Hatz Biplane Association

Thanks guys. I agree. I did do some more research. It looks like the general consensus on other forums is that if the bolt was designed to NOT rotate then a locking nut is all that was required. There was some discussion about failure of the bearing that would cause the bolt to rotate. The FAA Advisory Circular 23-607.1 states that you do not have to consider part failure in the choice of locking device. It also states that you can use castle nuts and cotter pins anywhere you want. I'll probably use a few but not on rod end or bell crank bearings.

Nope. When you tighten everything up, the bolt, washer, center bushing of the bell crank and nut all move together and the nut doesn't have the opportunity to loosen.
Castle nuts are needed when the bolt has the opportunity to rotate.
There is nothing wrong with using a castle nut here if you wish.

Jeff

Anywhere there is rotation, a castle nut and cotter pin should be used. Some also suggest them anywhere that the nut can't be seen and inspected after covering.

My neighbor (aircraft mechanic) was going through a set of Van's RV6 plans and changing them. Specifically he was changing all the bolts that hold rod end bearings and bell crank bearings from nylock to castellated nuts. See the examples of my Hatz project in the picture below.
Looking for opinions. Do these bolts need castle nuts with a cotter pin?