Wheel landings and (lack of) shimmy

[Bryan Cotton]

So today I ended up at 30.5 hours - 9.5 to go for phase 1. I had been reluctant to do wheel landings due to the shimmy I had been experiencing. Full stall seemed to work good, with the tailwheel on the ground before the mains. The trick with that is it is hard to see forward and keep it straight.

I have noticed that when I rotate onto the mains for takeoff, there is a bit where I get some shimmy and then it goes away once the airplane is level.

I flew 2 hours today, mostly in the pattern, and all wheel landings. I simply touched down gently and then immediately got the stick forward and a level attitude. I did 12 of them. They were actually all good. The airplane behaves really well on the mains, no shimmy, and it's a lot easier to see forward to keep the airplane straight. I'm using similar approach speeds as I do when I 3-point, and a similar amount of runway. I did them both with one notch of flaps and full flaps. It's actually really easy to wheel land and it is well behaved.

I'm not sure if the shimmy is caused by light gear loading in the 3 point attitude, or tailwheel low, or if is is the geometry change. But I really like wheel landings in the Waiex.

[mike.smith]

I did 3 point landings for the first year I flew my Sonex. But with such a low lift-off speed (37 kts indicated), if I had any excess speed at all, I'd get airborne again as the tail came down. So for the last 7 years I have been doing wheel landings. I reserve 3-point landings for practice and grass strips. I also normally take off from a 3 point stance (which Joe Norris told me is the preferred method), as you automatically have the right AOA, and I lift off at 37 kts. If I push the stick forward and take off from a 2-point stance, it takes me longer to get off the ground, as the AOA is too shallow to lift off at 37 kts.

[Bryan Cotton]

I've not had good luck taking off from the 3 point stance. As the wheels get light I get shimmy. It's harder for me to keep it straight because I can't see forward very well. On the mains I rotate at 50+ kts.

[builderflyer]

Probably more of a reflection of my ability as a pilot than anything else but in seventeen years of flying my Sonex, I've made 3 point takeoffs and landings almost exclusively. With the 3300 engine, liftoff occurs at about the same time it takes to advance the throttle to the stop, so not a lot of time to not see forward in the takeoff roll. The few times I've raised the tailwheel on takeoff or made wheel landings, it just doesn't go well for me. My Sonex is better behaved to have its tailwheel on the ground......it just isn't as friendly to me any other way.

Art,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,Jabiru 3300 #261/Aeroinjector

[T41pilot]

I'm 5'6 and my "B" model is an inch longer on the mains plus larger tires so I pretty much don't have a choice on my takeoffs since I can't see at all over the nose. I have to push it over to see where I'm going. If I try to do a 3 point takeoff, I end up off to one side of the runway before it rotates which is unnerving. Fortunately, I have not noticed any shimmy Brian. Perhaps a function of wheel balance or the rigging of toe-in might be to blame on yours. I haven't tried a wheel landing yet. 3 points are working for now. I just look out to the side after touchdown and try to keep it on the center as best I can. The roll outs on grass so far have been relatively short now that I have the hang of dealing with the nose pitching down a lot with use of any flap past 10 degrees.

[DCASonex]

I fly my A series tail dragger Sonex from a hilltop airport with a lot of variable winds from multiple directions. If taking off from three point position it often results in lift off due to a gust, then immediately setting down again, off well off center line. I bring the tail up ASAP, and keep plane nailed to the runway until about 65 MPH, then lift off cleanly. Much safe way for this airport.

David A.

[Skippydiesel]

Bryan - Just a thought; the wheel alignment (camber & toe in/out) may change as the aircraft rotates from tail low to tail up and more weight is taken by the wings. These changes could cause "shimmy".

[Jgibson]

Bryan;
Tried to give you a solution to the shimmy but the dreaded SQL server message won't let me. I saved it in 'draft' but can't find the damn thing.

Joe

[Bryan Cotton]

Bryan - Just a thought; the wheel alignment (camber & toe in/out) may change as the aircraft rotates from tail low to tail up and more weight is taken by the wings. These changes could cause "shimmy".

Yep, I agree. But it also seems that not everyone has the issue.

Bryan;
Tried to give you a solution to the shimmy but the dreaded SQL server message won't let me. I saved it in 'draft' but can't find the damn thing.
Joe

Thanks for the attempt Joe. The server message was good for a few days but bad today. You can always shoot a message to my gmail. My username is my first name, last name, and 3 digit serial number. All that info is in my signature.

[gammaxy]

Raise the mains off the ground sometime and twist the wheels and legs side to side to see if there's any play. The bolt hole on one of my axles got wallowed pretty early on and seemed to allow some shimmy. I welded the bolt hole closed and redrilled it to remove the play. I also added feeler gauges as shims between the titanium leg and inside of the socket. There was a pretty noticeable amount of play.