UL120 STICK VIBRATION

[geraldp]

Morning all,
I am a new to Jabiru's ( UL120 ) having only 22 hours on type.

I am concerned with the occasional vibration or stick shudder when flying through turbulence. I have also found that there is little or no pressure on the stick when doing a left hand turn but positive pressure on the stick when doing a right hand turn. ( with ball in the centre ) In calm air it seems to be fine. My guess is the ailerons need re setting.

The wings were recently re fitted by the Jabiru factory in George when my AC was in for repairs.

Has anyone else had a similar problem?

[RogerRoger]

Hi Gerald.

Download this manual from Jabiru:
http://www.jabiru.net.au/Manuals/Airfra ... Manual.pdf

Page 250 deals with the elevator setup and take note of the trim springs that applies some tension to the control rods in order to keep them centralized and I assume to also help prevent flutter (I am not a Jab mechanic!).

Your ailerons might very well be out of alignment. Same manual, page 274 onwards. If you are in the cruise and she is trimmed out, what happens when you let go of the stick when feet are off rudder pedals. I suspect she might bank to the left.

Please let a Jabiru qualified AME do any adjustments if needed. Good luck!

[T4flyer]

Do you have the strips attached to the underside of the wing struts? My previous Jabi, also a UL120, used to set up a vibration which emanated from the wing struts, the vibration could be set into motion by turbulence, wind gust etc. However, slowing down would stop the vibration. I fitted the strips and the vibration was gone for good.

Cheers, Don.

[happyskipper]

ANY vibration on the stick is a serious matter, in my opinion. The fact that work was done on the wings by the Jab Factory points towards a rigging/cable problem.

I would take it back to them and say "fix". Oh, and I would not try to break the sound barrier, either.

I am not an expert in aerodynamics, so, please don't consider this to be advice of a technical nature.

[singleton]

To set ailerons according to factory specs : Technical Manual page 154 : 6.54
I had flutter in turbulence on UL120 . Managed to sort by fine tuning aileron settings.
Sue

[geraldp]

My Jab does have the strips fitted on the underside of the wing struts.

[T4flyer]

My UL120 did not have the anti vibration strips factory installed, fitted them myself to cure my vibration problems, I think all the newer UL120 have them fitted during manufacture. My J170 came new from the factory with the strips already fitted.

Hope you find a solution to your problem, I was flying a UL120 this weekend, man I love my J170, but boy do I miss my UL120, brilliant little aircraft

Cheers, Don.

[geraldp]

Thanks for the encouragement Don, the UL120 does tick all the boxes for me so I hope to get this problem sorted out asap and then will feel more comfortable flying it.
My previous AC was a Cessna 150 which I had for 10 years so converting to the the Jab has taken a bit of getting used to, being so much lighter and especially getting the approach speed under control for landing on shorter grass strips.