Tailwheel Assy ATTACH bolts/nuts

[N2255D]

No mechanical problems whatsoever (after Del replaced a worn mainspring tailwheel bolt. Check YOURS before it breaks if you want to save an expensive rudder repair. Thanks again, Del!)
http://www.mountainairframe.com/

George, does that mean the bolt has a shorter recommended change interval than the main leaf or are you just extra hard on it?

[GAHorn]

EDITNOTE: Be certain to read page THREE of this discussion thread regarding the correct number of flat washers to use with the L-19 eyebolt to take up the shank or proper torque will not be met.

No mechanical problems whatsoever (after Del replaced a worn mainspring tailwheel bolt. Check YOURS before it breaks if you want to save an expensive rudder repair. Thanks again, Del!)
http://www.mountainairframe.com/

George, does that mean the bolt has a shorter recommended change interval than the main leaf or are you just extra hard on it?

HA!

Well, no, actually. Here's the deal: We replaced the tailwheel mainspring last year and RE-used the nylon locknut and eye-bolt which held the tailwheel assy to the mainspring. Unfortunately, the Nylon locknut apparently did not hold torque and required re-tightening on two occasions. While at Mena, I asked Del to remove some teflon tape I'd installed as an experimental anti-chafe strip between my leafsprings (as that experiement proved unworthy) and while performing that work the nylon locknut was found to be in need of re-torque yet-again. The eyebolt thusly also showed evidence of excessive wear due to it's loose condition, so we replaced it with the IPC called-for AN bolt, and a new STEEL locknut.

When I next order parts, I'll likely order another eyebolt and install it along with another NEW STEEL locknut.

Bottom Line: I recommend the fiber/nylon locknut on all tailwheel attach bolts be replaced with steel locknuts whenever the assy is removed/replaced.

[wingnut]

NO, George, we did NOT re-use the old nylon lock nut . We always replace nylon lock nuts with new, and steel locks on condition.

Although the IPC does call for a nylon lock nut, after this incident I do concur with George; use a steel lock MS21045-7 or MS21045L7.
George, it was kinda oily back there, which could have inhibited the locking. Was that MMO
Oil and temps are a reason to use steel locks firewall forward too, even if the IPC calls out nylon locks.
Listen to me; advise on nylon lock nuts, and steel lock nuts, from a wingnut

[Bruce Fenstermacher]

George made me aware of his bolt issue at the convention as well as he spoke of it at the convention forum. I believe he had also run into others who had the same type of problem, all using the L-19 eye bolt.

I also had an L-19 eye bolt which tended to come loose. It also had lots of oil on it and was a fiber lock nut. It had also been "adjusted" many many times and I did not have a stock tail spring set up all of which I thought might lead to the bolt loosening every now and then.

I like the eye bolt and need to buy one for my new to me 170 but I wonder if using it to tie down your airplane like I did all the time doesn't also lead to it loosening as well. I know that George's airplane lives in a hanger and probably isn't tied by the tail in there. I'm wondering if others using the eye bolt to tie down their airplane every day also find it getting loose?

[wingnut]

If you study the tail wheel assy, you'll note there is a roll formed aluminum "U" channel between the wheel assy mount and spring. This "U" channel acts as a shim somewhat and "cups" the spring. However, it is not a tolerance fit. If you just snug the bolt to the point of contact, you can still pivot the wheel assy on the spring a bit. The steering action places a pretty strong torque moment on the one bolt, which is a pivot point. It's also loaded in tension, so any movement would eventially loosen the nut, and never tighten it. Improper original torque, not enough washers to prevent the nut from bottoming on the bolt shank, and any lubricant would be contributing factors.

[GAHorn]

...George, we did NOT re-use the old nylon lock nut . We always replace nylon lock nuts with new, ...

OK. Well, in any case, the nylon/fiber locknut proved unsatisfactory in this application, and the strong recommendation is to replace them with steel locknuts.

Bruce, I do not believe the L-19 eyebolts contribute to this problem. (L-19's never seem to suffer excessively from this problem.) I believe the problem will be solved with the steel locknut. (At the very least, it will be better served by the steel nut.)

[N2255D]

So next time I order I'll get the new nut. I just replaced the main leaf spring using the L-19 tiedown and new fiber nut about 25 hours ago. Never had it loosen so I should be alright for a while.

[bsdunek]

I've noted that these things never 'work tight', just 'work loose'. Got to check mine before the next flight.

[Bruce Fenstermacher]

Bruce, I do not believe the L-19 eyebolts contribute to this problem. (L-19's never seem to suffer excessively from this problem.) I believe the problem will be solved with the steel locknut. (At the very least, it will be better served by the steel nut.)

You might be right George it's just a thought that the continual tugging of a rope might also aggravate the loosening as outlined by Del. The thought that popped into my head when you told me of your problem was that it seemed we were talking about the L-19 eye bolt in every case mentioned. I think going forward it would be interesting to note what type of bolt came loose, a normal AN or the Eye Bolt and of course the type of nut.

A quick story. I fly a fairly new model Eurocopter EC-145. We recently had an event with the computer controls operating the engines. Eurocopter had never seen the problem and after exhausting their first tech rep for a week, sent their number one tech rep. After nearly a week of test flights with the number one tech rep and many conference calls with the factory engineers in Germany, Eurocopter was still scratching their head. They repeatedly said that our helicopter, out of the 400 or so fielded, was the only helicopter to have this problem.

That is when I suggested to the tech rep that our helicopter was the only one they knew about, not necessarily the only one with a problem. And then I explained to them how many pilots didn't fully understand their system and it's indications and that they have an issue but simply modified their flight regime to avoid the idiot lights and failure mode. After all we were having conference calls with the engineers who designed the system who between themselves couldn't agree what indications we should see but bottom line we couldn't fly as long as we got the idiot light in any normal flight regime.

The point is I don't think we have enough information to say the eye bolt doesn't loosen more than a regular AN bolt. I'd been operating my 170 with the eye bolt for 10 years tightening the bolt about every two months thinking it was normal. How many folks are also tightening their AN bolt verses the eye bolt? How many people are even checking the tightness of what ever bolt they have?

I agree a fresh steel lock nut on a good bolt of any variety is likely to improve or eliminate any loosening.

(L-19's never seem to suffer excessively from this problem.)

George I didn't know you so closely monitored the pulse of L-19 maintenance issues as well as the 170.

[jrenwick]

Why not use a cotter pin?

[cessna170bdriver]

Bruce, I do not believe the L-19 eyebolts contribute to this problem. (L-19's never seem to suffer excessively from this problem.) I believe the problem will be solved with the steel locknut. (At the very least, it will be better served by the steel nut.)

George,

When I got to Benton Harbor, my tailwheel eyebolt tiedown ring was more or less lined up fore and aft, so that the rope went in from the side. When I went to untie the airplane before departure (after the several storms that had passed through), the ring was roughly 90 degrees to where it had been, and that was with a steel locknut. Pushing side to side on the tail I could see a very slight play of the tailwheel bracket on the spring. I didn't have a torque wrench with me, but it took between 1 and 2 flats before it "felt" tight. I don't remember the last time that nut was replaced, but evidently it's time for a new one.

[mike roe]

The L19 parts book shows the ring on the bottom,nut on top. How many are installed like that and whould it make a difference?

[Bruce Fenstermacher]

Why not use a cotter pin?

Good question. If your trying to hold a specific torque a cotter pin won't fit tight enough. In other words the play between the cotter pin and the nut won't hold a specific spot. Now a range of torque maybe a cotter pin could be used. You would torque to a minimum and then tighten to the next alignment. In this case some guidance as to what would be acceptable is warranted. In this case the parts manual does not call for a drilled bolt, cotter pin and castellated nut so I don't know what you would use for a torque.

Now for reality. For the last 10 years all I did was grab the appropriate size wrench and tighten the nut to what felt right. I might have been better served but not necessarily correct to just drill that bolt, tighten to what felt right and then a pinch to line up the cotter pin.

[mike roe]

Just a thought. Could the welding of the ring have altered the temper enough where the bolt after torque stretchs over time. Maybe torque the eyebolt on the bench and check it once a week with a dial wrench to see if it is loosening over the span of 4-6 weeks. Another way might be to measure the free lenth with a micrometer before and after torque, comparing the same test to identical bolt without ring to see if they stretch the same amount.

[Bruce Fenstermacher]

Mike I would think that the bolt would have to be rehardened to the AN standard it started after the ring is installed. Or perhaps the ring is attached by the bolt manufacturer before the bolt is hardened in the first place.

I think this is just a case where the design could be better. In otherwords a closer fit of the spring to the tail wheel assembly which didn't allow the wheel assembly to rotate a bit on the spring. Add to it the deposit of engine oil and the nut being removed and reused and it simply comes loose.