MD-11
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Troubleshooting; Situational Awareness; Distraction
Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Air Traffic Control Provided Assistance; Aircraft Equipment Problem Dissipated; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem
Aircraft
Crew was notified by ZZZ Maintenance during taxi out to runway that we had flames coming out of No. 2 Engine. Crew ran QRH Tailpipe Fire Checklist.  After communicating with ZZZ Ground; ZZZ Ground advised the crew they were sending the fire trucks as a precaution. ZZZ Maintenance suspected fuel pooled in the No. 2 Engine due to long time on ramp and advised the crew it was safe to continue to ZZZ1. The Fire Commander notified the crew that the thermal lenses indicated there was no fire.  All engine indications were within parameters throughout the event. After the second Engine start the fire commander advised crew there was light smoke but no fire on 2nd engine start.  During the entire event all engine indications were normal. The fire truck followed us to the runway and after takeoff the Tower advised the crew everything was normal; no flames or smoke observed.  Crew notified Maintenance Control enroute. Maintenance responded they are aware and will have ZZZ1 Maintenance inspect no.2 engine.
Notified by ZZZ Maintenance during taxi out to Runway XX that we had flames coming out of the number 2 engine. Myself and First Officer ran QRH procedure tailpipe fire checklist.  Communicating with ZZZ Ground; we were advised that fire fighting vehicles were sent to our aircraft to inspect number 2 engine for existing flames. Fire commander ensured with thermal lenses that there was no fire. ZZZ Maintenance advised us it would be safe to continue restarting the engine and depart if flames did not reoccur. Maintenance suspected pooled fuel causing tailpipe fire during extended aircraft on ground at ZZZ. During second start of number 2 engine; the fire commander noticed light smoke but no flames.  During entire event; all primary and secondary engine indicators appeared normal. Fire fighting vehicles elected to follow us to the active Runway XX to observe the takeoff. Once airborne ZZZ Tower communicated no flames or smoke during takeoff roll and climb.  Enroute we notified Maintenance of event.  Maintenance advised they were aware and would inspect number 2 engine upon arrival.  As a flight crew we are not able to comment. The cause would be explained by maintenance personnel. As a flight crew we would not have known of this event without an observing outside source.  This source as explained in the narrative was ZZZ Maintenance.
MD-11 flight crew reported ground personnel reported flames emanating from their number two engine during taxi out. After maintenance inspected the engine and fire personnel reported no fire the flight crew continued their taxi and flight.