Which cabin access door must be armed and cross-checked first on the ERJ 175?

The correct answer is the primary door, which must be armed and cross-checked first on the ERJ 175. This protocol is in place because the primary door serves as the main access point for cabin crew and emergency responders. Arming and cross-checking the primary door first ensures that it is secured and available for emergency use if needed.

In an emergency situation, rapid access can be crucial, and the primary door is typically designed to allow for quick egress from the aircraft. This emphasis on the primary door establishes a standardized procedure that prioritizes safety and efficiency during pre-flight preparations. Adhering to such protocols ensures that all crew members are aligned and ready for any situations that may arise, setting a strong foundation for performing effective safety measures.

While the rear, side, and aft doors also play important roles in the overall safety and operation of the aircraft, the primary door's designated status makes it the correct first choice when it comes to arming and cross-checking procedures.