Which of the following must be done before using any emergency equipment?

Before using any emergency equipment, it is crucial to obtain the Captain's permission. The Captain is responsible for the overall safety and operation of the aircraft and must oversee any actions that could affect the safety of passengers and crew. This protocol ensures that any emergency measures taken are coordinated and managed effectively, adhering to established safety procedures. The Captain's approval not only confirms that the situation warrants the use of emergency equipment but also provides an opportunity for the crew to receive specific instructions tailored to the current emergency scenario.

Other actions, while important in their own right, come after receiving the Captain's permission. Checking with the ground crew, announcing to passengers, and preparing a report are relevant in the context of emergency procedures but they do not take precedence over the Captain's authority in directing emergency responses. Ensuring that the Captain is on board with the actions being taken maintains order and clarity during stressful situations.