What must be done when servicing the hydraulic system?

To service the hydraulic system properly, it is crucial to have hydraulic pressure and ensure the flaps are up. This is because the hydraulic system plays a vital role in operating various components of an aircraft, including the flaps. When the flaps are retracted (up), it ensures that the system is in a safe configuration for maintenance and prevents any hazards that might arise from accidental deployments while servicing.

Additionally, having hydraulic pressure is essential to ascertain that the system is functioning correctly before proceeding with any servicing tasks. This allows for checks of pressure levels and leaks, ensuring that the system is sealed and operating as designed. Together, these two actions help maintain the efficiency and reliability of the aircraft's hydraulic systems, as well as the safety of the personnel working on the aircraft.