Tailwheel shimmy

[EDGEFLY]

My Chief has an SFS-P8B Series Maule TW. It was installed by the same A&P who done all of the maintenance and the annuals for the last 7 years. At my first preflight, I took note that the springs attached to the rudder controls were very slack (as in hanging loose) with the rudder in the neutral position. Seemed a little odd to me but, I went forward since the A/C had been flying and there was no report of problems. Since then, I have noticed a pronounced shimmy on all types of landings and even my Tailwheel Checkout CFI commented on it. So, as a follow-up, I asked the local A&P about it. His response was that the existing springs were too loose and that a set of "tension" springs should replace them. He installed them and -----back to flying. Last night after some grass field work, I returned to the hard surface field and on landing the shimmy became an "almost" controllability problem. Got to the taxiway and stopped and found one side disconnected and a missing part in the chain on that side!!! Needless to say, repairs have been made. But here, I ask: Have any of you had this change-out to a Maule TW made on your Chiefs ? I have previously flown a PA-12 and it would sometimes shake a little but nothing significant. Is this commonly characteristic on Chiefs ? Is a tension spring arrangement more appropriate for a Maule TW ?

For Paul, I think you previously said that "they all shimmy after about 300 hours" or words to that effect. Can you somehow quantify shimmy ?

Thanks for your input

Dale

[MikeB]

Dale,
I think I've tried every combination of springs and shim angles possible on my Pneumatic Maule tail wheel. On grass it's not too bad but 90% of the time it will shake the fillings out of your teeth on hard surface. I finally went back to my small hard rubber Firestone and my troubles were over (no shimmy at all). As much as I'd like to use the pneumatic for a little better taxi ride I just can't get it to stop shimmying. On the other hand, the hard rubber Maules seem to work better or at least my old one did before I replaced it with the pneumatic one. The Firestone is like a Scott 2000 and works fine. I doubt I put 50 hours (from new) on the Maule pneumatic before I replaced it. It was either replace it or wreck something.
Mike

[bsafran]

That Maule shimmy has caused Aeronca pilots more frustration than just about anything else on the airplane. A lot of smart people have tried several different fixes, but there seems to be no sure fired way to dampen out for good that model of tailwheel. Just a word of caution - that hard shimmy has been responsible for more trouble than just trying to keep the airplane rolling straight on landing. The bottom tailpost area of the Champs and Chiefs has always been a magnet for rust and corrosion and the tubing is not quite as strong as it was in the late 40's when it was brand new. We have had six different Aeroncas we had to repair where a previously undetected rusted lower tailpost separated from the longerons once that wild shimmy shook it hard. This is not a fun repair so the sooner you either fix the shimmy or replace the unit the better off you will be. Do a little test the next time you are at the airport. Lay on the ground on the rear right side next to the hand hold on the longeron. Grab the hand hold and try and rock the airplane back and forth while looking at where the longerons join the tailpost. If the longerons move back there, you have a broken tailpost.

[MikeB]

Brian makes a good point. Our 'club Champ' had a pronounced (worse than normal) shimmy. The tail post was broken loose from the longerons and required a welding repair including the rusted longerons.
Mike

[Paul Agaliotis]

Dale,
All of the Maule tailwheels I've used, installed new, have started to shimmy after about 300hrs. Generally the wear is very slight but the wheel just wont tolerate it. The pneumatic wheel is better than the solid one. I've used a bunch of Langs, they get a bunch of wear but don't shimmy like the Maule. The Scott is a good wheel but parts are getting too pricey.
The best wheel I've found is the Aviation Products wheel. Very simple and trouble free. I hate to see people struggle with a bad wheel when a great one exists.
Paul

[Nathan K. Hammond]

It shouldn't make a difference which springs you use. The Special springs maule has are a marketing gimmick.

I'd bet a case of beer, the arch on the tailwheel spring is the real problem. When the tail is heavy or the spring looses it's arch, you'll have problems. Add a large T/W tire and it exaggerates the problem.

Here's a good write up on the problem....
http://www.pierceaero.net/tws.php

And the acclimated picture...


Next time you're at the hangar, put a plumb bob on your tailwheel and I bet that will show the issue.

Good Luck.

nkh

[Roger Anderson]

I do not have a 3200, however do concur with a trailing tailwheel angle being the number one cause of shimmy. Be sure it is completely vertical. Correcting that cures mine, 3-24B, every time. In the case of mine, it is usually the pads under the springs compressing, or my terrible landings bending the spring slowly.

[MikeB]

Here's what Brian was discussing on a previous post. This occured on the Club Champ which had a pronouced shimmy in the tailwheel a couple of years ago. I don't remember if it was found during an annual or by accident (bad term ) but required some repair at the longeron and the tail post. You can see the crack radiating around the tail post. This plane is on skis during the winter months which doesn't help anything either as the tail section tends to fill with snow and then rust.
Mike

[EDGEFLY]

A little update on my tailwheel situation. After the repair of the broken link in the new tension springs, the A&P reinstalled them with more tension on them (both sides) and for now, at least there seems to be very little shimmy on normal landings both on grass and pavement. I did make the inspection suggested by bsafran and could find no evidence of the movement he described. Also, the A&P had a copy of the same pictures Nkh posted and showed them to me yesterday. Therefore, I assume he did not find this problem on my plane. I'm hoping the increased tension solves this problem and that I have no more broken parts. The taxi performance is measurably better too.

Dale

[EDGEFLY]

Another follow-up on the Tailwheel shimmy situation. Shortly after my last post the Wag-Aero set of springs & chain links & fasteners which had been "tightened" survived exactly 3 landings. On the 4th, on pavement, both fasteners failed and left neither of the springs connected to the Tailwheel ! Somewhat chagrined, I asked the FBO to simply reinstall the Maule hardware but to be certain that it was done in complete compliance with Manual and installation instruction sheet which I had. Since this was repair 3 without any improvement, I also asked to be present when the work was done. This happened and although the Maule installations could be better, and it took two installations to satisfy me that they had been religiously followed, the original Maule parts were reinstalled.

Since then, there have been a total of 35 landings on both pavement and grass with the result that there was s very minor shimmy on two of them ! Ground steering is excellent and I am now hoping this sad tale has come to a conclusion.

Dale

[Red(neck) Barron]

Ditto on Paul's post re: the API tailwheel. I put on one my Champ last winter and have lived happily ever after.