SB 14-01-31; RV-6, 7, 8

[YellowPeril]

Sid, I'm in the process of my annual condition inspection, and had completed the tailfeathers and reinstalled the fairing when I learned about the SB. I like to think I do a thorough examination, but did I go out to the hangar today and look at it again?

You bet.

[rvbuilder2002]

Originally Posted by JonJay

While all of this makes sense, that is a whole lot of assuming.
There are many high time, hard ridden aircraft that have no cracks....
Is it design, fabrication, use, nobody knows for sure yet....we may never know... How do you know the "real" fix, will fix whatever it is. Makes sense that it would and I trust Van's engineers, but, until the cause is fully known, I would not rule any fix "in our out." Everything about why these cracks are occurring is conjecture at this point.

Not necessarily Jon...

I agree that there has been a lot of conjecture here on VAF, but that doesn't mean the development of the modification was based on that.

A detailed CAD model and FEA (Finite Element Analysis) was done on the Horizontal Stab. after the problem was detected. The mod. was developed based on those results, and the knowledge that people will have to be able to successfully install it as a retrofit.

Couple other comments based on posts I have seen.
Yes, removal of the rivets will require some care. If the proper process is used, risk of hole damage is greatly reduced (I can't say avoided, because there is still some level of skills involved) Note I said removal of rivets... not drilling out rivets. They are not the same thing. If anyone attempts to do the mod by simple drilling out the rivets, it probably will not produce a good result. Refer to the Recently updated Section 5 of the Construction Manual for guidance.

Some have said they figure building a new stab would be easier.
I think it would be probably double the work time (assuming an already removed one getting the mod installed). One thing to consider before doing this... The bolt connections that attach the stab to the fuselage are just as important as any of the rivets that need to be removed are. Do you know for certain that when you drilled those holes, they were drilled exactly perpendicular to the parts involved. Are you confident, that you can accurately match drill, from below (in a very limited work space), to have a good close clearance fit between the fuselage and the new stabilizer?
I am not saying it can't be done. I have done it, and others have also. What I do think is that it has a higher level of risk than installing the mod on a finished stab. If people take their time removing the rivets (NOT drilling them out), I believe they can be successful (owners that did not build the airplane, I recommend they get assistance from someone who is).

[rv6ejguy]

QB 6A kit 1998 vintage, large notches, no cracks. No acro, no grass, no Lycoming. 2.5X dental mirror and blinding light used. If you are not confident in your inspection method, can use a dye penetrant kit, ACS has them.

[Walt]

I would suggest the area referenced in the SB be inspected VERY carefully using a 3X or stronger magnifier. The reason I suggest this is I was asked today to take a look at an RV6 tail that had already been inspected by a couple of mechanic types (one well known but name withheld to protect the guilty) and deemed "no cracks found", however, I took one look at it with the magnifier and it became obvious that there were indeed cracks in both upper corners (much to the owners dismay).

The cracks may not necessarily look like the one in the SB (which actually has seperation of the material making it easy to spot). It will start off as a very fine hairline that is almost invisible to the naked eye, and this is especially true if your eyes are old like mine hence the 3X magnifier.

Here's a close up pic of the crack on my aircraft for ref, with a 3X maginfier its obvious, I showed this to a half dozen folks and only one person could see it with the naked eye even thought I pointed right to it.

So you may consider re-inspecting some of those high time "no cracks found" aircraft using visual inspection aids!

[Danny King]

All you no cracks people might reconsider. This morning I was ask to inspect an RV-6. With my bifocal glasses, and a bright LED light, I failed to detect a crack. The owner also failed to detect a crack. We walked next door to Walt and ask him to take a look. With his glasses, and a small magnifying glass, Walt detected a crack on both upper sides of this RV-6 HS.

These cracks are difficult to see, and each aircraft will be different because of paint, and other factors. I failed to detect the crack on my RV-8 until I put on two pairs of 2.0 cheater glasses that gave me a narrow focal length, but lots of magnification. I then discovered a very faint crack on one upper side. If you are looking for an obvious crack as depicted in the service bulletin, you might very well miss a cracked spar in your aircraft!

I'd be willing to bet that some of you that reported "No Cracks" in fact have cracked spars! As stated in the SB, these cracks can be very hard to detect!
If in doubt, get a second opinion.

[Berchmans]

I will inspect my RV8 tonight but in the mean time called the factory and ordered the parts...they are not on the website yet but you can call. Will be shipping in a week and cost $15.00. I haven't decided to undertake the repair but thought I might as well have the parts on the shelf just in case.

[Mike S]

Please, those of you who are included in this SB, follow it.

I have a ten, so no "dog in this fight" as they say, but I am seeing a number of posts about how robust this ares is, and how the planes are not "falling out of the sky"-------and I believe both are quite true, but do not let that seduce you into ignoring the SB.

Pretty sure Vans would not have taken the action of issuing the SB if there was not a solid reason for it.

Take care, and fly safe.

[Andy Hill]

Hi Scott

Note I said removal of rivets... not drilling out rivets. They are not the same thing. If anyone attempts to do the mod by simple drilling out the rivets, it probably will not produce a good result. Refer to the Recently updated Section 5 of the Construction Manual for guidance

I'm probably being blind but having downloaded the Section 5 http://www.vansaircraft.com/pdf/revi..._Section-5.pdf I cannot see a section on "Removal of Rivets"?

I am sure from your post it is there - any chance of a page / section ref please?

[n468ac]

1000 hours ... no cracks. used iphone to take pictures and display them on my monitor at the office.


Double checked again tonight ... No cracks found

[Neil Moffat]

RV-8
300 hours
aeros
30% off grass strips
Push/pull with towbar and tractor
No cracks

Also inspected all other areas with borescope and no problems found.