As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RT PROP RPM SLOWED AFTER TAKEOFF. RT PROP RPM UNDERSPEED NOTICED AFTER TAKEOFF (1280 RPM) PROCEEDED IN ACCORDANCE WI/QRH AND RETURNED FOR LANDING. TORQUE MOTOR LOCKOUT WAS ACHIEVED, BOTH CONDITION LEVERS WERE AT MAX PRIOR TO THIS. AIR RETURN TO CRW. MAINTENANCE REPLACED RT PROP OVERSPEED GOVERNOR IAW SF340 MM CHAP. 61. ALL CHECKS GOOD AT THIS TIME. PN 8210-163, SN/ON 2163906.