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SB 18-02-02 Potential cracking in the horizontal stabilator front spar

Before Further Flight?

My RV 12 is here in Marco Island for the month, far from its home base in Marysville, OH and my Rotax/RV12 qualified shop in Delaware, OH. I concur as to some confusion in the wording of SB 10-02-02 (in no small measure owing to my lack of builder/repair skills). In particular it takes some effort to determine where the ?inspection? for cracks begins and ends, and where the ?fix? begins. This post raises a good question on the scope of the inspection ? is it required to fully remove the stabilator and spar brackets before conducting the inspection, or is it sufficient to bore scope, magnaflux or penetrant dye the spar area with just the tail cone fairings removed? I am very fortunate to have a master mechanic willing to do whatever is required, including fabricating the new parts and installing the full fix. But, it would be much more efficient if an inspection could be done short of removing the stabilator assembly. Because if no cracks are found, we can button up the fairings and fly until next annual/100 hours. I guess the bottom line issue is ? can the SB be read to permit a compliant inspection without removing the stabilator? Given the SB?s admonition about the potential difficulty in discovering any cracks, would this be safe in any event? My RV was built and flew the end of 2013, and has now 200 hours; always hangared. Thank you for any advice.
 
Exercoupeguy...in order to do the SB inspection the Stabilator needs to be removed and parts disassembled in order to inspect for cracks...according to the SB.
Things you need to know...
For SLSA RV12s the SB is required to be done.
For ELSA RV12s the SB is not mandatory for further flight, per the regulations, but recommended.

In my opinion...
Inspecting according to the SB without actually making the SB repair, would be a waste of time, since you would have to do it all over again. (Unless you are using it for training or something and need to get it flying again right away.)
Inspecting by only removing the fairings to look at the HS spar would not even begin to cover what the SB details.

So far, according to the previous posters, only high time RV12s have shown cracks, but that may not really mean anything, depending on how individual planes have been treated.

It is legal to continue flying an ELSA RV12 with this SB not completed, and I'm sure many ELSA RV12 owners will continue to do so until they get the parts and decide to do the SB.

So, you need to decide what is prudent, for you.

Just my 2cents worth
 
Thank you for the sound advice. I am very fortunate to have an experienced mechanic ready in the next couple of days to open things up and install the sb fix.
 
Exercoupeguy...in order to do the SB inspection the Stabilator needs to be removed and parts disassembled in order to inspect for cracks...according to the SB.

I'd like to see Van's publish an official ruling/clarification of this. The wording in the SB is vague regarding initial inspection requirements. Are you suggesting that the entire fleet of RV-12's be grounded immediately (including at remote airports) until the stab is removed, hinges removed, dye penetrant applied and inspected? That is unreasonable at best. The SB requires that the mod be performed at the NEXT 100 hour/condition/annual if no cracks are found in the visual inspection. That makes sense.
 
Are you suggesting that the entire fleet of RV-12's be grounded immediately (including at remote airports) until the stab is removed, hinges removed, dye penetrant applied and inspected? That is unreasonable at best.

No (at least not in a binding regulatory sense).

An E-LSA RV-12 owner is not bound to follow any inspection requirement published in a S.B. An E-LSA owner can make their own determination regarding what is an appropriate action for their airplane.

S-LSA is bound to follow it.

Most people would consider it also unreasonable if Van's was very casual about the inspection requirement, and someone died because of it.

This is a very new discovery with not a lot of information yet, and evidence of an airplane with less than 1/3rd the hours of the prototype, having cracks worse than the prototype (the cracks in the SB document photos) added to the uncertainty.
When dealing with uncertainty's, a very conservative approach is the right approach.
 
Stab Bearings

I plan to order the parts for SB 18-02-02 and SB 18-02-03.
I would also like to order parts for the SB 16-08-01 stab bearings service bulletin, which brings up 3 questions:

1: What are the MS 21256-1 Lock Clips. I saw no mention of them in the SB. Do I need them? And, if so where do they go?

2: Two different bearing are mentioned: (1) VA146 replacement or (2) Bearing DW4K2X.

I will have the stab off, and I will be removing the current bearings. Is it best to reinstall with the locktite, or just replace them with the new Bearing DW4K2X ? Since I will have them out anyway, I would like to perform the best fix.

Thanks. Any thoughts or help in understanding will be greatly appreciated.

Tom
 
The clips are used to lock the turnbuckles in the stabilator cables. You will need at least one if you elect to relieve the tension in the cables to facilitate reconnecting them. (Because the original will most likely be destroyed removing it.)

It?s a standard part, cheap, and a good idea to have a few on hand if you do your own work.
 
For what it?s worth

Tom,

I was following the same logic and concerns so I spoke with Support and parts at Vans on Wednesday.

What I learned was first if you followed the SB procedure on SB 16..... involving the bearing and if it checked out good no need to replace it. The new bearing is no different than the current bearing, and my choice is if it’s not broken or not a new design improvement, I’m not going to mess with it. Your choice however.

The clips mentioned are for the adjustment turnbuckle/s of the cables to the stabilator accessed through the belly inspection holes. These lock the turnbuckle after the correct tension is achieved. Parts at Vans said two clips are included with the parts for SB 18-02-02 in case there is a need to readjustment the cables after inspection or compliance of this SB. However this will only accommodate one turnbuckle

Hope this helps.
 
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My A & P and I removed my stabilator, inspected the spar and found no cracks. We will proceed with installing the band-aids when the parts arrive, hopefully today so I can get back in the air. My RV12 has 250 hours, is hangared and I place a gust lock on when parked outside.
 
The clips are used to lock the turnbuckles in the stabilator cables. You will need at least one if you elect to relieve the tension in the cables to facilitate reconnecting them. (Because the original will most likely be destroyed removing it.)

It?s a standard part, cheap, and a good idea to have a few on hand if you do your own work.

Thanks John. That answers the clip question.
Still looking for guidance on the bearings, per my post #57 above.

Tom
 
Tom,

I was following the same logic and concerns so I spoke with Support and parts at Vans on Wednesday.

What I learned was first if you followed the SB procedure on SB 16..... involving the bearing and if it checked out good no need to replace it. The new bearing is no different than the current bearing, and my choice is if it?s not broken or not a new design improvement, I?m not going to mess with it. Your choice however.

The clips mentioned are for the adjustment turnbuckle/s of the cables to the stabilator accessed through the belly inspection holes. These lock the turnbuckle after the correct tension is achieved. Parts at Vans said two clips are included with the parts for SB 18-02-02 in case there is a need to readjustment the cables after inspection or compliance of this SB. However this will only accommodate one turnbuckle

Hope this helps.

Thanks Patrick. I just saw your reply. When you called, did you get any explanation of the difference between the 2 bearing choices in the SB.
IE; VA146 replacement, and Bearing DW4K2X ?

Tom
 
The text in the SB says "If a bearing and flange becomes damaged order a ?VA-146 Flange Bearing? for replacement. If
you wish to just replace the bearing order ?BEARING DW4K2X? for replacement.


The bearing with flange is the VA-146 part #. The flange is what the bearing is a press fit into, and what you are loctiting it into if it is found to be loose.

This can be seen in the KAI Section for the tail cone.

So the Bearing part # is for just the bearing... should you need to replace just that portion (got loctite into it, etc.). If the SB work is completed properly, you should not need either part.
 
The text in the SB says "If a bearing and flange becomes damaged order a ?VA-146 Flange Bearing? for replacement. If
you wish to just replace the bearing order ?BEARING DW4K2X? for replacement.


The bearing with flange is the VA-146 part #. The flange is what the bearing is a press fit into, and what you are loctiting it into if it is found to be loose.

This can be seen in the KAI Section for the tail cone.

So the Bearing part # is for just the bearing... should you need to replace just that portion (got loctite into it, etc.). If the SB work is completed properly, you should not need either part.

Thanks Scott. That was exactly what I needed. Thanks, so much for your explanation and help.........Tom
 
Still unclear on SB 16-08-01

I know, wrong thread, but the questions have come up here and it is pertinent if the stab is removed for SB 8-02-02

If the bearing is not loose then you don't have to fix anything, but will still have to bang on the stab ends at each annual and make a logbook entry that satisfies SB 16-08-01. Plus, the bearing could become loose at some time in the near future, especially with all that pounding back and forth, and the stab would have to come off again!

BTW, how do the guys with fiberglass stab tips bang on those tips to satisfy the SB?

So fixing the bearing while the stab is off makes a lot of sense -- to me anyway.

Questions are:
How to tell if the bearing itself is bad and then just order the bearing and the green Loctite? Why green Loctite, isn't that the one that wicks in without disassembling the parts?

If you damage something and order the VA-146, I assume the bearing comes pressed into the flange but is it Loctited in? Apparently the original VA-146 were not Loctited, that is why they can come loose. If the VA-146 is now Loctited, should it not have a part number suffix indicating it is different than original?
 
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I know, wrong thread, but the questions have come up here and it is pertinent if the stab is removed for SB 8-02-02

If the bearing is not loose then you don't have to fix anything, but will still have to bang on the stab ends at each annual and make a logbook entry that satisfies SB 16-08-01. Plus, the bearing could become loose at some time in the near future, especially with all that pounding back and forth, and the stab would have to come off again!

BTW, how do the guys with fiberglass stab tips bang on those tips to satisfy the SB?

So fixing the bearing while the stab is off makes a lot of sense -- to me anyway.

Questions are:
How to tell if the bearing itself is bad and then just order the bearing and the green Loctite? Why green Loctite, isn't that the one that wicks in without disassembling the parts?

If you damage something and order the VA-146, I assume the bearing comes pressed into the flange but is it Loctited in? Apparently the original VA-146 were not Loctited, that is why they can come loose. If the VA-146 is now Loctited, should it not have a part number suffix indicating it is different than original?

The bearing being loctited in is not the engineering requirement. The requirement is that there be a proper interference fit so that the bearing stays tight in service.

The VA-146 used to be assembled by an outside vendor in which a quality control problem developed, so production was brought in house.

The use of the loctite as an alternate method of bearing retention when one is found to not be as tight as desired, to avoid needing to replace the bearing flange which would be a big job.

People do use the green loctite by letting it wick between parts in some situations, but that is not what Loctites installation requirements say is acceptable.

Tests were done, to see if wicking it from the outside would be sufficient.

It wasn't.
 
BTW, how do the guys with fiberglass stab tips bang on those tips to satisfy the SB?

Excellent point Tony.

I have the fiberglass tips on order and was going to install them at the same time I'm doing SB 18-02-02 and SB 18-02-03. Looks like I might be going through the loctite process on the stab bearings also, if I'm going to install the tips. All this on a plane that isn't even flying yet! Oh well!

Jim

PS: Just read the procedure in the "Maintenance Manual" for loctiting (is that a word) the bearing into the housing. Doesn't seem like too big a deal and will solve the stabilator tip issue.
 
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SB 18-02-02 and SB 18-02-03 parts backordered

Van's sent out email indicating that both these service bulletin fix-um-up kits are now out of stock, and delayed until March 5th. I did receive the SB 18-02-03 kit today, but no such luck on the SB 18-02-02 kit.
 
Found a crack

120323 290 hours on the Hobbs. I had not applied dye penetrant before but had watched the application on larger part.

Facing forward, it was at the right outboard hinge bracket, upper bolt nutplate, inboard rivet. It was about 1/8 inch and went into or came out from under the rivet. The good news is I need only one stop drill whereas it appears to me the SB example would need two.

I needed the dye to see it. In fact, I missed it the first time with the dye but was not satisfied with the developer cover, too thick I thought. Since it was a tight area, the spray dye was too much and is probably still wicking down the spar toward the tip. I did spray it lightly.

The next 3 or 4 times I wiped the dye on with a rag. Wiping on seemed effective as long as I kept the surface wet. Cleanup was much easier.

Once I knew where the crack was, I could see it with a 10x loop or use the macro setting on the camera. I could not have found it without the dye.

I tried it four times instead of three because when I wiped the third test, I could see the crack but could not see the end. On the fourth test, I center punched the spot with the dye and developer still showing the end, I hope.

The servo tabs did not present a dye indication.
 
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Van's sent out email indicating that both these service bulletin fix-um-up kits are now out of stock, and delayed until March 5th. I did receive the SB 18-02-03 kit today, but no such luck on the SB 18-02-02 kit.

Ordered the stab SB last week. Called and was told it didn’t ship. OK with grounding the plane while the parts come in (took it apart before I had the parts). Time to wash and wax.
 
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Some history on 120323

I built the airplane and have been the only one flying. From my -9A flying, I tend to keep the stick aft when taxiing. If there is wind, gusts or airplanes operating nearby, I tie the control stick. It certainly is possible that there were events where the controls were not tied, but it was not routine.

Of course, with fatigue, a single event could load the spar and initiate a fatigue crack.

There are two ways that could be an issue. Of course, a gust lifting the tail would put the top stop into compression. Also, holding the stick aft while taxiing or landing would do the same. If initiated from the aft stick, there would also be a load couple between the stop and the upper control horn.

Just some thoughts.

I did not look closely at the stop bushings until I had removed them. Two are more heavily marked. I need to remove the paint to see if the bushing is marked. As you start to remove the brackets and bushing, document the condition of the bushings.
 
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HS-1224

Taking a look at page 09.04, the four HS-1224 doublers ending at the bend of the flange of the HS-1202.

In my view this is the cause of the crack starting on the hard point at the end of the of the doublers.

Bending the HS-1202 flange causes the tension on the outside of the bend and the doubler adds a point load at the compression side of the bend.

If the end of the HS-1225 doubler was not deburred this would add to the problem.

This doubler should be wider and have rounded corners to spread the loads over a larger area.

For the people that have not built the spar may want to consider this.

If you are EAB you can change this or get a OK from vans to make a change in this.

In my View Vans should change this doubler design and make it available to the new builders.

The new HS-01231D doublers in the back of the hinge bracket are the fix for this problem.

The shear component added to the hinge is a good fix.

This is my view and Vans may have spent more time and have a better understanding of the problem

Joe Dallas
 
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This is my view and Vans may have spent more time and have a better understanding of the problem

Quite a bit of time was invested using FEA modeling to analyze the structure and develop a modification.

The cracks that have been detected so far don't coincide with the top and bottom edge of the HS-1224.

The purpose of the HS-01231D is to act as a stiffener for the web of the HS-1203 Spar Channel and reduce the flexing loads across the bolt holes. Added strength for shear loads was not needed.
 
This connection is needed

Scott
I was talking about the shear connection of the HS-0123C , HS-0123B and the HS-1202 Flange.

This connection is needed. ( it is taking the load to the top and bottom spar flange )

The crack is above the nutplates and at the base of the bend of the HS-1202 and above the HS-1224 doublers.

The bend of the top flange was probably in the break at that point.

I believe that crack started at the bend and was working to the rivet hole.

Also Note: that the crack almost matches the profile of the K1000-3 Nutplate

The bolts are in tension pulling on the nutplates.

The fix that Vans made is a lot better than the original.

I believe that my view is correct.


Joe Dallas





Quite a bit of time was invested using FEA modeling to analyze the structure and develop a modification.

The cracks that have been detected so far don't coincide with the top and bottom edge of the HS-1224.

The purpose of the HS-01231D is to act as a stiffener for the web of the HS-1203 Spar Channel and reduce the flexing loads across the bolt holes. Added strength for shear loads was not needed.
 
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Van's sent out email indicating that both these service bulletin fix-um-up kits are now out of stock, and delayed until March 5th. I did receive the SB 18-02-03 kit today, but no such luck on the SB 18-02-02 kit.

I was told the same thing about the SB 18-02-02 kit when I ordered it last Tuesday. However, it showed up today, so I hope your's is on it's way.

Jim
 
some photos of crack in 120323

When I saw SB18-02-02, I was thinking about blowing it off. Can't be me. I am too careful with the airplane. That thought was short lived as I know that Van's engineers are careful and thoughtful with subjects like this.

I ordered the dye penetrant kit and started in. It was a learning curve but not difficult at all. I did find a small (very small crack) and I played with the testing to see if the result was repeatable. I thought that it may be helpful for those trying dye penetrant for the first time to see some of the steps that I took.

It was hard for me to control the dye and developer spray into the tight corners. The first try was a mess with dye migrating into the stab skins (probably still migrating). And I did miss the crack.

Next, I used a rag to apply the dye. I kept wiping at several minute intervals for the next 15 minutes. The dye appears oily and did migrate into the crack and around the rivets.

1
i-rnSNdMK-XL.jpg


The next photo is out of sequence, but shows the crack, highlighted with the dye. Later photos show why the dye is a must.

2a
i-J4H7N7R-XL.jpg


In one series of tests, the dye is very visible at the rivet, but barely showing at the crack.

3a
i-qFq64t4-XL.jpg


Eight minutes later, the crack is visible.

4a
i-3tZQhNQ-XL.jpg


With the area wiped with the solvent, the crack is barely visible at this angle. It could be still damp with the solvent.

5a
i-Swn4JDL-XL.jpg


Another test shows the crack. This test used a lighter application of developer. You can see the dye from the first test migrating along the spar.

6a
i-XHdRXK6-XL.jpg


Five minutes later, the dye is spreading. Watching how the presentation progresses is helpful, at least it was to me. I did this last test so I could see the end of the crack. Wiped clean, you can see the crack but not the end. Noticed that I missed with the punch.

7a
i-M5fFfh4-XL.jpg


The second punch hit the end of the crack, then I wiped the area clean. The crack has again disappeared

8a
i-cfdCp2g-XL.jpg


For those of you that have this chore coming up, hope this helps. I would not have seen the crack without the dye penetrant test. I did flood the area with solvent, tried the developer without additional dye, and had a very weak signature. Wiping the dye as described above again produced very clear signatures at the rivet heads and crack, without the mess.

Van's staff said that the crack was not long enough to be a concern and just perform the SB.
 
Thanks John for the photos.

Your crack is consistent with my view.

Note: the nut plate rivets are at about a 20? angle to the top of the spar.

The photo in the service bullion the rivets are parallel to the spar.

It look like Vans made a change in this at some point.

Maybe to move the rivet away from the base of the bend in the spar flange.

The HS-1209 spacer at the back of the hinge is not doing the job in my view.

If the rib was shorter in the X access and the spacer was in between the rib and the spar the loads would be better dispersed. ( X to the left Y to the sky ) My View

The pulling back on the stick to fast or hard is putting a lot of stress on the top hinge bolts.
inertia of the stabilator and counter weight is not helping.

My View

I would like to see any photos of any cracks at the bottom of the spar.

For those that contacted me directory thanks for your help in understanding this problem.

Thanks to Vans for handling this before and failures.

Joe Dallas
 
Thanks for the pictures and explanation John.

In several pictures I see what looks like a crack by the left rivet of the nut plate. However, it doesn't seem to absorb dye.

Jim
 
Jim, thanks for the observation. I looked at it with a 10x loop and more camera shots, playing with the lighting. It looks like a crater but green primer is at the bottom. That means it was there before the airplane flew.

I did the dye penetrant test again. I "flooded" the area with dye using a Q-tip. No signatures at 12 minutes, but plenty of signatures around the rivet.

I will try to sand to get to the bottom of the green and test again. Whatever it is occurred at construction. It could be growing at the lower portion, but no indication.

Update: Buffed out with 400 grit paper. No marks, retested, no indication.
 
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Recommendations on Dye Penetrant Kits?

Looking at ACS, which dye penetrate kit would you recommend?

Thanks,
 
I used the Magnaflux Spot Check. It was $80-90 from Zoro, free shipping, no tax. They said a week or two for shipping, but it came in 4 days from Texas to Kansas, UPS.
 
I?m not going to bother with looking for racks, just install the fix. If you find cracks the solution is the fix, so what?s the point in inspecting if you just put in the mod?
 
Post #59

So sorry for some mis-information reference the clips for the turnbuckles. These clips are not in the SB18-02-02 parts. It was actually 2 cotter pins with also have an MS##### similar to the clips.

Bottom line....no clips so if you anticipate re-adjusting the turnbuckles order additional clips.
 
I got 2 clips and cotter pins with my kit.

Mitch Garner
RV12 flying year 3

I had ordered the SB package earlier and picked it up today. Two cotter pins and nso cable clips. Vans is out of these clips and so they’re now on ‘back order’. Could be a long wait so I was advised to locate clips from another vendor.

On another SB note, is there something special about the aviation penetration dye that is lacking in more common penetration dye kits available at the auto parts store? What are people using and where have they purchased it?

Thanks for info.
 
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Jane is having major surgery SB 18-02-02 the elevator.

Jane is very fortunate in that she is rich with friends that want to help her out.:) This time it was major surgery SB 18-02-02 the elevator.
Dave, friend and A&P mechanic, came over with his specially built table just for the RV-12 fleet.
His table is already reserved for use for another RV-12 at Wings Field.
Certainly made the job a bit easier, just slide it under adjust height to match and we were all set.

Service Bulletin 18-02-02 to address any potential cracking in the horizontal stabilator front spar.
Did not find any cracking on Jane:cool:, however, performed the SB as a prevention measure.

Had to hold for 24 hrs due to finding one of the bearings would slip out of the flange with little pressure.
Put Loctite on it and checked the following day and we were good to go for Elevator installation.

Click on image to see Time Lapse video of the surgery.
]

40580720461_1cd572de70_b.jpg

26709157108_0eb03ea29b_b.jpg

40538514912_8e13ffebc8_b.jpg
 
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Hey Skunkworks, Thanks for the visual. Did you loosen cables in the process couldn?t tell. Or, just detach at the HS horns? Does that table adjust for absolute fit or just stuff a magazine or something to align? Thanks again!!
 
I?ve done two so far and did not loosen the cables. Using the table, you might have to nudge the hs a little up or down when installing but works well and keeps the fuselage from getting scratched. I did my own using the table with no help whatsoever. You could use other stands, props,etc. having a stand that rolls is a big help.
 
Got mine done yesterday. 900 hours on plane no cracks found. I went ahead and installed the upgrade. The task is not as bad as it first appears. Vans did a good job designing this upgrade it really adds strength to that area. In the homebuilt world your really never done building.

Thanks to Vans for catching this and providing a fix at a reasonable cost.
Gone undetected this could have been a serious issue.

Brad Stiefvater
Salem SD
N124BJ First customer built RV 12 to get Airworthy and Fly
 
ME TOO - -

Just finished an hour ago. Was able to pull on cable enough to get hooked up again. Not easy, but doable. Agree, it certainly strengthened the hinges. Getting the two main bolts back in is not a fun job. Getting thin washers in place and pushing bolts in to hold them is a challenge. The new gussets make it even harder to get fingers into the area. No signs of any cracks. 1,185 hours.
 
Just finished an hour ago. Was able to pull on cable enough to get hooked up again. Not easy, but doable. Agree, it certainly strengthened the hinges. Getting the two main bolts back in is not a fun job. Getting thin washers in place and pushing bolts in to hold them is a challenge. The new gussets make it even harder to get fingers into the area. No signs of any cracks. 1,185 hours.

JB

PM sent.

JohnRussell
 
I haven?t got to thes skin doublets yet. Would it be easier to put the stabilator back on and then install the skin doublets?
 
Hmmm --

Don't think you could. Solid squeezed rivets would be hard to do. Flange to rivet to would still be there. I better say no you can't. Having smaller hands will help. Just not a fun job.
 
just finished today. Not mentioned in the instructions is the potential for interference between the top tailbone fairing and the gusset at full displacement of the stabilator. Mine did interfere and I had to file an eighth of an inch of the fairing above the gusset.
Hate putting those two bolts in.

No cracks, but only 150 hours.
N72DJ
 
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