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-   -   Elevator trim tab play (https://vansairforce.net/community/showthread.php?t=153635)

Chris Cooper 09-24-2017 03:06 PM

Elevator trim tab play
 
Fixed the elevator trim tab to the hinge and attached the motor and actuator. With the clevis pin in place I have about 0.5mm of play. The pin is very slightly loose in the trim tab horn. Is this acceptable?

Vlad 09-24-2017 03:26 PM

After couple thousand hours of flying I had considerable play in elevator trim tab due to an elongated hole. I fly an RV9A. A good friend of mine machined a bushing out of a rivet. Fits perfect feels tight. Thanks Julian! :)








F1Boss 09-24-2017 04:01 PM

"No"
 
Quote:

Originally Posted by Chris Cooper (Post 1206434)
Fixed the elevator trim tab to the hinge and attached the motor and actuator. With the clevis pin in place I have about 0.5mm of play. The pin is very slightly loose in the trim tab horn. Is this acceptable?

I think the consensus would be "no - get it fixed". There are various ways to bush the hole in the arm to get a better fit at the pin.

Good catch, by the way!

Best,
Mark

brad walton 09-24-2017 06:08 PM

When you say 0.5 mm play, is that at the trailing edge? I had about a 1/16 inch play at the trailing edge after 390 hours. I found the trim tab hole was about 3 one thousands inch larger than the clevis pin diameter. After reading your post, I fabricated a press fit clevis pin and now have no trailing edge play. I will be interested to see if its easier to hold altitude accurately.

vluvelin 09-24-2017 06:15 PM

Quote:

Originally Posted by Vlad (Post 1206437)
After couple thousand hours of flying I had considerable play in elevator trim tab due to an elongated hole. I fly an RV9A. A good friend of mine machined a bushing out of a rivet. Fits perfect feels tight. Thanks Julian! :)

Any time comaradishe!!!!

Chris Cooper 09-25-2017 12:25 AM

Yes, at the trailing edge.

rvbuilder2002 09-25-2017 08:29 AM

If my math is correct .5 mm is less than .020 "
.020 " free play at the the trailing edge is totally fine.

Chris Cooper 09-25-2017 08:33 AM

Thanks for all the replies. Is there a limit for this?

rvbuilder2002 09-25-2017 09:00 AM

In service experience and GVT testing (on an airplane that for the test had ~ 1/16" play) has shown it to not be very critical with even quite a bit of play assuming aircraft VNE limits are complied with.
I think a conservative limit would be .032 or 1/32".

MED 09-25-2017 11:00 AM

Quote:

Originally Posted by rvbuilder2002 (Post 1206558)
If my math is correct .5 mm is less than .020 "
.020 " free play at the the trailing edge is totally fine.

A millimeter is actually 0.03937 inch - interestingly, the same number as the number of inches in a meter. For quick calculations, for those of us who must make the conversion in our head, because we don't think in metric, we always just use 0.040 inch (40 mils) as "close enough for government work." :D


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