688-427 – Piper Aircraft Seal Washer
Available now on the Airparts.aero Marketplace.
Overview
The Piper Aircraft 688-427 is a genuine OEM bonded seal washer, a high-performance sealing component engineered for use in critical fluid and pneumatic line connections throughout various Piper aircraft. This is not a standard flat washer; it is a composite seal consisting of a metal outer ring bonded to an inner elastomeric ring. The 688-427 is designed to create a positive, leak-proof seal under the head of a bolt or other threaded fittings, providing a far more reliable seal than a simple crush washer in many applications. As a genuine Piper factory part, it guarantees the correct materials and dimensions for a safe and airworthy repair.
Key Features
- Bonded Seal Design: Features a robust metal outer ring that provides a defined limit for compression, preventing over-torquing and damage to the seal. The inner ring is made of a high-quality elastomer that creates the actual seal.
- High-Pressure Sealing: The design is engineered to create a leak-proof seal in high-pressure systems, such as hydraulic lines, fuel fittings, and oil pressure sensor lines. The metal ring prevents the softer elastomer from extruding under pressure.
- Self-Centering Action: The washer is designed to be self-centering on the fastener, ensuring that sealing pressure is applied evenly and concentrically, which is critical for a reliable, long-term seal.
- Vibration Resistance: The elastomeric element provides a degree of vibration damping and maintains constant pressure on the sealing surfaces, making it highly resistant to the leaks that can develop from vibration in a standard metal-to-metal seal.
- Genuine Piper OEM Part: As a genuine factory component, it ensures the use of the correct metal alloy and elastomer compound, which are certified for compatibility with aviation fluids (e.g., MIL-H-5606 hydraulic fluid, 100LL Avgas) and operating temperatures.
Technical Specifications
- Part Number: 688-427
- Associated Part Number: Also referenced as 494-063
- Component Type: Bonded Seal Washer
- Outer Ring Material: Plated Steel or Aluminum Alloy
- Inner Seal Material: High-Quality, Fuel/Oil-Resistant Elastomer (e.g., Nitrile/Buna-N)
- Primary Application: Sealing fluid line fittings, banjo bolts, and drain plugs.
- Certification: FAA Production Approval
Aircraft Compatibility
The 688-427 is a standard sealing component used in numerous systems across a wide range of the Piper Aircraft fleet. It is imperative to consult the specific aircraft's Illustrated Parts Catalog (IPC) for final verification of its application.
- Common Aircraft Families:
- PA-28: Cherokee, Warrior, Archer, Arrow
- PA-32: Cherokee Six, Lance, Saratoga
- PA-34: Seneca
- PA-44: Seminole
- And many other Piper models.
Applications
The 688-427 is the specified sealing solution for critical fluid connections where a leak cannot be tolerated:
- Hydraulic System Fittings: Used to seal connections on brake lines, calipers, and master cylinders.
- Fuel System Connections: Provides a positive seal on fuel line banjo bolts, fuel strainer plugs, and fuel pump fittings.
- Engine Oil Systems: Used for sealing oil pressure lines and sensor fittings.
Why Choose 688-427?
A leak in a fuel, oil, or hydraulic system can have severe consequences, from loss of system function to an in-flight fire. The Piper 688-427 bonded seal washer is an engineered solution that provides a more reliable and durable seal than standard gaskets or crush washers in many applications. Using a genuine Piper OEM part is the only way to guarantee that the washer's metal and rubber components are made from materials certified for aviation use and that the dimensions are precise for the intended application. For a flight-critical seal, trust only genuine Piper parts.
Order Your 688-427 Seal Washers Now
Ensure the leak-free integrity of your aircraft's critical fluid systems with genuine Piper OEM components. Visit Airparts.aero to order your 688-427 bonded seal washers today.
The 688-427 bonded seal washer creates a seal through controlled compression. The outer metal ring is slightly larger than the inner elastomeric ring. As a bolt or fitting is tightened, the metal ring makes contact with the mating surfaces first. As torque is increased, the metal ring controls the precise amount of "squeeze" applied to the inner rubber ring. The sharp edges of the rubber lip are forced against the inner and outer surfaces of the gland, creating a highly effective seal. This design prevents the over-compression that can damage a simple O-ring and provides a clear visual and tactile indication of when the fastener is properly tightened, as the metal ring bottoms out.
Note: This is a single-use sealing component. It must be replaced whenever the fitting it seals is loosened to ensure the integrity of the seal. 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.
*** REPLACES PIPER 494-063 ***
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