What type of applications commonly use castellated nuts?

Castellated nuts are commonly used in critical applications due to their unique design that provides a secure locking mechanism. This type of nut features notches or slots on the top, which allows for a cotter pin or similar locking device to be used, preventing the nut from loosening during operation. This quality is especially vital in environments subject to high vibration or extreme load conditions, such as in aviation, military, and heavy machinery applications. The design ensures that fastenings remain secure under demanding circumstances, making them indispensable in safety-critical systems where equipment failure could have severe consequences.