NAS1149E0463R – Stainless Steel Aerospace Flat Washer
Available now through the AirParts Aero marketplace.
Overview Section
The NAS1149E0463R is a high-precision Corrosion-Resistant Steel (CRES) flat washer manufactured to the National Aerospace Standard. This specific hardware component is a mainstay in the Textron Aviation (Cessna/Beechcraft) parts catalog, serving as a critical interface between fasteners and airframe structures.
The "E" in the part number designates the material as 300-series stainless steel, providing excellent protection against environmental oxidation and chemical exposure. The "R" suffix indicates that the washer has undergone a passivation process, a chemical treatment that removes surface contaminants and enhances the protective chromium-oxide layer. These washers are essential for distributing clamping loads and preventing the "galvanic corrosion" often seen when steel fasteners meet aluminum skins.
Key Features Section
300-Series Stainless Steel: Offers superior durability and rust resistance compared to standard cadmium-plated carbon steel washers.
Passivated Finish ("R" Suffix): Treated per AMS2700 to ensure a chemically clean surface, preventing the onset of pitting corrosion in high-moisture environments.
Precision Load Distribution: Engineered with a flat, parallel surface to ensure that bolt torque is converted into uniform clamping pressure across the substrate.
Vibration Resistance: Provides a stable bearing surface for nuts and bolt heads, helping to maintain fastener preload in high-vibration areas like engine cowlings and wing roots.
Non-Magnetic Properties: Safe for use in proximity to sensitive magnetic compasses, flux valves, and avionics suites.
Universal Standard Compliance: Directly replaces legacy AN960-series hardware while meeting the tighter dimensional tolerances of the NAS1149 specification.
Technical Specifications Section
| Specification | Detail |
| Part Number | NAS1149E0463R |
| Manufacturer | Textron Aviation / Various NAS Certified |
| Material | Stainless Steel (CRES 300 Series) |
| Fastener Size | Fits 1/4" (#4) Nominal Bolt/Screw |
| Inside Diameter (ID) | 0.255" – 0.275" |
| Outside Diameter (OD) | 0.495" – 0.505" |
| Thickness | 0.057" – 0.069" (Standard Gauge) |
| Finish | Passivated (Suffix R) |
| Specification | NAS1149 (Supersedes AN960C416) |
Aircraft Compatibility Section
The NAS1149E0463R is a "high-utilization" fastener found throughout the Textron Aviation fleet in the AirParts Aero inventory:
Cessna Single-Engine: Essential for wing-to-fuselage fairings and inspection plate attachments on the Cessna 172, 182, and 206.
Beechcraft King Air: Used extensively in the nacelle and empennage assemblies of the 90, 200, and 300 series.
Beechcraft Baron/Bonanza: Standard hardware for flight control surface mounting and engine baffle attachments.
Textron Jets: Utilized in the secondary structures and interior cabin framing of the Cessna Citation line.
Technical Applications & Safety
The primary purpose of the NAS1149E0463R is to protect the aircraft's primary structure. When a bolt is torqued directly against an aluminum skin, the rotating head can "gall" or "plow" the metal, creating a stress riser. This washer provides a hardened, sacrificial surface that takes the friction of the torque, preserving the integrity of the airframe.
Safety Warning: Always verify material compatibility. While the stainless steel (E) washer is excellent for corrosion resistance, ensure it is not used in applications where "intergranular cracking" is a risk due to specific temperature/material pairings specified in the aircraft maintenance manual (AMM).
Technical Engineering Insight
The engineering value of the NAS1149E0463R lies in its Surface Finish and Parallelism. Unlike commercial washers which may have "burrs" or an uneven thickness, this NAS washer is stamped and finished to ensure a consistent thickness across its circumference. This is critical in Preload Calibration; an uneven washer can lead to "false torque" where the wrench clicks at the correct value, but the bolt hasn't achieved the required tension.
Additionally, the Passivation (R) ensures that any "tramp iron" picked up from the manufacturing dies is removed. If these iron particles remained, they would rust, even on a stainless washer, creating "rust streaks" that can be mistaken for structural cracks. Choosing the genuine Textron-sourced NAS hardware through AirParts Aero ensures that the washer’s ID is clean and chamfered, preventing interference with the bolt-head fillet.
Installation & Maintenance Addendum
Correct Sizing: This washer is sized for 1/4" fasteners.3 Using it on a smaller bolt will result in "off-center" loading, which can bend the fastener.
Inspection for Damage: Discard any washer that shows "dimpling" or "cupping" from previous over-torquing, as it will no longer distribute the load evenly.
Chemical Compatibility: When using stainless washers on aluminum, it is a "best practice" to use a corrosion-inhibiting compound (like Duralac or CA1000) during assembly to further mitigate galvanic risk.