The bus tie contactors open or close automatically to maintain power supply to AC busses 1 and 2 when the bus tie switch is in which position?

The bus tie contactors operate automatically when the bus tie switch is in the AUTO position. In this setting, the system is designed to automatically open or close the bus tie contactors to ensure that power is maintained to the AC busses 1 and 2. This automatic function is critical for maintaining system reliability and ensuring that both busses can provide power to essential aircraft systems, especially in the event of a failure in one of the power sources. When the switch is in AUTO, the lighting associated with this function will be extinguished, indicating that the system is managing the power distribution without manual intervention.

In contrast, when the switch is in the MANUAL position, the bus tie contactors do not operate automatically; the crew must manually manage the power distribution. The ALTN and OFF positions also disrupt normal power management, with ALTN potentially implying an alternate source and OFF completely isolating the busses. The design of the system favors the AUTO position for optimal performance and reliability.