The International Cessna^® 170 Association

Hi All,

The holes where the rudder cables attach to the control horn on my plane are pretty worn. Is it permissible to ream these out and bush them back down? My rudder horn is in otherwise good shape, and I'd rather not drill out all those rivets and replace it if I don't have to.

Thanks,
DEM

That's what I did, I bought some Oilite bronze bushing stock from Spruce and Specialty ( part# 05-01857), drilled out to except the bushing, and cut the bushing stock to the appropriate length.

Joe

What you need to determine is, is bushing this part a legitimate best practice repair.

I personally don't see a problem so long as you don't go crazy with the size you bush it out to. I would use a steel bushing so I was not introducing a softer material to the control chain. The bushing should be tight so it does not spin in my opinion, them new wear with be located on the inside of the replaceable bushing or the AN bolt shaft.

Wouldn't a steel bushing risk further wear on the rudder horn if allowed to rotate?
How would you prevent the bushing (steel or brass) from rotating? I guess you could peen it but I'd think the brass bushing would lessen the risk of wearing the rudder horn hole even larger.

I'm pretty sure we but brass/bronze bushings in when when we did '81Ds.

So David, it is ok then to have the wear caused in the softer brass or bronze, which might actually happen at a higher rate.

I would fit the bushing tight so it does not rotate in the horn. It could also be glued in place with a sleeve retainer compound.

I would much prefer a soft brass bushing to wear faster than my expensive rudder horn.

How many decades of use will it take for that brass bushing to wear out anyway?

Brass is much more wear-resistant than the original aluminum. A bushing of any material will have a wider bearing surface than the thin rudder horn sheet metal with a hole drilled in it. A steel bushing has more dissimilar metal corrosion potential than brass and will rust over time creating more wear particles. A loose bushing is always better than a loose bolt of smaller diameter in the same hole. The rudder cable clevis should not be drawn up tight against the bushing.

So it looks like the consensus is that it is ok to drill over and bush. Can anybody point me to some approved data or regulatory guidance (other than common sense, which sadly isn't valid within the FAA)? Is there anything in AC 43.13 on this? A 337 I can reference, or a Cessna approved repair on a similar model?

Thanks,
DEM

I went the common sense route, which will probably land me in jail someday.

bagarre wrote:I went the common sense route, which will probably land me in jail someday.

Me too, I think it's called the Blue Elder route...I just heard that the Feds have been breaking into hangars at night looking for 170's that may have unapproved bushings in their rudder horns....

Joe

I believe I've seen short #3 eye bolts used in this application. When the eyes wear out, just replace the bolts. I have no clue on the legality or what the approval process might be.

Brass bushings mentioned in this post.

CNC Machinist friend replaces worn brass parts that he recreates in Tool grade BRONZE.

Parts last 3 X longer. Customers love him.

Bronze used in automotive transmission parts and ship screw propellers.

Think about it

cessna170bdriver wrote:I believe I've seen short #3 eye bolts used in this application. When the eyes wear out, just replace the bolts. I have no clue on the legality or what the approval process might be.

I believe you have Miles as the Scott installation drawings, you know, the only way we would install a Scott 3200, use eye bolts instead of AN bolts to attach the rudder control cables to the rudder control horn. Then the tail wheel control springs are attached to the eye bolt instead of the tab on the back of the rudder control horn Cessna used.

Whether you use AN bolts or eye bolts the wear the horn holes can still wear and bushing would make no difference. Actually I'd think using the eye bolt will apply a side load on the eye bolt shaft going through the horn hole causing even more wear than an AN bolt without the tail wheel control connected to one side of it.