Seals are used to prevent fluids from passing beyond a certain point and to keep air, dirt, or other particulates out of a system. The constantly increasing usage of hydraulics and pneumatics in aircraft systems has created a need for packings and gaskets of differing designs and functions to meet the needs of the speeds and temperatures to which they are subjected. Because no one type of seal is suitable for all installations, there are many different types of seal. Factors that dictate what type is necessary include the pressure at which the system operates, the type of fluid in the system, the metal finish and clearance between adjacent parts, and the type of motion it may be exposed to. Aircraft seals are divided into three primary classes: packings, gaskets, and wipers. This blog will explain all three, their types, and what differentiates them.