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3-Blade Sensenich Prop - Now available for RV-12is/RV-12

greghughespdx

Well Known Member
Advertiser
Van's has published updated RV-12/12iS powerplant kit order forms, a new plans section (47AiS/U) and a service letter (SL 19-12-31), all of which are related to the now-available optional 3-blade Sensenich propeller kit.

We displayed this prop on a stand in our booth at Oshkosh last year and flew it to the show on one of our factory aircraft. It garnered quite a bit of interest. Now that the engineering has been completed and testing of the final install package is all wrapped up, the three-blade prop and spinner kit is available to order as an option on new powerplant kit orders (you'll get to choose either a two-blade or three-blade prop when you order). You can also place a stand-alone order for the prop without the rest of the Powerplant kit (just use the powerplant kit order form and select only the 3-blade prop option in that case).

Note that when building your airplane, in order to register ELSA the parts - including the propeller - must be bought directly from Van's and tracked in our records under that aircraft serial number. Once an aircraft has been licensed and registered ELSA you may, of course, make any changes as you wish.

People will, of course, want to know what's different between the two-blade and three-blade prop. Our testing experience showed that:

  • Cruise performance was the same (at lower altitudes)
  • Climb performance was greater
  • Propeller braking action was slightly greater, which allowed a slightly steeper descent angle in the pattern
  • The sound/pitch is different, although the measured noise level is about the same (they are the same diameter).

And, of course, there's the aesthetics: The blades are wider on the two-blade prop. Some folks prefer the look of three blades, while others prefer two. Some people like a thinner blade, while others prefer the "beefier" look.

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new prop

Installed the new Sensenich 3 blade replacing my 6 year old 3 blade Sensenich a few months ago. Longer blades and thinner than the original 3 blade I had.

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Still dialing in the pitch, but performance is much improved from the older 3 blade. I picked up a few knots but still have the climb. Since I never had a 2 blade I can?t compare it since I started with a 3 blade. Performance seam very close when flying next to my buddies. Sound a little different on the ground, but smooth. :)
 
David,
I am glad to hear that your experience parallels what we discovered.

That the original 3 blade with wide cord blades did not perform up to the level of the two blade. We just didn’t feel that we could promote it as a viable option with the only virtue being cool factor, at the expense of slightly reduced performance.

Though to some, the skinny blades don’t have the same wow factor, but it at least does provide a slight performance boost over the two blade (as mentioned.... a modest increase in climb rate while maintaining the same cruise performance).

Because of some refinement that Sensenich was able to do to the hub while changing the blade design (likely allowable because the blades were lighter as well) the overall weight of the 3 blade install is lighter than the two blade which is good for helping to maximize useful load. The weight reduction is at a less than ideal location as far as baggage payload goes, but it doesn’t seem to be a factor on RV-12’s that have a standard build configuration.

Once dynamically balanced well, it is very smooth. The simplification and weight reduction do come at a price (besides just the higher cost)......... there is now 3 blades that need to be adjusted to have closely matching pitch angles, and there is no indexing methods incorporated into the propeller. Not a big loss in my mind because they don’t work well enough to set the blade pitch close enough to each other to get it running real smooth anyway. Just something to be aware of though.
 
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Does Sensenich require prop disassembly/visual exam at Annual Condition Inspection? Putting three blades back together correctly every twelve months doesn't sound like fun...
 
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Does Sensenich require prop disassembly/visual exam at Annual Condition Inspection? Putting three blades back together correctly every twelve months doesn't sound like fun...

I think the specified inspection procedure is the same for the 3 blade as for the 2 blade. It is not that big of a deal after getting a little experience doing the blade adjustment.

One benefit over the two blade is that the hub design is different in such a way that the propeller can be removed from the engine as a complete assembly without disturbing the blade pitch adjustment. This also allows for disassembly or assembly of the propeller with it laying on a work table.
 
One benefit over the two blade is that the hub design is different in such a way that the propeller can be removed from the engine as a complete assembly without disturbing the blade pitch adjustment. This also allows for disassembly or assembly of the propeller with it laying on a work table.

Oh this is super interesting - it means one could build a jig that would let you dial in all the blades precisely and hold everything fast while you tighten the bolts.
 
How much lighter is this prop as opposed to the two blade option?

I may be off a bit (memory is going bad) but I think it is just shy of 6 lbs lighter.
Seemed hard to believe when we first weighed it but each blade is quite a bit lighter than the what a 2 blade blade is, plus the lower hub mass. It all adds up......
 
steve from Sensenich here.

Yes, the disassembly time for the new 3 blade is every 2000 hours.
We bobbled our initial release of prop instructions and had annual disassembly on there by mistake, but the current revision instructions on our website have the correct inspection interval.
3Y0-Installation-Instructions-rev-C-20200204-1.pdf
 
Interesting that when landing it has increased braking action.

Will the POH be revised for the 3 blade prop to reflect this change, in terms of glide ratio /glide slope when dead stick landing, in the event of an emergency?

I believe with the 2 blade prop currently it's 13:1, or about 2.47 miles per 1000 ft elevation loss?
 
Gliding is usually the result of loss of engine power.

On a Rotax 912, the engine (and propeller) stops turning with loss of engine power.

The drag flat plate area of the 3 blade prop when stationary is about the same as it is for the two blade.
 
Ok - I'll bite!

It's likely that I will opt for this 'upgrade'. Don't know for sure if will happen before first flight or ever but, since I always have to fight my way thru Van's maze of 'how to order something' and how much? (I admit that I'm not the brightest light bulb in the bag of light bulbs), can somebody tell me how much this will cost me if I opt to install the three blade arrangement? Also, does anybody want to purchase my not yet installed standard two blade prop assembly and spinner? Thanks for answering.
 
It's likely that I will opt for this 'upgrade'. Don't know for sure if will happen before first flight or ever but, since I always have to fight my way thru Van's maze of 'how to order something' and how much? (I admit that I'm not the brightest light bulb in the bag of light bulbs), can somebody tell me how much this will cost me if I opt to install the three blade arrangement? Also, does anybody want to purchase my not yet installed standard two blade prop assembly and spinner? Thanks for answering.

The three-blade prop kit prices are on the RV-12/12iS powerplant order forms, which are located on this page.
 
Ordered power kit

Well just ordered my 3 blade prop power kit today.. The Check is in the mail and starting the wait time counter...I can’t wait!
 
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I am seriously considering this 'upgrade' (I know it's debatable) and wondering if Van's have created a set of instructions to go from the standard ELSA Sens 2-blade to the new Sens 3-blade? I know I can dig out the info by comparing both KAI sections. For example, do you have to disturb the original pitot tube setup? I am assuming all the offsets, etc are the same, but...?

Also wondering if there is a used market for the Sens 2-blade with 180 hours on it??
 
There is no conversion document to switch from the 2 blade to the 3 blade.
You take the one off and use the install instructions to put the 3 blade on.

The pitot tube installation is the same for both.
 
There is no conversion document to switch from the 2 blade to the 3 blade.
You take the one off and use the install instructions to put the 3 blade on.

The pitot tube installation is the same for both.

Thanks Scott, I will completely remove all 2-blade related components and start with the new instructions. Good to know the pitot tube install is the same.
 
RV-12 3-blade prop

I bit the bullet and purchased the new 3-Blade Sens prop from Van's. There was nothing wrong with my original 2-blade with only 180 hours on it. Everything was great, but I could not resist the look of 3 blades and hoped Van's would come out with an official offering for the RV12/912ULS. There were other offerings, but since I built ELSA, I wanted to stay in the spirit of 'Van's Approved'.

So far, very impressed with the apparent quality and design...the hub and blades are really nice. I just got a chance to do the initial mounting and spinner work over the weekend. I will start the pitch adjustments when I get time this week. Love the hub design, I was able to assemble the prop/hub on a nice, large table. Then it's easy to bolt to the back plate as a unit.

I will update this thread when I get the pitch set and am able to do some static and in-flight testing. BTW, if anyone knows someone that might need a perfect 2-blade setup with only 180 hours, please let me know. I had the later Sens hub that was not subject to cracking.

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When something causes me to repitch the two blade I groan. Can?t imagine the aggravation of trying to get THREE blades all singing the same song!😜
 
Looks sharp and love the two-tone grey paint job. Well done.

Thanks very much Stitch :)

When something causes me to repitch the two blade I groan. Can?t imagine the aggravation of trying to get THREE blades all singing the same song!😜

Hi Rich, I was thinking the same....I have to say it was not bad at all. I just finished setting initial pitch per the KAI (71.1 degrees +/- .1) The smaller blades are easier to work with and the new hub is really nice, clamp bolts work great and did not tend to disturb the setting when torquing. I was able to set all 3 blades to 71.1 without any trouble or drama!
 
Question for Scott or Greg....

Hi Van's, I used the KAI recommended initial prop pitch of 71.1 degrees. Interesting that the KAI said the setting should be exactly 71.1 for a 912iS install, and for a 912ULS, 71.1 is a good starting point (not sure how to interpret that). Is there a target RPM I should look for at Sea Level, WOT (stationary or rolling). Any data for RPM expected behind a 912ULS in any phase would be appreciated. Thanks, Paul
 
Assuming a Rotax 912ULS the Rotax manual states the static RPM should not be less than 5200 RPM at Wide Open Throttle (WOT). Rotax Owners website says that it is desirable to achieve 5500 to 5800 RPM WOT for Takeoff and Climb.
 
Rotax Owners website says that it is desirable to achieve 5500 to 5800 RPM WOT for Takeoff and Climb.

If you pitch prop for 5500 to 5800 RPM WOT for takeoff and climb you will have low cruising speed because blade pitch is too flat.

RV-12 sweet spot for prop pitch is 5150 - 5200 in initial climb at somewhere around 1000 MSL.
 
If you pitch prop for 5500 to 5800 RPM WOT for takeoff and climb you will have low cruising speed because blade pitch is too flat.

RV-12 sweet spot for prop pitch is 5150 - 5200 in initial climb at somewhere around 1000 MSL.

At Vy or Vx? Rate of climb at gross 1320 # ?
 
Hi Van's, I used the KAI recommended initial prop pitch of 71.1 degrees. Interesting that the KAI said the setting should be exactly 71.1 for a 912iS install, and for a 912ULS, 71.1 is a good starting point (not sure how to interpret that). Is there a target RPM I should look for at Sea Level, WOT (stationary or rolling). Any data for RPM expected behind a 912ULS in any phase would be appreciated. Thanks, Paul

Testing showed the speed performance of the 3 blade to be pretty much identical to the two blade, with the 3 blade providing a slight increase in climb rate.

With this being true, if you pitch for the same RPM you typically saw with the two blade in a specific cruise condition (possibly mined from your EFIS data) you will probably be happy with that setting).

As a rough suggestion, a couple tenths of a degree less pitch than 71.1 12iS value might put it pretty close depending on what you had chosen as an optimal setting for how you fly your airplane. The reason for this is that the 912iS torque curve peaks at a bit lower RPM than it does on the ULS, so a typical ULS pitch setting (for the preference of most people) will probably be a couple tenths of a degree less pitch than it would for an iS.
 
Thanks Scott and all for the comments/suggestions. I finished the work on the spinner tonight, so it's ready for at least some static testing. I ended up with all 3 blades set at 71.1, I will see what that yields and adjust from there. Hoping to fly in the next day or two depending on weather here in East TN.
 
I may be off a bit (memory is going bad) but I think it is just shy of 6 lbs lighter.
Seemed hard to believe when we first weighed it but each blade is quite a bit lighter than the what a 2 blade blade is, plus the lower hub mass. It all adds up......

The new prop looks great but I can?t seem to locate the weight of the new 3 blade prop, can anyone confirm? I don?t think there is much weight difference and the quote above could be an initial guess.

Thanks
 
Does prop, as furnished by Van's, come with datum station and weight specific to RV-12 so W&B can be corrected for this installation?
 
The new prop looks great but I can?t seem to locate the weight of the new 3 blade prop, can anyone confirm? I don?t think there is much weight difference and the quote above could be an initial guess.

Thanks

The nearly 6 pounds lighter is still valid.
The actual installation weight delta is slightly less because of differences in installation hardware so call it somewhere between 4 - 5 pounds lighter.
 
Now have some data

The new prop looks great but I can?t seem to locate the weight of the new 3 blade prop, can anyone confirm? I don?t think there is much weight difference and the quote above could be an initial guess.

I should have weighed the new prop/hub assembly when I had it put together on the bench, but I didn't! So I don't really know the weight. According to the Sens doc that ships with the prop, my old 2-blade (model 2A0R5R70EN) weighs 10.5 lbs. The new 3-blade doc says it weighs 10.0 lbs (model 3Y0R5C70MY). I am pretty sure those numbers include the hub, so the 3-blade weighs a little less!

Does prop, as furnished by Van's, come with datum station and weight specific to RV-12 so W&B can be corrected for this installation?

There was no W&B data included with the prop. The new KAI section for the 3-blade has no info, since it's written as part of the initial build of the plane. I need to do a new W&B anyway.

I was able to do a test flight yesterday morning. I had all 3 blades pitched to 71.1 deg per Van's KAI procedure.

Static, WOT runup averaged 4970 RPM.
Takeoff/climb RPM (@1400MSL) was 4960 - 5000
I was getting consistent 1100 FPM @ 70kts
Cruise @ 3000MSL, WOT was giving me 5650-5700RPM (and 124kts TAS!!)

I have not performed any type of dynamic balance, but I have to say this new prop is really smooth and to me, vibration free. The quality of the fiberglass on the new spinner was excellent. No drama at all on the install. I also love that you can remove the prop without disturbing any pitch settings.

Anyone who is on the fence, I will just say I am super happy with the results.
 
Correction

Looked at wrong line in table, new 3-blade weighs only 9 lbs, which puts the 2-blade at least 1.5 lbs heavier with just the prop/hub alone.

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Thanks for your updates and review of your prop transition. Glad to hear how good your experience was, and it looks like your performance is just right. If you get the chance to have the prop dynamically balanced you might be surprised it can be smoother, or at least have it checked.

Take care Paul
 
If you get the chance to have the prop dynamically balanced you might be surprised it can be smoother, or at least have it checked.

Take care Paul

Thanks Pat....if I find someone local that performs the balance service, I will go ahead and have it done. Good to hear from you.
 
colour

I have to say Paul: amazing colour combination, grey and silver, what exactly did u use if u don't mind?:)
 
I wanted to pass this along to others - I'm not sure if anyone else had this issue or not. I used the nuts that shipped with my propeller to install it by threading them on to the AN5-65A bolts. I should have known something was wrong because of how difficult they were to install (they became extremely hot while I was snugging them up for the initial fitting). Turns out these nuts were the incorrect nuts :( My tech counselor visited tonight and pointed out that these are actually metric nuts.

I went back and looked at Paul's photos. I can clearly see that he did not use these nuts for his install. I'm curious if anyone else had this issue? The plans say to use the hardware that was shipped with the propeller and call out this nut:

MS20365-524C

I went back and looked at the packing list for the 3 blade prop order. I did get 6 AN365-524's from Vans. So it looks like I was supposed to use those. I will email the support folks and point out that perhaps figure 2 on page 47AiS/U-04 should be updated to clarify this point.
 
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