High Reuse Locking Device

Reliability and maintainability of new generation aircraft such as the Boeing 777 and the F-22 Raptor will be improved with the use of a component called the Advanced Self-Locking Device (ASD). This new technology will be used in place of safety wire, tab washers, cotter pins, thread lock fluids, and the like to keep critical fasteners from loosening.

Moeller Manufacturing, Wixom, MI, provides fuel line coupling nuts, borescope and drain plugs, adjustable mechanical linkages, engine mounts, and other engine and airframe components which are now incorporating this technology. Made from Inconel 718, the ASD components typically engage within the last two turns prior to sealing. Once engaged, flexible beam fingers of a lockring act against a detent form on the mating part to provide a ratcheting-type prevailing torque which is sufficient to prevent loosening from all known causes. The material and design of an ASD fastener permit reusability -- they are rated for 100 cycles in applications up to 600°F, and 50 cycles where temperatures run between 600° and 1200°F. Inconel 718 is also capable of tolerating subzero temperature exposure.

Already in use for more than four years in many configurations for military and commercial aerospace, ASD components have reduced downtime and problems such as FOD, which can occur when bits of lock wire or bendable tabs break loose and drift within a structure. ASD fasteners also provide visual verification that the joint has been tightened, by the simple observation that the fingertips are overlapping the detent area.

Other components made by Moeller that use ASD technology, besides jam nuts and plugs, have included F-22 and F/A-18 aircraft brake bleeder valves, tapered roller bearing preload nuts, and self-locking nuts for adjustable grooved coupling clamps. Moeller has also prepared retrofit kits for several large-scale programs.

--RM

For more information, contact Moeller Mfg. Co., Inc., 30100 Beck Rd., Wixom, MI 48393. 800-321-8010. http://www.moeller.com Circle 455.