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FYI: New SB 18-07-05 on RV-12 Sensenich Props

Looking at this photo, I’m struck by three things. 1- The surface finish of the entire part (ignoring the paint) is riddled with irregulaities- not done to the standard I’d expect on a modern critical part. 2- It appears that one of the deep hatch marks may have served as a stress riser from which the crack initially propagated. 3- The irregularity and extreme granularity of the face of the actual failure zone makes me wonder about the consistency of the alloy.

My guess is Sensenich is re-running a Finite Element Analysis to try to find the mode of failure...
 
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A few more Photos

A few more Photos

RV12_Sensenich_001.jpg



http://joesrv12.com/Builder Log/RV12_Service_Bullitens.htm

I think the type of prop in the photo is the only one of concern.

I wish Vans would provide more information on this concern.

Joe Dallas
 
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Is this prop the only option out there that is recommended?

As is typical when info starts flying :rolleyes: on the internet.....

The prop (hub) that is the subject of this thread was phased out years ago.
If you purchased an RV-12 power plant kit within the past 5 years (maybe more, I can't remember the exact date of the change), you would have a different design prop hub that is not effected by this S.B.

As far as recommended goes? Yes. The Sensenich ground adjustable is the only prop recommended by Van's, but anyone with an experimental RV-12 is free to experiment to what ever degree they chose.
 
Joe,
What is your prop hub serial number? I am send my hub to Don at Sensenich to inspect due to clamping concerns and an irregularity I saw between two of the pitch numbers. My s/n is 29756C and was received with the power plant kit in July 2012, and I was wondering how close your s/n was to mine.

The clamping issue is the pitch changing after operation and Don voiced a concern about the bolts bottoming out. So it will be on its way to Sensenich today to check machining to insure the hub half?s are correct, and look at what I felt might be a crack starting. The down side is once Don receives my stuff he will be heading to Oshkosh. Oh well.
 
I'm using a WhirlWind GA_J2B

I install the new Jabiru 3300 Generation 4 Engine in my 12

45_02_01.jpg



I'm using a WhirlWind GA-J2B

https://whirlwindpropellers.com/aircraft/product/propeller-for-jabiru-3300-engines/

Joe Dallas




Joe,
What is your prop hub serial number? I am send my hub to Don at Sensenich to inspect due to clamping concerns and an irregularity I saw between two of the pitch numbers. My s/n is 29756C and was received with the power plant kit in July 2012, and I was wondering how close your s/n was to mine.

The clamping issue is the pitch changing after operation and Don voiced a concern about the bolts bottoming out. So it will be on its way to Sensenich today to check machining to insure the hub half’s are correct, and look at what I felt might be a crack starting. The down side is once Don receives my stuff he will be heading to Oshkosh. Oh well.
 
Joe, that?s a scary crack. Did you discover it without removing the forward spinner bulkhead? It looks like it would be visible at the edge with the bulkhead in place. Was yours one of the 3 Jabiru failures noted in the SB, or is this in addition to those 3?

Thanks,

Rich
 
Let?s see if I?ve got this correct? reading back through this thread I list three prop hub failures as follows:

? Robert Liddell - Hub failure in flight with safe landing. Hub sent to Sensenich ? awaiting disposition.

? David Heal ? Appeared to have found two cracks per SB. Hub sent to Sensenich ? awaiting disposition.

? Joe Dallas ? Hub cracked in half. Sensenich replaced with new design hub.

Joe Dallas ? I?m a bit confused? you say you installed a JABIRU 3300 and yet your builder?s log shows entry with picture of new design prop hub installed on RV-12 with Rotax 912 engine. See photo below.


28u7bqx.png
 
We inspected the hubs of both our RV12?s and found no cracks, but a very time consuming job to set the correct pitch again to get the specified rpm value at WOT.
As we are not keen at all to do this every 50 hours we ordered new design hub plates at Sensenich.
They charge $ 195 per unit. 😡
 
We inspected the hubs of both our RV12?s and found no cracks, but a very time consuming job to set the correct pitch again to get the specified rpm value at WOT.
As we are not keen at all to do this every 50 hours we ordered new design hub plates at Sensenich.
They charge $ 195 per unit. 😡

You replaced just the front plate or entire hub? I believe the hub is machined as a matched assembly with matching serial numbers...
 
They asked for the serial numbers of the hubs and quoted all the parts required including fasteners, so I may assume it is correct.
I will pick them up at Oskosh so will see what we get
 
We inspected the hubs of both our RV12?s and found no cracks, but a very time consuming job to set the correct pitch again to get the specified rpm value at WOT.
As we are not keen at all to do this every 50 hours we ordered new design hub plates at Sensenich.
They charge $ 195 per unit. 😡

Assuming you were happy with performance before removing the propeller, returning to a specific pitch/performance value is a rather simple process.
If the set pitch value is recorded in the log book or you measure it before removing the propeller.
As long as you have that number, getting setting back to that pitch will give you the same performance you had before.
 
Thats what I did but the plane needs to be exactly level and the angle tends to change a little when you tighten the bolts.
I took the spark plugs out to move the prop without disturbing the level of the plane.
After two iterations I got it within 100 rpm of the original WOT rpm.
It took me 4 hours for two 12?s
 
Thats what I did but the plane needs to be exactly level

Not so… Refer to Page 07 of Section 47 Construction Drawings. The plane does not need to be level at all and can even change angle between measurements.

The prop pitch angle is relative to the canopy longeron regardless of aircraft level. Each time the prop is moved recheck the digital level on the longeron before measuring the blade pitch. If the aircraft “level” has been disturbed while moving the prop simply re-zero the digital level on the canopy longeron before continuing to measure blade pitch.

It is not necessary to remove spark plugs or even upper cowling.

Tools required include a good quality bubble level and two wooden spacer blocks to level prop hub. Mark blocks L-R, forward and top-side so they are placed same exact position on hub each time. Likewise, mark bubble level so it is not “reversed” for each use.

I use Vans sheet metal TOOL-00002 Prop Pitch Bracket and same Craftsman Multifunction Digital Torpedo Level # 48295 as shown in construction drawings. For each measurement of blade pitch first place digital level on longeron and verify zero and re-zero if necessary. Next place the magnetic base of the digital level on the Prop Pitch Bracket (PPB) and finally place digital level/PPB onto the prop. Use gentle finger pressure to seat the PPB against the front edge of the prop.

I have not found tightening of the front prop hub to influence final blade angle. I snug only outer bolts and leave center bolts loose while adjusting blade pitch. When one blade pitch is correct, snug outer bolts even further before setting second blade.

Total time for above procedure is approximately 30 minutes and will attain relative pitch between both blades to within 0.1° angle.
 
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Not With my Inclinometer

SPI

0.10 dg Resolution Digital Combination Protractor and Inclinometer

SPI Tronic Price $243.97


0.10 dg Resolution Digital Combination Protractor and Inclinometer
Accuracy (Degrees) 0.1 (Level 10 ); 0.1 (Plumb 10 ); 0.2 (Maximum Error)

.1 Degree = 6 minute arc . 2 Degree = 12 Minute arc


With four moves of level and the built in error of .2 in the level how is this possible ?

Keeping the aircraft level makes this more possible ?

MY view


Joe Dallas


Not so… Refer to Page 07 of Section 47 Construction Drawings. The plane does not need to be level at all and can even change angle between measurements.

The prop pitch angle is relative to the canopy longeron regardless of aircraft level. Each time the prop is moved recheck the digital level on the longeron before measuring the blade pitch. If the aircraft “level” has been disturbed while moving the prop simply re-zero the digital level on the canopy longeron before continuing to measure blade pitch.

It is not necessary to remove spark plugs or even upper cowling.

Tools required include a good quality bubble level and two wooden spacer blocks to level prop hub. Mark blocks L-R, forward and top-side so they are placed same exact position on hub each time. Likewise, mark bubble level so it is not “reversed” for each use.

I use Vans sheet metal TOOL-00002 Prop Pitch Bracket and same Craftsman Multifunction Digital Torpedo Level # 48295 as shown in construction drawings. For each measurement of blade pitch first place digital level on longeron and verify zero and re-zero if necessary. Next place the magnetic base of the digital level on the Prop Pitch Bracket (PPB) and finally place digital level/PPB onto the prop. Use gentle finger pressure to seat the PPB against the front edge of the prop.

I have not found tightening of the front prop hub to influence final blade angle. I snug only outer bolts and leave center bolts loose while adjusting blade pitch. When one blade pitch is correct, snug outer bolts even further before setting second blade.

Total time for above procedure is approximately 30 minutes and will attain relative pitch between both blades to within 0.1° angle.
 
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SPI

0.10 dg Resolution Digital Combination Protractor and Inclinometer

SPI Tronic Price $243.97


0.10 dg Resolution Digital Combination Protractor and Inclinometer
Accuracy (Degrees) 0.1 (Level 10 ); 0.1 (Plumb 10 ); 0.2 (Maximum Error)

.1 Degree = 6 minute arc . 2 Degree = 12 Minute arc


With four moves of level and the built in error of .2 in the level how is this possible ?

Keeping the aircraft level makes this more possible ?

MY view

RV-12 owners who are adjusting their propeller pitch and actually flying their airplane usually learn quickly that the accuracy of the degree value on their tool is not important. Since most people adjust pitch based on what they see for cruise RPM / airplane performance, all that matters is that the reading on the tool be repeatable.

All of the digital levels I have used, regardless of their specified tolerance, have had very repeatable readings. I.E., you can set them down on a fixed / non-movable object (specific spot on your shop floor) for years and it will read the exact same value every time.

So, as long as you use the same tool, and the exact same procedure (always position the digital level on the blade measuring tool the same way, etc.) the measurement value is very repeatable. At least close enough that removal of the prop and re-installation to a specific measurement results in the same max. RPM in the same flight condition, and in this situation that is all that matters.

In the end, we don't need to know whether the pitch value is 70.8 degrees or 70.9 degrees. Only that we know how much change we made, or that we successfully adjusted back to the same # that we were using previously.

As mentioned, if the digital level is always zero referenced to the cockpit side rail (recommended in the RV-12 documentation), then it will never matter where the airplane is sitting when you are adjusting the propeller pitch. You could do it parked on a hill and your desired pitch value (hopefully recorded in your log book) could still easily be set.

BTW, the tightening order/process of the hub bolts does have an influence on the blade angle. as you alternate back and forth on the bolts while tightening, it is rocking the hub back and forth as well. This can move the blade angle very slightly. With practice, you can use this to your advantage as you are coming up on full torque by adjusting your tightening sequence slightly to get the blade to go that last tenth of a degree towards the value that you want.

Because very few digital levels read in hundredths, even if you have the exact same value on both blades there is still a potential for there being a .1 to .15 degree difference (set your digital level on a hard surface and see how much you can lift one end before the value changes to the next tenth). It is for this reason that I always strive to get both numbers the same. Experience has shown that if I do, the level of smoothness is worth the time.
I can set up the blade pitch on an RV-12 in 15 - 20 minutes. I have had some practice :rolleyes: but this is attainable by anyone with practice as well.
One important thing that helps a lot is devising some sort of tool that can be hooked on the blade to give you more leverage to rotate it. Our tool is about 3' long. The additional leverage provided by the tool is what allows for making a very small movement in the blade pitch
 
Not The Point

Scott
I also believe you can set the blades within .1 to .15 degrees to each other,
with proper use of a Digital Inclinometer, same end up, rotation from the same direction and the same place on the prop and only one reference point.


The point of my post was to confirm if you want to be a close as possible and you are using a none precision Digital Inclinometer

KEEP THE AIRCRAFT STATIONARY

MY View













RV-12 owners who are adjusting their propeller pitch and actually flying their airplane usually learn quickly that the accuracy of the degree value on their tool is not important. Since most people adjust pitch based on what they see for cruise RPM / airplane performance, all that matters is that the reading on the tool be repeatable.

All of the digital levels I have used, regardless of their specified tolerance, have had very repeatable readings. I.E., you can set them down on a fixed / non-movable object (specific spot on your shop floor) for years and it will read the exact same value every time.

So, as long as you use the same tool, and the exact same procedure (always position the digital level on the blade measuring tool the same way, etc.) the measurement value is very repeatable. At least close enough that removal of the prop and re-installation to a specific measurement results in the same max. RPM in the same flight condition, and in this situation that is all that matters.

In the end, we don't need to know whether the pitch value is 70.8 degrees or 70.9 degrees. Only that we know how much change we made, or that we successfully adjusted back to the same # that we were using previously.

As mentioned, if the digital level is always zero referenced to the cockpit side rail (recommended in the RV-12 documentation), then it will never matter where the airplane is sitting when you are adjusting the propeller pitch. You could do it parked on a hill and your desired pitch value (hopefully recorded in your log book) could still easily be set.

BTW, the tightening order/process of the hub bolts does have an influence on the blade angle. as you alternate back and forth on the bolts while tightening, it is rocking the hub back and forth as well. This can move the blade angle very slightly. With practice, you can use this to your advantage as you are coming up on full torque by adjusting your tightening sequence slightly to get the blade to go that last tenth of a degree towards the value that you want.

Because very few digital levels read in hundredths, even if you have the exact same value on both blades there is still a potential for there being a .1 to .15 degree difference (set your digital level on a hard surface and see how much you can lift one end before the value changes to the next tenth). It is for this reason that I always strive to get both numbers the same. Experience has shown that if I do, the level of smoothness is worth the time.
I can set up the blade pitch on an RV-12 in 15 - 20 minutes. I have had some practice :rolleyes: but this is attainable by anyone with practice as well.
One important thing that helps a lot is devising some sort of tool that can be hooked on the blade to give you more leverage to rotate it. Our tool is about 3' long. The additional leverage provided by the tool is what allows for making a very small movement in the blade pitch
 
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Just one other thought... sometimes electronics like to warmed up to a steady state condition and be at ambient temperature before best repeatability and accuracy are attained. I turn on the digital level about ten minutes prior to use and leave it on until job is completed.
 
Scott
I also believe you can set the blades within .1 to .15 degrees to each other,
with proper use of a Digital Inclinometer, same end up, rotation from the same direction and the same place on the prop and only one reference point.


The point of my post was to confirm if you want to be a close as possible and you are using a none precision Digital Inclinometer

KEEP THT AIRCRAFT STATIONARY

MY View

Ok, but I didn't see anything about that mentioned anywhere in your post. Only you raising the question "how is this possible".
I guess that now makes me wonder... How is what possible?
 
Just one other thought... sometimes electronics like to warmed up to a steady state condition and be at ambient temperature before best repeatability and accuracy are attained. I turn on the digital level about ten minutes prior to use and leave it on until job is completed.

Possible I guess, but I have used numerous tools winter and summer and have never noticed any variation.
 
Just one other thought... sometimes electronics like to warmed up to a steady state condition and be at ambient temperature before best repeatability and accuracy are attained. I turn on the digital level about ten minutes prior to use and leave it on until job is completed.

That can be a concern with devices that warm up during use. A digital level or inclinometer uses so little current that there will be no measurable rise in temperature during use.
 
Sorry Scott

I thought it was clear

From my Post

With four moves of level and the built in error of .2 in the level how is this possible ?

Joe Dallas





Ok, but I didn't see anything about that mentioned anywhere in your post. Only you raising the question "how is this possible".
I guess that now makes me wonder... How is what possible?
 
Sorry Scott

I thought it was clear

From my Post

With four moves of level and the built in error of .2 in the level how is this possible ?

Joe Dallas

Using words like it can make talking in details difficult at times; but regardless, as I already mentioned I have found even cheap digital levels to be extremely repeatable so being moved is not an issue.
 
I think the bottom line is that it can be a pain, but it can be done. I just hate to disturb the sweet spot I found 4 years ago!
 
TOOL-00002 Prop Pitch Bracket

Could someone please post a photo of the above tool. I am 2500 miles away from my plans and having heart burn about this discussion on this prop and the difficultly some are having in adjusting or re-adjusting the pitch.

I am replacing my existing wood prop for the Sensenich ground adjustable. The new prop is on order so I am not expecting it for several weeks. I know my pitch settings for the Jabiru engine will be different but I am interested if the above tool would also be helpful for me.

Regards,
Tom
 
Had mine inspected this week for the second time in compliance with amended SB. Nothing found at 280 hours. Has anybody found a crack (apart from the one that started it all)? I?ve ordered a replacement cover plate to avoid the repetitive inspections.

Jack
 
Instead of a version "D1" hub, which will eliminate repetitive inspections per Sensenich FAQ, I opted for the newest design front hub which is either "E" or "F". This design has the three smaller holes in-line with the prop axis. Normally the pins in the shank of the prop blade need to be relocated by the factory to allow use of the gage pins for setting rough pitch angle. I will keep my blades as-is and set pitch manually with use of digital level per the Van's setup procedure. This is how I did it with my "B" hub - not relying on the pitch cylinder.
 
Jack asked: "Has anybody found a crack (apart from the one that started it all)? I?ve ordered a replacement cover plate to avoid the repetitive inspections."

Yes, my original circa 2013 / 650+ hour prop hub cover plate was cracked exactly as depicted in the SB. I have just installed a new Revision D1 cover plate per Sensenich's SB and FAQ.
 
Thanks, David. How does the Revision D1 differ from the problem covers? I have the paperwork to order a D1 through the Australian dealer but in light of Jim?s comments, I am wondering whether I should go for the newer version.

Jack
 
Thanks, David. How does the Revision D1 differ from the problem covers? I have the paperwork to order a D1 through the Australian dealer but in light of Jim’s comments, I am wondering whether I should go for the newer version.

Jack

Jack
I am planning to send prop to US for the E or F conversion to eliminate all 50hour tightening ofbolts requirement.
John
 
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Jack -- The Rev D1 cover looks like it will work fine for me -- an easy fix. Check your PMs. -- David

ps -- I assume you have seen Sensenich's FAQ document for their SB -- it answers many questions.
 
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nord lock washers

I want to replace the nordlock washers as they seem to be loosing there effectiveness
can anyone tell me the vans part number or the outside diameter as the only ones I can find here ( australia) are only 13.5 mm ( .5" ) diam and I think the originals have a bigger outside diameter
 
I want to replace the nordlock washers as they seem to be loosing there effectiveness
can anyone tell me the vans part number or the outside diameter as the only ones I can find here ( australia) are only 13.5 mm ( .5" ) diam and I think the originals have a bigger outside diameter

Yes, the Nord-Lock washers used for the prop are a larger OD than the ones normally associated with that size bolt head. I found this out the hard way when I went to a large nut & bolt supplier locally and bought some replacements ... only to find out the outside diameter of the Nord-Lock Sensenich uses on the prop bolts were a much larger OD than the ones that were sold to me at the nut & bolt supply.

I ended up ordering new ones directly from Sensenich ... they were cheap. The Nord-Lock part number printed directly on the washers is 85397-1 and the OD measures out at 21/32" if that helps. Below is a link to my Blog that has a photo of a Nord-Lock washer from Sensenich being measured ... if you zoom in you can clearly see the part number on the washer.
http://www.dogaviation.com/2017/10/the-first-condition-inspection-tips-for.html
 
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I tried to use it and found it to be a very poor substitute for the sheetmetal stamping that Van's sells. Don't skimp on getting the right tool for this important job. I know Sensenich says their wooden gage is the next best thing to sliced bread but believe me - it isn't.
 
I have used it, and I liked it because it matched exactly the airfoil used on the prop, and it would measure accurately the angle of the chord line from leading edge to trailing edge. But I will say Vans little tool is a little easier to use.
 
Can anyone who has ordered a Rev E or later hub from Sensenich let me know how they did it?
My current plan is to get the Rev E or later hub replacement and manually set pitch with protractor, rather than send whole prop back to US.
But not able to find an order page on Sensenich web site that lists the new hub.
I plan to ring them tonight but maybe there is an easier way.
John
 
Can anyone who has ordered a Rev E or later hub from Sensenich let me know how they did it?
My current plan is to get the Rev E or later hub replacement and manually set pitch with protractor, rather than send whole prop back to US.
But not able to find an order page on Sensenich web site that lists the new hub.
I plan to ring them tonight but maybe there is an easier way.
John

Sure, I just did this. Call Sensenich and place order over the phone. They may give you a hard time about mismatching SN's and such but insist that they send you latest design hub. I received Rev "F" hub and set pitch manually with digital level per Van's instruction. I entered SN's for both halves of prop hub and both blades in my prop logbook stating compliance with latest SB and installed per Sensenich instructions. Now I feel good about integrity of prop.

Wanted to add more pitch so I could keep up with this airplane... :D

11txst0.png
 
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The old hub has the large center hole for the nylon pitch change cylinder. Photo of my "B" hub anodized a gold color is shown below. Hubs thru Rev "D" all have the large center hole.

I didn't take a photo of the new hub. I have included Van's assembly drawing of the new design hub which shows the three (3) small holes aligned with the prop axis. The new design started with Rev "E" and includes latest Rev "F".

Large center hole - Rev's thru and including Rev "D"
ddmi5e.png


Three (3) small holes aligned w/ prop axis - Rev's "E" and "F"
21amss7.png
 
Yes, the Nord-Lock washers used for the prop are a larger OD than the ones normally associated with that size bolt head. I found this out the hard way when I went to a large nut & bolt supplier locally and bought some replacements ... only to find out the outside diameter of the Nord-Lock Sensenich uses on the prop bolts were a much larger OD than the ones that were sold to me at the nut & bolt supply.

I ended up ordering new ones directly from Sensenich ... they were cheap. The Nord-Lock part number printed directly on the washers is 85397-1 and the OD measures out at 21/32" if that helps. Below is a link to my Blog that has a photo of a Nord-Lock washer from Sensenich being measured ... if you zoom in you can clearly see the part number on the washer.
http://www.dogaviation.com/2017/10/the-first-condition-inspection-tips-for.html

Re Nord-Lock washers.
Please excuse a stupid question, but how many of the Sensenich specific 85397-1 Nord-Lock washers are requred if I replace the hub front plate with a new D1 version hub cover half?
I want to get all parts I may need for the maintence organisation Iwill use before we start.
I am not the builder of my 12, so must use a licence shop for maintenance.
 
Re Nord-Lock washers.
Please excuse a stupid question, but how many of the Sensenich specific 85397-1 Nord-Lock washers are requred if I replace the hub front plate with a new D1 version hub cover half?
I want to get all parts I may need for the maintence organisation Iwill use before we start.
I am not the builder of my 12, so must use a licence shop for maintenance.

When you order the new from hub from Sensenich it will come with new bolts and Nord-Lock washers.
 
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