What does an illuminated FAIL light on the AUTO XFER switchlight indicate?

What does an illuminated FAIL light on the AUTO XFER switchlight indicate?

• A. AUTO XFER was inhibited due to a fault on AC Bus 1 or 2
• B. AUTO XFER is operating normally
• C. Auto transfer is in the standby mode
• D. A fault on the DC bus

Answer: (A)

An illuminated FAIL on the AUTO XFER light means automatic transfer of the AC buses has been inhibited due to a fault on one of the AC buses. The Auto Transfer system normally watches AC Bus 1 and AC Bus 2 and will automatically reconfigure power if one bus drops out. If a fault is detected on either bus, the logic stops automatic transfer to prevent unsafe or unexpected switching, and the FAIL indicator lights to warn the crew. With this light on, auto transfer isn’t operating normally, so you would verify the affected AC bus status and follow the procedures to address the fault, potentially using manual transfer if required. This condition is not normal operation, so the other possibilities (normal operation, standby mode, or a DC bus fault) do not fit.

An illuminated FAIL on the AUTO XFER light means automatic transfer of the AC buses has been inhibited due to a fault on one of the AC buses. The Auto Transfer system normally watches AC Bus 1 and AC Bus 2 and will automatically reconfigure power if one bus drops out. If a fault is detected on either bus, the logic stops automatic transfer to prevent unsafe or unexpected switching, and the FAIL indicator lights to warn the crew. With this light on, auto transfer isn’t operating normally, so you would verify the affected AC bus status and follow the procedures to address the fault, potentially using manual transfer if required. This condition is not normal operation, so the other possibilities (normal operation, standby mode, or a DC bus fault) do not fit.