. Lather, rinse repeat to home in on the 4950 - 5000 WOT.

0.3 degrees change makes a significant change in WOT rpm.

Bill_H said:

Tom, start midrange. Use the digital level with fixture. Make the prop horizontal. I attached a dowel vertically to a chair, positioned it next to the prop tip, and marked the dowel. Measure one blade at the extremes of its adjusting range and note the degrees you see. Then set it at the middle. Then (IMPORTANT!) ROTATE THE PROP 180deg so the other blade is in the same position as the first, next to the dowel. Adjust it to the same angle as the first. Check both again for equality. Then torque it down and do the test run up. Lather, rinse repeat to home in on the 4950 - 5000 WOT.

0.3 degrees change makes a significant change in WOT rpm.

Click to expand...

This won't work with the newer version propeller...... There is no adjustment range.
With no gauge pin inserted, you can rotate the blades 360 degrees.

Ohhhhhhh - no stops on these blades. Well, start with the 3 pin then. Get both blades to the same angle. Plot a data point for angle and WOT rpm. Make an adjustment and plot a second point. If you are still off a little, a straight line interpolation through those points to 4950 rpm will get you really close to the final angle.