Ex Bonanza Bucko
Well Known Member
I wonder if there is info on the percentage of RV12s that have suffered this.
If you have input i'd love to see it.
EBB
If you have input i'd love to see it.
EBB
If the cracks are the result of stress on the flapperons,
There not. (at least not because of deploying them as flaps)
The loads might be a bit higher with flaps deployed but the cycle loads are there from movement of the flapperons (in aileron mode) regardless of whether the flaps are deployed.
A crack such as this that occurs after many hours is a result of fatigue failure due to repetitive load cycles.
The same as if you bend a piece of aluminum back and forth in your hands over and over. If the piece is stiff enough, you wont be able to impart enough pressure with your hands to cause any flex so the load cycle has little effect on its fatigue longevity. If hand pressure allows it to flex a lot, after repeated cycles it will crack and then eventually break.
The modification to the bracket makes the area that was flexing much stiffer so that it is not flexing during normal load cycles which will in turn prevent the fatigue failure.
It was easy to complete this project when building the fuselage assy. and the cost was minimal. Do it then so you won't have to do it later
Scott,
Remember the fatigue usage factor is based not only on cycles, but the stress associated with the cycle. I dread that cycle at 105 KTS because I know it had a higher usage factor than one at Less than 82 KTS. I'm not talking about an over stress crack, but rather a reduced number of design cycles to cracking as a result of some over design stress cycles.
In the end all that really counts is no cracks yet!
Rich
FWIW, I had 438 hrs at my last annual with no crack, and I would guess 3/4 of that time was on the autopilot. Out here in the Phoenix thermals the AP gets a work out.
Interesting response, Scott. I didn't think about the constant load issue. Any chance there is some manufacturing issue that causes some to crack while others soldier on?
Well, I am a fanatical deburrer, and my part failed after only a couple hundred hours. I worked on another 12 yesterday that has over 400 hours on it, and the part was fine. As analytical as we builder types are, some things just dont have an answer that we can put in a neat little box. Best just to fix it, and move on!
Well, I am a fanatical deburrer, and my part failed after only a couple hundred hours. I worked on another 12 yesterday that has over 400 hours on it, and the part was fine. As analytical as we builder types are, some things just dont have an answer that we can put in a neat little box. Best just to fix it, and move on!