As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) THE AIRCRAFT TAKEOFF, LT PROPELLER ENCOUNTERED AN UNDERSPEED SITUATION. THE ACFT RETURNED TO DEPARTURE. THE AME TROUBLESHOT THE PROBLEM, WE FOUND THE PITCH LOCK VALVE AT FAULT. THE PITCH LOCK VALVE, PN 6506196 WAS REPLACED AND THE ACFT RETURNED TO SERVICE.