The S-0309-220 is an aircraft-grade O-ring (sealing element) used in aviation fluid systems such as fuel, oil, hydraulic, or pneumatic assemblies depending on installation location. It is a consumable sealing component referenced in aircraft parts catalogs (IPC/NSN systems) and is critical for maintaining pressure integrity and preventing fluid leaks in aircraft systems.

This part number is part of an S-series airframe sealing designation, where the exact application depends on the aircraft type (commonly Twin Commander and similar fixed-wing platforms). It is typically made from fluorocarbon rubber (FKM/Viton-type material), which provides resistance to fuel, oil, hydraulic fluids, and temperature extremes.

Key features include:

Aircraft-grade elastomer sealing O-ring
Used in fuel, oil, or hydraulic system interfaces (application-dependent)
Fluorocarbon (Viton/FKM-type) material for chemical resistance
High resistance to heat, fuel, and hydraulic fluids
Designed for vibration and pressure cycling in aviation systems
Controlled aerospace consumable part (not a generic hardware O-ring)
Used in OEM maintenance and overhaul procedures
Must match exact IPC dimensions for airworthiness compliance
Part of sealed system assemblies (pumps, valves, housings, glands)