[deltamike197]

I've occasionally felt some strange vibes coming from the front of the airplane on landing but wasn't sure what it was because it happened so seldom. I put a camera under the wing tip and caught it red handed a few weeks ago. It hadn't happened for quite some time before then and coincided with me filling the nose tire (~35 PSI) prior to the flight. Give a look on the you tube link below (first 2 minutes) and tell me what you think . Is it caused by higher pressure in the tire or? The thought of the gear leg coming apart from all that shaking makes me a bit nervous. Like to find a cure so that doesn't happen. I noticed at the last annual that the nose tire is wearing much more in the center and I have NOT installed a wood stiffener on the leg.

www.youtube.com/watch?v=p_CaaRJh3pA

Thanks

Dean (aka Deltamike)

 

[rvbuilder2002]

Dean

Two main things effect the tendency for shimmy as seen in your video.

Break out force adjustment, and tire pressure.

I have a feeling your break out is pretty low and that in flight the wheel got cocked off to one side. When it touched it violently flung it to the other side and shimmy starts. Higher tire pressure is another thing that can make shimmy more likely.

Another thing that can cause a higher tendency to have shimmy in any given situation, is high speed with very light contact of the tire.
The best landing technique is touch on the mains with the nose wheel well clear of the runway. This will be a condition that is ideally not very much above stall speed (only 10 knots or so). Then hold the nose wheel off for as long as possible but still be able to lower it under control (without it just plopping down). Then when the nose wheel is lowered, let it make full weight contact and transition to three point taxi technique with the stick fully back.

In instances where we find ourselves on the ground sooner (and faster than intended) the nose should be held off until speed is reduced to a point that it almost can't be held off any longer, then gently/deliberately lowered.

Now for a frank critical observation...

The landing in your video could be used as an example of how not to land a tri-gear RV. It was almost a three point landing. This would mean that in this landing you are going quite fast... at least much faster than you need to be. It is very fortunate that the shimmy wasn't more violent than it was. Please take this comment as constructive to work on high pitch attitudes / slower touchdowns.