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  #21  
Old 03-31-2016, 06:45 AM
John-G John-G is offline
 
Join Date: Jan 2012
Location: Northeast Ohio
Posts: 508
Default Add washers to the bolt

Jim -

Tightening the bolt where the F-1287E push-rod attaches to the horn may not be the fix for you .... because the nut is likely bottoming out on the shank of bolt. There was a thread about this here on VAF quite a while back.

The AN3-10A bolt used at that location is a tad too long. I ended up adding an AN960-10 washer under the head of the bolt and in addition to the AN960-10 washer that goes under the AN-365-1032 lock nut, I added an AN960-10L washer. In my case, doing the above allowed the shank of the bolt to pass through the horn and the additional washers prevented the nut from bottoming out on the AN3-10A bolt's threads and leaves about three threads showing beyond the lock nut. Also verify you have AN960-10 washers on both sides of the MM3 bearing ... (between the horn and the bearing).

Enjoy your 12
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www.dogaviation.com
RV-12 Wings, Empennage, Fuselage, Finishing, Avionics and Powerplant kits all completed
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  #22  
Old 03-31-2016, 07:39 AM
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DaleB DaleB is offline
 
Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 1,856
Default

I checked mine the other day and found essentially zero play at 240 hours or so. The only play I can get between the anti-servo tab and stabilator seems to be from the hinge, not the trim servo linkage. Just enough to feel, not even enough to measure.
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  #23  
Old 03-31-2016, 08:28 PM
Piper J3's Avatar
Piper J3 Piper J3 is online now
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 967
Default

Quote:
Originally Posted by John-G View Post
Jim -

Tightening the bolt where the F-1287E push-rod attaches to the horn may not be the fix for you .... because the nut is likely bottoming out on the shank of bolt. There was a thread about this here on VAF quite a while back.

The AN3-10A bolt used at that location is a tad too long. I ended up adding an AN960-10 washer under the head of the bolt and in addition to the AN960-10 washer that goes under the AN-365-1032 lock nut, I added an AN960-10L washer. In my case, doing the above allowed the shank of the bolt to pass through the horn and the additional washers prevented the nut from bottoming out on the AN3-10A bolt's threads and leaves about three threads showing beyond the lock nut. Also verify you have AN960-10 washers on both sides of the MM3 bearing ... (between the horn and the bearing).

Enjoy your 12
Went out to the plane today to resolve this issue and pretty much did as you say. A washer here - a washer there. Now virtually slop-free.

I bought my 12 from the original builder with 50TT. I knew of several discrepancies before I took delivery and this was factored into the price. I’m happy to say that today’s work, which culminated at the tail cone, completes a thorough examination of the airframe and supporting paperwork. I currently have no outstanding squawks. Remaining work are three service bulletins for prop hub, landing gear, and fuel tank. This work will be completed this summer.
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Hinckley, Ohio
EAA #499867
PPL/ASEL 1970 Sport Pilot since 2004
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 380

LSRM-A Certificate 2016
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  #24  
Old 05-07-2018, 03:01 PM
AirHound AirHound is offline
 
Join Date: Oct 2006
Location: OFallon IL now, everywhere before
Posts: 207
Default AST followup question.

Scott, where the potential recommendations you spoke of made?

And, in plan English, what does the pilot experience when the AST becomes ineffective? Thank you! Doug in IL

Quote:
Originally Posted by rvbuilder2002 View Post
Lets define a few terms first....

Trim tab - an adjustable tab (in flight or manually on the ground) tab used to move a control surface in a direction we desire (to induce a trimming force).

Servo tab - a controllable tab used to move a control surface. I a sense a trim tab is also a servo tab, but servo tabs (by name anyway) are typically considered more of an active control function. Some large aircraft built prior to hydraulically boosted controls had servo tabs connected to the control system. The control system moved the servo tab which in turn drove the main control surface to the desired deflection (I think the B-29 was one airplane controlled this way).

Anti-servo tab - A tab whose movement is used to counter the movement of a control surface. This is typically done to artificially induce control force / feed back.

The RV-12 has an Anti-servo tab. It also functions as a pitch trim tab by having an adjustable neutral point, but that is a secondary purpose.

With a horizontal stabilator with the hinge point somewhere close to the center of pressure (as we have on the RV-12), there would be nearly zero control force / feed-back without the anti-servo tab. The anti-servo tab adds artificial feed back force by deflecting in a direction that tries to move the main surface back to neutral when it is moved by the pitch control system. That is why the tab constantly moves whenever the stabilator is moved.

In a nut shell.... if the anti-servo tab was non functional you would have little to no control force in pitch, which would probably make the airplane challenging to control.

I think a future release of the POH is going to cover recommendations for dealing with this. I think the primary one is to induce a different trimming force (deflecting the flapperons) that would then allow you to work the stick against the control force induced by the trimming input. It would be very similar to flying an airplane that is out of trim in pitch.... to change pitch you increase or decrease the pull force on the stick but it never gets to neutral/zero.
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