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And this is why you do condition inspections...

Mark Dickens

Well Known Member
Patron
My relatively new (< 2 years old and about 120 hours of use) Sensenich ground adjustable prop surprised me this morning when I was inspecting it as a part of the condition inspection:

prop1.jpg


prop2.jpg


No, I haven't had a chance to discuss it with Sensenich and yes, I'll be on the horn first thing Monday to do just that. Just posting this as a heads up that anyone flying one of these might want to take a close look before next flight.
 
Look at this way, at least you caught it. That could have been a catastrophic failure.

If that’s carbon fiber advise replacing the blade. Repairs don’t seem to work out well on carbon fiber blades.

At least its a Sensenich and purchasing a single blade should be doable.
 
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That would probably be found on a good pre-flight. Don't wait until condition inspection to give your prop a close looking-over.
 
I concur that this sort of damage to the prop should be caught at the pre-flight inspection. This damage may have occurred during the last flight prior to the OP's CI so I am not pointing a finger. It just takes me right back to my original thread last summer about plane ownership and complacency of a thorough pre-flight inspection because of ownership which seemed to strike a nerve with some of the forum members here. ;) You need to do it and be serious of doing it right. http://www.vansairforce.com/community/showthread.php?t=161135
 
I personally like post flight inspections myself, you have to get the bugs off anyway so thats a good time to look things over closely while your wiping it down.
That way you also have time to deal with issues you find and are less likely to let things go because the wife is sitting in the airplane waiting on you :eek:
 
Appreciate the post

Mark, thx for the post. I hope the response will not scare the next person from showing his findings that could save someone?s life.
 
I also like postflights for the lack of any pressure to fly to meet a plan and less stress if parts or supplies need to be ordered.

I also really appreciate folks that post any such findings. In the Sq we'd remove nametags and discuss foibles, fouls and follies over beverages- no attribution left the room.

We can't do that here in anymouse/anonymous style- so please, tread lightly when anyone post such findings rather than keeping it private.

If a composite expert could explain if this is a single event result found on what happened to be an annual CI, but happened on the previous flight or flights, I'm sure more than one here will benefit from the education.

Is that where the extreme fibers receive the most tension stress?
 
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Thanks for posting and bringing this type of issue back front of my thinking for the future. Always good to be reminded of issues that pop up in the RV fleet.
 
I personally like post flight inspections myself, you have to get the bugs off anyway so thats a good time to look things over closely while your wiping it down.
That way you also have time to deal with issues you find and are less likely to let things go because the wife is sitting in the airplane waiting on you :eek:

I do too when I have the time. If i'm just out flying around for fun, I usually have time at the conclusion of the flight and I like to wipe it down, but the last few flights have been on a schedule with no time to really look at it at the end. Land, put it up and run to the office.

My hangar mate took a look at the other blade and thinks he's found another small crack...both of these blades are headed back to Sensenich. After my problem with my first prop (a catto), and now this, I'm really bummed out. I think I'll just put a metal prop on it next. 120 hours and cracks in both blades? The prop has a red line of 2700 RPM and I've never gotten much over 2600 in a descent and that would be for a moment or two only. I cruise at 2500 almost all the time, so I can't fathom it's RPM related. I thought I was babying this thing...very bummed out at the moment
 
Prop failure

WOW, Thanks for sharing that Mark. I'd be interested to hear what Sensenich has to say after examining the blade (if they're willing to share).
 
I personally like post flight inspections myself, you have to get the bugs off anyway so thats a good time to look things over closely while your wiping it down.
That way you also have time to deal with issues you find and are less likely to let things go because the wife is sitting in the airplane waiting on you :eek:

Yep.. I've been in the habit of a complete pre-flight, and then a thorough post-flight inspection.. Just gives me peace of mind and double the chance of finding something.. Can't hurt!
 
Wow Mark - really glad that you shared this! The essence of safety is to show others problems we encounter - with no worry about blame or criticism. Some don’t understand that, but ignore them. Good job.

So my thought on this is I wonder if Sensenich ever tested th prop on this engine with electronic ignition. There is some evidence that the power pulses on with EI are sharper than with mags, and can (or could) cause issues with props. This might be evidence of that.

Please keep the community informed on what you find out.

Paul
 
Pitch setting

Thank you very much for your post Mark, it will sure make me look much more closely at my prop on every flight.

I can't help but wonder if the pitch setting would contribute to this problem. What was your pitch pin number setting for the pitch?

Thanks, Steve
 
Paint crack only?

Can you tell if this is in the paint or surface filler only, or do you see broken fibers? From the photos it looks more like the paint has cracked than any failure of the composite. Can you chip back some of the paint to get a better look?

If you coin tap around the crack does it sound dull or deadened, or does it sound the same as other areas of the prop?
 
So my thought on this is I wonder if Sensenich ever tested th prop on this engine with electronic ignition. There is some evidence that the power pulses on with EI are sharper than with mags, and can (or could) cause issues with props. This might be evidence of that.

Please keep the community informed on what you find out.

Paul
I had the same thought around 2:00 am this morning. It will definitely be a subject of discussion and I'll keep everyone informed.
 
Can you tell if this is in the paint or surface filler only, or do you see broken fibers? From the photos it looks more like the paint has cracked than any failure of the composite. Can you chip back some of the paint to get a better look?

If you coin tap around the crack does it sound dull or deadened, or does it sound the same as other areas of the prop?

I thought about digging around the area a little, but didn't want to touch it so that Sensenich would have it as is for investigation. I don't want any discussion about how I made a bad situation worse
 
Thanks for the heads up!!

I thought about digging around the area a little, but didn't want to touch it so that Sensenich would have it as is for investigation. I don't want any discussion about how I made a bad situation worse

Thanks for posting, kinda scary. It shows that nearly anything can still happen at low hours. I have 70hr so will be checking my Hartzell composite closer.

BTW Hartzell has a short video on how to tap test a composite prop. Maybe not applicable to yours but might be interesting to see if it yields any indication other than what you have found. A "self training' tap-test.


https://www.youtube.com/watch?v=VZTDL41cUJA time:5:16 There is a better one but did not find it.
 
Thank you

Mark,
Thank you for posting this. If you are religious man and pray often, then you know they were answered in some way by you finding this before your next flight.
I'm not sure if you are aware of the hot water that Sensenich was under less than a ago by the FAA - If you are not, this will explain part of it. I'm not sure if that has any connection with how your prop was built, but that happened in the certified market. Personally I know that the guy that I sold my Cessna 310 to had to buy 2 new McCauley Props to the tune of almost $40K because of the shotty work that Sensenich did when I sent my props to them to overhaul. I sold my plane shortly after the overhaul and on the 3rd annual under the new owner they found cracks in both props. Unfortunately, Sensenich would not take responsibility because it was 3 years so it ended up costing the new owner some $38K plus labor. Later he found out that he was not the only one and that there were multiple cases of failure from Sensenich which I believe is why it got the FAA's attention.

I don't know all the details around the FAA getting involved and don't want to assume anything, but I would look into it especially if Sensenich does not take responsibility of this issue.

Good luck sir.
 
Similar Issue

Mark,

I found a very similar issue with the Sensenich ground adjustable prop on my Sport Cub. After working with Sensenich support, we determined it was cosmetic. The crack I have is in the paint where an internal metal strip ends and carbon fiber begins. Both blades had the paint crack in the same position with the same shape. Definitely work with Sensenich support.

Here's a picture:

SensenichGA.jpg
 
Can you provide a fairly accurate measurement of the position of the crack in relation to the overall length of the blade (and in respect to the length outside of the hub) ?

Wonder if the crack correlates to a vibration node? (my term)
 
Similar Issue

Mark,

Here is the email I received from Sensenich about my issue:

it's not uncommon to have slight stress cracks beside the metal erosion shield on a composite (or wooden) propeller.
the difference in metal and composite material properties can sometimes result in slight paint cracks where they overlap.

the primary concern here is not the crack, but whether there has been any loosening of the metal from the composite structure beneath.
small areas of loosening are allowable as long as they do not exceed airworthy limits.

a tap test with a quarter is done to detect any hollow or "dead" spots, which indicates a local debond.
a high pitch sound or tone indicates good structure or bond with no loosening.
a hollow or "dead" spot indicates loosening or an air pocket.
note: the tap tone is proportional to material density. it will change when going from all-composite to metal bonded over composite.
tap along the metal erosion shield to become familiar that that tone, and likewise tap the
inboard leading edge (without metal) to hear what all-composite should sound like.
if any hollow or dead spots are evident, then tap in a grid pattern to determine the overall debond dimensions.


airworthy limits:

total debond area under 0.39 in^2; this equates to a 5/8 x 5/8" square or a 1 x 3/8" rectangle.
no debonds over 1"

mark limits of paint crack with permanent marker and check during each preflight for growth.
if any growth is detected, then perform tap test and compare the airworthy limits above.


--------------------------------------


Here is the spanwise measurement of the crack. It's about 12 1/8" from the hub:

SensenichGA2.jpg


--------------------------------------


This may be related or not. The continued airworthiness for Sensenich GA propellers requires it be disassembled and inspected annually. It is very easy to get a mismatch in the blade pitch during reassembly. This sets up a very noticeable vibration. I found this out on a post condition inspection flight. The vibration actually got worse at lower RPM.
 
Absolutely...I've sent an email to Don Rowell at Sensenich and hope to hear from him tomorrow in re next steps. I have the blades in the car and can measure anything he asks for
 
Mark,

Here is the email I received from Sensenich about my issue:

it's not uncommon to have slight stress cracks beside the metal erosion shield on a composite (or wooden) propeller.
the difference in metal and composite material properties can sometimes result in slight paint cracks where they overlap.

the primary concern here is not the crack, but whether there has been any loosening of the metal from the composite structure beneath.
small areas of loosening are allowable as long as they do not exceed airworthy limits.

a tap test with a quarter is done to detect any hollow or "dead" spots, which indicates a local debond.
a high pitch sound or tone indicates good structure or bond with no loosening.
a hollow or "dead" spot indicates loosening or an air pocket.
note: the tap tone is proportional to material density. it will change when going from all-composite to metal bonded over composite.
tap along the metal erosion shield to become familiar that that tone, and likewise tap the
inboard leading edge (without metal) to hear what all-composite should sound like.
if any hollow or dead spots are evident, then tap in a grid pattern to determine the overall debond dimensions.


airworthy limits:

total debond area under 0.39 in^2; this equates to a 5/8 x 5/8" square or a 1 x 3/8" rectangle.
no debonds over 1"

mark limits of paint crack with permanent marker and check during each preflight for growth.
if any growth is detected, then perform tap test and compare the airworthy limits above.


--------------------------------------


Here is the spanwise measurement of the crack. It's about 12 1/8" from the hub:

SensenichGA2.jpg


--------------------------------------


This may be related or not. The continued airworthiness for Sensenich GA propellers requires it be disassembled and inspected annually. It is very easy to get a mismatch in the blade pitch during reassembly. This sets up a very noticeable vibration. I found this out on a post condition inspection flight. The vibration actually got worse at lower RPM.

The prop has been very smooth and I've been (up tp this point of course) very pleased with it.. I did pull the prop in accordance with their instructions last year and had no issues, so this is something that's happened in 2018. I haven't flown it yet this year.
 
The crack is 8-7/8" from the hub end of the prop.

Never having conducted a coin test, I thought I'd video doing this and put it up on youtube for anyone to watch and listen to. It's at https://youtu.be/_fzn2H0zJGg. I can't hear any difference between the area that's got the crack and other areas, but perhaps someone with a more experienced ear will hear a difference. Maybe it is just paint? I'll let Sensenich have a final word on that.
 
Did you ever put a dynamic balancer on to see if you had any strange vibrations prior to this issue?
 
Good grief...all I wanted to do was let others know....:rolleyes:

I'm sorry -- I really was not trying to be critical, just cautionary to others. It was a good catch to find it. The prop is one of the things that is easy to look at every time you fly, and can have a big impact on the outcome of your flight.

And I like Walt's idea of the post-flight. I don't do that very often, but will start.

From my composites experience, it looks to me like a bending failure of the thin composite wrap over a wood propeller. That wrap may or may not even play a significant role in the structural strength and stiffness of the prop. But it does get highly stressed if/when the prop bends. Another post observed the high-stressed fibers at the outer edge of the cross section.

It will be interesting to hear what Sensenich says.
 
I'm sorry -- I really was not trying to be critical, just cautionary to others. It was a good catch to find it. The prop is one of the things that is easy to look at every time you fly, and can have a big impact on the outcome of your flight.

And I like Walt's idea of the post-flight. I don't do that very often, but will start.

From my composites experience, it looks to me like a bending failure of the thin composite wrap over a wood propeller. That wrap may or may not even play a significant role in the structural strength and stiffness of the prop. But it does get highly stressed if/when the prop bends. Another post observed the high-stressed fibers at the outer edge of the cross section.

It will be interesting to hear what Sensenich says.

No apology necessary. I just didn't want the thread to veer off in a different direction. Truth be told, I should have found this on a preflight. It just shows you that even after flying for 37+ years and somehow managing not to bust my you know what, there's always something to learn. I've always run my hand along the leading edge of the prop. A holdover from what I was taught in 1981...long before composite props. An old dog has to learn new tricks!
 
Good find Mark!

I really want to like their GAP but after watching my neighbor replace a mag every 30 hours on his O-200D on the front of his Cub-a-like due to harmonics

Once he replaced it with a Catto, all his problems went away.

(It sounds like you struggled with a Catto, so I'm not going to recommend one to you only making the comment that maybe that your GAP is too stiff for our engines.
 
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I sure don't want to give the wrong impression in re my Catto prop. It is true that there was a problem with it regarding the adhesive for the nickel leading edge. It was oozing out very slowly and as I recall the issue was that they had bought a new mixing machine when they moved to their new facility and it hadn't mixed the adhesive as well as it should have. This was I think in the 2013 timeframe. They repaired the prop under warranty. I replaced it with the Sensenich because I wanted the ground adjustable option and I wanted to move away from the 3 blade to the 2 blade. As I said earlier, until this weekend, I was very happy with it. The coin tap test I conducted this afternoon did not indicate to my untrained ear (I'm deaf in one) any issues. In addition, I took the blade out in the sunshine and closely examined it. The crack stops exactly where the flat black paint on the back of the blade meets the gloss black paint on the front of the blade. Hmmm...I look forward to my discussion with Sensenich tomorrow.
 
No apology necessary. I just didn't want the thread to veer off in a different direction. Truth be told, I should have found this on a preflight. It just shows you that even after flying for 37+ years and somehow managing not to bust my you know what, there's always something to learn. I've always run my hand along the leading edge of the prop. A holdover from what I was taught in 1981...long before composite props. An old dog has to learn new tricks!

Mark I know exactly what you mean. On my WW 200RV I check the metal leading edge, and otherwise just run my palm for smoothness. It would not find a crack unless the edge of the crack was ragged or curled up. I will up my game based on your experience.

I admit I am speculating here, and you will certainly learn a lot from Sensenich, but my guess is that what you have is a more cosmetic wrap of bidirectional glass over a wood prop which failed from blade bend and/or moisture change in the wood rather than a structural composite shell like a WW prop.
 
Hmmm...I look forward to my discussion with Sensenich tomorrow.
Keep us in the loop Mark.

I have a Sensenich GA prop on my O-340 that I quite like and am about the same hours as you, but have noticed a few patches of the black enamel on the aft side have come off, so if there is a potential for something more serious, better to find out before it comes to fruition!
 
Just had a good conversation with Don at Sensenich and I will be overnighting the blades to him tomorrow for inspection. I have confidence that we'll get this resolved quickly and am looking forward to getting it back on the plane asap. Now that I'm propless, I'm sure the weather around Memphis will clear up for perfect flying conditions.
 
Thanks for that Walt! I've started doing post-flight inspections too. It just makes sense. And thanks for posting Mark, I learn so much from VAF!

-Marc


I personally like post flight inspections myself, you have to get the bugs off anyway so thats a good time to look things over closely while your wiping it down.
That way you also have time to deal with issues you find and are less likely to let things go because the wife is sitting in the airplane waiting on you :eek:
 
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Unfortunately, more and more on this forum, no good deed seems to go unpunished! Thanks for the reminder to closely inspect whatever prop we're flying behind.

BTW, I like the Hartzell CS. My previous RV-8 has the older non-Blended Airfoil version and my current RV-8 has the BA. No problems with either prop, and my previous RV-8 has a fair number of hours on it.

+1 on this.

I am new to this site but wow! Sometimes A person can get discouraged...
 
The crack is 8-7/8" from the hub end of the prop.

Never having conducted a coin test, I thought I'd video doing this and put it up on youtube for anyone to watch and listen to. It's at https://youtu.be/_fzn2H0zJGg. I can't hear any difference between the area that's got the crack and other areas, but perhaps someone with a more experienced ear will hear a difference. Maybe it is just paint? I'll let Sensenich have a final word on that.

It certainly did not exhibit that dull sound when tapped across the "anomaly". It will be interesting to learn what the manufacturer finds.

BTW- a rotating imbalance would have no effect on blade vibrations, so - - not a factor.
 
Thanks for letting us know. Was there any evidence of impact damage from FOD, or any vibration issues during your flights?
 
Definitely looks like a crack and not a fracture in the paint. Does anyone remember the Florida RV12/Sensenich thread way back? I guess something to remember is; every manufacturer can, and will, produce a defective product.
Kudos to you for sharing.
 
I personally like post flight inspections myself, you have to get the bugs off anyway so thats a good time to look things over closely while your wiping it down.
That way you also have time to deal with issues you find and are less likely to let things go because the wife is sitting in the airplane waiting on you :eek:

Instead she'll be in the car honking the horn. Unless you live on a air park.
 
Instead she'll be in the car honking the horn. Unless you live on a air park.

That was my thought as well. I find there's more pressure to "let's get going" after the flight than before. Thorough checks before takeoff seem to be helpful in reassuring the passenger that you're making sure it's safe. Time spent after the plane is in the hangar is just seen as faffing about...
 
Ramp damage

Definitely looks like a crack and not a fracture in the paint. Does anyone remember the Florida RV12/Sensenich thread way back? I guess something to remember is; every manufacturer can, and will, produce a defective product.
Kudos to you for sharing.

Didnt the Rv12 thing turn out to be ramp damage?
Cm
 
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