What was found
(CAN) ON APPROACH THE ENGINE RPM INCREASED RAPIDLY AND THE AIRCRAFT SUDDENLY LOST ALTITUDE. THE PILOT WAS ABLE TO MAINTAIN CONTROL BY OPERATING THE ENGINE IN THE UPPER LIMIT OF THE RPM RANGE. THE AIRCRAFT WAS SUCCESSFULLY LANDED ATTHE RAPID DES JOACHIMS WATER BASE. (CYDJ). INVESTIGATION REVEALED THE BLADES AT A REST POSITION ESTIMATED AT CLOSE TO ZERO DEGREES. THE DOME WAS REMOVES AND BOTH STOP DOWEL WERE FOUND TO BE SHEARED. THE COMPANY WILL ENLIST THE NTSB LAB FOR ASSISTANCE.CORROSION INITIATED FATIGUE FRACTURE.