If the bleed valves control selector is AUTO, what is the effect of the wind ISOL Valve switch and BLEED AIR SOURCE selector?

• A. They will override AUTO in all cases
• B. They will have a limited effect
• C. They will have no effect
• D. They will only affect start sequence

Answer: (C)

In AUTO mode, the bleed air system uses its own control logic to manage valve positions and source selection. The wind isolation valve and bleed air source selector are manual controls that are meant to override the automatic logic when needed. When the system is in AUTO, the automatic controller decides which bleed source to use and when to open or close the isolation valve, so these manual controls don’t change the operation under normal conditions. They won’t affect system behavior unless you switch to manual control or a fault disables AUTO. So, in this scenario, they have no effect.