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  • Steve

RV-8 and the Rusty Push-Pull Tube

Updated: Nov 28, 2021

11/27/21 - The only delayed discrepancy I had from last year's condition inspection was some minor rust on the bottom aft ends of both aileron push-pull tubes, the small ones that go from the bellcrank to the aileron. While inspecting the inboard aileron hinge brackets per SB 16-03-28, I found small areas of rust on the bottom of the push-pull tubes. The left side was worse, but it was present on both. They had both been removed several years before I bought the airplane for the same thing.

I wasn't looking for the rust, but it was pretty obvious.

The first step in any task like this, and the easiest one to overlook, is to take a photo or make a diagram of how the bolt goes in, noting the position of washers and spacers BEFORE you take it apart. This makes it much easier to get it back together the same way when finished. In some cases, putting the pieces back together in the wrong order will result in something not working correctly. It's better to have something to refer to than to have to rely on memory (at least mine).

Before shot showing the orientation of all the hardware.

In order to get this bolt out I had to drop the flap to get a little bit of room. That isn't too hard to do by taking out the bolt at the top of the flap push rod and dropping it through the floor.

It looks a little weird with everything disconnected.

I couldn't get a photo of the other end because it is up inside the wing and I couldn't get a good camera angle on it. It is much simpler and should be easy to replicate.

One of the hardest parts was getting the nut off from the bolt shown above. There is very little space to get a tool in there. Naturally, a regular wrench won't fit. The next thing I tried was an ignition wrench, but it was still a little too thick to fit. I could grind down the faces a little so it would fit, but they are my good Craftsman (from back when they were really Craftsman) wrenches. A better solution would be to grind on a Harbor Freight wrench, but I didn't want to go get one.

I started scrounging the hangar for anything I could use. I found a few things that came close, but didn't quite fit. Finally I found a wrench in the bottom of a tray that was thin enough, but wasn't quite big enough (probably metric). A few passes with a file and it fits like a glove.

Mystery wrench.

I have no idea where that wrench came from or what it was for, it most likely came with some other tool I bought. This is why I never throw anything away. You never know when something might come in handy.

Once both bolts are out, it just slides out the through the rear spar.

Rusted area, bottom side aft.

The longest section of rust is about 1/2" long. It looks for all the world like it was rubbing on something, but there is nothing for it to rub on. That section of the tube sits inside the wing and even at maximum aileron deflection doesn't go back as far as the rear spar.

A few minutes with some Scotch Brite and it was ready to put some paint on.

Cleaned up and ready for paint.

I put three coats of Krylon Rust Tough on it spaced about 15 minutes apart. In order for it to be fully cured, I will wait until tomorrow to put it back in. That, I'm sure, will prove to be the hardest part. That should have it taken care of for good.

According to the label, this stuff is pretty good at preventing rust.

Finished and ready to reinstall.

Sunday 11/28/21 - I'm happy to report that putting it back in was nowhere near as hard as I thought it would be. I started by attaching the forward end to the bellcrank, the part I thought would be hardest. It actually turned out to be the easiest part.

Orientation of the washers.

As it turns out, getting a photo of the bellcrank was easier than I thought, once I thought to come at it from a different angle, that is. This shot clearly shows the 2 thick and 1 thin washers on top and 2 thick washers on the bottom. Someone before me glued the washers together and glued the bottom washers to the bellcrank which made getting it back in easy.

If at all possible, when I take something apart, I put it back together with new hardware. I mean, why not? In this case I used the old bolt pushed from the bottom to get all of the washers in and lined up and then once it was correct, used the new bolt from the top to push the old bold back out and c'est voila, it is ready for the nut.

Once that part was done it was time to make the aft end connection to the aileron. This is where the before picture came in handy. As I expected, getting the bolt, washers and spacers in was easy. Getting the nut and washer on the end of the bolt, not so much. It took a while to figure out how to get the nut up there as there is really no access from the top. OK, no access from the top... is there any other direction than top... well, let's see, the opposite of top is... wait, don't tell me.. oh yeah... bottom.

The solution.

For just such a situation, I have a set of really long hemostats (or "holding scissors"). The straight jawed pair, just visible at the left end of the above picture, directly under the nut (actually, holding the nut). Since there is a slightly larger gap on the bottom, there was just enough room to get the hemostat with the nut on it up to the bolt.

Perhaps a somewhat smaller pair would have worked also.

Once the nut was started, the rest was easy. lubricate the rod ends, put the wing inspection panel back on (after doing a through FOD check first, of course), then reconnect the flap and put the flap actuator cover back on. The whole reassembly process took less than an hour.

Ideally, the sfter shot will look just like the before shot, but with new hardware.

I do feel better having this taken care of. The forecast for the next 10 days is pretty dreary also, so there is a good chance I will get to the other side next weeknd.

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