My CH750 from Zenith had a maiden flight back to December 2010 down here in Brazil. Besides de door problems, the aircraft seems to be a good project and I am a quite happy with her performance. However, this weekend turned to a sad one since a right part of the elevator (from the pilot view)  presented a dangerous wear coming from a friction among the elevator and the aluminum angle which has been eroded by the mechanical contact between them. I want to hear from Zenith, even thou from partners about this problem and how to fix it. It seems the movement of the elevator cause the contact. Obviously there's no enough gap between the parts to be free of friction. Very important to mention that we do have two CH-750 and both show the same problem in the same elevator area. I did not see any tech advice from Zenith related to this problem. This is an unacceptable project error that can cause an elevator grip that may even cause or result in an uncontrollable flight control.  Important to say that the kits were assembled locally by aeronautical engineers level experts. 

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That elevator nose skin should have been trimmed to clear the bracket. There should be no interference or contact with elevator throughout full elevator deflection/range. Don't fly until corrected.
Thank you very much for the input! We will provide the necessary trimming! It seems that the rudder and elevator itselves should be removed before the trimming due to a lack of enough room for trim tools! Any suggestion?

Yes I would remove them. Check the clearance of the rudder to rudder fairing interface as well. Also, be sure to check cable tensions, when hooked back up, in case there is some new slack due to free movement of elevator/rudder. Just check everything 3 times and have somebody else check it twice. Make sure everything is secure. I used metal shears to trim mine, then used a die grinder with a sanding drum to clean it up.

Was there any contact between these two parts when the planes were first completed or is the contact a new phenomenon?  On the 750 I worked on we paid very close attention to contact in this exact area and made sure there was no contact  but the clearance is very snug.  What the clearance on my buddy's 750 elevator will be like after a couple of years of use, who knows.

I had a similar potential clearance issue on my scratch built CH701 but I was able to file the stab mount as per the 701 instructions to allow adequate clearance.  I like the idea of trimming the elevator skin back a bit for clearance as it should have minimal affect on the strength of the stab mount.  Let us know what Zenith has to say on the matter.

Doug M

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