Covers for Flap and Aileron Hinges.

[whee]

To be fair, we need to refer to AC43.13B

If the aurora bearing seizes - this is not unheard of - then the nut is subject to rotation. Hence AC43.13B Part 7 Section 4 expressly prohibits the use of self-locking nuts.

That section is pretty much dedicated to when you mustn't use self locking nuts. That is an implicit message, if you read between the lines...

The nut can work it's way free if the bearing seizes, and you may never notice until the nut works it's way off. Aurora bearings can definitely corrode and lock up, especially in a coastal environment.

Ultimately it's up for interpretation, because the AC is not exhaustive. The safest approach is using a castle nut.

I totally agree with you Battson, the safest approach is a castle nut and I wish I had used them. Would save me from having to redo work...again.

However...

AC43-13-1B Par 7-64-d

d. Self-locking nuts should not be used with bolts, screws, or studs to attach access panels or doors, or to assemble any parts that are routinely disassembled before, or after each flight. They may be used with anti-friction bearings and control pulleys, provided the inner race of the bearing is secured to the supporting structure by the nut and bolt.

[Archer39J]

It’s worth noting that AC 43.13-1B is advisory in nature, as the name implies, so strict compliance isn’t a regulatory requirement here in the US. It’s also kind of out of date, last released 9/8/98. Section 7-64(a) states “DO NOT use self–locking nuts on parts subject to rotation”… seems pretty unambiguous, and one can see how this might mean pulleys and bearings as well.

The “Aviation Maintenance Technician Handbook- General” (FAA-H-8083-30A) provides for pulleys and bearings. From Page 7-44: “Do not use self-locking nuts at joints, which subject either the nut or bolt to rotation. They may be used with antifriction bearings and control pulleys, provided the inner race of the bearing is clamped to the supporting structure by the nut and bolt.”

To me this explains the reasoning behind why it’s ok to use self-locking nuts on pulleys and bearings (when captured as described), but not on the landing gear hinge. The former are specifically designed to be anti-friction and only if they fail will they then be functionally equivalent to the latter, so you have some redundancy in those joints. The figure Bcone attached complies with the AMT handbook, if the bearing seized it would then just be rotating around the bolt and (hopefully) not be imparting enough force to rotate it. Not ideal but probably plenty safe to keep flying until you discover the seized bearing at the next annual.

I have castle nuts for my gear bolts and will be using them for any rotating assembly, for good measure.

[Archer39J]

Didn't see Whee's reply, but now you have the info twice lol.

[Battson]

I totally agree with you Battson, the safest approach is a castle nut and I wish I had used them. Would save me from having to redo work...again.

However...

AC43-13-1B Par 7-64-d

d. Self-locking nuts should not be used with bolts, screws, or studs to attach access panels or doors, or to assemble any parts that are routinely disassembled before, or after each flight. They may be used with anti-friction bearings and control pulleys, provided the inner race of the bearing is secured to the supporting structure by the nut and bolt.

Sorry Jon - but...

I am a stickler for Engineering detail and I know you are too... so here goes.

Sliding contact bearings are referred to as plain bearings and rolling contact bearings are often called antifriction bearings.

Anti-friction bearings as found in the typical pulley or other device are not the same an aurora bearing on the rod ends for flaps and ailerons.

Therefore AC43-13-1B Par 7-64-d does not apply for flaps and ailerons. We need to use castle nuts and the DAR should have picked this up if they know their trade well.

[whee]

Battson, I appreciate the correction. You are certainly right. I obviously didn't know what defines a anti-friction bearing and never thought to look it up. The IA that that help us restore a Luscombe had us to use nylock nuts on the rod-ends and the following IA that did annuals never asked for them to be replaced. Looks like some A&P schools need a bit of education on bearings. Maybe a good topic for IA refresher training.

[PaulSA]

That's interesting because every RV uses nylock nuts on every control rod-end bearing.