NAS1149TN532H - Flat Aerospace Washer

NAS1149TN532H – Flat Aerospace Washer

Available now through the AirParts Aero marketplace.

Overview Section

The NAS1149TN532H is a high-precision Flat Washer manufactured to the National Aerospace Standard (NAS). This specific hardware component is widely utilized throughout airframe structures and engine assemblies to provide a smooth bearing surface, distribute fastener clamping loads, and protect the underlying material from damage during the torquing process.1

The "TN" in the part number indicates a Titanium construction with a Ti-6Al-4V composition, offering an exceptional strength-to-weight ratio and superior corrosion resistance. The "H" suffix denotes a "Heavy" or thick configuration, providing additional rigidity and load distribution compared to standard thin washers. This makes it an ideal choice for high-stress applications where weight savings are critical, such as in modern composite airframes or high-temperature engine environments.

Key Features Section

• Titanium Alloy Construction: Made from Ti-6Al-4V, providing high tensile strength and excellent resistance to salt-water corrosion and galvanic reactions.

• High Strength-to-Weight Ratio: Significantly lighter than equivalent stainless steel washers while maintaining the structural integrity required for aerospace applications.

• Precision Thickness ("H" Suffix): The "Heavy" specification ensures a thicker cross-section for better load bridging across oversized or slightly elongated holes.

• Non-Magnetic Properties: Essential for use near sensitive avionics, flux valves, or magnetic compasses where ferrous hardware could cause interference.

• Thermal Stability: Maintains its mechanical properties at elevated temperatures, making it suitable for areas near engine exhausts or bleed air ducting.

• Strict NAS Compliance: Manufactured to rigorous dimensional and metallurgical standards to ensure consistency across critical aerospace joints.

Technical Specifications Section

Aircraft Compatibility Section

The NAS1149TN532H is frequently specified in the illustrated parts catalogs (IPCs) of advanced aircraft found in the AirParts Aero inventory:

• Commercial Transports: Used extensively in Boeing 787 and Airbus A350 structures where titanium hardware is required for composite material compatibility.

• High-Performance Jets: Found in engine pylon mounts and control surface hinges for Gulfstream and Bombardier business jets.

• Military Airframes: Standard hardware for F-16 and F-35 structural assemblies due to its high fatigue resistance.

• Rotary Wing: Ideal for rotor head assemblies and transmission mounts where vibration resistance and weight are paramount.

Technical Applications & Safety

The primary role of the NAS1149TN532H is to act as a buffer between the fastener head (or nut) and the airframe skin. By increasing the surface area of the clamping force, it prevents the fastener from "pulling through" or crushing the soft aluminum or composite substrate.

Safety Warning: Never substitute a titanium washer with a cadmium-plated steel washer in high-temperature areas or in direct contact with certain composite fibers without engineering approval. Galvanic corrosion can occur if dissimilar metals are mismatched, potentially leading to structural embrittlement or failure.2

Technical Engineering Insight

The engineering value of the NAS1149TN532H lies in its Dimensional Stability under Torque. Unlike standard commercial washers that may "cup" or deform when high-tensile bolts are torqued to spec, the "Heavy" (H) series titanium washer provides a rigid platform that ensures the bolt remains in pure tension.

Furthermore, using titanium (TN) hardware is essential in Carbon Fiber Reinforced Polymer (CFRP) structures. Steel or aluminum hardware can cause an electrochemical reaction with carbon fibers, leading to rapid corrosion.3 The NAS1149TN532H is chemically compatible with carbon structures, ensuring the longevity of the airframe. Choosing genuine NAS hardware through AirParts Aero ensures that the washer’s ID is perfectly chamfered to clear the "large-radius" under-head fillet found on high-strength aerospace bolts like the NAS6605 series.

Installation & Maintenance Addendum

1. Burr Inspection: Always check the washer for burrs or sharp edges that could scratch the airframe coating, which can become a site for stress-corrosion cracking.

2. Orientation: In some applications, the "rounded" edge of the washer (from the stamping process) should face the fastener head, while the "flat" side faces the structure.

3. Reuse Policy: While flat washers are often reused, they should be discarded if they show any signs of permanent deformation, galling, or "dimpling" from the previous fastener.