As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 3390 - DURING FLIGHT, SPARK SHOWERS AROUND LEFT PROP HUB, CREW TURNED OFF PROP HEAT. SPARKS DISAPPEARED AND RETURNED TO DTW. MAINTENANCE FOUND NR 3 BLADE HEATER MAT BURNED ON LEFT PROP. REPLACED NR 3 PROP BLADE. OPS CHECK GOOD OF PROP HEAT SYSTEM. (M)