Stinson 108 stabilizer aft attach point, cracks?

Cubswede · Dec 16, 2022

I have bought a 108-3 with the O-470 STC. It has been sitting since 2011, so I am doing some thorough inspections before I take it “upwards”. I think I have found cracks in the small reinforcing angle at the AFT attach point bolts. Both sides. I will at least need to remove the elevator for a more close up inspection, but I believe there are cracks present. Other big motor powered Stinson owners, be aware!

/Henrik

Formandfunction · Dec 16, 2022

That's a pretty well documented issue. Not sure why some do it and others don't. The type of flying I do I almost expect it at annual but I've been lucky so far. I even have a painted spare ready to go if it shows up.

Hardtailjohn · Dec 16, 2022

If you pull the rear spar out, you're gonna find a bunch more!! It's totally common on 108's with the O-470, especially on floats. I built a bunch of new spars and ran the reinforcement angles out further on top and bottom. So far, it seems to have taken care of it.
John

Cubswede · Dec 17, 2022

Formandfunction said:
That's a pretty well documented issue. Not sure why some do it and others don't. The type of flying I do I almost expect it at annual but I've been lucky so far. I even have a painted spare ready to go if it shows up.

Thanks for the input. I remember I read something a couple of years ago about cracks in the tail somewhere, but when I looked for it now I only found the SB regarding the repair on the FWD attach point.
anyway, I believe My Stinson might be the only one in Europe with a 470. And Stinsons are pretty rare over here in general, so there is not much gathered knowledge around here.
I will have to investigate more if there is more damage.
My Stinson has around 500 hours with the O-470, and 3800 total time.

Cubswede · Dec 17, 2022

Hardtailjohn said:
If you pull the rear spar out, you're gonna find a bunch more!! It's totally common on 108's with the O-470, especially on floats. I built a bunch of new spars and ran the reinforcement angles out further on top and bottom. So far, it seems to have taken care of it.
John

Thanks for the input. I will have a deeper look. Where do you usually see the additional problems? Do they crack in the radius at the bend in the spar?
Would’nt some kind of brace be a good idea to help support that big wing of a tail? &#55357;&#56837;
or just as you mention, to beef up and extend the reinforcing doublers does the job. Mine is Experimental, so somewhat free to design and build.. &#55357;&#56397;

Stinson 108 stabilizer aft attach point, cracks?

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