Final answer:
This task is part of aircraft maintenance, which involves the removal of non-listed items for safety and weight management, and the maintenance of the hydraulic system for control system functionality.
Step-by-step explanation:
The task of removing all items except those on the aircraft equipment list, draining, and filling the hydraulic reservoir is typically completed during the phase of aircraft maintenance. This critical procedure ensures that the aircraft adheres to safety and operational standards. The removal of non-essential items is important to prevent unwanted weight and potential hazards, while managing the hydraulic system is essential for the proper functioning of many of the aircraft's control systems, such as the brakes, flaps, and landing gear retraction systems.