Fiber-type, self-locking nuts must never be used on an aircraft when the bolt is subject to which condition?

Fiber-type, self-locking nuts must never be used on an aircraft when the bolt is subject to which condition?

• A. Under shear loading
• B. Under tension loading
• C. Subject to rotation
• D. None of the above

Answer: (C)

Fiber-type self-locking nuts rely on a nylon insert that presses against the bolt threads to create friction and resist loosening. This locking action is effective when the nut remains stationary on the bolt and the assembly experiences vibration but the bolt does not rotate. If the bolt is subject to rotation, the insert is continually rubbed away as the bolt turns, quickly eroding the locking capability and allowing the nut to loosen. For aircraft use, that rotation compromises safety, so these nuts must not be used when the bolt will rotate. Under shear or tension without rotation, the lock can still function, but rotation is the specific condition that makes them inappropriate.

Fiber-type self-locking nuts rely on a nylon insert that presses against the bolt threads to create friction and resist loosening. This locking action is effective when the nut remains stationary on the bolt and the assembly experiences vibration but the bolt does not rotate. If the bolt is subject to rotation, the insert is continually rubbed away as the bolt turns, quickly eroding the locking capability and allowing the nut to loosen. For aircraft use, that rotation compromises safety, so these nuts must not be used when the bolt will rotate. Under shear or tension without rotation, the lock can still function, but rotation is the specific condition that makes them inappropriate.