1980 TR182 Nose Wheel Shimmy

[Danny Camp]

Had a bad day Saturday. Came in to land and had a slight crosswind so I came in a little faster than normal. As soon as the nose wheel touched the ground it shook so bad that I had no rudder pedal control and it took me left off the runway. Luckily there was no damage. Tomorrow I will be checking everything and tightening up every bolt I can find. Flat spotted the two mains trying to keep it off the grass so I’ll be changing those as well. What else can I check other than bolts and the shimmy dampner? I read something about pins so maybe that is something to check as well. The bungee seems to be working properly. I can’t have this happen again. It took a few years off my life as it is.

 

[455 Bravo Uniform]

Only advice I can give, if you’re not already doing it, is to keep that nosewheel off the ground by pulling that yoke all the way to your belly at full touchdown. If you rollout with some amount of elevator travel left, it’s not perfect.

100% of my taxiing is done with the yoke full aft, so it became a habit when all 3 rubbers are on the ground. I think it’s good practice. Pretend like you’re on grass/dirt all the time.

I can’t give specifics on maintenance because I am not knowledgeable enough other than to look for flex or wear. Also, tightening down too much is not good for the links, there’s a bushing in there. Experts will be by shortly to help you out.

 

[Danny Camp]

Yeah it is hard to do with the TR182. You’re basically looking at the sky when you touchdown.

 

[BillTIZ]

Landing a little faster than normal in a C182, most likely the nose wheel touched first compounding the problem. Landing in a wind, especially a crosswind, full flaps don't help. Best landings in a crosswind with the C182 is about the 20 degree flap setting. From the POH "when landing in a strong crosswind, use the minimum flap setting required for the field length". Granted, you may not have been in a strong crosswind, but consider the advice. Steering after landing is with the steerable nosewheel, if you had the rudder displaced for a wing low crosswind landing and touched nosewheel first, that may have started the vibration you experienced.

It is also interesting to note that they no longer publish "Max Crosswind", but state "The maximum allowable crosswind velocity is dependent upon the pilot capability as well as the airplane limitations. Operations in direct crosswinds of 15knts has been demonstrated."

 

[Dan Thomas]

Oh, boy. Another shimmy problem that will get "fixed" by tightening up everything (which risks overstressing all that hardware and having it then break on landing) and fooling with the shimmy damper.

I got tired of explaining the root cause of nosewheel shimmy on POA a long time ago. Hint: It's not the shimmy damper or loose hardware or even pilot technique. It's dynamic imbalance of the nosewheel/tire assembly itself, imbalance that causes some shimmy that then wears out the damper, torque link bushings, steering collar, and just about everything else. If a nosewheel gets any balance at all, it's a static balance which does not fix the dynamic balance and can actually make the dynamic balance worse. Most mechanics just don't get it.

To get an R182's nosewheel shimmying takes some serious imbalance. That airplane is not nearly the problem that the lighter Cessnas are.

Use POA's search function to search "nosewheel shimmy" and find some of my posts.

When you buy new tires for your car, your wheels get dynamically balanced. Every time, on every wheel, on every car or light truck. In the old days before dynamic balancing equipment, everybody's steering wheels shook constantly. Shimmy.

 

[Danny Camp]

Oh, boy. Another shimmy problem that will get "fixed" by tightening up everything (which risks overstressing all that hardware and having it then break on landing) and fooling with the shimmy damper.

I got tired of explaining the root cause of nosewheel shimmy on POA a long time ago. Hint: It's not the shimmy damper or loose hardware or even pilot technique. It's dynamic imbalance of the nosewheel/tire assembly itself, imbalance that causes some shimmy that then wears out the damper, torque link bushings, steering collar, and just about everything else. If a nosewheel gets any balance at all, it's a static balance which does not fix the dynamic balance and can actually make the dynamic balance worse. Most mechanics just don't get it.

To get an R182's nosewheel shimmying takes some serious imbalance. That airplane is not nearly the problem that the lighter Cessnas are.

Use POA's search function to search "nosewheel shimmy" and find some of my posts.

When you buy new tires for your car, your wheels get dynamically balanced. Every time, on every wheel, on every car or light truck. In the old days before dynamic balancing equipment, everybody's steering wheels shook constantly. Shimmy.

I have read some of your post. Not looking to crank down on anything. I just want to make sure nothing is loose and check that nothing is worn out. I’ve been in touch with an IA that has worked on these for years and he has given me some things to check. I just don’t want to miss anything. The smaller tires at higher speeds is not a good thing and the previous post has reminded me to not be lazy with the landings. Keeping the nose off the ground is some good advice. I came in a little too hot and let the nose touch too soon. That in itself was probably most of the problem. I should find someone that can balance the nose wheel properly and that would be the second part as long as everything else looks good. I’m in Shreveport,La if anybody knows somebody that can balance this wheel properly.

 

[Dan Thomas]

The smaller tires at higher speeds is not a good thing

Well, your tires are rated for 120 MPH, so there's that. The real problem is dynamic imbalance.

I came in a little too hot and let the nose touch too soon. That in itself was probably most of the problem.

Yes, landing hot is a very common and very bad habit. Once your instructor lets you get away with it, you can have an awful time unlearning it. Look at your POH to see what approach speed Cessna recommends for your TR182. That airplane, with full flaps, stalls at 50 knots (about 39 indicated), so approaching at 80 or whatever is way beyond sensible. And start bleeding off the speed before you get into ground effect where it's a lot harder to get rid of it as the drag falls. This is called the round-out, and most PPLs don't know the difference between it and the flare. Google it.

From the TR182 POH:




Motorcycle shops typically have dynamic balancers for small wheels, and some owners now swear by dynamic balancing.

 

[Danny Camp]

Thank you. I’ll start looking for a motorcycle shop that will do it.

 

[nrpetersen]

If you still suspect the linkage, You must ground test it only by first defeating that unobvious strut assembly feature that forcibly hard-centers the nosewheel on full strut extension after liftoff. This automatically centers the nose wheel on initial touchdown to help keep you out of the weeds.

You have to defeat this feature with the nosewheel off the ground for any evaluation of the shimmy linkage. This is easily done by first letting all the N2 out of the strut until it is fully collapsed. Then raise the nose wheel by pulling down the tail, then burp enough air back into the strut to allow it to re-extend to the middle of it's travel.

Now you can wiggle the nose wheel exercising the shimmy linkage. Any loose linkage should then be obvious.

Dynamic (and NOT just static) balance is an obvious cause of shimmy, but loose linkage components can contribute too. This procedure isn't in any Cessna manual that I know of, however.

 

[Danny Camp]

Thank you.

 

[brien23]

Your aircraft when it was new did not shimmy it's not tires or keep the nose pointed up it's poor maint. Find someone that can replace the bushings and slop in your nose gear or it will never go away.

 

[Dan Thomas]

Your aircraft when it was new did not shimmy it's not tires or keep the nose pointed up it's poor maint. Find someone that can replace the bushings and slop in your nose gear or it will never go away.

I learned to fly in a six-year-old 172 over 50 years ago. It had horrific shimmy. The airplane had less than 1800 hours on it. It is indeed dynamic imbalance, as I proved by dynamically balancing all the nose and tail wheels in the flight school fleet, for years, and we did not have shimmy at all on the nosewheels, even with worn linkages. If we had shimmy on the tailwheel it was because the tail was getting slammed down and the tailsprings bent so that the steering axis was bent forward. That will make shimmy. Surely you have seen a shimmying shopping cart caster? Its pivot is bent.

After I left the flight school for another shop I could not find a cheap enough dynamic balancer for aircraft wheels, so I built my own. Stopped lots of shimmy with it.

 

[Gary Ward]

I learned to fly in a six-year-old 172 over 50 years ago. It had horrific shimmy. The airplane had less than 1800 hours on it. It is indeed dynamic imbalance, as I proved by dynamically balancing all the nose and tail wheels in the flight school fleet, for years, and we did not have shimmy at all on the nosewheels, even with worn linkages. If we had shimmy on the tailwheel it was because the tail was getting slammed down and the tailsprings bent so that the steering axis was bent forward. That will make shimmy. Surely you have seen a shimmying shopping cart caster? Its pivot is bent.

After I left the flight school for another shop I could not find a cheap enough dynamic balancer for aircraft wheels, so I built my own. Stopped lots of shimmy with it.

View attachment 127188

I understand a dynavibe balancer can be used to balance wheels and tires? I have one. Just need a spinner.
What did you use to locate the heavy part of the wheel/tire?
It can be done on the plane I think? I have large spinner for truck tires but it is 3 phase power which I don't have at the airport.
Any thoughts?

 

[Clip4]

4 issues on the 182RGs.

1. The shimmy dampener needs to be serviced with fluid. The procedure is to move the nose gear so the rod is fully extended, add fluid, exercise the dampner, add fluid. You should get kinda if a burb a some point. Usually the issue.

2. The shimmy dampener requires o-ring replacement and service.

3. The bushings at the dampener attach points are worn out.

4. Nose wheel balance.

 

[Anthem]

check the collar to make sure that isnt damaged and the dampener shock (or use the mcfarlane one that doesnt have a serviceable shock inside).

 

[Bell206]

I understand a dynavibe balancer can be used to balance wheels and tires?

Yes. DynaVib or similar equipment can be used to balance any rotating component to include ceiling fans.

It can be done on the plane I think?

It could, but now you are including the unknown tolerances of the wheel bearings/races, etc. Performing a tire/wheel balance should be done separate from the aircraft. The downside to balancing on the aircraft is that you will usually mask the actual problem by balancing it out vs fixing the actual problem.

 

[Dan Thomas]

I understand a dynavibe balancer can be used to balance wheels and tires? I have one. Just need a spinner.
What did you use to locate the heavy part of the wheel/tire?
It can be done on the plane I think? I have large spinner for truck tires but it is 3 phase power which I don't have at the airport.
Any thoughts?

That dynavibe looks to be no more than a fancy static balancer. A true dynamic balancer spins the wheel on a shaft that is free to move a little, and sensors pick up both static inbalance (up-and-down movement) and dynamic imbalance (wobble). The dynavibe tests the wheel on the airplane's axle, which isn't going to let it wobble is any fashion so as to measure it.



To find the amount and location of shimmy-causing dynamic imbalance, the wheel must be spun, and the deflection location and degree must be found, then weights are attached to the wheel to balance those heavy spots.

My balancer was based on one of the earliest dynamic imbalancers from the 1950s. The wheel rides on a shaft, with machined aluminum cones centering the wheel on the shaft, and the shaft rides in low-friction ball bearings in an aluminum block that mounts to another shaft at 45° to the wheel shaft. That angled shaft sits in two more ball bearings inside the cabinet. The axis of the angled shaft intersects with the plane of inner bead seat of the wheel at the axis of the wheel shaft centerline. Any imbalance in that plane of the wheel will not wobble the shaft, but anything outboard of it will. The angled shaft drives a needle on a scale that shows the amount of outboard imbalance, and a precisely machined aluminum drum on the inboard end of the wheel shaft, positioned next to a fixed rest, shows the location of the imbalance. You use a fine-point Jiffy marker, resting on that rest, and advance it until the spinning drum touches it. The black mark on the drum is 180° to the heavy spot, so stop the wheel, position the black mark up, and attach weight to the inside of the outer bead seat area. Stick-on weights, on a thoroughly cleaned surface. Now we have to remove the imbalance on the inside of the wheel, so we let the wheel rotate on its own in those low-friction bearings and when it stops, the heavy spot is down. Attach weight to the inside if the inner bead seat at the top, enough so that the wheel will stay in an position you put it. This weight will not change the balance of the outboard sections of the wheel.

The wheel is spun for the outboard balancing by a small wheel driven by a small motor inside the cabinet. Moveing the lever puts that wheel against the tire to spin it up. It doesn't have to turn all that fast, either. Let the drive wheel fall off, turn off the motor, letting the wheel coast so you can read the needle and mark the drum.

It takes time, much more time than a modern electronic balancer takes, but I could afford this one. It's much more complicated to operate than the modern machines, so you have to think some, but it stopped destructive nosewheel shimmy so it was worth it.

 

[Dan Thomas]

 

[Dan Thomas]

One point this fellow does not make: The wheel wants to rotate around its center of mass. If there is a heavy spot, the center of mass moves away from the center of axis toward the heavy spot. That makes, believe it or not, the light side of the wheel move outward, not the heavy side.

This is not intuitive. Many folks think that the heavy spot will pull outward and it will move the wheel outward. Nope. The balancing weight has to go on the side NOT being pulled outward, in order to bring the center of mass back into line with the rotational axis.

 

[Danny Camp]

Your aircraft when it was new did not shimmy it's not tires or keep the nose pointed up it's poor maint. Find someone that can replace the bushings and slop in your nose gear or it will never go away.

Thanks for the reply. I found that the shimmy dampner seals are leaking and one of the torque link bushings needs replacing. My guess is the shimmy dampner was doing its job but working over time and the seals gave out. Ordered the torque kit and seal kit. Should be in the air again within the week.

 

[Dan Thomas]

Thanks for the reply. I found that the shimmy dampner seals are leaking and one of the torque link bushings needs replacing. My guess is the shimmy dampner was doing its job but working over time and the seals gave out. Ordered the torque kit and seal kit. Should be in the air again within the week.

So you trust the advice of an owner over that of a licensed aircraft mechanic?

 

[Danny Camp]

So you trust the advice of an owner over that of a licensed aircraft mechanic?

? I’m listening to everybody. lol. I have a bushing that needs to be replaced and a seal kit for the shimmy dampner because it is leaking. That gets my plane home so I can take the tires and have them dynamically balanced which I also believe is a good idea and makes since.

 

[Dan Thomas]

That gets my plane home so I can take the tires and have them dynamically balanced which I also believe is a good idea and makes since.

Can't dynamically balance the mains. The brake disc is in the way. Static is good enough for them.

I should have remembered to warn you to use really top-quality sick-on weights on the R/TR182. When retracted, the wheel is a fraction of an inch beneath the oil pan, and hot cooling air also flows over it, and will loosen the sticky stuff on cheaper weights. The weight will fall off somewhere, maybe when the gear doors open, or when the airplane touches down and the sudden acceleration rips the weight loose and it gets flung somewhere, maybe forward into the prop, or upward into the engine area. This happened to ours, but the wheel had its hubcaps, keeping the weight contained. I was using weights made for Goodyear and sold by Aviall, but "aircraft quality" really doesn't mean much anymore. The motorcycle shops might have better stuff. No biker wants to get shot by high-speed lead off his front wheel.

 

[Danny Camp]

Ahh. Makes since. I noticed the nose wheel had some type of glue, similar to JBL, to static balance. What is that stuff? Seems like that works really well.

 

[Danny Camp]

Ahh. Makes since. I noticed the nose wheel had some type of glue, similar to JBL, to static balance. What is that stuff? Seems like that works really well.

*JB Weld