I guess you do keep on learning..

OkieAviator

OkieAviator

Pattern Altitude
Joined
Aug 17, 2014
Messages
1,865
Display Name
Display name:
OkieAviator
So it's always said the PPL is a license to learn. I truly believe that as well and had a landing yesterday which reinforced that concept.

A quick background is I became 50% owner on a 1977 172N. We had the exterior repainting and the avionics upgraded. So we just got it back and yesterday was the first time for me to fly it. Today it's due for annual so I was eager to fly it knowing that it might be a week or so getting the annual done. The known issues with the plane right now is the right main has a leak and there's a shimming issue with the front strut. On my way to the airport I talked to the A&P and he confirmed he knew those issues but other than those he felt it flew fine.

So I got to the airport, put air in the tires, filled the plane with gas, checked the weather and took off for my destination. Everything was fine until I got about 6 miles out from my destination and started descending. It was obvious weather had changed and I confirmed via ATIS. Wind was a bit of a cross but was 18 gusting at 23. Based on this was going to approach at 65, coming in I was getting bumped around a bit and knew I was a tad high but it's a 5000 ft runway so I planned to touch at 1000 ft markers. I was fighting the wind a bit getting down but nothing unusual for flying in Oklahoma.

As I touched down the plane started shaking and I feared I popped the right main. So I gave some left aileron to try to take the weight off and not grind down the wheel pants and gave some right rudder. I gave too much aileron and started heading for the left side of the runway so I decided if the tire was popped I was going to go ahead and grind it on the runway rather than go off the side so I went aileron neutral and right rudder a bit harder. I could feel the plane slipping and now figured I was about to go into a ground loop so I gave a bit of left rudder and a blip of power... I was now straight and slow and I didn't hear any grinding. I exited the run way, taxied to parking and checked the damage.... nothing... no issues, no grinding, no popped tires.

It occurred to me that while I've encountered nose wheel shimming issues on taxing I've never had it so bad that I encountered it while landing. So this must be what it's like. I decided I only wanted to land one more time like this and that was going to be back at home field. I decided to cut out my other stops and B line it back to KHSD... well I did do a low approach at KGOK just to do a practice in this wind. Not landing back at KHSD my approach was solid, I let the mains touch and held back a bit, but once the nose wheel hit it shook like crazy and this time felt like it was porpoising a bit. Not a pleasant experience.

Here's a good example - http://www.youtube.com/watch?v=9Jc4usJLfds

at about :37 is what my plane did on touchdown.
 
Happens. Stuff breaks. Talk to CPA before repairing it. Many shops will flat do it wrong or recommend things that are band-aids.
 
Nose wheel shimmy is common in the 172 ,have the mechanic tighten everything up ,it should be fine.
 
OkieAviator said:
So it's always said the PPL is a license to learn. I truly believe that as well and had a landing yesterday which reinforced that concept.

A quick background is I became 50% owner on a 1977 172N. We had the exterior repainting and the avionics upgraded. So we just got it back and yesterday was the first time for me to fly it. Today it's due for annual so I was eager to fly it knowing that it might be a week or so getting the annual done. The known issues with the plane right now is the right main has a leak and there's a shimming issue with the front strut. On my way to the airport I talked to the A&P and he confirmed he knew those issues but other than those he felt it flew fine.

So I got to the airport, put air in the tires, filled the plane with gas, checked the weather and took off for my destination. Everything was fine until I got about 6 miles out from my destination and started descending. It was obvious weather had changed and I confirmed via ATIS. Wind was a bit of a cross but was 18 gusting at 23. Based on this was going to approach at 65, coming in I was getting bumped around a bit and knew I was a tad high but it's a 5000 ft runway so I planned to touch at 1000 ft markers. I was fighting the wind a bit getting down but nothing unusual for flying in Oklahoma.

As I touched down the plane started shaking and I feared I popped the right main. So I gave some left aileron to try to take the weight off and not grind down the wheel pants and gave some right rudder. I gave too much aileron and started heading for the left side of the runway so I decided if the tire was popped I was going to go ahead and grind it on the runway rather than go off the side so I went aileron neutral and right rudder a bit harder. I could feel the plane slipping and now figured I was about to go into a ground loop so I gave a bit of left rudder and a blip of power... I was now straight and slow and I didn't hear any grinding. I exited the run way, taxied to parking and checked the damage.... nothing... no issues, no grinding, no popped tires.

It occurred to me that while I've encountered nose wheel shimming issues on taxing I've never had it so bad that I encountered it while landing. So this must be what it's like. I decided I only wanted to land one more time like this and that was going to be back at home field. I decided to cut out my other stops and B line it back to KHSD... well I did do a low approach at KGOK just to do a practice in this wind. Not landing back at KHSD my approach was solid, I let the mains touch and held back a bit, but once the nose wheel hit it shook like crazy and this time felt like it was porpoising a bit. Not a pleasant experience.

Here's a good example - http://www.youtube.com/watch?v=9Jc4usJLfds

at about :37 is what my plane did on touchdown.
Click to expand...

Common on many Cessna singles. Get the Lord to help you, and the problem will be gone permanently.
 
This is usually caused by worn torque link bushings and shims, much cheaper than a Lord dampener.
 
My clubs 172N recently had the same shimmy issue. Glad nothing else got damaged


Sent from my iPhone using Tapatalk
 
Problem is you bought a plane with the little wheel on the wrong end :D

Try to hold the nose off till you're as slow as possible, then keep that stick back.

If it starts to shimmy, just keep slowing down STRAIGHT ahead, stick all the way back in your gut.

....ahh heck, you should see a amphib shimmy if you touch down those fronts too hard.
 
Last edited:
Yep, my old 150 did that fairly often when I still had it. A little back pressure on the yoke and it would stop instantly. Finally figured out I was getting lazy and letting that nosewheel slap the ground a bit. Hold it off, and it will behave just fine. Consider it prep for flying something with the third wheel where it should be ;)

I do miss that little plane terribly though.
 
Silvaire said:
This is usually caused by worn torque link bushings and shims, much cheaper than a Lord dampener.
Click to expand...

You get what you pay for. If you "service" the torque links and bushings, all you gain is more time, until the next event. Depending on use it might be a year or two, or perhaps less under heavy use (and maybe a couple of nose-first or hard landings).
OTOH, the Lord shocks take care of the problem permanently, possibly for the life of the plane.
 
My plane partner was out this weekend so haven't talked to him. I'm fine with all 3 solutions; more back pressure on yoke while landing, new bushings and links and a dampener.
 
Well I was (am) pretty well broke, and back pressure is much cheaper than the others :D
 
RotorDude said:
You get what you pay for. If you "service" the torque links and bushings, all you gain is more time, until the next event. Depending on use it might be a year or two, or perhaps less under heavy use (and maybe a couple of nose-first or hard landings).
OTOH, the Lord shocks take care of the problem permanently, possibly for the life of the plane.
Click to expand...

Well it kind of all goes together. The Cessna dampener works but they suffer neglect and most of these planes have five or maybe even ten thousand or more hours on them. If there is any shimmy and it's ignored for a length of time it wears out the torque links and the dampener mounting lugs. Rebuilding the dampener at that point is only addressing half the problem.

There is no argument that the Lord dampeners are a good product but it honestly is not necessary to spend a thousand dollars on what is admittedly not an unduly sophisticated component. With proper service and upkeep the original equipment is fine and you won't experience problems such as this. All of the shims, bolts, bushings and o-rings are readily available at reasonable cost.
 
Silvaire said:
This is usually caused by worn torque link bushings and shims, much cheaper than a Lord dampener.
Click to expand...


Ding ding ding. 30+ year old airframes...

But a tendency to replace the dampener first because the mechanic has been working on them since they were 10 year old airframes and has built a habit.
 
OkieAviator said:
My plane partner was out this weekend so haven't talked to him. I'm fine with all 3 solutions; more back pressure on yoke while landing, new bushings and links and a dampener.
Click to expand...


Just find a mechanic who has a clue and let them decide. :)
 
denverpilot said:
Just find a mechanic who has a clue and let them decide. :)
Click to expand...

I stopped by the hanger tonight to drop something off. The front cowl was off for the start of the annual and the dampener was missing. My guess is he's rebuilding it, so maybe that with a disciplined back pressure landing all will be good.
 
An empty or badly serviced shimmy dampener will allow oscillations but severe shimmy is the result of allowing that to continue and trying to avoid it by keeping the nosewheel off. After a period of time the torque link bushings get worn and you have a cascading effect.

You need to address this all at the same time. All of the parts are available including various sized shims to keep the torque scissors tight. If you don't the rebuilt dampener will soon wear out and the symptoms will return just as RotorDude said.
 
OkieAviator said:
I stopped by the hanger tonight to drop something off. The front cowl was off for the start of the annual and the dampener was missing. My guess is he's rebuilding it, so maybe that with a disciplined back pressure landing all will be good.
Click to expand...


Ask him specifically if the rest of the nose gear components are within factory tolerances.

If all he took off was the dampener, he won't be able to answer the question.

The dampener can cover up problems for a short time. Then the out of tolerance stuff will destroy the rebuilt dampener again and you'll get to pay twice to fix it instead of once.

Most rentals are maintained dampener only. Cheap. If you own it, ask and make sure the whole system is inspected.

Good luck.
 
They get really sloppy. If you're experiencing severe shimmy as you described then it definitely needs to be addressed. You can replace all of the bushings, bolts and shims at a very reasonable cost. It's a no-brainer.
 
Silvaire said:
An empty or badly serviced shimmy dampener will allow oscillations but severe shimmy is the result of allowing that to continue and trying to avoid it by keeping the nosewheel off. After a period of time the torque link bushings get worn and you have a cascading effect.

You need to address this all at the same time. All of the parts are available including various sized shims to keep the torque scissors tight. If you don't the rebuilt dampener will soon wear out and the symptoms will return just as RotorDude said.
Click to expand...

This ^^

I rebuilt the front strut on my old 172 I used to have after it kept leaking down. It was quite an aggregating job not pinching the O-rings.
I figured it was a good time to address some intermittent shimmy problems while I was at it so we checked the shimmy dampener, scissors, etc. BTW the shimmy dampener was a Lord installed by the previous owner.
Turns out the shimmy dampener was fine. Scissors were a little sloppy.
Mechanic says the tire is kinda old, might be a good time to replace it as well.
Ordered a new tire and was mounting it on the rim when a buddy stopped by the hangar and tells me I should get the new tire balanced.
I'm like "can you do that?" He says he has been doing that for years.
So I drop off the mounted tire at my local FAA certified tire shop. Never had another problem.
May pay to check out the tire while you have it down.....
 
You must log in or register to reply here.
Back
Top