[Robert McLinden]

Having worked as a structural analysis for the past 40 years or so, I must say I have never seen anyone in the aerospace business use a split washer. For non rotational joints the FAA allows locking nuts (either the insert type or the ovalated varity) and these can only be reused three times max. For joints under rotation then the prefered method is a cotter pin. Safety wire is used more as an inspection aid, much like the safety wire on our wheel spinners.

Other specific methods of locking the joint have been developed and are allowed in specific instances. The NASA fastener manual is useful along with AC43.

On my vehicles all instances of "lock washers" have been replaced with suitable locking nuts. Also make sure you are not running any threads in shear when put joints together. The shear strength through the threads is very poor.