As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED A VIBRATION OR SURGE FROM PROPELLER WHEN DESCENDING OR LANDING. GOVERNOR SHOP REPORTED THE SPOOL VALVE IS THE PROBLEM AND EVEN THOUGH HE PURCHASES NEW SPOOL VALVE FROM HARTZELL. IT DOESN'T ALWAYS FIX IT, NEW SPOOL VALVES ARE DEFECTIVE. HAVE TO INSTALL A MULTIPLE SPOOL VALVES BEFORE PROBLEM CAN BE FIXED.