Under a DC bus off advisory, what is the recommended immediate action?

Under a DC bus off advisory, what is the recommended immediate action?

• A. Ignore and continue flight.
• B. Reboot the bus by cycling the battery.
• C. Switch to alternate power sources only.
• D. Follow the electrical abnormal procedures.

Answer: (D)

Acting through the electrical abnormal procedures is the correct immediate action. When a DC bus off advisory occurs, you’re facing an electrical fault that requires a structured, documented response rather than ad-hoc actions. The procedures guide you step by step to determine exactly which DC bus is affected, check power sources, confirm breaker and load status, and manage power to preserve essential systems while you isolate or reconfigure as needed. This approach minimizes the risk of creating new faults or missing a critical step. Cycling the battery to reboot the bus isn’t the prescribed first action because it can introduce transients, mask the fault, or disrupt other systems before the proper checks are done. Ignoring the advisory or switching to alternate power sources without the procedures can bypass the intended sequence and leave the aircraft in an unsafe or degraded configuration. Following the electrical abnormal procedures ensures a safe, controlled handling of the situation.

Acting through the electrical abnormal procedures is the correct immediate action. When a DC bus off advisory occurs, you’re facing an electrical fault that requires a structured, documented response rather than ad-hoc actions. The procedures guide you step by step to determine exactly which DC bus is affected, check power sources, confirm breaker and load status, and manage power to preserve essential systems while you isolate or reconfigure as needed. This approach minimizes the risk of creating new faults or missing a critical step.

Cycling the battery to reboot the bus isn’t the prescribed first action because it can introduce transients, mask the fault, or disrupt other systems before the proper checks are done. Ignoring the advisory or switching to alternate power sources without the procedures can bypass the intended sequence and leave the aircraft in an unsafe or degraded configuration. Following the electrical abnormal procedures ensures a safe, controlled handling of the situation.