How is aircraft pressurization controlled in manual mode?

In manual mode, aircraft pressurization is primarily controlled pneumatically via the emergency outflow valve. This means that the pilot or the crew can manually adjust the outflow valve to control the rate of air that is released from the cabin, thereby influencing cabin pressure.

This process requires an understanding of the relationship between cabin altitude and the ambient pressure outside the aircraft. By adjusting the outflow valve, the crew can either retain more air in the cabin to increase pressure or allow some air to escape to reduce the pressure as necessary.

The other mechanisms referenced in the other options are part of a more automated or different approach to pressurization. The cabin pressure controller, for example, typically manages pressurization automatically in normal operating conditions by assessing inflow and outflow of air without manual intervention. Atmospheric pressure sensors are used to monitor the external pressure to aid in automatic control rather than manual adjustment. Understanding these distinctions is essential for effective manual operation of the aircraft’s environmental control systems.