If the BUS TIE annunciator is illuminated, what will occur if the battery bus fails?

When the BUS TIE annunciator is illuminated, it indicates a potential issue with the bus tie between the generator bus and the battery bus. If a failure occurs on the battery bus, items connected to the battery bus will not receive power. This is due to the design of the electrical system which isolates the battery bus from the generator bus in case of such failures.

The operational integrity of the battery bus is critical for the safe functioning of the aircraft systems. In the event of a battery bus failure, the systems that rely solely on the battery bus will become inoperable. This means that the power from the battery bus will not be available, aligning with the answer indicating that items on the battery bus will not be powered.

Understanding this concept is crucial for ensuring proper management of the aircraft's electrical systems and responding effectively to faults.