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Aircraft Locking Devices are sophisticated mechanical fasteners used in a wide variety of aerospace applications, including critical flight control and landing gear systems. These parts provide a positive lock to prevent rotation in mechanical linkages or actuator systems while simultaneously allowing for linear adjustment. Locking action is obtained via a keying device that locks a shaft to a keyway in a rod end terminal and is secured by a jam nut that is then attached to the locking device with safety wire.

FDI carries a full range of positive indexing locking devices that includes an array of sizes, finishes, and heat treatments.


  • NAS1193
  • MS14198
  • AS14227
  • NAS559
  • JSF23
  • M81935 (AS81935/3, MIL-B-81935/3)
  • EN2546

We also stock the jam nuts (in Stainless Steel Only) used in conjunction with the locking devices including:NAS509 and NAS1423

The NAS1193 Positive Index Locking Device functions as a washer with a locking tab, but is made up of two halves with serrations on one side of each. The serrations can allow for very fine linear adjustment of a mating rod end in some applications. Parts are investment castings, material is 17-4 per AMS 5355 or AMS 5343. FDI stocks the entire series of NAS1193 locking devices, along with similar parts with metric dimensions and special customer designs.

Single washer style locking devices are produced in a wide variety of materials, including 17-4, 15-5, 4130 Alloy and Inconel 718.

The NAS559 design is a locking key that seats in the keyway of the rod end and under the threads of the jam nut. In a typical actuator application the actuator rod is slotted on the end to accept the lug end of the locking key. Thus, the keyway of the rod end and a slot of the actuator piston rod are secured by the key. Finally, a jam nut holds the key securely in place after being properly torqued and correctly safety-wired.

These locking devices are stocked in standard sizes, as well as, with similar metric dimensions, or can be custom manufactured to your specific needs upon request.