What type of nut should not be used on an aircraft bolt subject to rotation?

The use of a fiber-type, self-locking nut on an aircraft bolt that is subject to rotation is not advisable due to the potential degradation of the fiber material over time and under dynamic loading conditions. Fiber-type self-locking nuts rely on compressing a fiber material to create friction against the bolt threads to prevent loosening. In the case of a bolt subject to rotation, the constant movement and vibration could cause wear and tear on the fiber, leading to a failure in the locking mechanism.

In contrast, other types of nuts, like standard nuts, locking nuts, and hex nuts, are more suitable for applications involving rotation. Locking nuts and standard nuts can maintain tightness through mechanical means (such as a nylon insert in locking nuts) that are more robust under rotational stress. Hence, avoiding the use of fiber-type self-locking nuts in these scenarios ensures better reliability and safety in aircraft operations.