VAF Forums - New SB issued 6 May 2016 (SB16-03-28)

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- - New SB issued 6 May 2016 (SB16-03-28) (https://vansairforce.net/community/showthread.php?t=137582)

Quote:

Originally Posted by StuBob (Post 1078156)

A quick note for those with wings under construction:

I emailed Van's, told them I was just starting on the rear spar, and asked for advice. They answered "new kits will have the fix included. You can do it, too."

So I ordered the SB kit for a whopping $10. For those of us under construction, it's just a matter of putting two doublers on the forward side of the rear spar, opposite the aileron bracket. No reason not to do it.

Seems as though a reason not to do it would be keeping the ability to inspect this area. Installing the doublers will hide both sides of the spar. This seems to be a relatively rare cracking issue without a fully understood (by me, at least) cause. I haven't had time to analyze it, but I'm wondering if a better enhancement for those of us still under construction might be a partial rib that would put the aileron bracket loads into the skin.

Where is the load coming from that causes the cracking? Stick input forces being reacted against the aileron stops, maybe?

350hrs, good mix of aero and cross country time. No cracks ! Took a total of 15 min to open, inspect, photo and close back up

Inspected my 1993 start 2000 completion RV-4 with 1050 airframe hours - NO CRACKS. I've flown a lot of aerobatics during the last 150 hours but I don't think the previous owner flew aerobatics often.

The first photo is a cell phone photo and was adequate to the task but the borescope provided a little closer look.

Cell Photo

Borescope

I think what's more important than the "what" here is the "why".

Is there an explanation as to what is causing the (few, apparently) cracks in these locations? For the wings, for example, could it be unsecured ailerons being smacked around by high winds and torqueing the brackets? Ham-handed pilots during aerobatics slamming the controls to the side? Or, worse, "normal" forces which are being transferred to the location and then fractures arising at improperly deburred holes, e.g.?

Random responses from a small sample of RVs about presence or absence of cracks doesn't tell us much (and as pointed out, what would you do, NOT inspect them anyway at each annual?).

2010 RV7 near 400 hrs. No cracks. Mild aerobatics.

2009 RV-9. 460 hrs. No cracks.

2007 RV7A 920 hrs on the Hobbs Loops and Rolls - Crack Free

210 hours, no cracks. RV9A.

Quote:

Originally Posted by RV7A Flyer (Post 1079284)

These two previous posts are a generalization of what is going on. I say that because there are many different variables that can come in to play.

http://www.vansairforce.com/communit...0&postcount=56

http://www.vansairforce.com/communit...91&postcount=7

I'm kind of torn on this one. My bottom skins are on, but I haven't riveted the flaps on yet. My wings are in the cradle and easier to work on. I'm wondering if it's worth it to go ahead with the mod while the wings are still somewhat easy to work on. I'm even willing to drill out and re-rivet a rib bay or so (bottom skin) if it'll lessen the chances of boogering up the spar. The hard part would be drilling out the hinge bracket rivets--IIRC I put the manufactured head on the inside.

Then again, it seems the odds of a crack are low, and the airplane could go its whole life without an issue.