NAS1611-015A – 80 Durometer EPDM O-Ring for Phosphate Ester Systems
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The NAS1611-015A is a high-performance, preformed packing O-ring manufactured in strict accordance with National Aerospace Standard (NAS) 1611. This component is a specialized seal, and it is absolutely critical for technicians and engineers to understand its specific application. It is fabricated from an 80 durometer Ethylene Propylene Diene Monomer (EPDM) elastomer, a material chosen for its exceptional compatibility with phosphate ester-based hydraulic fluids (e.g., Skydrol®).
This O-ring is the industry standard for sealing components in the high-pressure hydraulic systems of most transport category and business jet aircraft. The NAS1611 specification guarantees that the O-ring meets the stringent requirements for material composition, dimensional tolerance, and quality control demanded for flight-critical applications. The "A" suffix in the part number indicates a specific revision or tolerance class under the NAS standard. The chemical compatibility of this seal is a non-negotiable aspect of flight safety.
Key Features
National Aerospace Standard (NAS) Certified: Manufactured to the exact material, hardness, and dimensional tolerances of the NAS1611 specification.
Specifically for Skydrol® Hydraulic Systems: The EPDM material is the certified elastomer for creating a durable, leak-free seal in systems using phosphate ester-based fluids.
Ethylene Propylene Diene Monomer (EPDM) 80 Durometer Material: Provides excellent chemical resistance to polar phosphate ester fluids, good temperature stability, and the hardness required for high-pressure hydraulic sealing.
INCOMPATIBLE with Petroleum-Based Fluids: This material will catastrophically fail if exposed to jet fuel, engine oil (mineral or synthetic), or petroleum-based (red) hydraulic oil (e.g., MIL-PRF-5606).
Excellent Compression Set Resistance: Resists taking a permanent set after being compressed, ensuring a reliable, long-term seal in static applications.
Technical Specifications
Part Number: NAS1611-015A
Component Type: Preformed Packing, O-Ring
Governing Specification: NAS1611. Material compound specified by NAS1613 (e.g., Class 1).
Material: Ethylene Propylene Diene Monomer (EPDM) Rubber.
Hardness: 80 ± 5 Durometer Shore A.
Size (AS568A Dash Number): -015
Dimensions:
Inside Diameter (ID): 0.551 inches (14.00 mm)
Cross-Section (CS): 0.070 inches (1.78 mm)
Typical Operating Temperature Range: -65°F to 300°F (-54°C to 149°C).
Aircraft Compatibility
The NAS1611-015A is a standard hardware component used throughout the hydraulic systems of most modern business jets and commercial transport category aircraft from all major OEMs, including Textron (Cessna Citation/Hawker), Boeing, Airbus, Bombardier, Gulfstream, and Embraer.
Crucial Note: The correct part number for a specific application must be verified against the Illustrated Parts Catalog (IPC) or Component Maintenance Manual (CMM) for the component or aircraft being serviced.
Applications
This O-ring is exclusively for sealing in any component of a phosphate ester (Skydrol®) hydraulic system, including:
Flight Control Actuators (spoilers, ailerons, elevators, rudder)
Landing Gear and Brake System Valves and Actuators
Hydraulic Pumps, Reservoirs, Filters, and Accumulators
Thrust Reverser Systems
Why Choose NAS1611-015A?
Choosing a genuine NAS1611-015A O-ring is a matter of fundamental flight safety. There is no room for error in material compatibility. The installation of an incorrect elastomer—such as a Nitrile (Buna-N) or Fluorocarbon (FKM) O-ring—into a Skydrol® hydraulic system will result in the rapid chemical destruction of the seal, leading to a major hydraulic leak and the potential for a complete loss of a primary flight control or braking system. The NAS1611 standard is the only guarantee that the O-ring is made from the correct, certified EPDM compound that can safely contain this aggressive fluid.
The precise material selection for the NAS1611 O-ring is dictated by the chemical principle of "like dissolves like." Ethylene Propylene Diene Monomer (EPDM) is a non-polar elastomer, a terpolymer of ethylene, propylene, and a diene monomer which gives it its cross-linking ability. Because of its non-polar molecular structure, it is highly resistant to attack from polar fluids, the most notable of which in aerospace is the family of polar phosphate ester hydraulic fluids (Skydrol®). Conversely, this same non-polar nature makes EPDM highly susceptible to attack from non-polar fluids, such as petroleum oil and hydrocarbon fuels. If exposed to these fluids, the non-polar hydrocarbon molecules are readily absorbed into the EPDM's non-polar polymer matrix. This causes the O-ring to swell dramatically to several times its original size, lose all of its tensile strength and hardness, and effectively revert to a soft, gummy substance with no ability to contain pressure. This catastrophic material failure is why the strict segregation of EPDM and petroleum-compatible elastomers (like Nitrile or Fluorocarbon) is one of the most critical disciplines in aircraft maintenance.
Note: EXTREMELY CRITICAL SAFETY NOTE: This O-ring is made from EPDM and is for use in PHOSPHATE ESTER (SKYDROL®) HYDRAULIC SYSTEMS ONLY. It is ABSOLUTELY INCOMPATIBLE with petroleum-based fluids (fuel, oil, MIL-PRF-5606 hydraulics). Installation in a petroleum-based system will cause catastrophic seal failure. Always verify the system fluid type and the part number in the manual. This is a single-use component and must be replaced whenever a connection is broken.
Documentation
The definitive technical requirements for this component are detailed in National Aerospace Standard NAS1611. These proprietary documents must be sourced directly from the relevant standards organizations for complete engineering specifications.