AS9120B, ISO 9001:2015, and FAA AC 0056B Accredited
Among the many small elements that contribute to the performance of aircraft systems, grommets and O-rings are indispensable for preventing leaks, electrical faults, and mechanical wear. Though often overlooked due to their size, these components are engineered to meet rigorous demands for sustaining operational integrity. In this blog, we will explore the many ways in which grommets and O-rings support aviation systems, as well as what factors must be considered for proper selection and installation.
In aircraft, grommets are typically installed in cutouts across structural panels, bulkheads, and electrical bays where wiring harnesses or fluid-carrying tubes must pass through metal or composite surfaces. By isolating these elements from the edges of cutouts, they significantly reduce contact damage and insulation abrasion that can lead to electrical shorting or fluid leaks. In high-vibration zones, such as those near engines or control surfaces, grommets also help to absorb and diffuse shock forces so critical lines remain stable and undamaged during flight.
Aircraft grommets are usually manufactured from durable, flame-retardant elastomers like silicone, EPDM, or specially treated rubber that can withstand thermal cycling, corrosive fluids, and sustained vibration. Most are round or oval in shape, often featuring recessed locking grooves or expanded shoulders for secure panel retention, as well as split seams for easier installation around existing lines. Some grommets are also molded or bonded into larger assemblies to ensure proper positioning and structural reinforcement, while others are designed as snap-in or push-fit types for quick maintenance.
For specific use cases, subtypes like strain relief and blind grommets offer enhanced functionality. Strain relief grommets are engineered to manage cable tension, proving useful in avionic bays or control systems where wire routing is exposed to frequent movement or flexing. Blind grommets, on the other hand, are used to seal off unused panel holes or conduit access to block the intrusion of moisture and debris–or pressurized air–helping maintain ideal pressure and environmental isolation.
O-rings are essential for maintaining the integrity of pressurized systems, where they are compressed between two surfaces to form a tight seal that prevents fluid loss, cross-contamination, or pressure imbalance. Found across assemblies like hydraulic actuators, engine and fuel components, and landing gear, they help preserve connection points even under rapid temperature changes, vibration, and high operating pressures. Also used in dynamic applications like actuator pistons or rotating shafts, O-rings are able to flex while maintaining contact and resisting tearing or other forms of damage.
O-rings used in aviation must meet stringent material and dimensional specifications. Common materials include fluorocarbon (Viton) for high chemical and thermal resistance, nitrile (Buna-N) for robust fuel and oil compatibility, and fluorosilicone for applications requiring resistance to low temperatures and ozone. Furthermore, these O-rings are precision-molded and installed in specially machined recesses called gland grooves, which are designed to hold the seal in place while allowing for controlled compression, expansion, and movement.
In addition to standard round O-rings, several other variants are employed to help meet the demanding conditions associated with aircraft operation. For instance, backup rings are solid, non-elastomeric components that are placed to support the primary O-ring in high-pressure conditions, preventing extrusion and maintaining its integrity. Meanwhile, quad-rings feature a four-lobed design that reduces friction and allows for improved lubricant retention under dynamic motion, making them especially effective in piston and rotary applications.
Although O-rings and grommets serve distinct mechanical functions, both provide essential reinforcement where parts interface or experience movement. As such, selecting either for aircraft systems requires careful attention to material compatibility, sizing, and performance specifications. It is particularly important to choose the correct size, as using an undersized grommet or improperly rated O-ring can result in extrusion, cracking, or deterioration, negating their protection and leading to potentially hazardous system failures.
Meanwhile, material selection should be largely based on operating temperature range and fluid exposure. For instance, nitrile O-rings perform well with petroleum-based fluids, though they may degrade rapidly when exposed to synthetic hydraulic oils. Similarly, silicone grommets may provide superior thermal resistance, but they lack the fuel resistance necessary for certain zones within aircraft.
Above all, prioritize compliance with aviation quality standards, which ensures uniformity across suppliers and reduces the likelihood of failure caused by substandard manufacturing. These components should be verified against recognized certifications such as AS568, which defines standard dimensions and tolerances for O-rings, or AS23190, which outlines material and performance requirements for environmental grommets used in aerospace systems. Engineers and technicians are also encouraged to only source components from established distributors who supply traceable records, supporting regulatory compliance and easy maintenance tracking.
Posted on April 21, 2025 robin johnson
Share
All Orders are Fulfilled in the U.S.A. All shipments must comply with U.S.A export laws. No exceptions.
“We Proudly Support Intrepid Fallen Heroes Fund that serves United States Military Personal experiencing the Invisible Wounds of War : Traumatic Brain Injury (TBI) and Post Traumatic Stress (PTS). Please visit website (www.fallenheroesfund.org) and help in their valiant effort”.
We Hope that You Will Visit Us Again the Next Time You Need Aircraft Parts and Make Us Your Strategic Purchasing Partner.
Request for Quote