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  #1  
Old 01-31-2016, 10:51 AM
danielabernath danielabernath is offline
 
Join Date: Feb 2014
Location: Ft Myers, Florida KFMY
Posts: 145
Default ?Trim eye broken off by pushing Trim tab on stabilator

ordered a new trim servo as I am told that the trim (F-1287A part number) has separated fromhttps://www.dropbox.com/s/c26tughtfb..._3878.JPG?dl=0 the trim tab. Someone pushed on the trim tab on the stabolator. It is hanging down low and does not go up or down.
Am I on the right track?

https://www.dropbox.com/s/16deyp9p49..._3881.JPG?dl=0

https://www.dropbox.com/s/r5xn709epv..._3880.JPG?dl=0

https://www.dropbox.com/s/lh7t94019s..._3884.JPG?dl=0

RV 12 Assembly Manual Section 11 http://www.vansaircraft.com/pdf/revi...Section_11.pdf

(the saga continues)

Last edited by danielabernath : 01-31-2016 at 10:55 AM.
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  #2  
Old 01-31-2016, 02:46 PM
DHeal DHeal is offline
 
Join Date: Sep 2006
Location: Windsor, California
Posts: 672
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Looking at your pictures, it appears that your trim tab may have been incorrectly rigged. Note the indentation and wear marks on the actuator rod and mount. Something may have been incorrectly rigged and this may have contributed to the broken link. Alternatively, the actuator and mount may have been damaged when it was pushed?
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Last edited by DHeal : 01-31-2016 at 04:25 PM.
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  #3  
Old 01-31-2016, 05:00 PM
Dave12 Dave12 is offline
 
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Location: Elkton, Md.
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I think you can send the servo to Ray Allen Co. and have it repaired.
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  #4  
Old 01-31-2016, 05:45 PM
Pat Stewart Pat Stewart is offline
 
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Location: Granbury Texas
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Sorry to see that but thanks for sharing. I will be going back and double checking mine. When I do my preflight walk around I have a habit of taking all the flight controls through their full range of motion. In the future I will make sure I am moving the elevator and not the tab by hand.
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  #5  
Old 01-31-2016, 10:39 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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It looks like the threaded stud was pulled out of the servo. That likely took quite a bit of force.
It would be a good idea to inspect the entire anti-servo tab system very carefully.....
If a lot of force gets applied to the anti-servo tab(s), this is not necessarily the first place I would expect damage to occur.
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  #6  
Old 02-01-2016, 08:48 AM
todehnal todehnal is offline
 
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Location: Kentucky Lakes area in KY
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This brings into question another point of interest. Any thoughts about the controllability of an RV-12 in flight with the servo rod ripped out of the trim motor?? Maybe that rod to servo connection is the weakest link in that mechanism Anyway, that would be an interesting scenario to explore!!

Tom
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  #7  
Old 02-01-2016, 09:09 AM
Mitch757 Mitch757 is offline
 
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Location: Falmouth, MA
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A few months back we had an event with a Rans S-19 here that ended up on it's back while landing. It appears that the rod to the anti-servo tab came loose during a slightly firm landing/bounce. The aircraft porpoised 3 or 4 times, hit nose first collapsing the nose gear and flipping over. This is a similar setup to the RV-12. I think the guy was lucky it happened at touchdown.
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  #8  
Old 02-01-2016, 11:11 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by todehnal View Post
This brings into question another point of interest. Any thoughts about the controllability of an RV-12 in flight with the servo rod ripped out of the trim motor?? Maybe that rod to servo connection is the weakest link in that mechanism Anyway, that would be an interesting scenario to explore!!

Tom
Edit: After inspecting a disassembled servo and getting re-familiar with its interior mechanics I realized it was not likely possible for the threaded shaft to pull out of the servo, so I went back and looked at the posted photos again. They are pretty dark, but this time I was able to see that the shaft is actually broken off where it exits the servo arm. My assessment is still the same... that some pretty excessive force got applied to the system which caused a failure.

There is always a weakest point in any system. The key is that the weakest point not be too weak.....

All the components of the anti-servo tab / pitch trim system underwent load tests for certification.
For this threaded stud to pull out, the loads had to have been pretty high.
I am aware of damage that has occurred to the anti servo tabs on an RV-12 because of someone "helping" push the airplane by pushing on them (yes, even with "no push" placards installed) In this instance, no damage was done to any of the other system components.

As for control-ability with it disconnected?
Saying it would be difficult to fly might be an understatement.
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Last edited by rvbuilder2002 : 02-01-2016 at 05:01 PM.
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  #9  
Old 02-01-2016, 09:57 PM
RFSchaller RFSchaller is offline
 
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Location: Phoenix, AZ
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Scott,

I'm trying to imagine what the stick forces would be without the anti servo tab connected. Wouldn't the stab position be stable but with no feedback force trying to streamline it or would it being trying to go full deflection one way or the other?

Rich
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  #10  
Old 02-02-2016, 07:08 AM
todehnal todehnal is offline
 
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Location: Kentucky Lakes area in KY
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I imagine that if the link pulled out of the trim motor, the servo tab would trail, unless the link caught on something. You might experience some tab flutter if it wasn't held in place, and had some wind load on it. It would seem that the airplane would still have pitch controllability via the stick. This is purely a WAG.

Tom
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