MS35769-9 – Military Standard Gasket ID 1/2
Available now on the Airparts.aero Marketplace.
Overview
The MS35769-9 is a military-standard annular gasket, an engineered sealing component designed to create a robust, high-pressure seal in critical aerospace fluid and pneumatic systems. This is not a simple flat washer; it is a composite gasket, typically featuring a soft, non-asbestos fiber and elastomer core encased in a deformable copper shell. When compressed by a fastener, the soft copper casing yields and forces the inner core material to fill any microscopic surface imperfections, creating a superior, leak-proof seal. It is a single-use, flight-critical component for ensuring the integrity of high-pressure connections.
Key Features
- Copper-Encased Composite Construction: Features a soft, pliable inner core material encapsulated in a 99% pure copper casing. This design combines the strength and heat conductivity of copper with the superior conformance and sealing properties of the inner core.
- High-Pressure Sealing: Engineered to create a gas-tight and fluid-tight seal in high-pressure applications where standard elastomeric O-rings could extrude or fail. It is rated for pressures up to 200 PSI.
- Excellent Thermal Stability: The copper casing and internal materials are suitable for temperatures up to 500°F, making this gasket ideal for firewall forward applications, including fuel, oil, and hydraulic line fittings.
- Single-Use "Crush" Design: This gasket is designed to be plastically deformed during the initial torquing of the fastener. This "crush" action is what creates the perfect seal. Once compressed, the gasket work-hardens and must be replaced if the fitting is loosened.
- MS Certified Standard: As a certified Military Standard part, it guarantees the material composition, dimensions, and manufacturing process required for aviation use. It is the superseding part for the legacy AN900-8 gasket.
Technical Specifications
- Standard: MS35769 / MIL-DTL-35769
- Full Part Number: MS35769-9
- Legacy Part Number: AN900-8
- Component Type: Copper-Encased Annular Gasket / Crush Washer
- Material: Copper Casing with Fiber/Elastomer Core
- Finish: Plain Copper
- Nominal Size: For 1/2 inch bolt or fitting
- Dimensions:
- Inside Diameter (I.D.): 0.500 - 0.516 inches
- Outside Diameter (O.D.): 0.734 - 0.750 inches
- Thickness: 3/32 inches (0.094 inches)
Aircraft Compatibility
The MS35769-9 is a universal hardware component used across all categories of aircraft where a 1/2 inch high-pressure gasket is specified for a fluid or pneumatic fitting.
- Common Applications:
- Hydraulic Systems: Sealing banjo bolts and high-pressure line fittings on brake systems, landing gear, and hydraulic pumps.
- Fuel Systems: Used on high-pressure fuel line fittings, particularly on fuel control units, fuel pumps, and drain plugs.
- Engine Instrumentation: Sealing the fittings for high-pressure oil and fuel sending units and lines.
- Pneumatic Systems: Providing a robust seal in high-pressure air and vacuum system lines.
Applications
The MS35769-9 is the specified sealing solution for critical fluid connections:
- Banjo Bolt Sealing: Commonly used in pairs (one on each side of the banjo fitting) to seal a fluid connection to a bolt.
- High-Pressure Port & Plug Sealing: Used under the head of a bolt or a drain plug to seal a high-pressure fluid port in an engine case or system component.
Why Choose MS35769-9?
In high-pressure fluid systems, even a microscopic leak can lead to a complete loss of system fluid, resulting in brake failure, landing gear malfunction, or engine issues. The MS35769-9 gasket provides the most reliable type of seal for many of these applications. Using a genuine MS-standard part ensures that the gasket has the correct materials and construction to deform properly under pressure and create a perfect seal. A non-certified or reused gasket will not provide the same reliability, posing a significant safety risk. For a flight-critical, leak-proof connection, there is no substitute for certified hardware.
Order Your MS35769-9 Gaskets Now
Ensure the integrity of your high-pressure fluid systems with certified, military-standard hardware. Visit Airparts.aero to order your MS35769-9 copper-encased gaskets today.
The sealing principle of the MS35769-9 composite crush washer is superior to a solid metal washer in many applications. The soft copper casing provides the ductility to flow into surface imperfections on the fitting and the component body. As clamping force increases, the pressure is transmitted to the soft inner core. This forces the core material to extrude slightly against the inner and outer diameters of the copper casing, creating a powerful, multi-axis sealing force against the bolt shank and the outer perimeter of the fitting. This results in an extremely reliable seal that is highly resistant to vibration and pressure pulses within the fluid system.
Note: This is a single-use gasket. It must be replaced whenever the fitting is loosened. Ensure all mating surfaces are clean, dry, and free of scratches or gouges before installation. Tighten the fastener to the torque value specified in the applicable maintenance manual to achieve a proper seal.