M83248/1-908 - Premium Aerospace O-Ring Seal

M83248/1-908 – Mil-Spec Fluorosilicone Boss Seal O-Ring

Available now on the Airparts.aero Marketplace.

Overview

The M83248/1-908 is a military-specification, premium preformed packing (O-ring) manufactured in strict accordance with MIL-DTL-83248/1. This is an advanced sealing component engineered for a very specific and critical role: creating a positive, static face seal for -8 (1/2 inch) straight thread tube fittings in aerospace systems subjected to extreme temperature variations. The core of this component's performance lies in its material, specified by the "/1" designation as Fluorosilicone (FVMQ). This elastomer is uniquely suited for applications where excellent fuel and oil resistance must be maintained across a very wide temperature range, particularly at the extreme low temperatures encountered during high-altitude flight.

This 75-durometer O-ring is designed to be compressed between the shoulder of a male fitting and the flat face (boss) of a component like a pump, valve, or actuator. Its material properties ensure it remains flexible and maintains a positive sealing force even in deep cold-soak conditions that would cause other elastomers to become brittle and fail. For any fluid system requiring a reliable, wide-temperature boss seal, the certified M83248/1-908 is the definitive engineering solution.

Key Features

• Mil-Spec Certified: Manufactured and tested in strict accordance with MIL-DTL-83248/1, guaranteeing material composition, dimensional accuracy, and performance in extreme temperatures.

• Fluorosilicone (FVMQ) Material: A specialized elastomer that combines the excellent fuel and oil resistance of fluorocarbons with the superior low-temperature flexibility of silicones.

• Extreme Operational Temperature Range: Engineered to maintain a positive seal in temperatures ranging from approximately -85°F to 400°F (-65°C to 204°C).

• Boss Gasket Seal Design: The -908 size is specifically for creating a static face seal on -8 (1/2") AN/MS straight thread tube fittings.

• 75 Durometer Hardness: A medium hardness that provides an excellent balance of sealing force and conformability for static sealing applications.

*** NOTE THIS SEAL O-RING REPLACES THE FOLLOWING PART NUMBERS: MS9387-08 AND AS3208-08 BY SUPERSCEDURE ***

Technical Specifications

• Part Number / Specification: M83248/1-908

• Component Type: O-Ring / Preformed Packing (Boss Gasket Seal)

• OEM Manufacturer: Certified Mil-Spec Manufacturer

• Material: Fluorosilicone (FVMQ), 75 Durometer (Shore A)

• Size Standard: AS568 Dash Number -908 (for a 3/4-16 straight thread boss, corresponding to a -8 or 1/2" tube OD fitting).

• Governing Specification: MIL-DTL-83248/1.

• Typical Operating Temperature Range: -85°F to 400°F (-65°C to 204°C).

Aircraft Compatibility

• Universal Aerospace Application: This is a standard mil-spec O-ring used on a vast range of aircraft where a seal with these specific properties is required by engineering drawings. It is found on aircraft manufactured by:

  • Textron Aviation (Cessna, Beechcraft), Boeing, Lockheed Martin, Bombardier, Piper, Gulfstream, and others.

Note: The correct O-ring material and part number must be verified in the specific aircraft or component maintenance manual. Elastomer selection is flight-critical and system-dependent.

Applications

• Fuel Systems: Provides static seals for fuel system components, such as pumps, filter housings, and line connectors, particularly those located in unheated areas of the airframe like the wings.

• Engine & Propeller Systems: Used in engine accessories and oil system components that are exposed to wide ambient temperature swings from ground to altitude.

• Hydraulic Systems: Suitable for petroleum-based (e.g., MIL-PRF-5606) hydraulic systems requiring an exceptional low-temperature seal. Not for use with phosphate-ester fluids like Skydrol.

Why Choose M83248/1-908?

The engineering reason for this part's existence is its unparalleled low-temperature performance. In aerospace applications, substituting an O-ring is a critical error. Using a standard Fluorocarbon (FKM) seal in a location specified for the M83248/1 Fluorosilicone will lead to a guaranteed leak at the low temperatures of high altitude. This is not a possibility; it is a certainty based on the material's glass transition temperature. Such a leak of flammable fuel or critical hydraulic oil can be catastrophic. Sourcing a fully certified, traceable M83248/1-908 is the only way to ensure the integrity and safety of the fluid system across the entire flight envelope.

The superior performance of the M83248/1-908 is a direct result of the material science of its Fluorosilicone (FVMQ) elastomer, specifically its extremely low glass transition temperature (Tg). All elastomers have a Tg, the temperature below which the polymer chains lose their mobility, causing the material to become rigid and brittle. Standard Fluorocarbon (FKM) has a Tg around -4°F (-20°C), making it unsuitable for high-altitude applications where temperatures can plummet to -65°F (-54°C). The FVMQ elastomer, with its flexible siloxane backbone, possesses a much lower Tg (below -85°F / -65°C). This means that during a high-altitude cold-soak, an FKM seal can cross its Tg and lose its ability to conform and seal against the gland surfaces, while the FVMQ seal remains fully elastic, energized, and functional. This superior low-temperature characteristic is the fundamental engineering reason for specifying the M83248/1 slash sheet.

Note: The M83248/1-908 is a flight-critical seal. Never reuse O-rings. Always install a new, certified O-ring whenever a fitting is disconnected. Inspect the sealing surfaces on the fitting and the boss for any nicks, scratches, or corrosion before installation. Lightly lubricate the new O-ring with clean system fluid to prevent damage during installation and consider the use of a backup ring (e.g., MS28774) in higher pressure applications as specified by the maintenance manual.

Documentation

• MIL-DTL-83248/1: The military detail specification sheet defines all material, dimensional, and testing requirements for this O-ring and is publicly available through the Defense Logistics Agency ASSIST database and various online mil-spec libraries.