When the cabin pressure regulator operates in the differential mode, which component is vented to the atmosphere?

When the cabin pressure regulator operates in the differential mode, the component that is vented to the atmosphere is the outflow valve. The outflow valve is designed to control the outflow of air from the cabin to maintain the desired cabin altitude.

In this scenario, the differential mode utilizes a pressure reference to determine how much cabin pressure is above the ambient atmospheric pressure. As a result, the outflow valve adjusts its position to ensure proper ventilation and to maintain the correct pressure balance within the cabin.

The other components listed, such as the pressure relief valve, differential metering valve, and cabin pressure sensor, play specific roles in the system, yet they do not directly vent the cabin pressure to the atmosphere. The pressure relief valve functions to prevent over-pressurization of the cabin, while the differential metering valve regulates airflow based on pressure differences. The cabin pressure sensor monitors the pressure levels to provide feedback for the automation control systems but does not vent air. Thus, the outflow valve is pivotal for maintaining cabin pressure and is indeed the component that vents to the atmosphere during differential pressure regulation.