As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ANC FLIGHT 8663: AIR TURNBACK AND ENGINE SHUT DOWN: ON CLIMBOUT NP DROPPED 20-30 PERCENT W/POPPING NOISE & A/C SHUTTER ACCOMPANIED BY MFC 1B FAULT. CREW SHUT DOWN THE NUMBER ONE ENGINE; DECLARED AN EMERGENCY. AIRCRAFT LANDED WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED NR 1 MFC IAW ATR-72 JIC-31-48-81-RAI-10000. OPS CHECK IAW ATR-72 JIC-31-48-81-RAI-10000. FUNCTION CHECKS GOOD.