A320
Flight Crew Air Transport Pilot (ATP)
Workload
Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Gate; General Flight Cancelled / Delayed
Aircraft
As we taxied into position on the runway; two following flights reported that significant flames and smoke were coming from our APU compartment.  We verified the APU had shut down; exited the runway; and requested CFR support. The QRH provided no guidance given the lack of ECAM indications; and I elected to deploy the APU fire extinguishing system as a precaution.  Once we were able to communicate with the CFR crews on a discreet emergency frequency; we determined that the event was over. We returned to the gate and debriefed with the CFR and cabin crews.
The flight crew of an A320 was alerted by other aircraft of significant smoke and flames emanating from their APU while taking the departure runway.  The Captain activated the APU Fire Extinguishing system and contacted the CFR personnel; determined the event was over; and returned the aircraft to the gate followed by a crew briefing.