Aircraft Bolt Applications

Recently in my inspections I have been seeing improper use of Nyloc nuts and bolts.  AC 43-13 is very clear in that nyloc nuts should not be used on assemblies that rotate.  Important assemblies that rotate are the push rod ends in the flight control system, elevator, rudder and aileron hinges and any other rotating assemblies.  These areas should have a drilled bolt and a casellated nut with a cotter pin. 

The other not recommended practice is bolts that don't go through the nyloc nut.  There must be a minimum of 1 1/2 threads showing past the nyloc insert and nore more than 5 threads.  If too little are showing then the nut may not remain on the bolt, if too many are showing then the nut is bottomed out on the threads, neither a good practice.

AC43-13-1B/2A  is a manual published by the FAA entitled Acceptable Methods, Techniques, and Practices Aircraft Inspection, Repair and Alterations.  It is THE definitive word how to do things on aircraft properly.  This book only costs $20 and has an untold wealth of information.  I recommend anyone that is planning on maintaining their aircraft get a copy of this book.