Near catastrophe event!

[Shadowrider]

That?s not Harlan?s plane in the video. Just trying to figure out what caused it. I am guessing it is also the prop wash buffeting. Maybe it was a bad weld with a poor stop that a fracture propagated from? There are many running higher horsepower and this is the first I have heard of this happening. Not sure what the fix is but defiantly needs addressing.

[alexM]

Harlan,

Since I am a nose gear kitfox guy with manual elevator tab trim rather than the adjustable HS, I am not familiar with all the hardware items. What does the little link on the front of the assembly do?

The same thing that the scissor portion of a typical oleo strut does. On your typical Cessna nose wheel strut you'll see that double link. It allows the up and down motion while preventing the nose wheel itself from rotating around on its own, and allowing a steerable nose wheel.

In this case it is holding the upper portion of the jack screw from rotating so the threaded portion can do its job. Without it you would just hear the trim motor run and the upper portion would spin around without changing the stab trim position.

[Dave S]

Hi Alex,

That makes total sense. THX

[jiott]

I would recommend Kitfox use a couple of their factory 915/916 powered aircraft and mount a vibration sensor on that tube, and do some test flights at max power. Vibration sensors are readily available; you use one every time you dynamic balance a propellor. This would quickly verify whether the horizontal stab vibration is the culprit, or should we look elsewhere.

[Geek]

On my first flights, I had a pretty good horizontal stab buffet (stick pulsed) when I put the flaps down and the forum consensus was that it was prop wash off the flaps. Wasn't sure I agreed that it was 'norma' so I went through and tightened my stab braces a bit more and put the spring on the elevator control which seemed to fix (or maybe hide) the issue along with not putting in any flaps till below 65KIAS. That's with the mighty 100HP 912is so not sure this is limited to only the big boys (915/916) but this sure looks like a result of that type of buffet. What was in the video looked like what I was feeling in the stick but it also appeared that the flaps had been retracted already. Don't think the sky is falling here but it is certainly something that we all should take a look at. Know that I am going to check it much more closely in the future. Really glad to have you still here to report on this Harlan!!!

Gary

[Kitfox Pilot]

Thanks Gary.
The video of the red plane was a 912is so yes they will shake to.

Nothing much to report yet. We are full into harvest so it may be a while. Thanks to John, Kitfox is 100% behind me in finding a solution so I'm sure we will.

[rocketman2tm]

Well you got me a little paranoid. I went out to the hangar tonight and inspected the area thoroughly. Fortunately for me at least, I didn't see anything.

Normally on preflight, I grab the front of the stabilizer and try and move it up and down on both sides. I would think that would catch this, but I could be wrong. I'll keep an eye out for it.

[Kitfox Pilot]

Hi John. Mine was still solid feeling after I knew it was broke. My break started on top of the pipe. About 1/4 of the pipe was rusty near the top of the pipe.

[ken nougaret]

Soooo scary. I will be inspecting today.

[ohlhausenr]

I'm inspecting mine tomorrow and including it with my annual inspection.
Thanks for the information.