B777-200
Time Pressure; Situational Awareness
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance
General Maintenance Action; General Evacuated; General Declared Emergency
Aircraft
12 minutes prior to departure. Approximately 1 minute after switching from external power to APU power; APU auto shutdown. APU FIRE illuminated and bottle discharged. Commanded deplaning via jet bridge and contacted Ground for Airfield Rescue and Fire Fighter equipment to respond. No fire. Maintenance inspected; MELed; and we departed. Repeat on switching power to external at our destination. APU FIRE illuminated. [I] contacted Ground for Airfield Rescue and Fire Fighter equipment to respond. No fire. Maintenance took aircraft. [I was] surprised that a power spike would cause a fire warning/auto shutdown.
A B777 APU auto shutdown with a fire warning and bottle discharge about one minute after the APU assumed electrical both before flight and again at the destination.