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  #11  
Old 09-04-2018, 11:43 AM
DaleB's Avatar
DaleB DaleB is offline
 
Join Date: Sep 2012
Location: Omaha, NE (KMLE)
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As promised, pics of the cracked part. The crack was pretty obvious. Some of the paint had flaked off before (appears not to have been scuffed before priming). I used a screwdriver blade to verify the crack, hence the battering of the end. The other side was fine with no crack. I have been inspecting this part at each CI, so it went from zero to pretty bad in the space of a year and maybe a hundred hours.



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Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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  #12  
Old 12-18-2019, 02:25 PM
Strappe Strappe is offline
 
Join Date: Jul 2017
Location: Omaha, NE
Posts: 42
Default A new issue with this?

Yesterday, while routing 1/4" tubing during the installation of the AOA Retrofit Kit, I discovered the crack (complete break) in the bearing brace Part# F-1206F affected by SB 14-12-06. We bought the plane from its builders in 2017 and have put about 200 hours on it. The aircraft documents reflect compliance with the SB via replacement of the brace. I have done two condition inspections, most recently in September, and never noticed this crack, though I admit I was not looking for it. I had checked the torque seal on each occasion, but I believe the crack would have been hidden behind the flaperon push rods.

This break looks to me to be the result of a rather violent force. The support tech at Van's thought it the result of a direct blow of some sort. He shared the photos with their engineers, and they arrived at the same conclusion.

That seems very odd. That's not a place where it would be easy to strike the brace with enough force to break it. Even so, the dent in the brace away from the crack and what looks like a scrape in the metal are hard to dismiss.

(I have also posted an image of a problem I found at the last inspection in September where 3 of 4 rivets were missing from a rib.)

Anyone have other thoughts?





Last edited by Strappe : 12-18-2019 at 10:03 PM. Reason: add image links
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  #13  
Old 12-18-2019, 03:22 PM
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Piper J3 Piper J3 is offline
 
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Count me in... I have been monitoring the Flaperon Bearing Bracket now for four years at Annual Condition Inspection. This year I see a small propagation of a crack on the right flange of the bracket. I really didn?t want to remove the fuel tank and so I satisfied this SB with yearly inspection. TT is 520 hours. I have the parts for the SB compliance and will complete the work before flying season resumes in the spring.
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 750

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Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father - CFI) - USAAF 1st Lt. Captain B-17H
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  #14  
Old 12-19-2019, 07:43 AM
bobg56 bobg56 is offline
 
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Location: Peachtree City, GA
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I found mine cracked as well. The cracking is due to the support bracket attach flange when made was bent with the grain of the metal. There are two bends, one is against the grain the other with the grain which will usually crack in time. It was easier to drill out the rivets after cutting the bracket out using a cutting wheel. The kit uses an extruded angle instead of a double bent piece of aluminum. It's not easy working contorted plus it was June and plenty hot, I had to have fans blowing on me to keep all the sweat out of my eyes.
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  #15  
Old 12-19-2019, 10:42 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by bobg56 View Post
I found mine cracked as well. The cracking is due to the support bracket attach flange when made was bent with the grain of the metal. There are two bends, one is against the grain the other with the grain which will usually crack in time. It was easier to drill out the rivets after cutting the bracket out using a cutting wheel. The kit uses an extruded angle instead of a double bent piece of aluminum. It's not easy working contorted plus it was June and plenty hot, I had to have fans blowing on me to keep all the sweat out of my eyes.
Though it is a "best practice" to make bends in light aluminum stock perpendicular to the grain of the material, as you pointed out, it is not always possible, and it was not likely a factor in this instance.
FEA analysis done after the first discovered crack indicated that for long term durability, a different part design would be required. If it had been as simple as realigning the grain direction, that change would have been done for the production of the part.
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  #16  
Old 12-19-2019, 10:50 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Strappe View Post

Anyone have other thoughts?




A major abnormal load event would have had to occur to cause the damage visible in the photos.

I think the flapperons and the entire flapperon system, including all hinge brackets, etc., should be very carefully inspected.

missing rivets - In the photo it looks like all 4 are missing. Were any loose rivet pieces found loose in the bottom of the tail cone? An abnormal, high localized load applied under the bulkhead (such is lifting from below) could have sheared all the rivets.
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Scott McDaniels
Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop Manager
FAA/DAR
RV-6A (aka "Junkyard Special ")
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  #17  
Old 12-19-2019, 07:03 PM
Strappe Strappe is offline
 
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So, #rvbuilder2002, do you think this was related to unusual load on the fuselage rather than to a direct impact on the brace instead? I ask, because last year during the CI, I was trying to get better placement of pads on a saw horse by lifting the aircraft with my back in the bulkhead line of rivets and hear a long pop at one point. I was afraid I had damaged something, but I did not find anything after lookin it over carefully inside the fuselage. I did not see any rivet parts anywhere.

This year, however, I noted the missing rivets and I saw a single rivet head lying on the fuselage floor in the tail section between the bulkhead I had lifted on and the next one aft. That's when I also noticed the 4 missing rivets, all of which I replaced. I don't know if I looked behind the flaperon tubes at that point. The bulkheads and all fuselage metal is not distorted or bent anywhere on the inside or outside of the airplane, and it never flew any differently after the CI last year (for what that's worth).

There is a rivet intact in the lowest hole.

Here is a wider view of what I found this past fall.
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  #18  
Old 12-19-2019, 08:02 PM
RFSchaller RFSchaller is offline
 
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Did the rivet head show any signs of being drilled out? It may a remnant from the SB compliance or one that was replaced during construction.

If those three rivet holes without rivets are in alignment it seems unlikely there was an overload especially if the rivet holes show no deformation.

On the other hand I think Scott is right about the bracket crack being an overload. It looks like a ductile tear in the picture.
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  #19  
Old 12-19-2019, 08:02 PM
AirHound AirHound is offline
 
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Quote:
Originally Posted by Piper J3 View Post
Count me in... I have been monitoring the Flaperon Bearing Bracket now for four years at Annual Condition Inspection. This year I see a small propagation of a crack on the right flange of the bracket. I really didn’t want to remove the fuel tank and so I satisfied this SB with yearly inspection. TT is 520 hours. I have the parts for the SB compliance and will complete the work before flying season resumes in the spring.
Jim do the wings have to come out or off, and flaperons and push-rods disconnected to take out the original and install the new SB bracket? Doug
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  #20  
Old 12-19-2019, 08:32 PM
AirHound AirHound is offline
 
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Anybody, do the wings have to come out or off, and flaperons and push-rods disconnected to take out the original and install the new SB bracket?
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