As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE, NR 1 ENG PROP RPM STARTED TO FLUCTUATE +/- 12 PERCENT, A FEW SECONDS LATER, TORQUE SLOWLY DROPPED TO ZERO. ALL ENGINE GUAGES ALSO DROPPED THEN CLIMBED BACK TO ABOUT 50 PERCENT THEN DROPPED AGAIN. FLT CREW FEATHERED PROP BUT DID NOT SHUTDOWN ENGINE. AIRCRAFT LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE REPLACED LT HMU. AIRCRAFT RETURNED TO SERVICE.