AS3209-018 - Textron Aviation OEM Packing Preformed Fluorocarbon O-Ring

AS3209-018 – Textron Aviation OEM Fluorocarbon (Viton®) Boss Seal O-Ring

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Overview

The AS3209-018 is a high-performance, preformed O-ring packing seal that holds dual authority as a component built to the exacting Aerospace Standard (AS3209) and as a genuine Textron Aviation Original Equipment Manufacturer (OEM) part. This O-ring is fabricated from a Fluorocarbon (FKM) elastomer, a material widely known by its DuPont trade name, Viton®, and is specifically engineered for creating a static seal on -10 size straight thread tube fittings in high-temperature system bosses.

The FKM material gives this O-ring an exceptional operational temperature range, up to 400°F (204°C), making it the specified component for applications where standard Nitrile (NBR) O-rings would fail. As a genuine Textron Aviation part, this AS3209-018 seal is the factory-specified component for numerous high-temperature connections on Cessna, Beechcraft, and Hawker aircraft, guaranteeing the correct material compound and performance.

Key Features

• Textron Aviation OEM Certified: Guarantees the part is the factory-approved, fully traceable component for the Textron Aviation family of aircraft.

• High-Temperature Fluorocarbon (FKM): Fabricated from a Viton® or equivalent FKM elastomer, providing a continuous service temperature rating of up to 400°F (204°C).

• Designed for -10 Boss Seals: Specifically sized (AS568-018) for static axial sealing of -10 (5/8") tube fittings in their corresponding ports.

• Excellent Fluid Resistance: Offers superior chemical resistance to a wide range of petroleum-based and synthetic lubricating oils, hydraulic fluids, and jet fuels.

• 75 Durometer Hardness: The 75 Shore A hardness provides an excellent balance of sealing force and resistance to deformation for standard pressure applications.

• AS Standard Compliance: Meets all dimensional, material, and quality requirements of AS3209, ensuring airworthiness and interchangeability.

Technical Specifications

• Part Number: AS3209-018

• Component Type: Preformed O-Ring Packing, Boss Seal

• OEM Authority: Textron Aviation

• Governing Specification: AS3209

• Material: Fluorocarbon Elastomer (FKM / Viton®)

• Hardness: 75 ± 5 Durometer Shore A

• Color (Typical): Brown

• Dimensions (AS568-018):

  • Inside Diameter (ID): 0.739 inches

  • Cross-Section (CS): 0.070 inches

• Typical Temperature Range: -15°F to +400°F (-26°C to +204°C)

Aircraft Compatibility

As a Textron Aviation OEM part, this O-ring is specified for numerous high-temperature fluid connections on their aircraft. The underlying AS standard makes it common across the industry.

• Primary Textron Aviation Platforms:

  • Cessna Citation Series Business Jets

  • Beechcraft King Air Series

  • Hawker Business Jets

• General Aerospace Usage: Used in any aerospace application requiring a high-temperature resistant boss seal for a -018 size fitting.

Note: Verification of applicability is the responsibility of the installer. Always consult the current version of the aircraft or engine's Illustrated Parts Catalog (IPC) to confirm part number eligibility.

Applications

• Sealing of -10 size (7/8-14 thread) straight thread tube fittings on firewall-forward components.

• Connections on main hydraulic system lines.

• Large-diameter fuel and oil line connections on engine accessories.

Why Choose this AS3209-018?

This component provides the dual assurance of meeting the public AS aerospace standard and the specific endorsement of Textron Aviation. This guarantees the seal's physical properties and, critically, ensures that the specific FKM compound used is the one tested and approved for the system fluids on Textron aircraft. Using the genuine OEM part is the only way to guarantee you are installing the correct, certified high-temperature material required for a safe and airworthy repair.

The performance of a high-quality O-ring like the AS3209-018 is critically dependent on the condition of the mating hardware surfaces. The engineering standard for a static O-ring seal, such as a boss fitting, typically requires a surface finish of 32 Ra (Roughness average) or better. A surface that is too rough will create microscopic leak paths across the seal face. More critically, any scratch, burr, or sharp edge on the fitting or port can damage the O-ring during installation. A longitudinal scratch across the sealing surface, even one that is barely visible, can provide a direct path for high-pressure fluid to bypass the seal. Similarly, forcing the O-ring over sharp threads or un-deburred port edges during installation can create a small cut or nick. This damage creates a significant stress concentration in the elastomer, which can rapidly propagate into a complete rupture once the system is pressurized, leading to catastrophic seal failure. Meticulous inspection and preparation of the sealing surfaces is therefore a mandatory step for a reliable repair.

Note: This component has a finite shelf life defined by standards like ARP5316. The cure date marked on the packaging must be verified prior to installation. It is a single-use part; a new O-ring must be used every time a fitting is reinstalled. The port and fitting sealing surfaces must be impeccably clean and free of scratches or damage. The O-ring must be lubricated with clean system fluid before installation.

Documentation

The base standard for this part is the Aerospace Standard AS3209. This is a controlled document managed by SAE International. OEM-specific application and installation data is contained within the Textron Aviation maintenance and parts manuals.