Because non-metallic washers compress (creep), the torque retention is lower than metallic washers. Using standard torque tables for steel bolts will over-stress an NAS523 assembly. Always refer to the torque recommendations in the NAS523 PDF or the specific fastener procurement standard.
Use the following format: Aerospace Industries Association (AIA), “NAS523: Fastener, Captive Washer, Non-Metallic, Assembly, Procurement Specification,” [Revision Date], Washington, D.C.
The NAS523 is not just a nut; it is a high-performance component engineered for reliability in the harshest environments. Whether you are performing maintenance on a legacy airframe or designing a new UAV, adhering to the NAS523 standard ensures structural integrity and flight safety. Always verify your technical data against the latest revision of the official document.
The NAS523 (National Aerospace Standard 523) is a vital fastener coding system used throughout the aviation industry to standardize the identification and installation of permanent fasteners, particularly solid rivets. This system simplifies complex engineering drawings by consolidating critical data—such as part numbers, diameters, material alloys, and hole preparation methods—into a single four-quadrant "crosshair" symbol. What is the NAS523 Fastener Code? nas523 pdf
The NAS523 code is a standardized practice that includes all types of fasteners that undergo permanent deformation during installation. Removing these fasteners typically requires their destruction, making precise initial installation essential for structural integrity.
The system uses a symbolic "cross" located on blueprints to give technicians immediate instructions for a specific location: NW (Northwest): Part number and material alloy code.
NE (Northeast): Fastener diameter and manufacturer head location. The NAS523 is not just a nut; it
SW (Southwest): Required hole preparation (e.g., dimpling or countersinking). SE (Southeast): Fastener length. Breakdown of the NAS523 Symbol Quadrants
Understanding the "crosshair" is critical for any aviation maintenance engineer (AME) or technician working with sheet metal. ↖️ Northwest (NW): Identity & Material
This quadrant specifies the fastener's basic part number (often AN or MS standards) and the material it is made from. ” [Revision Date]
BJ Code: Often identifies an MS20470AD rivet (2117 aluminum alloy).
BB Code: Often identifies an MS20426AD rivet (countersunk 2117 alloy). ↗️ Northeast (NE): Diameter & Head Placement
This quadrant indicates the shank diameter, typically in increments of 1/32 of an inch.
Manufacturer Head Location: Indicated by "N" (Near side) or "F" (Far side) to show where the manufactured head should rest. AIA/NAS - NAS523 - FASTENER CODE | GlobalSpec