AS3209-011 – Textron Aviation OEM Fluorocarbon (Viton®) Boss Seal O-Ring
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Overview
The AS3209-011 is a high-performance, preformed O-ring packing seal, supplied with the full certification and traceability of Textron Aviation as an Original Equipment Manufacturer (OEM) component. This O-ring is manufactured to the precise Aerospace Standard (AS3209) from a Fluorocarbon (FKM) elastomer, a material widely known by its DuPont trade name, Viton®. Its specific engineering purpose is to create a robust, leak-free seal for straight thread tube fittings in high-temperature hydraulic, fuel, and oil 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 due to heat degradation. As a genuine Textron Aviation part, this AS3209-011 seal is the factory-specified component for numerous high-temperature connections on Cessna, Beechcraft, and Hawker aircraft.
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 Boss Seals: Specifically sized and specified under AS3209 for static axial sealing of straight thread tube fittings in their corresponding ports (bosses).
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: AS3209-011
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 (for material identification)
Dimensions (AS568-011):
Inside Diameter (ID): 0.299 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 -011 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 straight thread tube fittings on firewall-forward components.
Connections on engine accessories such as fuel control units, oil filter housings, and hydraulic pumps.
Hydraulic and fuel lines located in close proximity to high-temperature bleed air ducts or exhaust components.
Any fluid system application where operating temperatures exceed the ~250°F limit of standard Nitrile (NBR) O-rings.
Why Choose this AS3209-011?
The selection of the correct elastomer for the operating environment is a flight-critical decision. Substituting a standard black Nitrile (NBR) O-ring in a location specified for a brown Fluorocarbon (FKM) O-ring will result in the seal hardening, cracking, and failing from thermal degradation. This will cause a leak of hot, flammable fluid in a critical area of the aircraft. Using the genuine Textron Aviation OEM AS3209-011 is the only way to guarantee you are installing the correct, certified high-temperature material required for a safe and airworthy repair.
The exceptional performance of the AS3209-011 O-ring is rooted in the molecular structure of its Fluorocarbon (FKM) elastomer. FKM is a family of synthetic rubbers based on fluorinated hydrocarbon polymers, most commonly vinylidene fluoride (VDF). The key to its thermal and chemical stability is the presence of strong carbon-fluorine (C-F) bonds, which are significantly stronger and more stable than the carbon-hydrogen (C-H) bonds that form the backbone of general-purpose elastomers like Nitrile (NBR). This high bond energy makes the FKM polymer chain highly resistant to scission from thermal energy (heat) and attack by aggressive chemicals and oxidizing agents. This inherent chemical inertness and thermal stability are why Fluorocarbon is the specified material for static seals in aerospace applications that must reliably perform at temperatures approaching 400°F.
Note: This component has a finite shelf life defined by standards like ARP5316. The cure date 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.