EMB ERJ 170/175 ER/LR
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Workload; Time Pressure; Situational Awareness; Confusion
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown; Ground Event / Encounter Other / Unknown
Flight Crew Became Reoriented; Flight Crew Took Evasive Action; General Maintenance Action; General Release Refused / Aircraft Not Accepted
Aircraft; Procedure
We were delayed 30 minutes leaving the gate due to an EDCT time (1 hr 13 min past scheduled departure). After pushing and beginning taxi ground gave us a spot to sit and wait out our extended delay. We had shut down the APU and taxied out on one engine to comply with the new APU directive on running for no more than 10 minutes. However; once we heard from ground that we would be sitting in the same spot for more than 20 minutes we elected to restart the APU and sit with that running and the engines off to conserve fuel. We had been sitting for several minutes with only the APU on when all of a sudden; unpredictably; the APU failed. This resulted in only battery power being available. Knowing we had only 10 minutes of electricity on batteries we contacts everyone we could to inform them of the situation and request a tow back into the gate. We told ground that we would be uncontainable. We told operations that we had lost power. We made a PA informing the passengers and Flight Attendants (FA) what had happened. We then called dispatch on the phone and informed them. Now sitting on [the] taxiway with no power I realized that we had no way to speak with the FA's and/or passengers so I elected to open the cockpit door to allow communications with the cabin. Once the tow and the airport authority arrived at the aircraft I opened the cockpit window and spoke with the ground personnel to get us towed back into the gate. Upon arrival maintenance met the aircraft and attempted a restart on the APU. It ran for just under a minute and failed again. At this point we changed aircraft to continue our flight. Even though I wouldn't normally expect the APU to fail; in the future during ground delays I may consider keeping at least one engine running to make sure we have a source of air. Once the APU failed we were stuck. With at least one engine running a crossbreed can always be performed.
An ERJ-175 crew with a delayed departure time; elected to hold with both engines shutdown; APU power only. After the APU failed the crew scrambled to notify ATC and company to secure a tow before the 10 minute battery power expired.