Final answer:
The AC ESS FEED pb in the normal position controls the power supply to essential AC electrical buses from the main AC bus, ensuring redundancy and power to critical systems.
Step-by-step explanation:
The AC ESS FEED pushbutton (pb), when in the normal position, typically refers to a feature found in aircraft electrical systems, specifically within the cockpit's overhead electrical panel. The purpose of this pb is to control the power supply to essential AC electrical buses, which are the power distribution pathways crucial to the aircraft's operation.
In the normal position, it ensures that the essential AC electrical buses are powered by the main AC bus, providing redundancy and ensuring that critical systems remain powered during specific scenarios, such as the loss of the main AC power supply.