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Aileron Control Rod is Binding

Pilotjim77

Well Known Member
I have been doing some work on my wiring and have the floor pans out. This is a photo of the pilot side aileron control rod with the stick pushed full forward and full left. As you can see, the nut on the autopilot servo arm is getting up under the aileron control rod. If I try to move the control stick to the right while it is pushed full forward, this nut binds itself under the control rod. A very slight rearward movement of the stick prevents this binding.

Is this dangerous? Will I ever be in a flight condition where I need to go from full left aileron to right aileron while pushing full forward on the stick? I did not feel comfortable when I discovered this. Any help would be appreciated.

Click on the photo for a larger view.
 

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Tough answer, because there are a few (very few) situations where this is fine. The canned answer (and safest answer) is that: at no point should a flight control be binding through all control inputs including autopilot servo inputs.
 
I would definitely not leave it in that condition. It looks to me like you may be able to reverse the bolt so that the head is under the aileron tube; or use a shorter bolt with a thin spacer washer between the servo arm and rod end bearing instead of the thick one; or make an adjustment to the mounting of the servo to give a little more clearance. But whatever you do, make sure your solution doesn’t create a new problem.
 
Is that an optical illusion?

Or is your servo mounted at an angle to the control system?
 
The servo looks to be rather old and does not include the SB that TT published a number of years ago. The center screw that holds the arm could come off and since, TT has provided remedy for that.
 
Are the elevator control stops installed? If so one solution would be to readjust the elevator push rods to change the position of the stick slightly. If you move the neutral point of the control stick rearward this would possibly add enough clearance to prevent the binding issue you are seeing.

Bill
 
Rod end free?

The rod end should be free to pivot left and right in the picture. One should be able to swivel the rod end back and forth. Sometimes when people tighten them, the ball end gets twisted over and is no longer free to pivot on the ball; this will cause binding. JMHO
 
I would definitely not leave it in that condition. It looks to me like you may be able to reverse the bolt so that the head is under the aileron tube; or use a shorter bolt with a thin spacer washer between the servo arm and rod end bearing instead of the thick one; or make an adjustment to the mounting of the servo to give a little more clearance. But whatever you do, make sure your solution doesn’t create a new problem.

I've seen some pictures which confirm this. I may try to reverse the bolt and see if that works.

Is that an optical illusion?

Or is your servo mounted at an angle to the control system?

I'd say optical illusion. There's no off angle I can detect.
The servo looks to be rather old and does not include the SB that TT published a number of years ago. The center screw that holds the arm could come off and since, TT has provided remedy for that.

I was unaware of this SB until you mentioned it. TT no longer has info on this. Does anyone know where I might get the retainer that TT used to provide?

Are the elevator control stops installed? If so one solution would be to readjust the elevator push rods to change the position of the stick slightly. If you move the neutral point of the control stick rearward this would possibly add enough clearance to prevent the binding issue you are seeing.

Bill

I do not know the answer to this. I will have to investigate.
The rod end should be free to pivot left and right in the picture. One should be able to swivel the rod end back and forth. Sometimes when people tighten them, the ball end gets twisted over and is no longer free to pivot on the ball; this will cause binding. JMHO

I will check this next time I'm at the hangar (tomorrow). Thanks for all the input.
 
I was unaware of this SB until you mentioned it. TT no longer has info on this. Does anyone know where I might get the retainer that TT used to provide?

If you can not find the retainer, you can replace the screw with a set screw using a red Loctite, then put a nyloc to hold the arm in place.
 
Other considerations?

The forward/aft travel of the control stick is limited by the stop plate in the area of the elevator horns (under the VS). Depends on the UP and DOWN movement of the elevator to meet travel limits. The stop plate should be installed and it may be allowing forward stick movement beyond the specification of travel.

You might want to check the elevator up/down travel (Degrees) and ensure the stop plate is properly limiting that movement.

Should be observable by removing the VS fairing and look down at the elevator horns.

If the stop plate and elevator travel limits are within spec, the stick fore/aft position can be adjusted slightly by adjusting the control tube to the elevator, too. Need to be careful with these changes and properly understand operation.
 
My RV6 servo installations must have been mounted a bit farther back for more aileron tube clearance as I always ended up notching the big hole in the seat rib to clear the A/P servo link.
 
Update

I installed the bolt the opposite way, and it solved the problem. No more binding. Thanks to all for the assistance.
 
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