What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Enroute mso to gtf at 13,500 feet:flight 7820:pilot encountered a slight yaw to the left and a momentary torque decrease of 5% on the #1 engine. Pilot then smelled smoke. All engines readings were normal except the itt on the #1 engine which had incresed to 780 degrees. Soon after, pilots received an engine fire indication on number 1 engine. Number one engine was then shut down; smoke began to subside. Pilots then declared an emergency and returned to mso without further incident. On 11/19/2012, the airline reported that it appears that the vent line for the #6 and 7 bearing cavities had broken and allowed hot high pressure internal engine gases to flow into the engine nacelle. The internal engine component that caused the vent lne to break is unknown pending engine teardown by the manufacturer.
As the FAA filed it
ENROUTE MSO TO GTF AT 13,500 FEET:FLIGHT 7820:PILOT ENCOUNTERED A SLIGHT YAW TO THE LEFT AND A MOMENTARY TORQUE DECREASE OF 5% ON THE #1 ENGINE. PILOT THEN SMELLED SMOKE. ALL ENGINES READINGS WERE NORMAL EXCEPT THE ITT ON THE #1 ENGINE WHICH HAD INCRESED TO 780 DEGREES.SOON AFTER, PILOTS RECEIVED AN ENGINE FIRE INDICATION ON NUMBER 1 ENGINE. NUMBER ONE ENGINE WAS THEN SHUT DOWN; SMOKE BEGAN TO SUBSIDE.PILOTS THEN DECLARED AN EMERGENCY AND RETURNED TO MSO WITHOUT FURTHER INCIDENT.ON 11/19/2012, THE AIRLINE REPORTED THAT IT APPEARS THAT THE VENT LINE FOR THE #6 AND 7 BEARING CAVITIES HAD BROKEN AND ALLOWED HOT HIGH PRESSURE INTERNAL ENGINE GASES TO FLOW INTO THE ENGINE NACELLE. THE INTERNAL ENGINE COMPONENT THAT CAUSED THE VENT LNE TO BREAK IS UNKNOWN PENDING ENGINE TEARDOWN BY THE MANUFACTURER.