Air Force-Navy AN310-3 Castle Nuts comply to spec QQ-P-416, Type 2, Class 3 and are constructed of steel with a cadmium surface treatment. Castellated or Castle nuts are used with drilled-shank bolts, clevis bolts, eye bolts and studs. The bolt or axle has one or two holes drilled through its threaded end. The nut is torqued properly and then, if the slot isn't aligned with the hole in the fastener, the nut is rotated to the nearest slot. The nut is then secured with a cotter pin or safety wire.
This is nearly identical to my first pilot logbook, but with a new smooth matte black cover. This logbook checks all the boxes from student pilot through Commercial. It might just be the only logbook you’ll ever need. Fly safe!
