In what application are castellated nuts primarily used?

Castellated nuts are primarily used in critical applications because they play a vital role in ensuring that fastenings remain secure under extreme conditions. The design of a castellated nut, which features a series of vertical grooves and is often used in conjunction with a cotter pin or safety wire, allows for added security by preventing the nut from loosening due to vibration or movement.

In critical applications, such as those found in aviation, the structural integrity and safety of components are paramount. Castellated nuts provide a reliable locking mechanism that is crucial in situations where there is a risk of failure if fastenings loosen, maintaining the stability and safety of the aircraft's structure. The usage of castellated nuts thus aligns perfectly with the stringent safety requirements present in critical systems where failure is not an option, highlighting why this choice is correct.