When will the cross bleed valve open when in Auto mode?

The cross bleed valve, when in Auto mode, opens primarily in response to specific conditions regarding engine operation and wing anti-ice (WAI) system status. When WAI is selected off, the aircraft systems recognize that there is no need for additional bleed air to support wing heating, which can lead to maintaining a balance in engine performance and preventing unnecessary pressurization in the bleed air system.

In contrast, when WAI is active, the system utilizes bleed air to heat the wings, which usually means that the cross bleed valve would need to remain closed or in a specific configuration to support this operation. Similarly, if the heat exchanger ventilation jet pump is closed or if one-engine inoperative (OEI) conditions are present, these scenarios generally do not dictate the valve opening under normal operations, as they involve different considerations for engine and bleed air management. Therefore, with WAI off, the valves will open as part of normal operations to optimize airflow management without excess demand on the engine bleed air.