A321 Captain reported being notified of a tailpipe fire on one engine at the gate by the First Officer and a maintenance technician. Airport crash fire rescue extinguished the fire; contained to the engine nacelle.

Narrative

During the requisite ETOPS briefing for Flight ABCD; I was informed by ZZZ Maintenance Control that the arriving Aircraft X; Flight ABCE (ZZZ - ZZZZ) was found to require 6 quarts of oil for Engine #2 during the Pre-Departure Service Check maintenance check. It was unknown at that time if the additional oil quantity was due to a possible internal or external leak; or potential over servicing and; as such; the aircraft was going to be taken out of service for a period of one hour to ascertain the reason. The only indication of any potential external oil leak was discovered by the second officer on the preflight walk around where he noted a small (less than 3oz.) of oil had collected in the bottom inside shroud of the #2 Engine nacelle. (This was also observed by the technician on duty who was conducting the Pre-Departure Service Check (PDSC) for the flight). He expressed confidence that the oil was serviced to the appropriate level and based on his experience in dealing with many other Airbus operators at the field; his observations seemed accurate. In addition; the engine manufactures guidance paperwork he was referencing indicated a leak of undetermined origin would most likely require a borescope inspection. After a period of time and a conversation that the flight crew was not a party to; ZZZ Maintenance Control contacted me and asked if we would be willing to conduct an engine run on the affected power plant for a period of 15 minutes at idle power. They also requested Pack #2 be run to determine if there was any possible contamination of the associated e system. We agreed and after relocating to a remote hardstand; the engine run and pack evaluation were completed per their request with no anomalies noted; other then a potential drop of approximately .5 - 1 quart of oil quantity in Engine #2. Upon shutdown; the first officer and I walked the length of the cabin interior to check for any potential fume issues. As we approached Row 23 a distinct odor was observed; but not that of the typical fume profile (dirty socks; magic marker). To note; post shutdown; no bleed source was being used. Upon returning to the front of the aircraft ; the second officer opened the L1 door and exited to see if the technician; who was monitoring the engine from the exterior for any visible leaks; had seen anything. I briefly used the forward lav at this time and then returned to the aft cabin to see if the introduction of fresh air from outside the aircraft had eliminated the odor. While walking back to the front; the second officer re-entered and expressed we had an Engine #2 fire. I briefly looked into the flight deck and determined there were no ECAMS present and confirmed that with the first officer who was still sitting at his duty station. Upon exiting the aircraft; the second officer and I observed dry chemical fire retardant being discharged into the aft nacelle area due to a post-shutdown engine fire. Concurrent with this; Crash Fire Rescue were responding with several crash tenders and rapid intervention vehicles. No fire was visible from the front of the engine; however the technician did see flames from the turbine section prior to the application of fire retardant. Once the fire was determined to be out; I coordinated with the fire chief to have the engine dry swept to have as much retardant removed as possible due to minimize any corrosive affects. He also offered to spray down the engine and right landing gear assembly with low pressure water to aid in removing the powder. Upon his further suggestion and coordination with the maintenance technician we conducted a dry crank of the engine for 60 seconds to wash as much residual retardant out of the engine as possible. The fire chief expressed reservation in regards to spraying the back of the engine due to the potential to force any chemical into the hot section. This was mutually agreed upon buy the fire chief; technician and flight crew. The technician said the remainder wouldbe vacuumed out prior to return to service or further maintenance action.