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My SB 14-12-06 experience

DaleB

Well Known Member
So, during our condition inspection I checked the bearing bracket brace for cracks, as usual... and there it was. A big ol' horizontal crack. Nuts!

So, for whoever at Van's designed this particular part of the airplane... I'm really sorry for all the bad things I said. Heat of battle and all that, you know. I'm sure it's simple to install all this stuff while the airplane is being built, and you never imagined some wheezing, sweating, chubby old guy would have to spend a couple hours contorted into a VERY uncomfortable position to drill it out and replace it.

I don't know how widespread these cracks are, but it was pretty impressive and I'm glad I was checking it every year per the SB.
 
Yeah, it was a pain, but actually easier than I anticipated to remove the old rivets and bracket. It helped that I had the rear window out for replacement.
 
Like you, I have not replaced, but instead do inspection annually on this SB.

Is it possible to post a picture of the actual crack so I know better what to look for?
 
Sure, I'll get a couple of pics when I'm at the hangar again tonight (assuming I'm not on this "emergency" work call for the rest of my natural life). The location is pretty much exactly as shown in the SB, opposite side I think. In the last couple of inspections I'd used a borescope to get a close up look; this year I didn't need it. I found it on the right side... it was pretty obvious.
 
Does fuel tank need to be removed to drill out old parts and install new flap bracket SB? I have split baggage floor and 2-pc rear bulkhead.
 
It?s been awhile since I did it, but I did pull my tank when I did the mod. I also split the baggage floor and bulkhead when I had the tank out. Even if you can do it with the tank in it is certainly easier with the tank out of the way.
 
I found it difficult to get to the work area even with the fuel tank, rear window and rear bulkhead removed.
One thing helped was a small 90 degree drill used to remove the existing rivets.
Also, it would be good if you can find a young small person to help.

I wonder if the side loads due to taking wing on and off could be the cause of these cracks. There?s good deal of pressure on that part while pushing the wings inplace while being installed.
 
SB14-12-06

I'm one of the few RV-12 owners that actually trailers to the airport. 183 hours total HOBBS time, and about 65 wing installations. Annual in June, inspected the bracket, no cracks yet. I think I just jinxed myself 😀
 
I wonder if the side loads due to taking wing on and off could be the cause of these cracks. There’s good deal of pressure on that part while pushing the wings inplace while being installed.

With the way the flaperon system is designed, wing removal/installation has no bearing on cracking in the bracket as long as everything is built and assembled correctly.
As designed, the cylindrical guide bushing is intended to be a slip fit into the torque tube (the KAI specifies removing burns a and any paint or powder coat from the inside of the tube, and the service intervals chart specifies a light application of grease periodically).
The KAI also specifies a small gap at the inboard end of the clevis tab on the flaperon.
If these two details are correct, there is no way for the insertion of the wing to induce a load on the bracket.
FEA analysis showed that flaperon movement under flight loads, does induce a cyclic load that could, over time induce cracks.
It is entirely possible that the reason some airplanes have had cracks occur at a much lower total flight time than others, is because of one or both of these factors.
 
Back Country,

Thanks for the unintended compliment about young small people! At 65 (when I did it) and undisclosed weight I would qualify for neither descriptor!😝

Rich
 
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.

IMG_0497.jpg


IMG_0496.jpg
 
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?

IMG_0168-L.jpg

IMG_0181-L.jpg


Bulkhead-missing%20rivets-L.jpg
 
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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.
 
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.
 
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.
 
Anyone have other thoughts?

IMG_0168-L.jpg

IMG_0181-L.jpg


Bulkhead-missing%20rivets-L.jpg

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.
 
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.
IMG_0865-X4.jpg
 
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.
 
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
 
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?
__________________
Doug
 
The original SB 14-12-06 advises to remove both wings, and the fuel tank. Some have written that they were able to do it without removing the fuel tank. Not sure how, however, unless you can get out the blind rivets on the R side by going at it under the fuel tank from aft of it.

The engineers at Van's are convinced there was a direct impact on the brace, and assured me that load forces on the airplane would not affect it that way, and would have done damage elsewhere that would be obvious.
 
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The engineers at Van's are convinced there was a direct impact on the brace, and assured me that load forces on the airplane would not affect it that way, and would have done damage elsewhere that would be obvious.

The damage visable in the photo could have occurred from a direct impact on the flapperon torque tube. Such as a hard hit during wing installation when a flapperon wasn't properly aligned.
Please do a thorough inspection of the flapperons and related systems.
 
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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.

That is the exact type of scenario I was thinking of.
The pop you heard was likely the rivets letting go.
The last one didn't because once the others shear, it just became a pivot point that the two parts rotated on.
 
Yes, the wings come off so you can remove the flapperon linkage to get access to repair area, I also removed fuel tank, it's pretty tight if your a big guy.
 
The damage visable in the photo could have occurred from a direct impact on the flapperon torque tube. Such as a hard hit during wing installation when a flapperon wasn't properly aligned.
Please do a thorough inspection of the flapperons and related systems.

Will do. I will ask some other RV-12 owners to take a look as well.

This is the only time I have ever removed the wings, and I have yet to install them. I removed them to install the AOA kit.
 
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?

IMG_0168-L.jpg

IMG_0181-L.jpg


Bulkhead-missing%20rivets-L.jpg

The AN3-?A bolts through the rod ends looked a little long to me, then I noticed that the nuts are AN364 instead of (probably) AN365 -- might want to check those. Also, I think the servo arm angle looks a little much, could be the washer stack-up? Usually it's bolt head, Big 5702 washer, Small 5702 washer, rod end bearing, small 5702 washer, arm, AN960 washer, AN365/MS21042 nut.
 
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The nut is correct. The 12 KAI 32 specifies an MS21083-N3 which is similar to the AN 364. Saving weight wherever they can. :)
 
The AN3-?A bolts through the rod ends looked a little long to me, then I noticed that the nuts are AN364 instead of (probably) AN365 -- might want to check those. Also, I think the servo arm angle looks a little much, could be the washer stack-up? Usually it's bolt head, Big 5702 washer, Small 5702 washer, rod end bearing, small 5702 washer, arm, AN960 washer, AN365/MS21042 nut.

32_12%206-L.jpg
 
SB 14-12-06

I'm in the process of my condition inspection right now. When inspecting for this service bulletin, I noticed a crack on the pilot's side of the bracket. I called and ordered the fix and today was able to remove the fuel tank. I don't see how you could possibly do this repair without removing the fuel tank. My airplane has 575 hours on it.
 
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