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Rudder Pedal Misalignment

New RV8 owner (non builder).

I have noticed that I tend to fly out of trim quite often with my feet on the pedals. When my feet are flat on the ground my ball is centered.

I am convinced that when my feet rest on the pedals it induced a right yawing tendency.

Had a friend stand behind the aircraft as I naturally place both feet on the rudders and sure enough I get a deflection to the right. He then positioned the rudder in the center position and asked me to put my feet back on the pedals and I can feel my left pedal is depressed, or right pedal is sticking out further (whichever you prefer).

Either one of my legs is longer (not likely) or my pedals are not centered.

I searched the forums but cant find anything that adequately describes my scenario.

Can anyone recommend where to start troubleshooting or link me to a thread where a similar question as been posted?

Is there a rudder turnbuckle that can be adjusted?

Should I, how do I verify my rudder deflection?

Thank you,

RV8 owner
 
For flight adjustable pedals, there is a stack of washers that can be adjusted via the number on the engine side and cabin side to change the cable length slightly.
 

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For flight adjustable pedals, there is a stack of washers that can be adjusted via the number on the engine side and cabin side to change the cable length slightly.

Thanks Mike for the quick reply. I crawled in as far as I could and see approximately the same number of washers on both sides. IF they are different, its only by 1 washer. The engine side had no washers.

Perhaps this weekend I can remove the baggage compartment and get an accurate washer count.

I do have the in-flight adjustable pedals.

Any other ideas should it not be #of washers? I would think it would have to be several to create an appreciable difference.
 
Thanks Mike for the quick reply. I crawled in as far as I could and see approximately the same number of washers on both sides. IF they are different, its only by 1 washer. The engine side had no washers.

Perhaps this weekend I can remove the baggage compartment and get an accurate washer count.

I do have the in-flight adjustable pedals.

Any other ideas should it not be #of washers? I would think it would have to be several to create an appreciable difference.

I have never seen one that didn’t have at least a few (and usually quite a stack) on the firewall side, so that might be the first thing you do to try and adjust. It might be that the builder didn’t read or understand the plans and simply didn’t know that having some on the engine side is normal. Easy to miss.
 
Disconnect the rudder cable from the idler arm on the rear of the gear tower. This will allow you to pull the cable through the S shaped tubing on the rudder pedal and slightly adjust pedal angle on one or both of the pedals to make them equal. Then reconnect at the idler arm.
 
cable routing?

This is perhaps a bit of a long shot, but there is at least one "wrong" way to route the cable through the spar carrythrough bulkhead and aft from there. It might be possible to have one cable routed correctly and one routed incorrectly, creating a difference in effective length.

I seem to recall a post from someone a while ago that had a cable issue, and found that his had been routed incorrectly by the builder. So this is probably worth checking, even if it is a long shot.
 
Disconnect the rudder cable from the idler arm on the rear of the gear tower. This will allow you to pull the cable through the S shaped tubing on the rudder pedal and slightly adjust pedal angle on one or both of the pedals to make them equal. Then reconnect at the idler arm.

That's a good first step. Could be out of whack.
Did you know the new kits don't use the idlers? Only if installing rear rudder pedals.
 
Disconnect the rudder cable from the idler arm on the rear of the gear tower. This will allow you to pull the cable through the S shaped tubing on the rudder pedal and slightly adjust pedal angle on one or both of the pedals to make them equal. Then reconnect at the idler arm.

I have attached a photo from this link. https://rv.squawk1200.net/2020/02/04/rudder-system-rigging/

Is the area circled in red the idler arm? If so, I do not have one of them, although from one of the additional comments below it would seem as thats normal for me since I dont have rear rudder pedals.

I am trying to understand how the angle of the pedals are determined. From your comment, do I understand correctly that the pedal angle is set by "choking up" on the rudder cable that resides within the "S passage" that the cable runs through?

Once set appropriately, what prevents the pedal from sliding back down the cable? Does this tend to happen when the pedals are adjusted with asymmetric pressure on them using your feet?

Thanks for answering questions from the FNG :cool:
 

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If you don’t have the idler arm than you just need to get slack in the cable enough to slide it in the S tube. Under tension the cable won’t slide in that tube.
 
If you don’t have the idler arm than you just need to get slack in the cable enough to slide it in the S tube. Under tension the cable won’t slide in that tube.

Going to give this a go as soon as I get home. When I first purchased the airplane I had a lot of trouble fitting inside since the previous owner was a very small guy and I am 6'2". I cut layers off the seat and slid the pedals back. Wondering if during that process I slid one along the S guide and misaligned it. I most likely didnt use both feet at the same time since its soo hard to reach the release cable. I could certainly see myself leaning to the right to grab it with my right hand and then push on the right pedal to move the whole mechanism towards the firewall.
 
the idlers are only installed if you install the rear-seat pedal kit. Doesn't matter old kit or new kit. Same.

The angle of the pedal is determined by the hole location in the pedal for the brake master cylinder, and the length of the master cylinder. You might check to see that both your master cylinders are identical. (one might have been replaced with a different brand?)

The cable finds its natural place in the S-bend tube. You can not change the angle or position of the pedal by sliding the cable in the S-bend. It will just slide back when you put tension on it.

The only sources of left-right asymmetry are:
1: different cable adjusted lengths, from the washers on the firewall;
2: different hole position on pedal for master cylinder attachment, or different length master cylinder;
3: different routing path of cable through fuselage, in combination with #1.
 
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Also, since you are a tall guy, take care of your pedal adjustment position. It is possible to slide the assembly far enough forward so that full rudder deflection plus full brake application will cause the pedal to hit the firewall. You can end up with not being able to apply brake pressure when the rudder is hard over.

Ask me how I know....
 
Also, since you are a tall guy, take care of your pedal adjustment position. It is possible to slide the assembly far enough forward so that full rudder deflection plus full brake application will cause the pedal to hit the firewall. You can end up with not being able to apply brake pressure when the rudder is hard over.

Ask me how I know....

Or a dent in your firewall....:rolleyes:

I put an Adel clamp on the tube to limit forward travel for just this reason.
 
Or a dent in your firewall....:rolleyes:

I put an Adel clamp on the tube to limit forward travel for just this reason.

That is a good solution to add to a completed airplane. I put a short piece of tube over the slider tube and pop-riveted it to the slider tube. But one would have to disassemble the slide assembly to do that.
 
Also, since you are a tall guy, take care of your pedal adjustment position. It is possible to slide the assembly far enough forward so that full rudder deflection plus full brake application will cause the pedal to hit the firewall. You can end up with not being able to apply brake pressure when the rudder is hard over.

Ask me how I know....

Or pinch and snap a brake fluid supply line against the firewall. Ask me how I know ;)

Was my third or fourth flight. Fluid everywhere...
 
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