The cabin pressure of an aircraft in flight is maintained at the selected altitude by?

Maintaining cabin pressure at a selected altitude during flight is primarily achieved by controlling the rate at which air leaves the cabin. This process is vital because as an aircraft climbs, the external atmospheric pressure decreases. To ensure the cabin pressure remains stable and comfortable for passengers and crew, the system manages the outflow of air to match the internal cabin pressure to the desired altitude.

By regulating the outflow of air, the cabin environment can be adjusted based on the differential pressure between the cabin and outside air. If the outflow is too rapid, cabin pressure would drop excessively; if it is too slow, pressure could build up beyond a comfortable level. Thus, the pressure control valves and outflow systems play a crucial role in maintaining this balance.

In contrast, increasing cabin air supply and adjusting the bleed air source are more related to providing fresh air and controlling temperature rather than directly maintaining pressure at a predetermined altitude. Monitoring external pressure is also important for understanding the environment, but it does not directly regulate cabin pressure. Therefore, controlling the potential escape of air is the most accurate method for maintaining cabin pressure effectively during flight.