Wednesday, May 03, 2006

Oh drat, that's gonna have to be fixed

The annual condition inspection had been proceeding nicely, and for the most part there have been only minor problems found. A couple of oil seeps (they aren't significant enough to justify the moniker 'leaks') and a slightly slipping alternator belt looked to be the worst of it, until...

If you look closely at this picture of the elevator trim tab, you can see a small crack developing where the control arm is riveted to the side. Click on the picture for the full size view if you can't see it. The short-term fix is very easy: drill a stop hole at the very end of the crack. That should keep the crack from growing for awhile, but the long-term fix will be more involved, and will probably take the form of building a new trim tab. My concern is that the new tab would eventually break in exactly the same way - it's apparent from looking at it that the skin is stressed inappropriately with the current design. I solicited advice from the Van's internet forum (run by a fella named Doug Reeves, it's a peer-level support group) and the first respondant opined that the control arm should really be on the bottom of the trim tab, not on the side as mine is. I haven't looked at the plans yet to determine whether that is a recent change brought about by this existence of this very problem, or if for some reason the builder of my plane strayed from the plans in this case. It doesn't really matter, I think when I repair it I will move the control arm to a better, less stressful location.


This part of the plane was built according to the plans, which were later amended using a different mounting point because this very problem arose with a lot of the RV-6s built during the 90's.

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