What bus provides an alternate source of power for the AC ESS bus?

The AC ESS bus is a critical component of the aircraft's electrical system, as it powers essential systems required for flight safety and operation. An alternate source of power for the AC ESS bus enhances the redundancy of the aircraft's electrical system, ensuring that if the primary power source fails, an alternate can take over to maintain the operation of vital systems.

In this context, AC bus 2 serves as the correct alternate source of power for the AC ESS bus. It is designed to support the AC ESS bus in the event of a failure in the main power source, providing backup power to essential systems. This redundancy is crucial for maintaining operational integrity, especially during critical phases of flight.

The other options present different power sources or systems that do not directly alternate with the AC ESS bus. For example, the AC ESS SHED bus may provide additional load management capabilities under certain conditions but does not serve as a direct alternate power source. Similarly, DC Bus 1 and DC Bus 2 provide direct current power and fulfill different roles in the aircraft's electrical architecture.