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While doing my annual I noticed a black substance streaming down from my aft elevator pushrod bushing. I am using the plastic bushing per the plans. After trying to take a closer picture of it by taping my phone to a yardstick, I decided to crawl back there as far as I could. Sure enough, the plastic bushing had worn all the way through on the bottom. The pushrod was rubbing against the bare aluminum and scraped off all of the powder coating. I was able to rotate the bushing 180 degrees so that the bottom has fresh plastic. A band aid until next annual. I figure all the white lithium grease will keep the pushrod from rusting.

My plane only has about 140 hours on it. Has anyone else had this happen? The aft bushing is a nightmare to get to, and replacing it requires pulling the pushrod out the back. I can't imagine this is a standard wear item every 100 hours.

I'm thinking the only way to replace it is going to be to cut an inspection hole in the tail floor. Any other suggestions? Has anyone ever pulled their pushrod? Is it as easy as a few bolts and pulling it out the hole in the vertical stab spar? Does the rudder have to come off?

I’m pretty sure all my bushings are bronze.

Sees like the inspection hole that is on the right side would provide access.

My guess is you are talking about a plastic bushing where the pushrod passes through a bulkhead, nothing to do with rod ends and such? I don’t recall my Waiex having anything like that. Where the pushrods (two ruddervators) pass through bulkheads the hole is large enough nothing touches, no bushing. The elevator pushrod doesn’t move strictly in and out, it is following arcs at both ends so there must be a little up and down movement included. I must be misunderstanding your situation because a bushing wouldn’t work in this case.

Sorry for the confusion guys. Yes, I am using therm “bushing” pretty loosely here. It is not the bronze bushing at the ends. I am talking about where the elevator pushrod goes through the vertical channels. There are 2 on the Sonex, and both call for these plastic inserts. The aft one is definitely not reachable by either of the inspection panels in the fuselage sides.

In regards to the pushrod not moving strictly in and out. This is correct, but the pushrod is so long and thin that the weight of the pushrod, and the sag, make it rest on the bottom of the bushing, regardless of the arc.

That doesn’t sound good. If it wears through the plastic I think the aluminum edge will start wearing through your pushrod.

When I was building my Sonex in the previous century, I thought that running the elevator push tube through the vertical channels (and the plastic bushings) at an angle would be prone to binding. So I added what you see in the attached photo so that the tube is at right angles to the bushing. Seems to have worked well but it would be more difficult, but not impossible, to add to a flying airplane. Oh, and by the way, I lubricate the push tube with bar soap at each annual.

Art,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,Jabiru 3300 #261

This is a place where I recommend changing the build order noted in the plans. Sheet SNX-F21 shows the elevator support channel drilled and then riveted in place as the Aft Fuselage is constructed, but this is well before the elevator pushrod is actually installed (which doesn't happen until much later - after the fuselage halves are mated and the horizontal stab and elevator are installed - SNX-C01). The elevator pushrod tube is flexible enough to pass through the hole in the support channel (with the snap bushing in question), but will rub continuously if the alignment is out by very much.

A better way to approach this is to leave the elevator pushrod support channel undrilled and unriveted until after the elevator pushrod is installed (near the very end of the final assembly sequence), then drill the support channel to the cross-ties when the alignment is perfect. If you've also left the belly skin in cleco until the last step before airworthiness inspection ;-) access to do the drilling and riveting will be easy.

Lastly, I also recommend adding a round inspection hole and cover plate in the belly skin in the vicinity of the elevator pushrod support channel to make lubricating the bushing convenient. Many Sonex have a distinctive "honking" noise when the control stick is moved, and this is caused by a lack of lubrication on the bushing and some rubbing/chattering against the pushrod. The fuselage turns into a resonating chamber, giving us the melodic "Moose Call" as Bob Mika likes to say!

Jeff

An easy alternative would be to convert it to a Waiex.

What a timely post!

I'm dealing with this moose-call and have been trying to figure out how to deal with it. So now I have a plan. I'll install an inspection plate (today) that I have sitting on the bench then lubricate the bushing/grommet. Easy peasy.

There seems to be two suggested lubricants here. Lithium grease and bar soap (Irish Spring?). What other lubricants have folks been using?

BRS wrote:
There seems to be two suggested lubricants here. Lithium grease and bar soap (Irish Spring?). What other lubricants have folks been using?

Haven't tried the lithium grease but I found that various oils I tried wouldn't last long in their effectiveness. The bar soap I've used is Ivory because that's already in the house. The soap's effectiveness lasts longer than the oils and it's not as messy and doesn't attract dirt as the grease would. Part of the "noise" solution, however, is not trying to move a round tube through an oval hole which is what you have if the plastic bushings aren't at right angles to the push tube.

Originally, my elt was installed in the rear of the tail cone and a belly inspection plate (with skin doubler) was installed there to service the elt. That opening also allows for access to the rear plastic bushing through which the elevator push tube passes.

Art,,,,,,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,,,Jabiru 3300 #261