What is a common use for the flight deck's communication system during a sterile flight deck phase?

The flight deck's communication system during a sterile flight deck phase is primarily utilized for emergency communication only. This phase is critical as it is designed to minimize distractions and maintain focus for the flight crew during specific phases of flight, such as takeoff and landing. During this time, the crew is expected to concentrate on the operation of the aircraft, ensuring safety is prioritized.

Emergency communications are necessary to convey critical information or alerts that may arise, which can impact the safety and operation of the flight. This specific use aligns with the sterile flight deck regulations, which restrict non-essential communication to prevent interruptions during these high-stakes moments.