Date: 201512
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: APU
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant
When detected: Aircraft In Service At Gate
Result: Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Just after calling for push back from gate we lost AC power to the aircraft (similar to what happens when GPU is inadvertently pulled without any other power source). We were on battery power alone at this point; however the APU was still running. We did not see any messages that directed us to any specific problem; just the messages that are generated when AC power is lost. Since we did not have power I opened up the cockpit door to establish direct communication with the cabin crew. Since we were on DC power only and communications were limited I quickly called dispatch from my cellphone and gave a brief description of the events; but told them that I was too busy to speak with them; but please notify ZZZ operations; MX control and ZZZ emergency services. As FO and I were attempting to diagnose this non-annunciated problem; FA indicated to me that smoke was filling the cabin at a rapid pace; coming from the vents; and most severe in the rear of the aircraft. I instructed FO on COM 2 to contact operations and have them immediately reconnect the jet bridge. Suspecting that this smoke source was the APU itself (APU gen had kicked offline also) and recognizing the need for immediate and decisive action to a problem that was not exactly clear I decided to press the APU fire extinguisher button; and instructed FA to open the front doors to get fresh air in to the cabin. FO was having some difficulty getting operations to get the jet bridge back so while this door was open I was shouting to ground personnel to reconnect the bridge immediately. I then started walking through the cabin to check that all the passengers were OK and found that they were OK; but just a bit startled; with 2 passengers in the very rear requesting fresh air. I walked to the very rear of the cabin and asked FA to describe what she saw. She indicated that the smoke was coming from an unspecific source in the very back of the plane; and none of the smoke was from the rear LAV. Furthering my suspicion that the smoke source was in fact the APU I instructed FA to open the rear doors to bring fresh breathable air in to the cabin. I brought the 2 passengers who had complained of the smoke to the very front of the plane to provide access to the fresh air from the front open doors; and the cross breeze that resulted from 1LR and now 2LR being opened mostly just about completely cleared the cabin of smoke. I once again walked through the cabin and checked with each passenger to make sure they were all OK; at the same time trying to downplay the situation with them so they would remain as calm as possible; just indicating that it was a minor mechanical malfunction; and we would have them off the airplane very soon. At first I was considering conducting an emergency evacuation because of the slow response of the ground crew bringing the jet bridge back; but then elected otherwise due to the fact that the situation now seemed stabilized; and the emergency evacuation would only introduce new unnecessary risk. The jet bridge was now being connected as we were able to take all passengers off safely. I told them that it was unlikely that we would be using this A/C to take them to [destination]; but customer service would soon re-accommodate them. As each passenger got off I once again checked to make sure they were OK; and apologized for the inconvenience. After all the passengers were off I went down to the ramp to get a better look at the rear of the aircraft. There were no obvious signs of damage or malfunction; but at this time the Port Authority had arrived. The Port Authority FD did a thorough inspection on the aircraft inside and outside; and indicated that if there was a fire at any point; it was no longer any issue. We then waited for MX personnel to arrive to begin diagnosing the problemMechanical problems are difficult to prevent; discussion of this scenario with all crew members in case of future occurrence. There was not a clear checklist to follow; wasmore of a case of needing to take immediate action to prevent a problem from escalating.


Second narrative: [Report narrative contained no additional information.]


Synopsis: ERJ-170 flight crew reported the cabin began filling with smoke while at the gate awaiting push back. Crew shut down the APU and passengers exited the aircraft through the jetway.