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Lock nuts or castle nuts with cotter pin

Tim

FRIEND
Petersburgh, NY
There was an old thread that talked about what to use on landing gear, can't find it, any help appreciated.

Tim
 
Anything that rotates should be cotter or safety wired, but.............................................almost ever gear bolt has a nylock on it.

Glenn
 
If something normally rotates about the axis of the bolt, then it should have a castle nut and cotter pin to prevent the motion from, potentially, unscrewing the nut. Landing gear bolts do have a rotation around them, however it's a small amount and most everyone uses nylocs on them for convenience. Especially with aircraft that change from wheels to skis to floats a lot.

Web
 
If something normally rotates about the axis of the bolt, then it should have a castle nut and cotter pin to prevent the motion from, potentially, unscrewing the nut. Landing gear bolts do have a rotation around them, however it's a small amount and most everyone uses nylocs on them for convenience. Especially with aircraft that change from wheels to skis to floats a lot.

Web

Thanks Web.
 
I believe the phrase is, "if the bolt is subject to rotation" , if I recall it was an FAA test answer almost 30 years ago.

Now most Cubs, Pacers, later T crates, and my Tripacer have a tab to lock the head of the bolt against rotation. So as an IA if it has the tab, the bolt is not rotating, then the "fiber locking" nut may be used. God I sound like a lawyer. This keeps the bolt from rotating in the weld on fuse fitting and wearing this fitting out.


Anyway, I use a minnie nut in this location, the six point all metal one, because of the ease of attaching a socket and it firmly engages the bolt threads every time.


If you are going to use the fiber locking nut on your gear throw them away after about two uses; they are cheap enough. If it bothers you use a new one each time. If it's old and rusty and the insert is black and oily throw the damn things away.


If in doubt use the castellated one with a cotter pin. Better yet consult with the A&P/IA who is signing off your aircraft maintenance or who has trained you to perform your "preventative maintenance"


There are a number places I use a fiber locking nut where a castellated one had originally been used most of them being a function of the float to wheel change world I am involved with as well as one installation where a properly torqued and pinned castellated nut will work loose before the next 100 hour, a non rotation situation, and a fiber locker will not, but this is rare.


Ok, one more thing to keep in mind: if it takes a cotter pin this does not mean the bolt is meant to be loos!!!!!!! The ball rod end, say at your throttle if it takes one, this bolt is meant to be tight. A hundred places on spam cans and Beavers with KSP4 bearings-tighten the dang bolt! I replace hundreds of dollars of fittings etc where the previous mechanic left the bolt loose thinking it needed to rotate and it hogged out the hole. The ball in the bearing rotates not the bolt.


The little bug on your cub mixture and or carb heat... Ha ha ha haaa. Don't mix them up and pay attention, it could cost you your life. It takes a cotter pin, it needs to rotate in the hole, one is thick and one is thin, and that's all I'm saying.



Rocket

ps. say, where is MCS Mike on this one?
pps. I do mostly DHCII and C100/200 float birds so YMMV.




 
even if the bolt is held, the rotation can still push on the nut, and unscrew. So for me even with a tab you would require the cotter pin.


But for me, yea, a fiber one because it comes off in three months anyway...
 
I don't see how, on those upper bolts. However, the shock strut bolts have no such anti-rotation flat, so the lock nut is probably inappropriate. In thousands of hours I have never seen one back off of a shock strut.

On a Cub, the seriously important places for cotter pins are control bolts. I have seen them back off of tail brace wires, and if you use them there, a new one is really good advice.
 
even if the bolt is held, the rotation can still push on the nut, and unscrew. So for me even with a tab you would require the cotter pin.

Yeah, and some of us (not me of course) have landing gear bolts that see more rotation than others......
 
I stick with castle nuts and cotter pins on the gear bolts. I've seen plenty of them with self-locking nuts on them, but I stick to the castle nut/cotter pin setup. Easy to inspect, and more secure. I never worry about them.
 
Ski cable tabs tend to twist or rotate under adjacent washers and nuts. All-metal high temp locking nuts are better than nylon inserts if the bolt threads are in good condition and not flattened from being driven through gear fittings. Cotter-keyed nuts are best.

Pick your battles and enjoy flying.

GAP
 
I haven't lost a nut yet... but of course I've stayed married to the same woman for almost 35 years!

Nylocks if you can... but won't pass an MDRA inspection if a new amateur built!
 
You also gotta use common sense. Even if a nylock & bolt somehow rotates and loosens some, then it has lengthened and will not be bound and able to loosen any more.
 
I have some original Piper Landing Gear Bolt Kits. Nylon lock nuts on the gear to fuselage attach and cabane Vee attach. The shock struts top and bottom were drilled bolts, castle nuts and cotter pins since they rotate some on the end of the axle and cabane vee. J3s and early PA18s had castle nuts on everything but that was slowly changed over. Find lots of drilled bolts with nylon and in later models steel lock nuts in wings etc.
 
My other plane is a glider. Factory built in germany without a single castle nut. 100% nylocs.
Looking in a new motor glider engine compartment you will not find a castle nut or safety wire. Lots of Nylocs.
Are Castle nuts a remnant from a time past? or are German glider builders idiots?
 
The main reason I still use castellated nuts on the so call rotating parts (so called as in like on the gear legs, just a few degrees of movement, not a continuous rotation) is so that when my homebuilt is getting eyeballed by some self designated inspector at a fly in or on a ramp, he can't go "don't you know you need a castellated nut there?" I'd feel fine using nylocs there, but don't, old habits..etc

One thing I picked up from the hang glider and ultralight aircraft time is using castellated nuts but no cotter pin, rather a circlip/safety pin/latch pin (pick the term) done right, makes for a as secure as a cotter pin install but lets you quickly and tool free remove it repeatably. That's how I do my gear nuts, castellated but no cotter pins, so quick and easy to get on and off and nobody gives me static over using nylocs.
 
Ha, it made for interesting reading. I think I have my answer, do it anyway I want. I used castellated nuts and cotter keys. Thanks for all the replies guys

Tim

Only because the bolts you removed were installed 20 + years ago and new ones will never be looked at again

Glenn
 
image.jpeg
I seen this picture somewhere else never seen a cotter pin done that way before. What is the proper way
 

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Service Bulletin on Cub Crafters CC18-180 to cotter pin the bottom of the sticks in the torque tube this way because the cotter pin hits the torque tube.
 
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