A Guide to Aircraft Seals and Their Importance in Hydraulic System Longevity

For many aircraft, the functionality of landing gear, brakes, flight controls, and other critical equipment highly depends on hydraulic systems that use compressed fluids to create the immense force necessary for reliably actuating various processes. Central to the efficiency and longevity of these systems are hydraulic seals, which ensure that fluids remain contained, pressure is maintained, and contaminants are kept out. Aircraft seals are specifically designed to operate under the extreme conditions found in aviation, where temperatures, pressures, and mechanical loads can be highly variable, and many types exist to perform specific roles.

In order to best prevent leakage and maintain pressure in hydraulic systems, seals are typically made from materials like rubber, polyurethane, or polytetrafluoroethylene (PTFE) for their flexibility, durability, and resistance to various chemicals. Beyond basic differentiators like material, hydraulic seals are primarily categorized as being static or dynamic. Static seals in particular are found in applications where they remain stationary relative to the surfaces they are sealing, while dynamic seals are used where there is relative motion between sealing surfaces. The selection of the appropriate seal type and material is vital to ensure that various parts of a hydraulic system function correctly and efficiently, as each section will have different factors and conditions present.

Able to handle motion between surfaces, dynamic seals in aircraft will often be found in assemblies like cylinder pistons in the form of piston and rod seals. Piston seals are specifically installed on the piston head to prevent fluid from bypassing between it and the cylinder wall, ensuring that hydraulic pressure is effectively transmitted. Aerospace rod seals, on the other hand, are generally installed on the piston rod itself to prevent fluid from leaking out of the cylinder.

On the other hand, there are various types of static seals as well, one of the most widely recognized being the O-ring. O-rings are perhaps the most commonly used type of static seal for aircraft design, valued for their simplicity, effectiveness, and versatility. Generally coming in the form of a flat, ring-shaped rubber piece with a hole in the middle, these seals are often found in fittings, flanges, and many other connection points where leakage is a concern. Wiper seals, another type of static seal, are also commonly found throughout aviation hydraulic systems to keep contaminants like dirt and moisture out, thereby protecting more sensitive components inside.

Despite the durability of many seals, they will be subject to wear and tear over time, which can lead to hydraulic system failure if not properly maintained. Common causes of seal failure include improper installation, exposure to extreme temperatures, chemical degradation, and physical wear. For instance, seals that are exposed to temperatures beyond their design limits can harden, crack, or deform, leading to leaks. Similarly, exposure to incompatible hydraulic fluids or contaminants can cause chemical degradation, weakening materials and compromising overall effectiveness.

To ensure the longevity of hydraulic seals and the systems they protect, regular inspection and maintenance are essential practices. This includes checking seals for signs of wear, cracking, or deformation on a scheduled basis, with replacement being carried out as needed. Using high-quality seals that are designed for the specific conditions of an aircraft hydraulic system is advantageous for preventing hastened wear, while correct installation is also critical. There are also various forms of hydraulic system components that aid in deterring wear and tear for certain seals, such as guide rings that reduce seal damage by preventing the metal-to-metal contact of pistons and rods.

In conclusion, hydraulic seals are a fundamental component of aircraft hydraulic systems, playing a major role in maintaining pressure, preventing leaks, and keeping contaminants out. By understanding the different types of seals, their applications, and the factors that can lead to their failure, aviation professionals can better maintain the integrity and performance of their hydraulic systems. For those in need of reliable hydraulic system seals and other aviation components, Broadline Aerospace offers a wide range of top-quality solutions. As you explore our extensive vast selection, you are always welcome to utilize our online Request for Quote (RFQ) service to obtain pricing information on any desired items. Our staff is on standby around the clock and would be delighted to assist you with your needs, so do not hesitate to get in touch.