What happens to the XBLEED when the OFF position is selected?

When the XBLEED is placed in the OFF position, the XBLEED valve is closed. This closure prevents any crossflow of bleed air between the left and right engine bleed air systems. The XBLEED system allows for the transfer of bleed air from one engine to another to assist with engine starting and environmental control system operations, among other functions. Therefore, selecting the OFF position effectively isolates the bleed air systems.

This isolation is particularly important for certain operational scenarios where bleed air balance or system integrity is critical. Closing the valve helps ensure that all systems operate independently, which can enhance safety and reliability during flight. Choices that indicate the valve is opened, remains operational, or that switches are disabled do not accurately reflect the operational functionality of the XBLEED system in the OFF position.