M25988/1-012 - McFarlane Aviation FAA-PMA Fluorosilicone O-Ring

M25988/1-012 – McFarlane Aviation FAA-PMA Fluorosilicone (FVMQ) O-Ring

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This M25988/1-012 is a premium, FAA-PMA certified O-ring from McFarlane Aviation, manufactured in strict accordance with the military specification MIL-PRF-25988, Type 1. This is a specialized seal, fabricated from a 70 durometer Fluorosilicone (FVMQ) elastomer. This unique material is specifically engineered to solve a critical sealing challenge in aerospace: providing excellent resistance to hydrocarbon fuels and oils, while simultaneously maintaining its flexibility and sealing ability at extremely low temperatures.

As an FAA-PMA approved part from one of the most trusted names in general aviation components, this McFarlane O-ring offers a certified, high-quality, and cost-effective alternative to other sources. It is the definitive choice for static sealing applications in jet fuel and avgas systems, particularly on aircraft that operate at high altitudes where ambient temperatures can drop dramatically and cause standard elastomers to fail.

Key Features

• FAA-PMA Approved: Fully certified by the FAA as a safe and airworthy replacement for any M25988/1-012 O-ring.

• Meets or Exceeds MIL-PRF-25988 Specifications: Manufactured and tested to the exact material, hardness, and dimensional tolerances of the military standard, ensuring reliable performance.

• Fluorosilicone (FVMQ) 70 Durometer Material: A specialized hybrid elastomer that combines the excellent low-temperature flexibility of silicone with the robust fuel and oil resistance of fluorocarbon.

• Exceptional Low-Temperature Performance: Maintains its elasticity and sealing force at temperatures down to -100°F (-73°C), preventing leaks that would occur when other elastomers become hard and brittle.

• Excellent Resistance to Aviation Fuels: Provides a durable, long-lasting seal in the presence of hydrocarbon fuels (Jet A, JP-8, Avgas), synthetic turbine oils, and petroleum-based hydraulic fluids.

Technical Specifications

• Part Number: M25988/1-012

• Component Type: FAA-PMA Preformed Packing, O-Ring

• Manufacturer: McFarlane Aviation Products

• Governing Specification: MIL-PRF-25988, Type 1

• Material: Fluorosilicone Rubber (FVMQ).

• Hardness: 70 ± 5 Durometer Shore A.

• Color: Typically Blue (for easy identification).

• Size (AS568A Dash Number): -012

• Dimensions:

  • Inside Diameter: 0.364 inches (9.25 mm)

  • Cross-Section: 0.103 inches (2.62 mm)

• Typical Operating Temperature Range: -100°F to 350°F (-73°C to 177°C).

Aircraft Compatibility

The McFarlane M25988/1-012 is FAA-PMA approved for installation in any application where the MIL-PRF-25988, Type 1, -012 O-ring is specified. It is commonly used in fuel systems across all categories of aircraft, including those manufactured by Textron (Cessna, Beechcraft), Piper, Cirrus, and others.

Crucial Note: The official FAA-PMA supplement for this part and the specific aircraft's Illustrated Parts Catalog (IPC) or Component Maintenance Manual (CMM) are the final authorities for verifying installation eligibility.

Applications

This O-ring is specified for static sealing in systems requiring both hydrocarbon fluid resistance and extreme low-temperature performance. Common uses include:

• Aviation Fuel System Fittings, Valves, and Flanges

• Fuel Control Units (FCUs), Fuel Pumps, and Fuel Quantity Probes

• Engine Lubrication System components exposed to extreme cold environments

• Low-temperature hydraulic and pneumatic systems

Why Choose M25988/1-012 from McFarlane?

Choosing the McFarlane M25988/1-012 provides the confidence of a high-quality, FAA-certified part from a manufacturer renowned for its engineering and commitment to general aviation. A fuel leak at high altitude due to a cold-hardened seal is a catastrophic failure scenario. McFarlane's PMA parts are a trusted and economical solution for ensuring your aircraft's fuel system is sealed with the correct, high-performance FVMQ material required for flight safety across all operational temperature extremes.

The unique performance of Fluorosilicone (FVMQ) is a triumph of polymer engineering, creating a hybrid material that solves a specific aerospace challenge. The polymer's foundation is a polysiloxane (-Si-O-) backbone, the same structure found in standard silicone rubber. This silicon-oxygen bond is extremely flexible and has a very low glass transition temperature, which is the source of FVMQ's outstanding low-temperature performance, far superior to any carbon-backbone elastomer like Nitrile or FKM. To provide the necessary fluid resistance that standard silicone lacks, trifluoropropyl side groups (-CH2-CH2-CF3) are chemically grafted onto the siloxane backbone. These fluorine-rich groups create a polar, low-energy surface that is non-receptive to (and thus resists swelling from) non-polar hydrocarbon fuels and oils, a characteristic borrowed from fluorocarbon (FKM) elastomers. This unique molecular architecture—a flexible silicone backbone protected by fluorinated side groups—creates a material that provides a reliable seal for hydrocarbon fluids in an environment that experiences an exceptionally wide temperature range, from a cold-soak on an arctic runway to the heat of a firewall-forward installation.

Note: O-rings are typically considered single-use components in aerospace applications and have a finite shelf life (cure date) which must be observed. CRITICAL: Ensure the correct elastomer type is used for the application. FVMQ (typically blue) is specified for its low-temperature performance in fuel systems and must not be confused with other materials. Due to its lower abrasion resistance, it is generally not recommended for dynamic sealing applications. Installation must be performed by a certified A&P mechanic.

Documentation

The definitive application and installation eligibility for this FAA-PMA component must be confirmed using the official FAA-PMA database and the Illustrated Parts Catalog (IPC) and maintenance manuals for the specific aircraft model.