What was found
(CAN) ACFT EXPERIENCED HEAVY VIBRATION, AND MANAGED TO LAND SAFELY AT DEPARTURE AIRPORT. ON THE GROUND, MAINTENANCE FOUND THAT LT PROPELLER BLADE WAS IN A ZERO PITCH ANGLE WHEN ALL THE OTHER WERE IN FEATHER. AFTER DISSASSEMBLY, THE PROPELLER BLADE PIN WAS FOUND IN THE BOTTOM OF THE HUB. THE SET SCREW THAT SECURES THE PIN WAS STILL IN PLACE, BUT IT SOMEHOW CAME LOOSE AND ALLOWED THE PIN TO SLIDE OUT. WE ARE CURRENTLY IN COMMUNICATION WITH THE O/H FACILITY IN ORDER TO OBTAIN FURTHER DETAILS.