Cessna 120-140 Association

Was taxying across some grass after returning from a flight and the bottom tailwheel spring snapped off just in front of the bolt/connection to the tailwheel itself. Obviously left me with a tailwheel dangling on the chain with little chance of steering - glad it happened as I was pulling up to the hangar and not on landing.

Any suggestions on why this may have happened - metal fatigue? Could the fact the tailwheel tyre was replaced prior to this flight by the maintenance workshop have anything to do with it (I can't really imagine a wrong assembly could have been the issue...?)?

And more importantly, what would be quickest and/or lowest cost remedy - should I replace with a complete set of new springs (my a/c is sub 14000 serial number) or can I simply replace the longest bottom one? Also, since I would like to get it done asap, should I expect any other parts that need to be replaced from taking apart the spring assembly?

Many thanks for your thoughts!

I would replace the entire spring stack. along with bolts at both ends of the spring. it is not all that uncommon. If you should happen to go to Oshkosh or the 140 Convention you will see quite a few of our airplanes with doublers on the lower rudder. In fact my 120 might have a repair.


Bill

Good reply, replace the entire stack. Use an AN 6 bolt to connect the spring set to the tail wheel attach bracket. Some were produced with an AN 5 bolt which is not adequate...later models used AN 6.

Thanks heaps for your replies. Since both of you recommend replacing the whole stack, just wondering why the individual springs are sold separately rather than only as a stack?

I imagine it should be a fairly easy fix as long as I can place the tail onto a support or does the rudder have to be removed to access the upper bolt? Will those springs have to be treated/painted or can I assume they are protected against rust?

@337 - not quite sure what a doubler is.

If you are lucky the last person will have installed the bolt upside down and the rudder will not have to be removed. I haven't looked lately but I think the springs can be bought individually - owner's choice. A doubler is a repair. When the spring breaks the tailwheel will go bouncing along on it's chains damaging the bottom of the rudder. Be sure to replace the attach bolts and don't be surprised to see a rubber hose as a bushing on the attach bolt. There a couple of different spring sets. Maybe someone on the web site can comment on the different styles. Another problem is the springs go flat and change the angle on the tailwheel and that aggravates tailwheel shimmy.

Bill

I tried to attach a pdf article to this message, but the system wouldn't allow it. Call me 734 645-3187

Neal Wright wrote a great article on tail wheel springs and attachments. I know Rob is working to restore them. Hopefully it'll happen soon.

I have Neal's article on a pdf, but it's too large to try and attach to a PM and for some reason has the wrong file extension to attach here, which is pdf.

Thanks again everyone!

@6277 - if the article you tried to send me was the Neal Wright one "CESSNA 120/140/140A TAILWHEEL Spring Set Details, Mysteries and Secrets", I have found it.. Need to get through the 17 pages first though..

@337 - Bill. Fortunately the leaf broke where it attaches to the tailwheel itself as I transitioned from the taxiway to the grass area, so it only dragged a little on the remaining spring without damaging the rudder. Not sure about the upside bolt, need to check.

Unless I am mistaken, I will order this leaf set - seems to be all I need apart from replacement bolts? - http://www.univair.com/cessna/cessna-12 ... pring-set/