Tailwheel Springs

[Ratso]

It was time to replace the tailwheel tire on N3244A, sn25888. Searching the forums for guidance I decided to also replace the bearings and tailwheel main spring at the same time. After the parts arrived and the aircraft elevated on a jack it was then I noticed two main leaf springs have been installed on top each other. The third leaf spring (p/n 0542105 (pg. 54, item 12)) has been omitted from the tailwheel spring stack. Leaf #1 and #2 are present in the stack.

Any advice on where I can find just one leaf spring (p/n 0542105) so I can return the assembly to it original configuration?

Thanks in advance.

Steve
N3244A
25888
Member 8990

[canav8]

Call Univair Aircraft Corp

[bagarre]

You could cut one of the main springs down to the right length.

[C170U2]

When I found two main springs on my tailwheel I cut one of them down. Make sure you bevel the edge on the one you cut. It will be thicker than the book setup but I really don't see that as a bad thing.

[akclimber]

There sure seems to be a lot of tailwheel springs activity going on lately!
I hope ya'll don't mind me adding my question.
During the recent trip to the Wrangells, almost every cabin logbook had at least one story of broken tailwheel springs.
I even found this specimen on a wall:
https://lh4.googleusercontent.com/-gum_ ... 000583.JPG

This made me rather nervous for my ageing and sagging spring:
https://lh4.googleusercontent.com/-U8DD ... 000367.JPG

Considering I've been battling fairly substantial tailwheel shimmy, as is obvious after reading the threads here and looking at my tailwheel spring geometry above, I decided I better order a replacement.
The question is what should I get, considering I go to mostly rough strips or off airport.
Would the one spring replacement:
06-15100 or the stack 06-15000 from Aircraft Spruce:
http://www.aircraftspruce.com/catalog/a ... ckkey=9943
or one of the 3 options offered at Univair:
http://univairparts.com/shopping/advanc ... c_subcat=1

Any help would be greatly appreciated!

[canav8]

Yes, The main spring only for the 170. generally the main spring is to absorb the shock and wears out the fastest. Aircraft Spruce gets its inventory from Univair. I have gotton springs from Spruce with the Univair tags still on them.The other springs in the stack are there to dampen but generally do not wear out. The TIC170 has inferred average life of the spring for normal 170 flying is 500 hours. If you are harder on it,life span will be shorter, it is always best to increase your observance for any signs of fatigue as noted above. I notice when doing tailwheel checkout or biannual, pilots kinda gloss over the tailwheel rather then really get down and look. Please never take it for granted. You should say, As soon as it starts to shimmy, something is wrong! It might just be air pressure but that should be the flag waving thats says Hey Look At Me! D

P.S. There are many threads on this forum discussing this topic. Important thing since you are ordering a new spring is making sure the nut that holds the tailwheel is a metal stop nut not the nylon lock nut called out in the IPC. The nylon locknut does not seem to hold the proper torques for longperiods of time. You need an AN363-720 stop nut. Also getting a new bolt is important anytime you take the tailwheel assembly off the spring. That is the cheapest insurance policy you can buy right there. You dont wanna donate your stack like the rest of those guys. That should be the Wall of Neglect and Shame!

[170C]

Bruce/George, you have advised replacing a nylon type locknut with a steel one and there is some question regarding replacement of the bolt itself.

1) Did the L-19 bolt we purchased have a steel nut or a nylon locknut?
2) Any advise on when or if the L-19 bolt should be replaced?

[canav8]

Bruce/George, you have advised replacing a nylon type locknut with a steel one and there is some question regarding replacement of the bolt itself.

1) Did the L-19 bolt we purchased have a steel nut or a nylon locknut?
2) Any advise on when or if the L-19 bolt should be replaced?

Pokey, There should never be a question about it. Best thing to do when servicing the tailwheel is check the torque in the bolt to see if it has changed. If the bolt has stretched due to heavy use and neglect you should change the bolt. It is simple insurance. There is really no excuse to see the examples that have been on this forum about broken tail springs. They just dont break unless there is movement. I remember someone bringing up a very good point about the burrs on the end of each leaf in the spring stack. If you have never worked on the stack but you know it has been worked on( ie by a previous owner) it would behoove you to check for those burrs. Doug

[GAHorn]

Bruce/George, you have advised replacing a nylon type locknut with a steel one and there is some question regarding replacement of the bolt itself.

1) Did the L-19 bolt we purchased have a steel nut or a nylon locknut?
2) Any advise on when or if the L-19 bolt should be replaced?

The 0642105 eyebolt (L-19) was not furnished with a nut. The all-steel locknut is recommended.
The nut and bolt should both be replaced when the mainspring is replaced at 500 hours, or whenever the tailwheel assy is overhauled.

Doug, I don't agree that tail mainsprings only break when there is movement of that bolt/nut. The mainspring receives considerable stress where it contacts the trailing edge of the #3 spring, as that is where the loads are transferred to airframe. That #3 spring trailing edge abuses the mainspring whether or not it is radiused... but the mainspring durability is doubtless increased when the #3 spring lower, trailing edge is radiused/smoothed as that reduces wear and abrasion of the mainspring at that point (which is exactly where the mainsprings eventually fail if left in-service too long.)

[Bruce Fenstermacher]

Bruce/George, you have advised replacing a nylon type locknut with a steel one and there is some question regarding replacement of the bolt itself.

1) Did the L-19 bolt we purchased have a steel nut or a nylon locknut?
2) Any advise on when or if the L-19 bolt should be replaced?

frank, you can almost always, at least every case I can think of, replace a nylon lock nut with a all metal locking nuts, the reverse is not the case.

The L-19 bolt IS a bolt. Only special thing about it is it has a ring welded to to head. Treat it as you would any other bolt.

[GAHorn]

At the risk of appearing to discount Bruce's opinion, (which I most certainly do not), .... I'd not treat any bolt as if it were automatically a re-useable, permanent fastener.
Bolts (and many other fasteners) are used in differing service all over the airplane. Some bolts/screws are reuseable virtually forever ...until their threads wear out from repeated reinstallations..... but each should be considered expendable if it is in critical-service such as landing gear attach, wing-spar or strut attach, primary flight controls, etc.
Also, consider the type nut used in conjunction with it. The Nylon "nylok" friction nuts which are only moderately tightened by hand place almost no wear upon the bolt... but the all-metal locking friction nuts such as we're discussing on this tailwheel attach bolt (a landing gear item, as well) ... places additonal wear on the threads of that bolt.
It is normal practice to replace nylok nuts after second-use in non-critical applications (or anytime they can be turned on fasteners by hand). All-metal nuts and bolt combinations wear much more during installation, and expecially when high-torque is applied (in-fact, the bolt actually "stretches" when highly torqued, and in this installation each time the tailwheel hits the ground. That's why they become loose and should be checked/re-torqued and frequently replaced.)
I replace my tailwheel attach bolt anytime I replace the mainspring or overhaul/rebuild the tailwheel. It's much cheaper and faster than repairing/reskinning the rudder.

[akclimber]

That tailspring in the picture looked brand new. I think it broke due to either poor landing practice (3 pointing it) on those strips or just having the too small, stock tire for the rough strips.
So before I order the bolt, nut and the spring - which spring do you guys recommend? It seems like I have 4 options (the single leaf) or one of the 3 full leaf packs.
Any thoughts would be greatly appreciated!

[GAHorn]

The single leaf.(mainspring) is all you need. (and the bolt and nut)

[akclimber]

Thanks George,
The mainspring is 0542106
The steel lock nut is AN363-720

What is the part number for the L-19 eyebolt and do most people install it eye up (easier to tie-down) or down?

Thanks again!

[canav8]

Bruce/George, you have advised replacing a nylon type locknut with a steel one and there is some question regarding replacement of the bolt itself.

1) Did the L-19 bolt we purchased have a steel nut or a nylon locknut?
2) Any advise on when or if the L-19 bolt should be replaced?

The 0642105 eyebolt (L-19) was not furnished with a nut. The all-steel locknut is recommended.
The nut and bolt should both be replaced when the mainspring is replaced at 500 hours, or whenever the tailwheel assy is overhauled.

Doug, I don't agree that tail mainsprings only break when there is movement of that bolt/nut. The mainspring receives considerable stress where it contacts the trailing edge of the #3 spring, as that is where the loads are transferred to airframe. That #3 spring trailing edge abuses the mainspring whether or not it is radiused... but the mainspring durability is doubtless increased when the #3 spring lower, trailing edge is radiused/smoothed as that reduces wear and abrasion of the mainspring at that point (which is exactly where the mainsprings eventually fail if left in-service too long.)

George, your so literal.It is symantics. Okay the stress riser from the #3 spring trailing edge only causes failure when it looks at the main spring. How is that! lol