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Tail wheel Bolt

Posted: Wed Mar 15, 2017 2:06 am
by MoonlightVFR
I am reading in the IPC issued Sept 1, 1956. Chartreuse / Black cover imprint.

Am I correct in understanding that the tail wheel bolt can sometimes fail?

Page 155 Fig. 94- 5 Bolt AN7-20A.

My question to the forum is concerning an improved stronger bolt availability.

70 years later can we source a better stronger bolt? Aviation grade obviously.

Re: Tail wheel Bolt

Posted: Mon Mar 20, 2017 7:57 am
by GAHorn
The AN bolt specified is an aviation grade part. Yes, even aircraft parts sometimes fail. :wink:

Many have replaced that bolt with the L-19 part, an eyebolt, PN-062105, which accommodates a tie down rope.

Re: Tail wheel Bolt

Posted: Mon Mar 20, 2017 11:33 am
by Bruce Fenstermacher
Answer #1, yes the bolts fail.

Answer #2, no there is nothing stronger readily available and legal to install.

The L-19 Cessna part George mentioned is a modified AN7 bolt. Presumably, it has at least the same strength as an unmodified AN7. I wouldn't think it is stronger than a standard AN7.

Re: Tail wheel Bolt

Posted: Tue Mar 21, 2017 5:20 am
by GAHorn
I suppose one might find a NAS bolt with higher tensile strength than the average AN bolt (typically 160,000 psi vs 125,000), but tensile failure is not the typical failure mode. Usually the failure is due to a stress riser created in shear due to marking of the bolt. The best answer is to inspect and replace on a regular basis, especially if you find the bolt is marked or scratched by the assembly.

Re: Tail wheel Bolt

Posted: Tue Mar 21, 2017 5:53 am
by c170b53
Crazy I guess George and I can't sleep tonight and crazy we are both replying to this question at the same time. Here's my take;
I would think that you could use a NAS bolt which would have a higher tensile/shear strength than an AN bolt. Con; the higher cost and the NAS bolt may not be as malleable as the AN bolt, which might lead to other problems if neglected.
Then again, any neglected item will come back to be a pain. If the bolts are changed when the spring is changed and the install is checked at annual, there should be no surprises. Just did mine.