B737-700
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 307
Troubleshooting; Confusion; Communication Breakdown
Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
The Captain and I were operating Aircraft X. On taxi out; we received several reports from the flight attendants; ramp personnel via ATC and a company crew behind us that the aircraft had produced a flame and two loud bangs. We received no indication of a fire or malfunction in the cockpit. It took a moment to put the information together and into context as we initially thought it was the #2 engine; but it ended up being the #1 engine. At first there was some confusion from outside sources as I was talking to the Captain; ATC and the company crew. We ran the Engine Fire Checklist and got the engine shutdown. Ground Control dispatched a vehicle and they confirmed there was no fire. We taxied back to the gate and deplaned.
On taxi out; the FA (Flight Attendant) chimed us. She said the number 2 engine was on fire. We did the checklist for engine fire. We then heard on the radio that flames were seen coming out of the number 1 engine. Crash fire confirmed that no fire or smoke was coming from either engine. We then taxied to the gate; and took another aircraft [for the flight]. Subsequently we found out from Maintenance that the event was caused by oil leaking onto the tailpipe; and then the oil caused a brief fire condition.
B737-700 flight crew reported being notified during taxi of a flaming engine due to oil leaking into the tailpipe.