Dash 8-300
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor; Ground Event / Encounter Other / Unknown
General Evacuated
Aircraft
An electrical anomaly occurred upon taxi in to the gate. After deplaning the passengers all electrical power was removed from the aircraft. Under direction from maintenance control ground power was introduced to the aircraft to try and diagnose the problem. At that point the 'Check Fire Detect' warning light illuminated with no other indications. I smelled what I believed to be smoke. I exited the aircraft to perform a visual inspection from the exterior and saw smoke pouring from a vent in the tail section of the aircraft. The automatic thermal fire suppression system had not discharged. I got back on the aircraft and ordered the remaining crew members to evacuate. I manually discharged the APU fire bottle and called ground control to send the fire trucks then removed all electrical power from the aircraft again. Some sort of electrical malfunction caused a fire to start in the tail section of the aircraft.All appropriate check lists and immediate action items were performed. Nothing really could have been done to prevent this other than being extremely cautious when diagnosing an electrical problem. In my opinion it would have happened regardless.
After landing; started APU taxiing in to the gate. APU starter light did not extinguish. Cycled APU off; then on; but it did not restart. Noticed APU AUX breaker (N8) was popped. GPU voltage was low; so we requested a different one. Began getting erroneous lights; such as 'touched runway' along with others. After hooking up different GPU; the 'check fire detect' light illuminated; but we had no other signals from the control panel. We went outside to check; and saw smoke coming from the APU. The Captain went back onboard; discharged an extinguisher bottle; and advised ATC to roll Crash Fire Rescue to our location.
DHC8 flight crew reported attempting to start the APU during taxi in to the gate but the APU starter light did not go out and the APU did not start. A second attempt is also unsuccessful. After deplaning at the gate; smoke was detected coming from the APU compartment; the APU fire handle was pulled and Crash Fire Rescue was called.