So, I looked inside my Sonex wing to do a random check on my aileron linkages. I’ve never done this yet because I recently bought this plane. When examining the aileron bellcrank plate, I noticed all was in order, and nothing was lost. However, when I pressed up on the plate, it had some play that I didn’t know if was normal or not. I had my A&P look at it, and we noticed it has about the same amount of movement on both bellcrank plates. For those who have owned their Sonex planes for a while, is this normal? Lastly, I have had my aileron pushrod rubbing against my wing, as you can see in the picture. This only seems to happen sporadically, doesn’t hinder my ability to fly at all, but I wanted to see if this was something that others have experienced and what you would recommend to remedy it. Thank you all for any help here!
My wings, although complete, have not been rigged to the fuselage yet so I don’t have experience with how loose or how much play will develop over time. A lot of play would be concerning especially if I had not done the original assembly. I assume you have verified that the bellcrank assembly matches what the plans call for. Regarding the aileron pushrod rubbing on the wing - there is no photo showing where that is happening. I would want to figure out how that is happening, and try to determine if it can progress/worsen.
If I get a chance I can see how much play mine have. I agree with Kevin, a picture of the interference would help. Sounds like you meant to include one.
Thanks for the quick replies, gents! I had a bunch more pics to send, but for some reason, the system here wouldn’t let me. You’ll have to forgive me for the lack of mechanical lingo, but here is what I am trying to say. When I push up on the aileron bellcrank plate (in this pic), it moves and is not stiff. Both of my bellcrank plates do this. I just don’t know if that is a design feature of a Sonex A. In the other picture, you can see where my push rod has scraped against the inside of the wing spar. It doesn’t do this often, but once in a while, when it’s really cold out, it may do it. I’m not as concerned about this, to be honest.
I’m going to have to take a look at mine and the plans tomorrow afternoon when I get to the hangar. But just looking at your photos, there are a few concerns - and most are completely unrelated to the play you have. I’ll just add a comment to each of your photo posts.
This one (IMG_4753) - The cotter pin in the bolt that fastens the long pushrod (on the right in the photo) - you might want to replace that one. If you don’t know the correct way to install a pin and bend/cut the legs, research it. That one is not correct. Same deal with the one on the left in the photo. I can’t tell if that one is engaging the castellated nut or not. One other thing, that rod end does not have a witness hole drilled in it. I know the rod ends that were supplied in my kit did not have holes - I drilled them myself at the minimum engagement measurement point. Without it, and not knowing the length of the threaded portion of the pushrod, you are just assuming it is threaded in far enough. Based on the exposed portion of the threads, it probably is in far enough but again It is just an assumption.
It would be nice to replace those cotter pins and install them better. The one on the right in this photo fastening the short pushrod - that bolt looks to be a bit long or perhaps it is missing a washer under the bolt head - when you put the pin through it should engage the castellation better/more.
The other bolt - the one fastening the bellcrank plate - something is wrong there. Either that bolt is way too long or something else is wrong with that assembly with bushings/spacers etc. I’ll take a look at my plans tomorrow and take a photo of what mine looks like. Note that the cotter pin does not engage the castellated nut at all as far as I can see.
Photo IMG_4741:
Pushrod rubbing - that looks like it is rubbing the lightening hole in one of the ribs. Because I haven’t rigged I don’t know if that indicates something is way off, or it is a normal possible occurrence. If anyone says that is a possible normal occurrence I would probably opt for filing some of the hole flange to give clearance. Better than letting it rub. In order to do so, I think you would need to disconnect one end of the pushrod to give you the space to get a file in there. If I were you, I’d be replacing those cotter pins that are ‘less than ideal’, so you can use that as an opportunity to pull the bolt then get in here with a half round file and make some clearance here.
Those bolts are too long. The cotter pin needs to go through the castles on the nut. No way should the pushrods rub on the rib. Check the plans for how the pushrod mounts to the stick, make sure you are on the correct side.
Based on what I see in this photo and if that bolt and pin are any indication of pin installation across the board, I would go through the plane and look at every bolt you can find that has a castellated nut and cotter pin - push rods, tail control connections, etc, and check the length of the bolts and the installation of the cotter pins.
Welcome to the group!. yes, the cotter pin isnt correct, and should fully engauge the nut,or as much as possible. secondly, yes, had the exact same problems you describe with play in aeileron bellcrank, on both wings. 90 hrs isnt much tim e for TT, but no problems with play. Hitting the mount has not occured on mine, so maybe just needs a bit of fieling to remove interference. as for hitting the wing rib, yes, me too. all I did was to bend the area of the opening so it would not hit the push rod. also when I rigged the pushrod, I only tightened one nut on to the heim end, which allows the push rod to rotate slightly without binding anywhere at full deflection. otherwise, I think you are able to correct these areas, with your A/P’s ok, of course! Let us know what, and how thing work out!
Some of the things in your photos show some sloppy workmanship by the original builder, including possibly a bit of ‘close’ rivet hole edge distance in the wing rib flange. Your first order of business would be to look at the length of every single bolt to verify correct length and if castellated nuts, correct installation. Two things for you to look at first:
There was an article in March 2026 EAA Sport Aviation by Kerry Fores - “The nuts and bolts of nuts and bolts”. I’ll try to attach the pdf here.
Then, if you are a member of the EAA, you should take a look at this Hints for Homebuilders video: Hardware Installation Basics . Starting at 06:23 they show and talk about the proper installation of a castellated nut and cotter pin.
I didn’t want to be the one to say this but it needed to be said. Thanks Kevin.
There are a few things (already mentioned in this thread) that should make the owner want to do a real good inspection of this build. If possible get a Sonex builder or an EAA tech guy to do an inspection and note what needs to be remedied. There may be something discovered that’s ready to bite.
Not trying to instill fear but simple things (like the lack of witness holes in the rod ends) that are overlooked and assumed to be OK can cause real trouble if not corrected. One of the things that a few builders miss are the aileron stops built into the control stick. If the rigging is correct these stops work exactly as designed. The pushrod hitting the rib indicates to me that perhaps the rigging is also not correct.
Mine have very little play. But keep in mind they don’t have usage wear yet. I’ll try to attach images of some of my fasteners. Note the way my pins are shaped and legs cut to length. Also note length of bolts. And see the witness hole in the rod end.
While you’re in there checking on things, use a mirror and just verify that there is a large OD washer under the head of the bolt on top of the heim/rod end. That should be there just incase that rod end/heim fails so that it doesn’t just completely disconnect.
Regarding the pushrod clearance/rubbing, if that is the #7 rib, I don’t see how that is possible. Take a closer look at the plans for how it should be rigged on the control stick end - that could be incorrect. Also double check the dimensions of the bellcrank plate itself, especially hole to hole distance if that can be calculated from the plans.
It is possible that you might find every other fastener on the plane looks good, but based on what you posted you’d be doing yourself a disservice by not at least taking a look at all of them.
When bolts seem too long, it is possible that the nut could be bottoming out without clamping the material correctly. When bolts seem too short for an application, it is possible that the threaded portion of the bolt is inside the material and that could fail in shear.
The bolt holding your bellcrank is too long - is it possible that the nut is tightened all the way down against the bolt shank and is not quite tight enough for the application and it is another source of some slop? Maybe - but even if not the correct length should be used. I believe the plans call for an AN3-14 there.
Good on you for finding the issue. I wouldn’t fly it like that.
You’ll probably want to remove the bell crank and ensure it’s not worn improperly. My guess is that the (soft aluminum) bell crank has been pivoting against the (hardened steel) AN3 bolt and the hole in the bell crank has become egg-shaped (or worse), which is why it’s moving now.
The only part that should wear is the bronze flanges against the stainless steel bushings. It appears to me that whoever built this assembly didn’t understand how to use a castellated nut, nor how to properly verify that the nut isn’t running up against the grip.
Here’s a link to a YouTube video of my bell crank assembly. I discuss the entire assembly and speak to EXACTLY what you’re seeing toward the very end of the video:
Thanks for sharing your video of the bellcrank build process. I just bought a set of plans from a guy who had a spare. I’m going to be doing a detailed inspection of my plane since I still have the wings off. I will definitely be checking out the bellcranks, though I don’t remember feeling any play when I removed hardware to pull the wings.
