I have made a decision on final assembly all moving parts in the flight control system will have castle nuts and cotter pins. It is moves or changes direction or can cause a major failure then it will have a mechanical locking device on the nut no matter what.
I am not saying that is a bad idea, just pointing out that you shouldn't assume it is automatically better.
There are instances of accidents caused by cotter pin safetied fasteners that came apart. Depending on the technique and skill level applied by the installer, a cotter pin can be left vulnerable an many different ways. It is not unheard of for pins to become bent open because of catching on tall grass, rags while washing the airplane, etc.
The fact is, that pretty much every aircraft that flys, has many (sometimes hundreds) of critical system connections held together with self locking nuts.
If they are appropriately chosen for the location used (I.E., not using nylocks in high temp locations, etc.), and are installed properly, in most instances they are as reliable as a cotter pin safetied fastener would be. There are specific instances where a cotter pinned fastener is the only appropriate choice and then should be used.
I think this thread has taken a wrong turn and people are loosing site of the fact that you can just as easily forget to install a cotter pin, as you can forget to install a self locking nut (or install it properly).
I do not know if that is even for a fact the cause of this accident, but it is always a possibility that we as airplane builders need to be doing all we can to mitigate.
Since there is often more than one of us doing final assembly work in our shop, keeping track of what has and has not been final torqued can be even tougher than for someone working alone. For that reason we have a policy that parallels what has been mentioned by others already.
When we are at a point that final assembly has begun, we torque seal each fastener immediately after we torque it.
When the airplane is finished and ready for flight (other than all inspection panels open), we physically follow the complete control circuit of all critical systems and inspect every fastener along the way....
Stick grip attachment to control stick
Control stick attachment to rod end on push rod
Rod end attachment to pushrod end.
pushrod end attachment to push rod tube
and on and on.
If this thought process is used in the context of "the airplane is finished... I am no longer an airplane builder... I am now an airplane inspector, and you inspect without distraction (no one hanging around asking questions, etc), you will probably find everything that needs to be found. Then give a flashlight and mirror to someone else and ask them to do it all over again (again, without any distraction).
BTW, inspecting means just that, if you find something not right, make a note for resolving it later (when you switch back to airplane builder mode) and continue. If you jump back and forth between finding and fixing, you will always skip over things (this is the standard procedure used by aircraft mechanics... Inspect,
then resolve any problems that were found).
My 3 cents...