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Prop Pitch

todehnal

Well Known Member
I need to make another attempt at getting the right prop setting. The first setting netted me a 5200 static RPM. In my clumsy effort to make an adjustment, I lost my starting point and just had to take another swag at it. When I tested, I was 4950 static. Wow, I was excited. Admittedly, there was a little breeze during the run up, but I thought that I was good to go. The flight test later, revealed a much longer ground roll. Another static test, in a no wind condition, revealed that I am only getting 4750 static. No wonder I have such a long ground run. Lesson learned. I didn't realize just how much effect a little wind can have on that test. Anyway, my plan is to be very careful, not to loose the current position, and to only do a small tweak. In the interest of trying to simplify the process, I thought I would ask if anyone has plotted there corrections, and could give me a heads up. My goal is to get as near to 4950 as I can. So, what is your best guess for the amount of pitch correction necessary; .1, .2, or .3 degrees?

Thanks for your thoughts and for sharing your experience............Tom
 
Tom. Mine is at 4930. If you use the setting marks on the hub, mine is just shy of number 4...not exactly on it but just enough that it doesn't look exact. As you are finding out, a hair-width can make a difference. Perhaps as important though is what Scott has mentioned; make sure the two blades are set at the same pitch (within 1 tenth of a degree). If not, you can guarantee yourself vibration. Both blades move when you change one but there is still room for a difference. As Scott said, put a "smart level" on the same inside flat portion of both blades and make them match. Don't use the tips...line up with most inboard stripe for instance. Put in on the identical location of the 2nd blade.

Before you fine-tune it, tighten the two middle clamping bolts by hand and then the outside bolts in a "star" until just before the blades won't move. While they will still move, get them to match...and stay on your setting mark. Like I said, mine is just a hair before "4".

You want 4930 because you climb great and still have enough throttle in cruise to make changes. Not that you want to, but you should be able to push it to 5800 if desired. Cruise nicely at 5300/5350 around 115 knots TAS.

Pete
 
Hi Tom,

You need to forget about static. It should only be used to get in the ball park to do a flight test for the first flight. You are already there. With a ground adjustable prop your real concern is the wide open throttle (WOT) at your average cruise altitude. Average cruise is a little important because if you live in Florida and never fly over 2K the prop should be set different than the guy who lives in Colorado and takes off at 7K and is always at 10K.
Set your WOT rpm to achieve around 5600-5650 (even 5700 depending on your use and where yo live). This will give you the best overall performance between cruise, climb and fuel economy. We have to average these out since we can't in flight adjust. Too course and too little pitch just cost you performance. Too course is absolutely the worst scenario.
Tweaking the prop after the first flight is easy and I can tell you about how many degrees +/- if I know what the WOT rpm was during the flight. The other reason you can not go by static is props are not created equal and static for one is not the same for the other. Also some props static rpm does not correlate to the same WOT rpm as others due to design. 2 blade props many times may have different static than a 3 blade. I did a research project about 1.5 years ago with 9 different props (different air foils, lengths and # of blades). Static was different on some. I got to do all the setup and fly 4 exact same planes side by side for real time testing. There was 1-2 better props, but for 95% of them the deciding factor which made all fairly equal was WOT rpm.


Read this and it may help.

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


If you have any questions please call me. I have reset well over a hundred LSA props and not a single person has ever gone back.

There is no perfect world, but flight characteristic balance is key.
 
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Also consider your climb performance. Out here in Phoenix the density altitude can be a real factor especially in the high country to the north. My static WOT RPM is little over 5000 which means my cruise suffers, but even in the summer I usually get 800 FPM on climb out in the valley
 
Getting a Better Starting Point

You guys have been great. I went ahead and re-pitched today, and went .4 degrees flatter. I did that to have a better starting point for my top speed test. I know that I did not like the take off, and climb performance that I had on the last flight, plus all I could get was about 5400 flat out, which netted me right at 120 kts., as I recall. Although my temps were all in the green, I felt that the manifold pressure seemed awfully high at a 4900 to 5000 RPM cruise. Hopefully this adjustment has gotten me close. With that small adjustment, I like the way it statics, and sounds. I will know much more after my morning flight, in smooth air, tomorrow.

Tom
 
I Like It!

Okay, here are my prop "post re-pitch" results. By the way, I am flying out of a field with an elevation of 400 ft. My flight this morning was in very nice weather, with light winds, 68 degrees, 61% humidity, and clear skies. The take off roll displayed very good performance. Climb out at 75 to 80 was indicating 5050 rpm, which gave me right at 1000 fpm climb, at just under 1100 lbs gross weight. At 5000 rpm, I was indicating 119 kts tas, and full throttle netted 5700 rpm, with some impressive speeds. Also, I must have lucked out in getting a very precise match with both blade settings, as it feels much smoother than after the last change. After the flight, I did a static run-up and it seems a little low, at about 4800, but as Roger Lee pointed put, the static numbers don't tell the whole story. Basically, I am pretty happy with what I have. It remains to be seen as to what it will be like at the full 1320 lbs.

Thanks for everyone's help...........Tom
 
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Hi Tom,

Sounds like a good place to be and now you can get the best all around performance from your plane.
 
Another Milestone Reached

Roger, Thank you so much for your help. I'm ecstatic with the results!! ...........Tom
 
Tom, good job.


I have tried for 25 years to get some to understand how pitch can affect their planes and performance and it seems that with the introduction of SLSA that more people are taking a hard look at prop pitch and its effects. Because of our setup with the Rotax engine and its design we do well with a pitch to achieve between 5600-5700 rpm at WOT at our average cruise altitude. Some have special circumstances to consider, but the majority of us are in the same boat.

If we could use in flight adjustable props we could have the best of all worlds, but since we have only ground adjustable we should strive for a good balance between engine and aircraft.

Early on (pre June 2006) with the older Rotax crankcases those who chose to use WOT rpms down below 5300 for their WOT settings have cracked crankcases from stress. It happens on the top of the case. Over loading a prop also cause more engine temp and stress on the entire engine which was never designed to operate at WOT in this rpm range. You loose everything when over pitched. Under pitched just gets you a good climb, but you suffer loss at cruise and top end performance. I also think with today's engines and planes that using a fixed pitch (non adjustable) can limit your performance choices.
 
This thread has caused me to go back and address prop pitch once again. When I put the digital angle finder on the blades, there is a difference of at least 5 degrees between them. I find that hard to believe. Is there a trick to measuring the angle? I've leveled the prop, and measured the angle the same distance from the hub on each blade? What am I missing?

I thought I'd ask before going any further. Thanks.
 
For the most part, all of the 300 + RV-12's now flying are built pretty close to the same, and they are flying with the exact same propeller blades / propeller, and engine.
With this being the case, and because of all of the data that has been acquired during extensive flight testing, using static RPM as a cross check has proven to be a very reliable way of setting propeller pitch.

All of the S-LSA RV-12's produced so far (~ 25) have had the prop pitch set to a specific pitch value (established by testing), and then cross checked using static RPM. They all perform nearly identical.

Density altitude condition at the time the static RPM check is done has some effect, but to a large degree it automatically compensates.
I.E., someone flying from a higher elevation airport (say 5000 ft) will be adjusting pitch to a slightly lower value to attain the proper static RPM, because of power loss with the higher altitude. This will automatically dial them in to a pitch that is better for the environment they are flying in. If someone is flying in a wide variety of density altitude conditions, they will probably want to adjust towards a slightly higher static RPM than nominal, if the are doing their checks and adjustments at a low density altitude.

A static RPM of only 4800 is not a best all around performance setting for an RV-12. In fact it is likely that the airplane is not any longer legal as an LSA because it will be able to easily exceed 120 Kts at zero density altitude and max continuous power (as already hinted at in a previous post made by the O.P. in this thread ). Also, at higher weights and density altitudes, it's takeoff and climb performance will be noticeably worse than most RV-12's

On an RV-12, a full throttle static RPM of about 4950, does provide a good all around performance pitch setting. The check needs to be done with no wind, the oil fully warmed to normal operating temp, and the density altitude on the ground, somewhere in the ball park similar to the conditions being flown in most often. If this process is used, doing the check at different times of the year will automatically compensate for major temp swings with the seasons (such as people in the mid west flying in the winter with temps in the teens and 20's, but in the 90's or higher in the summer).
After some experience, most owners learn a preferred pitch value for summer and winter, and then just switch back and forth between them. Here in the pacific north west, we don't have nearly that big of temp (density altitude swings so we pretty much use the same pitch all year round).
 
This thread has caused me to go back and address prop pitch once again. When I put the digital angle finder on the blades, there is a difference of at least 5 degrees between them. I find that hard to believe. Is there a trick to measuring the angle? I've leveled the prop, and measured the angle the same distance from the hub on each blade? What am I missing?

I thought I'd ask before going any further. Thanks.

Randy
Hard to answer that question without seeing how and with what you are measuring the angle. There really is not a straight surface on the prop blade that you can rest a digital level against and be consistent. Some of us therefor made a fixture of sorts for the digital level that can be placed with consistency against the blade. Here is a picture of mine, a search will turn up others and many past posts about how to do this. Most of us can get the blades within about 0.1? of each other:
CTT_4019-L.jpg

CTT_4021mod-L.jpg

This fixture contacts the blade at three points and has a notch that lines up with the inner paint stripe. You have to be rather careful and take several reads and average them but 0.1? is possible.
 
Hi Randy,

No magic bullet here. I find more prop blade pitch unequal blades a little too often and it doesn't matter what MFG. After I found a few this way I check all my clients the first time I see them.

Here is an easy way to do your prop.
Since you already have a flying aircraft and pitch is in the proper area it should be an easy reset.


For general info for those that have an issue.
(best to remove 1 spark plug from each cyl)
First measure back from the tips about 8-8.5 inches and place a mark on each blade. You will need at least a 12" digital protractor or a prop protractor or both. I use both, but it isn't required. These will make your reset easy. I'll explain this as if we only have the 12" digital level. Stand in front of the plane facing the blades. Rotate each blade around one at a time and place the level on top of the right side blade and level the blade. (accuracy here does not seem to matter as I have found being off 1 degree off level doesn't change the pitch reading, but I personally like level) Once the blade is level on your right side place the level on the back flat side of the blade and get that reading. Do this to all three blades. I like to pick one blade as the master blade that all must be equal to. Hopefully at least 2 blades are equal and your 5 degree blade is a loner.
Loosen the 6 large 8mm hub bolts, but only so you can rotate the bolt by hand. Making things too loose will affect your blade tightening accuracy. Now rotate the off pitch blade back to your right side and level it. Put the level on the back of the blade and see what the reading is. Now you may want to put a rubber band around the level to hold it in place for a hands off operation which is much easier. Now loosen the bolts on the blade hub and turn the blade to the exact degree setting as your other two. Then snug the bolts back up. Then run all three blades around one more time to check your accuracy. It should be within at least .1 degree from each other. If you pay attention to detail this can be done to this accuracy with a bubble level. Once all three blades are equal tighten the 6 main 8mm hub bolts first and torque in 2-3 stages to their proper torque. Then tighten the smaller prop hub bolts. The large through bolts are the first to be loosened and the first to be tightened because they can and will change the torque on the other smaller hub bolts.

p.s.
If the pitch is set up for a good (5600-5700) WOT rpm for your average cruise altitude (this is the key) then you usually don't have to worry about summer verses winter. You may loose a little rpm during the cold dense air winter, but if the pitch is in a good place it may be about 50-75 rpm which isn't worth messing with because you'll have better performance in the winter any way.

p.s.s. LOL
When I did all the prop research I did find static could vary. It could vary from 4750 to 5000 rpm depending on the prop pitch, stiffness, number of blades and length and my target rpm was 5600-5650 at that time.
 
There is a good article in an old RVATOR about RV12 prop pitching. Don't have it handy. Use Tony's jig on a Sears digital level. Make a mark or notch on the jig and index it on the same point on the paint stripe. NOTE you must rotate the prop and measure each blade on the same side of the engine! Use something to make sure it is exactly the same position like a dowel on a sawhorse or something. I can get mine to agree to 0.1 degrees but it takes some doing!

A friend is finishing a new RV9 with a new type of ground adjustable sensenich that is easy, fast, repeatable, and precise. Uses a set of 6 pre-machined rods that you insert into the hub and twist the blades to bump against. Each rod produces a predefined different pitch. No measuring. Wish it was on the RV12!
 
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NOTE you must rotate the prop and measure each blade on the same side of the engine! !

Bingo. That's what I was doing wrong. Once I rotated and re-leveled, the props where the same.

Thanks Scott. I'm going back to the static RPM test. I've run several flight tests with the prop changes and it's hard to find the sweet spot with so many variables.
 
My final comment...

This is the RV-12 forum on the Van's Airforce web site.
Because of that, everything I post is in the context of an RV-12, and I think anyone else doing so should also keep that in mind

Experience that someone has on multiple different Rotax 912 powered airplanes with different propellers, many different blade shapes and diameters, etc, is really only relevant for the 2% of the flying RV-12's that are not a mostly stock build. For those few, Rogers advice can be of a lot of value.
I do not think it is helpful for the other 98% that for all practical purposes are as identical as any other production line airplane would be. In fact, some of the advice I have seen will result in performance that has no chance in matching what is in the RV-12 POH, so consider the value of that info based on what propeller pitch you have chosen to use.


The majority of what I post is for the 90+ % of the viewers that never post here in the forum. I attempt to pass along information from the viewpoint of Van's Aircraft. It should not be considered the official word from the high up office (but a lot of that results from what I or someone else in engineering tells them when they come and ask).

Hundreds of RV-12 owners are now flying using the prop. pitch adjustment process prescribed by Van's, and they are happy with the result.

As always, the builder is the one with the responsibility of making the final decision of what they will do.
 
In fact, some of the advice I have seen will result in performance that has no chance in matching what is in the RV-12 POH, so consider the value of that info based on what propeller pitch you have chosen to use.

And that's exactly what happened to me yesterday. I spent many hours fiddling with the prop pitch only to find out that I had lost 10 knots at cruise and found it terribly easy to overspeed the engine. Today, I'll pull the spinner off multiple times until I can get the static RPM back down to the range of 4950.
 
Hi Scott,

"Experience that someone has on multiple different Rotax 912 powered airplanes with different propellers, many different blade shapes and diameters, etc, is really only relevant for the 2% of the flying RV-12's that are not a mostly stock build."

I wasn't implying there are many different props on RV12's. I know for the most part they are all the same except for a small handful.

I was relaying for those that think one static rpm fits all isn't the case for all props. It was just an information and educational comment.
 
I've been following Scott's guidance since I first flew my RV12 in '09. While he is not an official Van's RV12 advocate on here, he does work on their plane. He built it and rebuilt it and rebuilt it. He has always been very generous about passing on discoveries he makes about this aircraft when he runs across them.

Plus, he speaks his mind (don't we all!) when he's trying to be convincing. Regardless, I have been convinced over and over. He does know RV12's.
 
After some experience, most owners learn a preferred pitch value for summer and winter, and then just switch back and forth between them. Here in the pacific north west, we don't have nearly that big of temp (density altitude swings so we pretty much use the same pitch all year round).

Scott hit nail on the head with this one. I find that .3 of a degree change in the Spring and Fall works well to maintain my static setting.
 
If your prop pitch is set to achieve 5600-5700 then I wouldn't think messing with the prop each season would be necessary. .3 degree change should only be about 75 rpm +/-. Changing the pitch .3 degrees for the denser winter air may shouldn't be necessary because the plane and prop air foil is already benefiting from the cooler air.
I don't personally know of any one that changes that often. If you do that then bolt and nut replacement due from all that torquing and bolt stretch from going back and forth would be warranted.
 
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There is no operational requirement to change propeller pitch with the change of seasons, and for many owners it probably isn't of much value. For others it can be of value if the summer density altitudes are extremely different from winter and they are looking for the ultimate overall performance (within the compromises that we have to make with a fixed pitch propeller).

The Sensenich propeller used on most RV-12's does not have any replaceable nuts (they are steel inserts pressed into the aft half of the propeller hub)for the bolts loosened when repitching the propeller, so replacing nuts is not an issue.

Replacement of the bolts would only need to be done on condition (damaged threads, etc.). Replacement just because they have been removed installed multiple time is in contrary with the Sensenich 2A0 Installation Manual and AC43.13.
In fact The Sensenich Manual specifies to full disassemble the propeller at each condition inspection (this would require removal of the bolts in question) but makes no mention of replacing the bolts after a specific interval.

If an owners does make a pitch adjustment a couple times per year, the only thing that might need replacement sooner would be the nordlock washers, and even that is on an on-condition basis.
 
Nord washers are replacement items after a while (1-2 times no big deal, same for the bolts). Bolts that get torqued get stretched and if done more than a few times should be measured as per the Sensenich instructions and at the annual. That was confirmed by calling Sensenich. They are supposed to be automatically replaced at 2000 TBO. Personally I see no reason to remove bolts at an annual just to remove them. Sensenich says to measure all bolts and any that have stretched to be tossed. Torquing stretches bolts just some are more resistant than others. You can actually measure a new bolt with one that has gone though several torque cycles and it will be longer. Many bolts have stretch limits from an MFG especially in services with heating and cooling cycles and high vibration areas. The bolt torqued a few times is longer and there are guide lines for bolts under stress and torque cycles to get replaced. Each bolt has its own characteristics. Some stretch easier than others depending on service and its metal make-up.
Most prop Mfg's don't figure people for many duty cycles on bolts, washers and nuts.

These bolts are expensive so if you measure them and they have stretched then replacement is easy and finding them is usually a local event.

"Replacement of the bolts would only need to be done on condition (damaged threads, etc.)"
The excreta is your supposed to replace them if stretched which is determined by measuring and comparing to the others.

This came right from Sensenich.
 
What the Sensenich documentation actually says -
"Remove the mounting bolts -- The bolts should be dimensionally checked against one another. Any bolts that exhibit stretching, corrosion or damage such as cracks or nicks are to be replaced."

It is not possible to measure the bolts individually for stretch because they are standard AN bolts (not close tolerance). Because of this, the lengths when new can very by quite a bit between one bolt and another (the length tolerance is pretty large on standard AN bolts). The only way they could be measured for stretch is if the were serialized and measurements recorded during the original installation.

In the past few weeks, we have been working extensively with Sensenich regarding the new version of the prop. hub they are now shipping. We have gone through many blade install / removal, and repitch processes... they have not sent replacements, nor suggested that the bolts be replaced...
 
I have a Sensenich and it has no AN hardware on the prop or hub. They are allen head hardened bolts on the prop and hex head on the hub. You may be switching over to what I have now. Most of the Sensenich props I have seen in the shop on different LSA don't have AN hardware. I believe this may be a little older setup. Bolts don't need replacement every time, but if done repeatedly they should. I talked to Sensenich this afternoon and they agreeded that bolts need to be checked for stretch and replaced IF necessary. I did a big research project for them and when I was done my bolts needed replacing, but they had been torqued way more times than on any normal prop & plane.
 
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We have sold nearly 400 of these props in the last few years and every one of them has been supplied from Sensenich with AN bolts.

I just worked with Sensenich testing the latest version (that uses the steel indexing pin tools to establish the prop. pitch), and that prop, along with the half dozen they just shipped to us for customer delivery, also have AN bolts.
 
Then you have a different model. Many don't use AN from them and it may depend on the MFG. All of mine are grade 8.8 SHCS bolts. This is what I normally see on most Sensenich now days. The pin indexing tool is okay, but final hand setup works best. Even their top engineer said that. I really disliked the pin index tool. It gets stuck, it's slow and I'm more accurate by hand. They said it looked good on paper, but not as well in real life. I didn't just test one prop from them, but several all at one time in all stiffness and blade configurations. It was quite enlightening. Went through three sets of hub bolts.
I have an RV12 right now. I'll have to pull the spinner and get a mental refresher.
 
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Then you have a different model.

As I have said before... this is the RV-12 forum on VAF... I think it would be far more helpful to people that come here looking for info, if the info provided was specific to the RV-12

The pin indexing tool is okay, but final hand setup works best. Even their top engineer said that.

We have been recommending for years (such as the article in this RVator)that builders/owners check the blades with some type of measuring device, and that will continue even with the introduction of the new prop hub design.

The benefit of the indexing pin system for the RV-12 builders is that it will allow them to set the prop very close to an optimal pitch angle (using the pin number that will be specified), tweak it so each blade is exactly the same. After they have confirmed that the static RPM falls within a specified range they can go fly go fly, and know that poor climb, or engine over speed in level flight are two less things for them to worry about on there first flight.
 
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Hi Scott,

You wouldn't expect a doctor to only learn one thing. You want him to know the whole human system because one thing many times does affect something else. How would he diagnose any thing if he only learned a few specific things.

Learning the whole enchilada and what makes a system work well is far better than only learning one little aspect. This is one reason I posted the Rotax blog on understanding the ground adjustable prop. Just because we talk about concepts that may apply to all aircraft doesn't mean it doesn't in some way apply to the RV12. Learning overall concepts and complete system mechanics tells us what to look for when things are right, when they are wrong and how to diagnose issues and not just shoot in the dark. A few of the RV12's that have come to me are not what you might classify as stock.
If the experienced mechanics and educators only talk about a specific item and never how it works and intertwines then we fail as educators and mechanics.

Here's an example of knowing a system and not just one point:

It just so happens it's an RV12 I have here now. It lost its Dynon Skyview tach reading. If we tell owners just to push this button on the Dynon and that's all we failed and we should have explained where the signal for the tach comes from where it goes and how it was connected.
This is where understanding the system helps and not just knowing the tach comes off the engine. You disconnect the wire connector where it comes off the engine and where Vans makes the connection in the engine compartment. You take a 9 volt battery or your regular 12V battery will work. The tach wire is only two wires. A ground and a signal or output wire through to the Dynon. You ground the black wire to a known good ground. Then take the white green striped wire and tap it on one of the batteries real fast. If your system is in tact and doesn't have a bad connection then you will generate 400 rpm on the tach. This way we diagnose more than one connection and the Dynon.

Scott,

Did you know this?
My point for this example is now not only one person can do a 5 minute trouble shooting for a tach signal continuity, but many can and it didn't start with Vans nor does it apply only to Vans, but it works for Vans.

I you never take the time to learn a whole system and only where the wire plugged in how would you know how to trouble shoot.

Learning only one thing or how it intertwines with everything else is too educationally restrictive especially when you absolutely must know when things aren't right in your plane.

Vans may set things up a certain way and so do other aircraft Mfg's, but we owners don't tend to leave things alone. I see it actually daily. It's a good thing the Wright Brothers expanded their learning and tried something new and didn't focus on only one aspect of flying or we wouldn't be enjoying our hobby today.

Strive to learn it all and strive to understand it all and apply what fits for you.

Meritocracy is always happy with itself, but excellence never is.


The brain is a terrible asset to waste. When the light goes on when you learn something new and how it all ties together it feels good.
 
Did you know this?

Yes I did know this.

This is actually a good example of the type of info that is good to share, but a bad example of the type of info that is not helpful.

When you are pushing your personally preferred procedures/processes, that contradict what is in all of the documentation for the RV-12, it is in my opinion not helpful to builders/owners.
All it does is give them another decision they have to make.

Bottom line....

There is a big difference between offering info as "here is another way to do it", versus "Van's is wrong, this is the right way you should do it"
 
As I have said before... this is the RV-12 forum on VAF... I think it would be far more helpful to people that come here looking for info, if the info provided was specific to the RV-12
One point to ponder on this aspect of the discussion. There are multiple ways to peruse this website and glean information from the various forums. You are describing just one method of use in which a user might specifically navigate to a particular forum thread from the front page based upon the topic of the thread (s)he is interested in reading. This allows a user to focus specifically on that one piece of information (i.e. RV-12 issues ONLY) (s)he is most interested in viewing. This is effective if one is specifically ONLY wanting to read about that one topic. However, one of the other methods that I use, and I am sure many others may also use, is to click on the TODAY'S POSTS on the front page. Here is a screenshot of today's front page with that button highlighted:

VAF%2520Today%2527s%2520Post.jpg


This will show a list of EVERY thread that has a new post to it since the last time the web browser was last refreshed, regardless of which forum thread it came from. Using this method I do not necessarily always know right away that any particular thread I am viewing is specific to RV-12's or maintenance only or whatever, unless I specifically look at that thread's FORUM column on the right of the list.

I am sure there are many others who view the forum with this method. In my case, I consider it a much more efficient method of following ALL of the forums on VAF since it helps me organize on the fly what I have/have not seen already, or, more to the point, topics of which I am not interested in viewing at that time. It is much more efficient than going to the FORUM page and looking at the individual topic groups, deciding which one to click onto and then browse through each one individually to see if maybe there is something posted in them of interest, then navigating back to the FORUM page and look for another forum I am interested in viewing.

Anyway, just a different perspective to consider when reading a post from someone who might comment about other RV models on a(n) RV-12 thread.
 
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Hi Scott,

Please copy and paste where I have said Vans is wrong.

Vans isn't wrong as there is more than one way to skin or in this case build the proverbial cat. If your analogy and approach to this conversation is correct then learning anything about a Chevy, Ford or GM is not applicable to the other MFG and that when one person learns about a brake system in one then they can't make a decision about another. It's different from one MFG to the other not wrong. If learning about systems is wrong then why learn about Rotax engines in Rotax school in general and not just from Vans, or brake systems, flight controls and as we have here props and how pitch affects engine temps, performance, climb, cruise and fuel economy. Non of these aren't unique to Vans, but fairly universal with LSA with Rotax. Vans didn't re-invent the wheel their knowledge comes from many years of other people's time and of course from their own experience and building. Vans does a good job and is a good company. Learning all the components and how they all affect one another is just education. Then you apply the education to your specific application. If your principle about only learning about Vans then no one needs to attend a Rotax scholl or any aircraft school because they teach general specs and techniques then it's up to you to apply it to your application.
How many here are on the Rotax or Dynon forums? Might as well not be there because it isn't Vans?

If I explain how to bleed brakes on a CT or Sport Cruiser does that mean that knowledge is not transferable to an RV12? The RV is different maybe on a specific item, but the system is fairly standard.

"All it does is give them another decision they have to make."

Are you implying that your owners aren't capable of individual decisions? From what I have seen these are a bunch of bright and knowledgeable aviation enthusiast that don't limit their training.

Telling people to limit their education to only what you want them to know is wrong. We are all in the same boat with vary similar components like, brakes, engines, instruments (Dynon), tires, and rules and regs, ect.... Saying only learn what I want you to learn is a bad idea and I doubt few would want that limitation.

As far as the Dynon test, I have been working with your people on this and no one else new it, matter of fact not even Dynon support until the right tech chimed in.

Limiting education is a terrible precedent to start.
 
Scott,
How many RV12 kits are in the field?
They will all need to know about prop pitch, how to achieve to best pitch for them and why they are doing it that way.


Here is the first post.
"I need to make another attempt at getting the right prop setting. The first setting netted me a 5200 static RPM. In my clumsy effort to make an adjustment, I lost my starting point and just had to take another swag at it. When I tested, I was 4950 static. Wow, I was excited. Admittedly, there was a little breeze during the run up, but I thought that I was good to go. The flight test later, revealed a much longer ground roll. Another static test, in a no wind condition, revealed that I am only getting 4750 static. No wonder I have such a long ground run. Lesson learned. I didn't realize just how much effect a little wind can have on that test. Anyway, my plan is to be very careful, not to loose the current position, and to only do a small tweak. In the interest of trying to simplify the process, I thought I would ask if anyone has plotted there corrections, and could give me a heads up. My goal is to get as near to 4950 as I can. So, what is your best guess for the amount of pitch correction necessary; .1, .2, or .3 degrees?"



Understanding the why's and how's will help this person make an informed decision for his specific application. Prop pitch for Rotax engine's aren't MFG specific.
Owners at sea level that never fly over 2K ft. should have a different prop pitch than people that fly out of Mammoth, CA or Leadville, CO.
Prop pitch is not limited by any LSA rules unless specified in the POH and actually I don't know any other MFG's that have specific limits just recommendations which most tell owners to follow Rotax engine recommendations.
 
I told my self I was done posting in this thread since it didn't seem to be productive, but since you specifically asked.....

Please copy and paste where I have said Vans is wrong.

You need to forget about static. It should only be used to get in the ball park to do a flight test for the first flight.




Owners at sea level that never fly over 2K ft. should have a different prop pitch than people that fly out of Mammoth, CA or Leadville, CO.

Exactly!

And if a builder in Leadville or Mammoth were to use static RPM to set up his prop pitch, he might have the same static RPM as the guy at an airport with fiel elevation of 200 MSL, but since he did the checks and made the adjustments at a much higher density altitude he will get about the same end result.
Higher density altitude - lower power output of the engine. End result will be a slightly lower pitch than the guy at the lower elevation.
So, they are using the same RPM value, but it will result in a totally different prop pitch.
Higher density altitude also reduces thrust from the prop slightly, which influences the overall result, but in the end, each person will have a different prop pitch that (for most people) they will be entirely happy with.

I will reclarify this again, so there is no confusion.
This works with the RV-12, with a specific engine and propeller mounted to the front. I can say this because of the level of testing that has been done with this one airplane.
If you use a different engine or prop (or both) or your airplane is not an RV-12, then you will have to do your own in flight testing to determine what propeller pitch is ideal for you airplane/configuration.
 
Your reaching and where in those quotes does it say "Vans is wrong".

Originally Posted by roger lee View Post
You need to forget about static. It should only be used to get in the ball park to do a flight test for the first flight.

Quote:
Originally Posted by roger lee View Post
Owners at sea level that never fly over 2K ft. should have a different prop pitch than people that fly out of Mammoth, CA or Leadville, CO.

Exactly!
--------------------------------------------------------------------------

Both statements are absolutely true and any good prop MFG and Rotax will tell you the same thing.
This is what we teach in school. Fundamentals and concepts are important to understanding and education.

The thing is neither says Vans is wrong.

See you do agree on concept which isn't specific to Vans.

Your quote:
"So, they are using the same RPM value, but it will result in a totally different prop pitch. Higher density altitude also reduces thrust from the prop slightly, which influences the overall result, but in the end, each person will have a different prop pitch that (for most people) they will be entirely happy with.

p.s.
Leadville, CO is the highest airport in North America.

So you did get the general concept that I was stating all along and it didn't just apply only to Vans aircraft.

your quote:
"This works with the RV-12, with a specific engine and propeller mounted to the front."

True taken only when applied to Vans, but not true if we consider all 912 engine and prop applications and then the fundamentals and concepts are the same. It works for many different 912 aircraft (tractor and pusher) and with different MFG props and we'll leave the 912ULS as the engine which will cover EAB, ELSA and SLSA. I have run and tested as many or more Sensenich props than Vans has not to mention about a half dozen other prop MFG's. You work on one MFG plane and I work on all of them and a service center for several.

You can't win this one and I'll say this right up front.
VANS DOES IT RIGHT and the theory and concept isn't specific to Vans and is applicable to all. Understanding the fundamentals makes a better informed owner a happier end user with his RV12 that can then exercise his own decision making.
 
Hey guys. As one of the RV-12 audience interested in getting a broad education, I appreciate the input and advice that both of you provide. When it comes to my aircraft, I'll follow Vans advice since they know it best, but maybe do so with greater understanding based on what both of you say. How about we call it a draw on this one and move on?
 
Nothing personal with me.
I love to swap ideas, training methods, shortcuts and especially new information just out hot off the press from MFG's like Rotax and of course cat skinning. It is just like debate class was back in school. It would be a dull world if we all thought alike and then nothing would ever get done. If you can't be opened minded and learn why live. ;)

I have heard from several friends with RV's that Scott and I are entertaining and we don't even get paid for it. :D

p.s
Just an FYI
I just had an RV12 owner call this afternoon from northern AZ. with overheating problems. He was using Evans coolant. It is not recommended by Rotax any longer and carries a 20F-30F temp penalty. Better to stay with the now more conventional recommended 50/50 mix with more heat absorbing properties.
 
I always preferred the water mix. My reasoning was it offered more flexibility on cross countries if I ever had to add coolant. So far (175hrs) I have never had to add any.
 
The 50/50 water mix is easier to deal with for sure. A little extra 50/50 if needed or just some distilled water in the reservoir. I usually only see mild oozing from a screwed in joint on a water connection if the reservoir leaks down a tad. It is usually very slow and easy to fix.



Rotax 912is engine:
There are about 35-40 engines in the US right now and 100 is projected by year's end. The only issue right now is mechanics for this engine are limited. Maybe 10 in country. It will take some training and not just anyone will be able to work on it with out some education. Plugs and oil changes remain the same. You'll need a laptop and a dongle ($1087) to work on it or do computer updates. The Rotax computer program is unbelievable to what it can see within the engine and alert you to what is going on. The on board computer records everything 10 times a second for the life of the engine and records every single start and keeps a lo of all error codes. You won't be able to stretch the truth and say I didn't do this or that or that it just happened 1 hr ago because it's all recorded. No schools currently out for this engine. I had to go back to Nassau last Sept. for my class.
 
Last edited:
"Had" to go to Nassau? WAZAMATTA, Roger, does your wife monitor this site? :D

You're not alone. I convinced my wife I "had" to go to Laughlin for an IPC and stay in the casino resort!
 
You don't think she let me go by myself. LOL
Not a chance.
I told her I had to go and she said when are WE going. Go figure. LOL

I was supposed to go back this month, but it has been canceled until June -July and I doubt that will be by myself either.:D
 
I just made Tony's fixture to help measure prop pitch and used a digital level as described. I found one blade at 65.7* and the other at 66.3* a whopping .6* difference -- no wonder I'm getting vibration. My static rpm is 4700 +/-20. I was shooting for 66.5 degrees on both blades, but after an hour of fiddling, I ended up with 66.3* and 66.2*. Now the next item on the checklist is to ground run the engine at just under 2500 rpm (1/2 estimated static) for 5 min. I'm assuming that it's safe to run the engine without the spinner --- but since assumption is the mother of all errors, I'm double checking with those who've gone through the procedure before.

I'll probably have to do this again since an average difference of the before and after adjustment is only .25* and I'd like to get to 4950 rpm static.

TIA

John
 
Your on the right track, keep pushing ahead.;) If the pitot tube is installed you need the spinner, if not then it should be ok.:)
 
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