What do fuel filters primarily prevent from entering the fuel system?

Fuel filters play a crucial role in the overall performance and safety of an aircraft's fuel system by effectively preventing solid contaminants from entering. These solid contaminants can include dirt, rust, and other particulates that may accumulate in fuel tanks or lines. If not filtered out, these solids can cause clogging, impede fuel flow, and lead to engine performance issues or failures.

By ensuring that only clean fuel reaches the engine, fuel filters help maintain optimal operation and longevity of engine components, thereby enhancing reliability and safety. This filtering process is essential in preserving the integrity of the fuel supply and supporting the efficient combustion process within the engine. Thus, the primary purpose of fuel filters is to keep the fuel system free from solid debris.