On Jul 6, 4:45*am, wrote:
On Jul 4, 4:56 pm, "Mike" wrote:

*Obviously, you haven't seen some of the things I have seen. *One of the
more tender, and more invisible spots on some airframes is where the
horizontal stabilizer connects to the fuze. *Many designs allow a
tremendous moment arm for any non-balanced load on the stabilizer to
stress the attachment points. *This shows up as *cracked spars on Cessnas,
and I have seen stressed and cracked fittings from another airframe. *How
can this happen? *Well on Cessnas it happens from folks using improper
procedures to back the plane into a parking spot. *It can also happen from
innocent (but ignorant) bystanders, mowers, animal activity, or any of
thousands of other posibilities.

I always give each side a good heave up and down for this very reason, so
such can easily be checked on the preflight for impending failure.

* * * * *A good heave up and down on the end of the stab of a 172
flexes the center of the forward spar, eventually cracking it. A
gentle bit of push-pull is all that's needed, to see if there's
unusual tip travel. I bet your spar is cracked now. Many are. Cessna
calls for stopdrilling the crack unless it has reached the spar
flange, in which case it has to be repaired. I once flew a 172 that I
subsequently found had a broken spar, busted clear through both
flanges so that the skin was all that was holding it.


Why did your push-pull test not detect it? I prefer to give a shake
and feel the nature of surface response.

Cheers