What is a characteristic of control valves?

Control valves are crucial components within various systems, and one key characteristic is that they can require manual operation by the crew. This manual operation allows aircrew members to adjust the flow and pressure of fluids or gases according to operational needs and conditions.

In many aviation systems, especially in older aircraft or in specific operational scenarios, crew members may need to intervene directly with control valves rather than relying on automated systems. This manual operation provides flexibility and control over critical parameters, ensuring safety and performance.

The other characteristics, while relevant to different aspects of aircraft systems, do not accurately reflect the fundamental function of control valves as related to crew operation. Therefore, recognizing that control valves can necessitate manual adjustment by the crew underscores their role in active systems management during flight operations.