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Crack??? Second/third opinions please....

Paul 5r4

Well Known Member
I was doing a preflight this evening and discovered this on the rudder control horn. It sure looked like a crack and seemed to be verified because of the spot on the end that wraps to the thinner fore/aft surface. It's only on the aft side of the rudder horn. No sign of anything on the forward side. With the exception of the crack appearing to go around the corner like you see in first picture, the right side was exactly the same as the left pictured here.

IMG_7497 by Paul Gray, on Flickr

On closer inspection.... I removed some paint with a scribe from the end and saw nothing below the paint. Feeling better. Here's a pic of that.

IMG_7502 by Paul Gray, on Flickr

Here is a picture with some of the paint removed. Note the paint that's not completely removed toward the left side. No split or crack noticed so, I'm thinking just a crack in the paint.

IMG_7506 by Paul Gray, on Flickr

Located at the end of the scribe is where the crack was. I could not get the paint removed all the way into the corner. I see no sign of a crack now. Reinforced my belief of paint only.

IMG_7511 by Paul Gray, on Flickr

One last picture with the area cleaned as good as I can get. The "crack" would have run in the middle of the wide area of thinned paint. I see nothing. I felt confident enough to fly afterwards.
I was thinking that this could NOT be a true crack into the angle because of a couple things. One, there is never much force applied to my rudder. I've never done any acrobatics, not even lite stuff. Nothing more then keeping the ball centered on takeoff and during flight. Now I just need to touch up the paint. Thoughts are appreciated.

IMG_7513 by Paul Gray, on Flickr
 
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the part is flexing at that location during use and it appears to have only cracked the paint. dye-penetrant will confirm. check all the attachment locations (rivets) for this rudder horn to make sure they have integrity.
 
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Perhaps I'm not seeing this correctly, but didn't the original crack appearance follow approximately this line? If so, more paint needs to be removed, ideally with some stripper and not sandpaper, and then dye. The sanding may obscure the crack.
 

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If there is a crack, you've probably smeared over it while removing the paint mechanically. I doubt dye will find the crack, or it will be obscured by the sanding/grinding marks holding penetrant.
 
Vlad. Painters tape line creating a weak spot in the paint is what an AP friend thought at the airport today. I know the mechanical removal really changed the appearance. I am convinced this extended no deeper than top layer of paint. I will get the dye penetrant and see what that yields. Your right, this side may or may not yield results but I still have the same on the right side. See it I can get the paint removed another way. I did have a good look at the rivets and everything appears normal. Thanks everyone for your input.
 
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Be careful when performing dye penetrant inspections. It may seem like a simple inspection but, if done improperly, can be a completely invalid inspection. Make sure the area to be inspected is both free of paint/coatings but also make sure to clean the surface with solvent and allow it to dry thoroughly before applying the penetrant. Allow the penetrant to be on the surface for at least 10 minutes or more before removing. Remove with a solvent dampened cloth. Do not put the solvent directly on the are to be inspected. Again, allow to dry completely. Next apply the developer and allow at least another 10 minutes before inspecting. Red dye is not typically use in the aerospace industry any more because if there is any left on a surface, future inspections using fluorescent dye may not be effective. A very small quantity of red dye will destroy the fluorescing ability of the fluorescent dye.

If you have any Non-destructive inspection questions (Liquid Penetrant, Magnetic Particle, Ultrasonic, Eddy Current or X-ray) please feel free to send them my way. I have almost 35 years experience in the inspection industry.
 
Just me

This thread has taught me to look at these paint lines fresh after paint and make sure I document what is a paint line and not a crack. I have been fooled before on race cars, and i forgot that lesson. thanks for bring it back from the depths of my mind.
 
If there is a crack, you've probably smeared over it while removing the paint mechanically. I doubt dye will find the crack, or it will be obscured by the sanding/grinding marks holding penetrant.

Smeared Aluminum, due to sanding the suspected crack area, can be removed by locally applying, Pasa-Jel 101, for 20 minutes. Rinse thoroughly and dry. Then Penetrant Inspect.
 
Been painting for 30 years . To me that looks like a simple paint edge from being painted while a portion of the part was taped off .
 
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