Hello everyone! This is my first post in this blog, my name is Bernardo, I'm Brazilian and recently bought a CH750. I'm the third owner of this aircraft, and friend of the first owner. the aircraft was built by a company in Brazil in 2011. It is powered by a rotax 912 100hp. Both engine and airframe with 184 total hours.

          The Aircraft was bought on july, and a few days after I brought the plane to my hangar, while washing, I noticed a crack on the center hinge gusset (75T2-8), as shown on the picture Below

A local mechanic made the part new and ,in theory, the problem was solved. the brackets were inspected for cracks and every seemed to be ok.

        After aprox. 10 hours of flight, on one single day, I made 5 flights, flying for approximately 1.5 hours total. Before the first flight, the aircraft was inspected and everything looked ok. A week later, I went to the hangar to make another flight, and while making the inspection, I noticed the HS outboard hinge being torn out of the stabilizer on the left side. the right side was loose but still in place. the hinge gusset was also torn out, on the 3 rivets (Stab side). I also noticed new cracks on the stabilizer front brackets, as shown on the pictures below.

That scared me a lot, because it could have caused me to lose the elevator.
I decided to build a completely new Stabilizer, but first, I need to figure out what was the root cause for this issue.
Some facts I think are important for the analysis

• The propeller installed on this aircraft is a warpdrive, and when I bought the plane, one of the blades was 5 degrees different from the other 2. This was fixed right after I bought the plane.
• The previous owner was not in the habit of using the trim tab.
• Rudder cables were a bit loose.

I started disassembling the HS and called a friend of mine that already built a CH701 and is currently building a CH750.

He told me that by his analysis, the whole stabilizer was a bit loose while forcing it by hand. on the disassembly of the stab we noticed that the two front brackets rivets were a bit loose on the rivets, but still in place. This could be a consequence of a previous vibration that was already causing the cracks.

I'm putting below the images of the progress of disassembly of the Horizontal stabilizer.

So... My intention with this post is figure out the root cause of this issue before just replacing the parts and maybe this happening again, not having the luck to see it on the ground. Also the community to be aware of this event, and preventing that to happen with someone else. I count With the help of experienced pilots and builders in this group to help me figure this out.

Thank you very much!

Bernardo S. Nickel