After a malfunction of the pressure controller at FL310, what changes occur?

When a malfunction of the pressure controller occurs at Flight Level 310, it leads to an imbalance in the cabin pressurization system. In this scenario, the cabin altitude (CAB ALT) refers to the pressure level within the aircraft cabin, and DELTA P is the differential pressure between the cabin and the outside atmosphere.

Due to the failure of the pressure controller, the cabin altitude begins to increase, as the controller is responsible for maintaining a constant cabin pressure. As the cabin altitude rises, the cabin vertical speed (CAB V/S) also increases because the cabin is not able to maintain its former pressure altitude, causing a rapid change in pressure.

The decrease in DELTA P signifies that the differential pressure between the cabin and the outside air has lessened. This is primarily due to the cabin altitude rising without corrective action, which consequently reduces the effective pressure difference the cabin can maintain.

Therefore, it's logical to conclude that, in the event of such a malfunction, CAB V/S increases, CAB ALT increases, and DELTA P decreases. Understanding these dynamics is crucial for pilots to ensure they can respond appropriately to such emergency situations.