As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING DESCENT AN OPERATOR EXPERIENCED AN INCIDENT IN SEVERE TURBULENCE WHERE BOTH PROPELLERS/ENGINES WERE OVERSPEED. THE NR 1 ENGINE HAD THE TORQUE SHAFT BREAK AND THE POWER TURBINE BLADES SEPARATE. BOTH PROPELLERS/ENGINES TO BE REPLACED.