Before using the emergency system for flaps operation, what must be done first?

The correct procedure before using the emergency system for flap operation involves prioritizing system readiness, which includes securing the landing gear first. Lowering the landing gear using the emergency system ensures that the aircraft is in a safe configuration for landing. Since the flaps and landing gear are controlled by hydraulic systems, and the flaps need to be extended for landing, it's essential to ensure that the landing gear is down and locked to avoid any potential for an incident during an emergency flap deployment.

Engaging the primary hydraulic system is important for normal operations; however, if you are resorting to the emergency system for flaps, it indicates that there is a failure in the primary system, making this step less relevant. Checking hydraulic fluid levels is a routine maintenance action but does not directly relate to the immediate need for emergency flap operation. Releasing the parking brake is also a standard procedure but does not pertain to the emergency operation of flaps, as it is already assumed that the parking brake would not be engaged during an emergency situation requiring flap adjustment.