Cessna 120-140 Association

Should the control surfaces be held on with drilled bolts, castle nuts, and cotter pins? The parts manual just has them held on with self locking AN365's. Just curious what most people have done?

I used the hardware called out in the parts manual.

I don’t know if this helps but my mechanic that did the prebuy on my new 140 last week noticed that mine had locking nuts (on the throttle linkage too) and said he always replaces with drilled and cotter pinned hardware. Just one mechanic’s thoughts...

2356 wrote: ↑Wed Sep 02, 2020 11:50 am I used the hardware called out in the parts manual.

Agree. Unless there's an STC that I'm adapting, possibly a related SA, or/and instructions from my IA (that I agree with and that are back up by applicable FARs), I use what the Cessna engineers provided. With few exceptions, it's amazing how right they got it "way back then" . RE the throttle connection, that does need to be with drilled/cotter plus a large "safety" washer to prevent possibly "slipping" off if rod end fails (best I recall the OEM was a "ball & socket" type fastener, most of which have long since worn out on most of the "fleet"(?)). Mac

The "rule" is, if the part turns relative to the bolt, then use a cotter pin or other positive locking device (e.g. safety wire), otherwise, an elastic stop nut is OK. Things like our aileron hinges, where there is a sleeve inside the bearing that is captured by the bolt and hinge fittings such that it doesn't rotate on the bolt, do not require a cotter pin. That said, if it loosens up then it will rotate and also wear the fitting such that the fitting will need replacement.

I don’t know about back in 46, but more Modern airplanes the factory drawings are FAA approved, and that trumps any rule. It’s one way non aviation hardware gets onto aircraft legally, Maule for instance uses stainless steel pop rivets to skin their wings. You would never be allowed to do that, except the factory drawings are FAA approved, and they call out pop rivets so you pop rivet a Maul’s wings.
Having said that castellated nuts and cotter pins are more conservative and I doubt anyone would fault you for that.
Normally a parts manual isn’t considered the data source, the maintenance manual is, but we don’t really have one do we?

I think our aircraft pre-date many of the FAA rules?

Thanks for the replies. I think I'll just stick with the lock nuts. They've lasted this long, I'm sure they'll be ok!!