Which of the following is NOT a component of hydraulic systems?

The correct answer identifies air filters as not being a component of hydraulic systems. In hydraulic systems, the primary components include pumps, actuators, and valves, all of which are essential for the movement and control of hydraulic fluid.

Pumps are crucial because they generate the flow of hydraulic fluid necessary for system operation. Actuators convert hydraulic energy into mechanical motion, enabling precise control of various systems such as landing gear and flight controls. Valves are essential as well; they regulate the flow of the hydraulic fluid, directing it appropriately to different system components.

Air filters, on the other hand, are typically associated with pneumatic systems, where they serve the purpose of cleaning air before it enters the system. In hydraulic applications, while it is important to keep the hydraulic fluid free from contaminants, this is usually managed through oil filters rather than air filters. This distinction reinforces the role of different types of filters in specific systems, clarifying why air filters do not fit within the category of hydraulic system components.