MS35769-11 – Military Standard Copper Crush Annular Gasket
Available now on the Airparts.aero Marketplace.
Overview
The MS35769-11 is a military-standard annular gasket, commonly known as a copper crush washer, engineered to create a superior, high-pressure seal in aerospace fluid and pneumatic systems. Manufactured in strict accordance with MIL-DTL-35769, this gasket is fabricated from 99% pure, solid copper that has been fully annealed. The annealing process softens the copper, allowing it to deform under the pressure of a torqued fastener, filling microscopic imperfections to create a robust, leak-proof, metal-to-metal seal. It is a single-use, flight-critical component for ensuring the integrity of high-pressure connections.
Key Features
- Annealed Copper Construction: Made from solid copper and then annealed (softened) through a precise heat-treating process. This makes the gasket extremely ductile, enabling it to conform perfectly to the surfaces of the components it seals.
- High-Pressure Sealing: Designed to create a gas-tight and fluid-tight seal in high-pressure applications where elastomeric seals (O-rings) would fail or extrude. It is capable of withstanding thousands of PSI when properly installed.
- Excellent Thermal Conductivity: The solid copper construction provides excellent heat transfer, helping to dissipate heat away from the fitting, which can be beneficial in high-temperature applications like brake and hydraulic systems.
- Single-Use Design: Engineered as a mandatory single-use component. Once the gasket is "crushed" or yielded during the initial torquing, it work-hardens and will not provide a reliable seal if reused.
- MS Certified Standard: As a certified Military Standard part, it guarantees the material purity, annealing process, and dimensional tolerances required for certified aviation use. It is the superseding part number for the legacy AN900-4 gasket.
Technical Specifications
- Standard: MS35769 / MIL-DTL-35769
- Full Part Number: MS35769-11
- Legacy Part Number: AN900-4
- Component Type: Annular Gasket / Crush Washer
- Material: 99% Pure Copper, Annealed
- Finish: Plain
- Nominal Size: For 1/4 inch bolt or fitting
- Dimensions:
- Inside Diameter (I.D.): 0.265 inches
- Outside Diameter (O.D.): 0.437 inches
- Thickness: 0.050 inches
Aircraft Compatibility
The MS35769-11 is a universal hardware component used across all categories of aircraft where a 1/4 inch copper crush washer is specified for a fluid or pneumatic fitting.
- Common Applications:
- Hydraulic Systems: Sealing banjo bolts and fittings on brake lines, landing gear systems, and hydraulic pumps.
- Fuel Systems: Used on high-pressure fuel line fittings, particularly on fuel control units and fuel pumps.
- Pneumatic Systems: Providing a seal in high-pressure air and vacuum system lines.
- Engine Instrumentation: Sealing the fittings for oil and fuel pressure sending units.
Applications
The MS35769-11 is the specified sealing solution for critical fluid connections:
- Banjo Bolt Sealing: The most common application is to be used in pairs (one on each side of the banjo fitting) to seal a fluid connection to a bolt.
- High-Pressure Port Sealing: Used under the head of a bolt or a plug that seals a high-pressure fluid port.
Why Choose MS35769-11?
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 other critical emergencies. The MS35769-11 crush gasket provides the most reliable type of seal for many of these applications. Using a genuine MS-standard part ensures that the copper has been properly annealed to the correct softness. A non-annealed or improperly annealed copper washer will be too hard to deform correctly, resulting in a poor seal. For a flight-critical, leak-proof connection, there is no substitute for certified hardware.
Order Your MS35769-11 Gaskets Now
Ensure the integrity of your high-pressure fluid systems with certified, military-standard hardware. Visit Airparts.aero to order your MS35769-11 copper crush gaskets today.
The sealing principle of the MS35769-11 crush gasket relies on plastic deformation. The soft, annealed copper is designed to have a lower yield strength than the fasteners and components it is sealing (typically steel or aluminum). When torque is applied, the clamping force exceeds the copper's yield strength, causing it to flow like a very thick fluid into the microscopic valleys and tool marks on the mating surfaces. This creates a perfect, void-free metal-to-metal interface that is impervious to high-pressure fluids and gases. This is also why the gasket is single-use; the initial compression work-hardens the copper, significantly increasing its yield strength and preventing it from properly deforming a second time.
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.
MS35769-11 Gasket is annular copper-asbestos gaskets (crush washers) that are suitable for temperatures up to 500 F. and pressures up to 200 PSI. Ring width is 1/8″; thickness is 3/32. Also, it is used on Gasket Kits P/N: G-KT (-1, -2, -3 & -5)
Gasket oil screen housing plug for the following Continental engines:
- • A (-65, -75)
- • C (-75, -85, -90)
- • O (-200)
Fits in:
- • Bombardier Challenger 300
- • Bombardier Challenger 604
- • Bombardier Global Express
- • Dassault Falcon 7X
- • Gulfstream G-IV/GIV-SP/G-400/G-450/G-300
- • Piaggio Avanti II
- • Textron Aviation Beechcraft King Air 200 - all variants
- • Textron Aviation Beechcraft King Air 300 - all variants
- • Textron Aviation Beechcraft King Air 90 - all variants
**Continental Engine Models A50, A65, A75, and A80 Parts List [ Click Here ]