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M83248/1-277 – Mil-Spec Fluorosilicone O-Ring
Available now on the Airparts.aero Marketplace.
Overview
The M83248/1-277 is a large-diameter, military-specification o-ring manufactured in strict accordance with MIL-DTL-83248-1. This is a high-performance seal engineered for creating static face seals on large-diameter access panels, covers, and housings in critical aerospace fluid systems. The "/1" in the part number designates the material as Fluorosilicone (FVMQ) with a 75-durometer hardness. This advanced elastomer is specifically chosen for applications that demand both resistance to fuels and oils, and reliable sealing performance across an extremely wide temperature range, especially in deep cold.
The "-277" size code corresponds to a very large o-ring with a nominal 12-inch inside diameter. Its primary application is in sealing large circular flanges, such as fuel tank access panels or hydraulic reservoir covers. The FVMQ material ensures that the seal remains flexible and energized, compensating for the thermal expansion and contraction of large metal components from ground level to high altitude. For any large static sealing application exposed to extreme temperatures, the certified M83248/1-277 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 excellent fuel and oil resistance 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).
Large Diameter for Access Panels: The AS568-277 size is specifically for creating static face seals on large, 12-inch nominal diameter flanges.
75 Durometer Hardness: A medium hardness that provides an excellent balance of sealing force and conformability for large static face seal applications.
Technical Specifications
Part Number / Specification: M83248/1-277
Replaces Part Number / Specification: M83248-1-277
Component Type: O-Ring / Preformed Packing (Static Face Seal)
OEM Manufacturer: Certified Mil-Spec Manufacturer
Material: Fluorosilicone (FVMQ), 75 Durometer (Shore A)
Size Standard: AS568 Dash Number -277 (Nominal Dimensions: 12.000" ID, 0.139" [1/8"] Cross-Section).
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 and dimensions is required by the engineering drawings or maintenance manual. It is found on aircraft manufactured by:
Boeing, Airbus, Lockheed Martin, Textron Aviation (Cessna, Beechcraft), Bombardier, 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
The large diameter of this o-ring makes it ideal for static face seals on:
Fuel Tank Access Panels: The primary seal for the large, circular panels on the underside of wings that provide access to the fuel tank and its components.
Hydraulic Reservoir Covers: Sealing the main cover on large hydraulic fluid reservoirs.
Large Filter Housings: Providing the main canister or housing seal for large hydraulic or fuel filter assemblies.
Engine & APU Gearbox Covers: Sealing large inspection covers on engine or Auxiliary Power Unit accessory gearboxes.
Why Choose M83248/1-277?
A leak from a fuel tank access panel is a catastrophic failure. The M83248/1-277 is specifically engineered to prevent this. Its Fluorosilicone (FVMQ) material is the critical design choice for seals on large metal panels that experience significant thermal contraction in the deep cold of high-altitude flight. A standard Fluorocarbon (FKM) o-ring can become too hard in these conditions, lose its "memory," and fail to compensate for the contracting metal gland, creating a leak path. The M83248/1-277 remains flexible and energized, maintaining a positive seal. For the integrity of a large-diameter fluid system seal, the use of this correct, certified material is non-negotiable.
The unique performance of the M83248/1-277 O-ring is a direct result of the molecular architecture of Fluorosilicone (FVMQ). This elastomer is engineered by incorporating trifluoropropyl groups onto the siloxane backbone of a silicone polymer. The siloxane (silicon-oxygen) backbone is what gives the material its outstanding thermal stability and extremely low glass transition temperature (Tg), allowing it to remain flexible and resilient at temperatures far below the brittle point of hydrocarbon-based rubbers. The pendant fluorine groups, which are highly electronegative, create a polar molecule that is chemically resistant to non-polar hydrocarbon fuels and oils, preventing swelling and degradation. This molecular hybridization creates a material that uniquely combines the extreme temperature range of a silicone with the fluid resistance of a fluorocarbon, making it the ideal engineering solution for static seals in aerospace fluid systems that must perform from -85°F to 400°F.
Note: The M83248/1-277 is a flight-critical seal. Never reuse O-rings. Always install a new, certified O-ring whenever a panel or housing is opened. Inspect the sealing grooves and mating surfaces for any nicks, scratches, or corrosion before installation. Lightly lubricate the new O-ring with clean system fluid or an approved lubricant to aid installation and prevent twisting in the groove. The panel bolts should be tightened in the sequence and to the torque value specified in the maintenance manual to ensure uniform compression of the seal.
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.
