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Prop Damage help


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After my flight yesterday and while cleaning bugs I noticed a little divit about 1/8" wide on backside of prop in meaty section close to spinner area.  I brought it up to my mechanic and he is concerned because after inspecting it with one of those jeweler magnification things he noticed a pinhole inside the divit.  Prop was OH'd with one new blade and hub in 2005 and has about 700hrs since.  What do you think are my options?  Does insurance cover things like this?  Close up pics below are with magnification.

Lucas

1962 M20C

 

 

 

 

 

 

prop1.jpg.9455ee9b84aba66f58aade37700d1db8.jpgprop5.thumb.jpg.b967fac98a57c8e1068c3e633f650915.jpgprop2.jpg.c43dd8d5e882c5546f94479fd305ef8d.jpgprop3.jpg.013a2f82694546948acefbc572571357.jpg

prop4.jpg

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9 hours ago, LucasC said:

 

After my flight yesterday and while cleaning bugs I noticed a little divit about 1/8" wide on backside of prop in meaty section close to spinner area.  I brought it up to my mechanic and he is concerned because after inspecting it with one of those jeweler magnification things he noticed a pinhole inside the divit.  Prop was OH'd with one new blade and hub in 2005 and has about 700hrs since.  What do you think are my options?  Does insurance cover things like this?  Close up pics below are with magnification.

Lucas

1962 M20C

 

 

 

 

 

 

prop1.jpg.9455ee9b84aba66f58aade37700d1db8.jpgprop5.thumb.jpg.b967fac98a57c8e1068c3e633f650915.jpgprop2.jpg.c43dd8d5e882c5546f94479fd305ef8d.jpgprop3.jpg.013a2f82694546948acefbc572571357.jpg

prop4.jpg

What's the face of the prop look like in this area?

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3 minutes ago, kmyfm20s said:

I have scratched but not chip my prop in that location when putting my cowl back on. Do you have any sharp corners on you cowl that could have done that? Just an idea.

I was wondering about that as well. If you look at the pictures, there clearly is a scratch headed to the chip.

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27 minutes ago, Marauder said:

I was wondering about that as well. If you look at the pictures, there clearly is a scratch headed to the chip.

No way could the cowling have made that deep of a crater, this definitely happened with the prop in motion...I fear the worst for that prop blade:wacko:

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That picture of the damage is on the blade face. I’d have a look at the manufacturer’s specs for blade damage and if there is none, this AC is a good reference. Proceed with caution and sound measurements and data  

Link  https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_20-37e.pdf

and relevant section 

 

243EF337-FA08-4865-BB0C-2D028786251D.png

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That’s a very Odd place for rock damage.

However, depending how many times that Propeller has been O/H that is the thickest part of the blade.

That being said, at 2700rpm there is a lot of tonnage being supported in that area.

If that nic was 3 inches in from the tip it wouldn’t be nearly as big of issue as it is where it’s at.

You will want the bottom(deepest) portion of that damage relived before it has a chance to propagate.

Very high Stress in that area.

I will attach photo of what that can end up looking like if not addressed.

Same area of the blade

 

In my Opinion:

Both Blades should be ground in that area to keep weight an aerodynamic contouring between the blades consistent while removing the damage.

To do a localized grind on that in the field will take care of the bottom of the damage, but it will also lead to potential balance issues an aerodynamic differences in the blades which cannot be dynamic balanced out.

 

 

C09B2342-827E-47D2-B1D0-2202EDEB3A60.png

Edited by Cody Stallings
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A few weeks ago, I found a gouge on the backside of my prop at an almost identical location to that of the OP's, so his type of damage is not a totally unique event. I thought my defect was tiny -- barely 1/16th of an inch at widest diameter and maybe  1/32 of an inch in depth in the middle of the thick heavy part of the prop  - I just ignored and kept flying.  I imagine there are are tons of folks flying with this type of damage, though blade failures are a rare event.  

 Now this thread makes me uptight enough look up the specific guidance in my Hartzell's manual posted below.  I'm surprised it requires reworking an area almost an inch wide.  I presently have nicely balanced blades with minimal vibration  :(.

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image.png.1f98439ea3dd294b5d4d94a5f433a5e6.pngimage.png.1f98439ea3dd294b5d4d94a5f433a5e6.png

 

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