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-6A rudder rigging problem

brian

Well Known Member
I've owned my -6A for 2 1/2 years now, and am the 4th owner. It's been flying since 1995. In all that time, and in all those preflight inspections and annual condition inspections by lots of professionals, no one seems to have noticed what I found when I preflighted my plane for a flight yesterday.

What I discovered is that the rudder does not hit either the left or right rudder stops when activated from the rudder pedals (as opposed to activated by hand during a preflight). It's the old style rudder pedals mounted on the floor. The rudder travel is limited only by the top part of the rudder pedal (the top part of the sideways "H") hitting the top of the brake master cylinder.

The left rudder comes within about 1/16" or so of hitting the rudder stop. Not right, but not a huge problem. The really hairy thing was that I observed that the right rudder only has about half of the travel as the left rudder, and doesn't even come close to the rudder stop - maybe 1" from hitting.

I realize I can easily fix this by just shortening up the control links between the rudder pedals and the rudder cables. I wonder if the builder or a previous owner was quite tall and decided to lengthen the leg room by lengthening the control links and thus moving the tops of the pedals forward.

But now we get to the really weird part I don't understand. The left link needs to be a bit shorter. The right link needs to be a lot shorter. But the left rudder pedal link is already much longer than the right one. On the right one, it appears someone drilled a second hole to move the attachment a bit further forward. So, after the rigging is adjusted to give proper full travel to the stops, this difference in length between left and right will be even more exaggerated. I may even have to eliminate the right link entirely to get the pedal back enough to get full right rudder travel. It appears to me that both left and right rudder pedal sets are mounted at the same point fore/aft. Unless one cable is longer than the other one, I don't understand how this can be.

So, some questions for those with experience in older -6As with the pedals mounted to the floor:

Why does it appear that one cable is longer than the other? Did they come that way? Both ends of the right rudder cable appear to be in normal condition, and don't look at all like either might be pulling out of the swaged end.

Is this difference in control link lengths normal and why?

Is there a set length these control links are supposed to be?

Here are pics of the left and right rudder pedal configurations:

RVrudderLT.jpg

LEFT SIDE - see how much longer the control link already is than the right side


RVrudderRT.jpg

RIGHT SIDE - at the top of the master cylinder, you can see where the rudder pedal has been hitting it as a "rudder stop"

I'd appreciate any insight other older -6A owners/builders can share on this.

On another note, I see that pilot's left brake master cylinder has some seepage at the top. Are these master cylinders rebuildable, or should I get a new one (presumably from Van's)?
 
I don't have any insight on the floor mounted pedals, but the rudder cables that came with my 6A kit are not exactly the same length. Mine are off by around 3/8". Now if there is some variation in the pedl weldments, the cable, and the rudder horn that could all stack up to quite a bit. From what I recall, the pedals don't pivot on the same axis, so the cable length would have to be different in that case.

I would lock the rudder in trail, put some tension on the cables and then measure from the front of the main spar to the cable end. This should tell you what variation you have in the cable/rudder system. Also look to see if the rudder pedals and actuator arms are all in alignment to see what issue may be there. Take a close look for cracks or damage, that is always a potential cause.

The master cyl are rebuildable. I don't have the part numbers handy, but there is a stat-o-seal and 1 or 2 o-rings. You just need internal snap-ring pliars to take them apart.
 
Last edited:
Pedals

Hi

It may be just the angles the photos are taken from but it looks like the cable levers are welded at different angles relative to the pedals. Left one appears to be almost in line with the pedal upright, the right one appears to be set about 15 degrees back which could account for some of this.

Anyway, unless one of the cables is stretched, in which case it might fail, I would not worry about this. Just aim to get the two pedals in line with each other with the rudder centered and adjust the link length as required to get full throw each way.

I have not heard of a cable snapping on on RV but have on another aeroplane so it not impossible.
 
In the picture it appears the return spring installed on the right pedal is in straight alignment with the link & cable. Could it be that when pushing the rt pedal forward it is running into this compressed (solid) spring?
Unsure if it's a requirement with floor mounted pedals, but most suspended pedal RVs don't bother with return springs on the pedals.
 
As for the seeping M/cyl, yes there are rebuild kits available. Note that the kit for Cleveland brakes are different from Matco's.
Also, would mean grounding the plane while getting kits or parts, but would be a good idea to disassemble m/cyl before ordering parts. I have run into 2 RVs & a Rocket so far where m/cyls had scuffing damage on the shaft & piston & had to replace the assembly.
 
Hi Ralph - sorry I didn't get to chat with you more at AirVenture 2012. I hope I run into you again. The springs are such that they are loose and just move out of the way when the pedal goes forward

In the picture it appears the return spring installed on the right pedal is in straight alignment with the link & cable. Could it be that when pushing the rt pedal forward it is running into this compressed (solid) spring?
.
 
THANKS TO ALL

Thanks to all the people who responded. I'll check out the angles next time I'm at the hangar, and will proceed with getting the link lengths right.
brian

Hi

It may be just the angles the photos are taken from but it looks like the cable levers are welded at different angles relative to the pedals. Left one appears to be almost in line with the pedal upright, the right one appears to be set about 15 degrees back which could account for some of this.

Anyway, unless one of the cables is stretched, in which case it might fail, I would not worry about this. Just aim to get the two pedals in line with each other with the rudder centered and adjust the link length as required to get full throw each way.
 
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