B717 (Formerly MD-95)
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
General Evacuated; General Declared Emergency
Aircraft
After landing while taxiing to gate we started the APU. After we arrived at gate we shut both engines down and turned off seatbelt sign. At this time we were powered by the APU and aircraft deplaning began as normal. After a few minutes the ground personnel connected the gate power to the aircraft. I had the electrical page up and noticed that the jetway power looked a little on the lower side. The power read about 103/109. I elected to turn the APU generator off instead of [shutting down] the APU because if the jetway power did not take; all I had to do was turn the APU generator back on rather than waiting for the APU to shut down and then have to restart. The moment I turned the generator switch off I heard a pop and a slight shudder in the aircraft. At this time there was also a momentary break in power. The next thing I noticed was that we got an APU auto shutdown. I looked at the engine display page and saw that the APU had gone from 100 percent to 0 in a second. As I was putting this all together I called Flight Attendant who was flying in the rear of the aircraft. I asked if he heard or felt anything. He said yes. The Lead Flight Attendant was in the cockpit telling passengers goodbye and second Flight Attendant was in galley heard this. [Forward Flight Attendant] picked up his interphone; so he could hear what was going on as well. I instructed [aft Flight Attendant] to be careful and assess rear door and open it to see if he sees or smells smoke or fire. I could feel the door slam shut from the front of the aircraft and he reported he could see and smell smoke. The passengers were already in the process of deplaning thru jetway so at this point I got on the PA; identified myself as the Captain and instructed the passengers still on board to leave their belongings and exit thru the jetway exit immediately. I said this three times for them to exit the aircraft thru forward entry door. The flight attendants then picked up right where I left off and began getting the remaining passengers off the aircraft as quick as they could. I called Ground and informed them I needed the fire truck to our gate as I had something happen to the APU and had smoke in the back of the plane. Even though I did not have a fire indication at this time I elected to run the APU fire QRH. We followed the checklist and made sure APU was secured. By the time we had finished this; the last couple of passengers were exiting the aircraft. Once all passengers were off the flight attendants exited the aircraft and went with passengers up to terminal. At this point First Officer stayed on flight deck and I went back to check on APU. When I open aft door there was still smell of smoke and a slight smoke still in the air. I closed door and went outside to meet the Fire Chief. As I got to back of aircraft I told all ground personnel to just get away from the aircraft. As I got to the back the Fire Chief was arriving with 6-8 fire trucks close behind. I informed him of our situation and he took over from there. He positioned his fire truck around back of plane and had a couple of his men start checking with thermal cameras for any signs of fire. The fire crew took a few minutes outside the aircraft to determine it was ok for them to proceed inside aircraft. I then took the Fire Chief and one of his men to the aft APU compartment. They again checked out the APU compartment and determined it was safe and no longer had any danger of fire. The Fire Chief then cleared us to allow the passengers to re-plane and gather their belongings. Maintenance and Dispatch were then notified. They then sent Contract Maintenance out to check the airplane. It was determined the APU could be MELed and ok to fly.
B717 Captain reported the APU shutdown suddenly at the gate after arrival; generating a smokey smell; so the aircraft was evacuated through the already open forward entry door.