My TB20 goes to annual, and I have noticed, that the elevator linkage has some play. At the control I can feel approx 1 inch of play, when actually the elevator is not effectively responding. I see the same thing, when the autopilot works, in ALT HOLD, he struggles sligjhtly within this play too.
For this annual /100 hour insp., I asked the mechanics to replace the spacers in the trim tab linkage/mechanism since the tab has excessive play at the end.
My question is (since my technicians have lower experince on TB) what may the weakest point in the linkage to start with, in order to avoid changing all rods. The connection assembly at the end is obivous, but I am curious about your feedback. My guess is, and this is the worst case scenario for me, that all (most of) the rods have some wear, and needs to be replaced.
Thanks and regards
What’s the problem with following the whole mechanism to find where the play is? Doesn’t sound difficult to me.
Do you mean elevator, or elevator trim?
If you have 1 inch of play in the yoke before the elevator even moves, that is unbelievable and probably something is so badly worn it is about to fall off. It is beyond airworthy.
However if you mean there is 1 inch of movement on the trim wheel before the trim tab linkage moves, that’s different. See here – search for “Elevator Trim Mechanism”. There are several bushings which are quite cheap to replace, although some parts are potentially expensive if the plane has been neglected – because officially you can’t replace the brass/bronze bushings which are press-fitted into an aluminium bracket etc and the whole part has to be bought from Socata. Replace these first and see how much play remains on the trim tab. Next, replace the trim tab hinge pins. Officially only the teflon ones exist and if yours aren’t teflon then you have to change the hinges too and the whole kit is about 2k. See here. I got criticised as usual for criticising the design but nobody has thought up an explanation for why it was done that way. If your pins are already teflon then initially change just the pins.
I got criticised as usual
I don’t see any criticism of you at all in that thread – just discussion of why it may be like that…
Thanks for the feedback.
Well, there are two things. The elevator tab is a clear issue. I read your article, my tech staff is instructed to follow the the secquence. Anyway we examined the trim linkaged and the result of it, the spacers are ordered. I have teflon coated hinges, the play exist there as well, but the most of the tab-play comes from the linkages.
The other issue is the elevator linkage. Tomorrow will know more. I stopped flying until it is not crystal clear, where the play comes from. When the autopilot is coupled, (Century) I can move the stick approx 1 inch freely until the pitch would really would be affected. During manual flight, you are not able notice is so significantly compare when the servo holds the linkage. Anyhow, something is really worn there.
1 inch elevator play (at the yoke) is massive. It may be that something has come off or come loose, rather than worn bushings.
On a TB the ailerons and elevator are solid links all the way; only the elevator trim uses a cable.