Interesting video on rudder bracket failure

[GordonTurner]

Kai

The picture is pretty dark, but are we looking at a cracked tailwheel leg just aft of the weldment?

Gordon

[Scott Todd]

According to my plans (Onex 017) the horn does NOT go inside the rib but on the bottom, just like in the video.

[racaldwell]

My technique is to send the copilot back to the tail for a quick inspection. Here he is pointing out the nick in the rudder horn the jam nut made before I lengthened the rod end for some clearance.

Tail Inspector 4 Sm.jpg (150.26 KiB) Viewed 3053 times

Here the inspector is doing some pull ups on the modified Flyboys tailwheel. If my weld can hold through that, then it can take anything.

Tail Inspector 5 Sm.jpg (139.75 KiB) Viewed 3053 times

As you can see, I built my Xenos the way I want it. There are AN470 AD 4-6 rivets on the horn which is almost visible in this picture. The steering linkage was placed that best gives proper rudder and tailwheel movement. The steering arm is homemade and gives sufficient movement about the ball joints.

This is why experimental aviation is a wonderful thing.

Rick Caldwell
Xenos 0057 49 hrs
Camit 3300

[daleandee]

According to my plans (Onex 017) the horn does NOT go inside the rib but on the bottom, just like in the video.

Interesting ... I don't doubt what you are saying but I wonder why Sonex LLC would change from the way it is done on the Legacy aircraft. As I understood from Jeremy the OneX is just a Sonex that was downsized.

Can someone confirm how it's done on the new B model?

Curious ...

[Scott Todd]

I had lots of conversations with Jeremy about the Onex design. He appreciated I always asked Engineering based questions. I didn't know him as well as the Sonex staff so maybe they can comment here. I don't recall him using the term 'clean sheet' directly but he implied it often. He took all the lessons learned from the Sonex and tried to incorporate them. He also often talked about ease of build and simplifying things to make them quicker and simpler. He was very proud of his Dad's accomplishments but also proud of the Onex and the fact he called it his. I didn't build a Sonex but I did own one and have flown a few others. While they look similar, I think as you dig down you'll find lots of differences.

[n502pd]

WOW!! Sure glad he found the damage prior to flight!! Since my field is a bit rough, I took carefull attention to the landing loads on the tail wheel spring 'jouncing' about, and made sure nothing hits anything, including the jamb nut. I have used several washers on both thru bolts to keep the hiem ends above everything. A longer rod was needed, and the thru bolt at the rudder horn is supported by a heavy duty large washer on the bottom and top, then assembled. simular at the tail wheel horn. So far, no damage, however. I will take the hint, and set it up on a saw horse and view everything on walk around., thanks for that hint!!!

[Kai]

Kai

The picture is pretty dark, but are we looking at a cracked tailwheel leg just aft of the weldment?

Gordon

Nope!

The tailwheel leg is just fine- no issues. This is just the length of 4130 steel pipe that protrudes out of the flat steel tailpost bracket: cracked just to the rear of the weld heat zone.

[13brv3]

Thanks for the thread and heads-up. Mine is fine so far, but only 41 hrs and smooth pavement. this is definitely getting added to the pre-flight though.
Rusty

[flyingbear]

After I saw the video I checked mine again and found 3 rivets were a smidgen loose, but barely. I will replace soon.
240 hours on rain grooved runway--which is LOUD!! I never land hard.
GlenB

[peter anson]

But,

Since we are scrutinizing the Sonex tail- how many of you have come across this one?

Failure of the tail spring mounting bracket is fairly common. I know of at least three just in Australia. The problem is that the 4130 steel tube is nearly twice as stiff as the titanium tail spring so that it takes most of the load, but it has lower strength than titanium which is already pretty highly stressed. After my original bracket broke at about 400 landings I replaced it with a stronger fitting which is also designed to flex a bit more. All good so far after another 400 landings.


Regarding Kerry's assertion that the rudder failure on the Onex is due to the non standard push rod arrangement: I agree that mounting the rod end on the top of the rudder horn increases the forces that are pushing the horn up and down and it's a really bad idea to mount it on the top, but even the standard arrangement does tend to push the horn up and down, just not quite as much. One reason that so many builders go off plan on the push rod is that the original Sonex part is so obviously not ideal. The tail spring bends a long way and the only way the standard push rod can cope with the vertical deflection is by having plenty of slop in the holes. Not really a good engineering solution.
Peter