NAS76A5-008 – Bushing Sleeve, Flared, Anti-Friction, Aluminum Alloy
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Overview Section
The NAS76A5-008 is a precision-manufactured Bushing Sleeve governed by the National Aerospace Standard (NAS), specifically engineered for load-bearing joints requiring low friction and high wear resistance. This part belongs to the NAS76A family, which signifies a bushing intended for applications where a smooth, protective surface is critical. The nomenclature breaks down as: NAS76A (Bushing series), 5 (Nominal Inner Diameter code), and -008 (Nominal Length/Thickness code). This bushing features a flared head (shoulder) that prevents axial movement after installation and distributes clamping forces over the mounting structure.
Unlike the NAS74 series which is typically plain, the NAS76A often implies an Anti-Friction coating or treatment on the inner diameter (bore) to minimize wear and friction with the bolt or pin, making it ideal for joints that experience slight rotational or oscillatory movement. Constructed from certified Aluminum Alloy (providing a high strength-to-weight ratio), this component ensures that the primary structure's integrity and fatigue life are protected by acting as a sacrificial wear element.
Key Features Section
National Aerospace Standard (NAS) Compliance: Ensures absolute adherence to material composition, dimensional tolerances, and mechanical performance for flight-certified installations.
Flared Head Design: Incorporates a robust shoulder to prevent pull-through and to accurately set the bearing face against the structural assembly, ensuring precise alignment.
High-Strength Aluminum Alloy: Manufactured from heat-treated aluminum (e.g., 2024 or 7075 series) chosen for its high compressive strength and corrosion resistance.
Anti-Friction Surface (Implied): The NAS76A standard often dictates an anti-friction coating on the inner bore, such as a Teflon or PTFE-based dry film lubricant, to reduce the coefficient of friction and combat fretting corrosion.
Precision Tolerance: The inner and outer diameters are machined to extremely tight tolerances to achieve the specified fit (e.g., press-fit into the structure and a slip-fit or close clearance fit for the pin).
Structural Preservation: Functions as a replaceable insert, absorbing wear and tear to extend the operational life of the expensive primary airframe structure.
Technical Specifications Section
Part Number: NAS76A5-008
Component Type: Flared Bushing Sleeve, Anti-Friction Grade
OEM Manufacturer: Various NAS-approved suppliers (Full Traceability is Mandatory)
Material: Aluminum Alloy (Exact alloy must be confirmed by CoC)
Inner Diameter (ID Code 5): Nominal diameter (must be confirmed with NAS76A specification table)
Length/Thickness (Dash 008): Nominal length (Exact dimension in inches must be confirmed by the NAS76A table).
Head Type: Flared (Shouldered)
Finish (Implied): Anti-friction coating on the inner bore; outer surface is typically plain or anodized.
Application: Joints with low-speed rotation or oscillatory movement (e.g., control linkages, hinge points).
Governing Specification: National Aerospace Standard (NAS) 76A.
Certification Status: Must be supplied with a Certificate of Conformance (CoC) documenting material and dimensional compliance.
Aircraft Compatibility Section
Flight Control Surfaces: Used extensively in the hinge points and control horn attachments of ailerons, flaps, and rudder systems.
Landing Gear Linkages: Employed in secondary linkages and static pins where occasional movement and high load occur.
Engine Mount Components: Used in certain strut or brace attachments to protect structural holes.
Universal Application: Used across all airframe types (e.g., Boeing, Airbus, Bombardier) that rely on NAS standard hardware for structural integrity.
Note: Structural drawings and the relevant aircraft maintenance manual are the final authority for verifying the required diameter and length of the bushing for any given structural application.
Applications Section
Friction Reduction: Providing a low-friction surface for pins in control systems, ensuring smooth, low-effort control input from the cockpit.
Wear Mitigation: Preventing abrasion, scoring, and fretting corrosion between the moving bolt/pin and the stationary airframe structure.
Load Isolation: Distributing compressive load forces from the fastener over a broader surface area via the flared head.
Why Choose the NAS76A5-008?
The NAS76A5-008 is indispensable for maintaining the kinematic accuracy and reliability of flight control systems. Using a non-NAS or incorrect bushing can result in the immediate degradation of the joint due to high friction, leading to stiffness or binding in the control system. Furthermore, the failure of the anti-friction layer (if present) rapidly accelerates wear on the costly structural components. This NAS-certified component guarantees the precise dimensional fit, the certified alloy strength, and the necessary wear resistance to ensure the longevity of the entire structural joint assembly, minimizing maintenance downtime and safeguarding against structural failure caused by bore elongation.
The defining characteristic of the NAS76A series is its approach to boundary lubrication. For joints with limited oscillatory movement, traditional hydrodynamic lubrication (where a full oil film separates the surfaces) is often not achievable. The NAS76A, with its implied internal anti-friction coating (e.g., a PTFE-impregnated or dry film coating), utilizes a solid film lubrication principle. This coating has an extremely low coefficient of friction and chemically bonds to the bushing's bore, preventing metal-to-metal contact during movement. This solid film is crucial for mitigating galling (material transfer and adhesion) and fretting, which occur at high contact pressures with limited motion. The precise interference fit between the bushing OD and the structural hole ensures zero movement between those two surfaces, confining all permissible motion and wear to the bushing's lubricated inner diameter.
Note: The NAS76A5-008 is a flight-critical component. Installation often requires a specific press-fit or shrink-fit procedure. It is mandatory to consult the Component Maintenance Manual (CMM) for instructions on cleaning, inspection, and the application of corrosion protection and/or bonding agents before installation. Final verification of the bore size and pin/bolt fit is required post-installation.
Documentation
National Aerospace Standard (NAS) 76A Specification: Contains all dimensional tables, material composition, and finish requirements.
Aircraft Structural Repair Manual (SRM): Required for specific installation procedures, torque limits, and interference fit dimensions.