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Manual elevator trim

T

texdog

Well Known Member
we have excessive movement in the elevator trim tab. We got a new manual trim from Vans and it still moves to much. I worried about flutter. It isn’t my airplane and the lady inherited the airplane from her father. Any ideas would be appreciated.
 
Describe in more detail the excessive movement. Is it in the trim tab itself? Does it move excessively without the trim tab control moving? Does the trim tab control move without movement of the trim tab? How are both ends of the control cable housing secured? What model of RV is this? There is a difference in how the various models are set up. Is it a -4, -6/7, -8? More information would be helpful!
 
It’s in a RV6A, I will check about the controller moving. I did a walk around and the tab itself moved about a half inch. On my electric trim tab it might move a quarter of an inch. I appreciate your question. I will check on the security of the cable. The local shop is working on the problem and aren’t familiar with the experimental world. Thank you.
 
texdog said:
It’s in a RV6A, I will check about the controller moving. I did a walk around and the tab itself moved about a half inch. On my electric trim tab it might move a quarter of an inch. I appreciate your question. I will check on the security of the cable. The local shop is working on the problem and aren’t familiar with the experimental world. Thank you.
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There is a service notice on the bracket that holds the trim end of the cable. Check with Van's website.
 
gasman said:
There is a service notice on the bracket that holds the trim end of the cable. Check with Van's website.
Click to expand...
The fitting that holds the cable on to the elevator is a small steel plate with a nut welded to it which, in turn, is riveted to the under skin of the elevator. The original fitting was welded on ONE side of the nut and had a tendency to break off.:oops: The new fitting has the bolt welded on BOTH sides of the nut, that is fore and aft. You might be able to look up there and see if it has welds on both sides. If it does not, you can order a new one that replaces the old one. It is a little bit of a PITA to replace but doable. When I did mine, I took the old, one weld fitting after I had replaced it and just barely pushed on it and it snapped off.:oops::rolleyes: It MIGHT be where your play is coming from. Crawl under the elevator and move the trim tab. If the nut the cable runs through moves, that could be the problem.

When you manually move the trim tab itself, there should be NO movement without a noticeable resistance. You should hear/feel the trim cable move in the cable housing. If it moves half inch without resistance, that is a problem....... What do the clevis fittings at both ends of the cable look like? Are they ovaled out? Is the horn on the trim tab loose or ovaled out? Just thinking......... :unsure:
 
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The manual trim cable used here is notorious for having some slop. Most of us just live with it, and as far as I know there's never been an issue with flutter. That said, 1/2 inch of play is probably more than what can be accounted for by that, so definitely worth tracking down.
Note: some have been known to utilize a solution using a spring to keep some tension on it.
 
There is a certain amount of slack between the internal cable & outter housing (has to be to operate). Multiply that looseness over the length of the cable assembly, it results in some movement, less if the cable assy has to snake a bit thru the fuselage.
Even with this looseness, I have never had an indication of flutter, rather enjoyed the positive & solid adjustability of the manual trim setup.
 
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