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762-551 – Piper Aircraft OEM Ring Seal
Available now on the Airparts.aero Marketplace.
Overview
The Piper Aircraft 762-551 is an OEM ring seal, commonly referred to as an O-ring, engineered for a precise sealing application within the fuel systems of numerous Piper aircraft models. This component is specifically designed to create a positive, leak-proof static seal, typically used on fuel selector valve assemblies, fuel tank drain valves, or fuel line fittings. Its function is absolutely critical for preventing the egress of volatile aviation gasoline (Avgas), which could result in fuel starvation, fire hazards, or environmental contamination.
Manufactured from a specialized elastomer compound, the 762-551 is formulated to exhibit specific material properties essential for its demanding environment. It must maintain its elasticity, dimensions, and sealing force across a wide range of temperatures, from cold-soaking at altitude to engine compartment heat. Critically, the material must be resistant to swelling, hardening, or degradation when in continuous contact with aviation fuels and their additives. As a flight-critical component whose failure could have catastrophic consequences, the use of a genuine, fully traceable Piper OEM 762-551 seal is non-negotiable for ensuring the airworthiness and safety of the aircraft.
Key Features
OEM Certification: Genuine Piper Aircraft part, guaranteeing correct material composition, dimensions, and durometer (hardness).
Fuel-Resistant Material: Fabricated from a high-grade fluorocarbon (Viton®/FKM) or nitrile (Buna-N) compound specifically chosen for its low swell characteristics and compatibility with Avgas.
Precision Dimensions: Manufactured to exacting dimensional tolerances (inner diameter, outer diameter, and cross-section) to ensure correct compression and gland fill.
Wide Temperature Range: Engineered to remain flexible and effective at the low temperatures encountered at high altitudes and the elevated temperatures of engine operation.
Positive Sealing: Designed to provide a reliable static seal, preventing fuel leaks that are a primary fire and safety hazard.
Technical Specifications
Part Number: 762-551
Component Type: Ring Seal / O-Ring
OEM Manufacturer: Piper Aircraft, Inc.
Application: Aircraft Fuel System (Fuel Selector, Drain Valves, Fittings)
Material: Aerospace-grade elastomer, typically a Fluorocarbon (FKM/Viton®) or Nitrile Rubber (Buna-N). The specific compound must be verified by the OEM Certificate of Conformance (CofC) or the aircraft's maintenance manual, as different applications may require different materials.
Finish: Standard black elastomer finish.
Governing Specifications: Manufactured to Piper Aircraft proprietary specifications and meets applicable FAA standards for fuel system components. May cross-reference to an MS or AN specification O-ring.
Aircraft Compatibility
Piper: PA-28 Series (Cherokee, Warrior, Archer), PA-32 Series (Cherokee Six, Lance, Saratoga), PA-34 Seneca, PA-44 Seminole, and other models.
Note: This is a partial list of common applications. The aircraft's specific Illustrated Parts Catalog (IPC) is the final and absolute authority for determining part applicability for a given serial number and component.
Applications
Fuel Selector Valve: Used to seal the valve body, shaft, or detent plate, preventing internal and external fuel leaks.
Fuel Drain Valves (Curtis Drains): Provides the primary seal for the valve mechanism.
Fuel Line Fittings: Used in specific B-nut or flareless fitting applications to ensure a leak-proof connection.
Fuel Tank Components: May be used to seal various access plates or sending units on the fuel tank.
Why Choose 762-551?
A fuel leak, no matter how small, is an unacceptable hazard in aviation. The Piper 762-551 OEM seal is not a generic hardware store O-ring; it is a specifically engineered component made from a precisely controlled elastomer compound. Using a non-certified seal introduces the immense risk of incorrect material, leading to rapid degradation, swelling, or hardening when exposed to Avgas. This can cause a catastrophic fuel leak, potentially leading to an in-flight fire. Sourcing a genuine, traceable Piper 762-551 is a critical, low-cost investment in the absolute safety and airworthiness of the aircraft.
The material science behind the 762-551 seal is critical to its function. The choice of elastomer, typically a fluorocarbon (FKM) or a specific high-grade nitrile (NBR), is dictated by the chemical polarity of the fluid it must contain—aviation gasoline. Avgas is a non-polar hydrocarbon solvent. An effective seal must have a different polarity to resist being dissolved or swollen by the fluid. FKM, a synthetic rubber with fluorine atoms bonded to its carbon backbone, is highly resistant to non-polar solvents and exhibits an extremely low compression set. "Compression set" is the permanent deformation of an elastomer after being held in compression; a low value is vital for a seal to maintain its elastic "memory" and continue exerting force against the gland surfaces after thousands of pressure and temperature cycles, thus preventing leaks over its entire service life.
Note: This is a flight-critical safety component. Installation must be performed by a certified A&P mechanic in strict accordance with the current Piper Aircraft maintenance manual for the specific aircraft model. Replace seals whenever a component is disassembled. Ensure the gland and surrounding surfaces are clean and free of nicks or scratches. Lightly lubricate with the system-appropriate fluid prior to installation.
