Nose wheel shimmy

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1 week 4 days ago #2971 by STEVE ELLS
Replied by STEVE ELLS on topic Nose wheel shimmy
Thanks for letting us know.
A very comprehensive article.
Steve

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2 weeks 9 hours ago #2969 by McFarlane Aviation
Replied by McFarlane Aviation on topic Nose wheel shimmy
Hi John,
Our founder and CEO Dave McFarlane wrote an article that details his experiences fighting nose wheel shimmy and gives solutions. You can find it here: can-you-stop-nose-gear-shimmy.pdf (mcfarlaneaviation.com). I see that you’ve already put extensive work into fixing the problem – but thought this may be helpful in understanding the nose wheel shimmy and give some effective steps to prevent them in the future.

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2 weeks 1 day ago #2964 by STEVE ELLS
Replied by STEVE ELLS on topic Nose wheel shimmy
1977 182Q

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  • PAOLO MONTANARI
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2 weeks 2 days ago #2960 by PAOLO MONTANARI
Replied by PAOLO MONTANARI on topic Nose wheel shimmy
what is the cessna model we are speaking of ? 182 ,182 RG or 210 ? I do not find the info in john profile

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2 weeks 2 days ago #2959 by STEVE ELLS
Replied by STEVE ELLS on topic Nose wheel shimmy
Hi John,
What a bummer.
I think you're referring to what's called the steering bungee. It is the connection between the rudder bar and the nose wheel.
There have been more than a few nose gear stop limit tangs broken off by using a tug and a long tow bar. A close inspection of the lower part of the nose gear attach casting will show if the stop has been sheered.
If it has, it's possible that the steering bungee was damaged.
The bungee is a spring loaded tube that connects what's called "the whiffletree" a part of the rudder/nose wheel steering mechanism.
One the ground the nose wheel is steered by connection with one end of the bungee. On the ground everything--the whiffletree, the fwd and aft end of the bungee and the steering collar on the nose gear.
Once the nose gear extends, it's locked forward by the centering lug on the upper torque link; that locks the forward end of the bungee in a static position--it can't move.
But the rudder pedals must move to move the rudder; that's where the spring connection in the bungee comes in.
I haven't spoken with a Cessna engineer on this, but I wonder how much the springs in the bungee contribute to suppressing nose gear shimmy.

What you are describing is violent--please look extra closely at the cast parts at the top of the strut and at the bottom that secure the nose gear assy to the firewall. I have heard of those parts being broken during violent shimmy episodes.

It seems that the steering bungees, part number 0760622-1 are aging. And some have started to fail. The only source, besides a used one from a salvage yard is McFarlane. ($2048)

You should be able to tell if your bungee is bad by removing pushing and pulling on the end that sticks through the firewall; the spring loading should be felt both ways.

Please let me know what you find and of possible take pictures of any damage.

Sorry your vacay plans had to change.

Steve

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  • JOHN QUIMBY
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2 weeks 6 days ago #2957 by JOHN QUIMBY
Replied by JOHN QUIMBY on topic Nose wheel shimmy
Well after buying the Macfarlane rebuild kit the shop replaced the bushings; shims, bolts, bearing felt, repacked the bearings, serviced the dampener, AND replaced and balanced the tire. Apparently the wheel had a ton of extra weight RTV’d on and had worn very unevenly.

After all that I have a more serious problem that was only discovered on the check ride. It appears the violent shimmy x 2 times sheared the jack screw that connects the pedals to the nose wheel / tail. They will have to dig into to see how bad it really is. I’m praying for no firewall damage. I don’t understand why it happened since I didn’t have a nose heavy landing when it happened. It’s not clear to me when it broke as I had two non-eventful landings on my way to drop it off at the shop.

Wondering out loud - it’s hard to imagine I didn’t notice it on the flight and taxi over to drop it off, could it have been broken by the tug moving it around off the ramp? Not that speculating will get it fixed any sooner. Scrubbing the vacation flight and getting in the car to drive 10 hours.

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