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Reported to factory. But thought I would mention it here......

SNX-L03-31 - 6” Tailwheel

Time in Service – 285 hours as originally fitted to Sonex Serial 1153 by original builder.

Original Supply Date – not clear – originally supplied to the builder of the aircraft.

Symptom – slight “wallowing” of bracket to tube about the main vertical bolt.

Assumption – Top Hat bushings worn

Finding 1 – The 4 Top Hat bushings and bolt were in fair shape with no significant play between the bushes and the bolt. However the top hat bushes were actually wallowing in the machined - and worn - aluminum part that bolts to the titanium rod.

Finding 2 – See attached picture. I assumed that the “line” was a crack. Removal of paint showed it was probably a machining mark / limit (factory would know better). However closer inspection of “the line” and subsequent Dye Penetrant testing showed a hairline crack had started to develop and propagate in the vicinity of the machining mark. Also not clear about the orange tone / heat discoloration towards the bolt hole?



Action – replaced with new previously ordered.

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Had the tailwheel been abused? Well sure - it came with some "wallow" already present when I bought the plane. I had ordered a new bracket to firm stuff up asap and when the bracket came in - went to fit it. But it was only when I removed paint from the original bracket that the crack became apparent. Till the paint was off - it looked just like a painted over machining mark.

Good to know, something I'll add to my inspection while 541 is in the garage.

Thanks Graeme!

Any word from the mfr?

Mikegaydos wrote:Any word from the mfr?

My picture currently at the machine shop for review.

Not had any other reports of this.

Very interesting. Would be curious to know (and there may not be a way to ascertain), assuming no defect with the part, whether the cracking was as a result of prolonged fatigue, or a single (or few) instance of high load. (I.e., would a pneumatic tailwheel increase shock absorption and possibly prevent such damage?)

It's fatigue. There appears to be a small step left by the machining operation that has formed a local stress raiser and landing gear parts are already pretty highly stressed. You could significantly improve the fatigue life of the part by polishing out the notch using a small cylindrical sanding drum, although if the new parts come painted it might be difficult to pick that a step is there. If you do all your landings on nice smooth runways it might never be a problem.

Peter