What was found
PITCH TRIM WHEEL COULD ONLY BE MOVED WITHIN A VERY SMALL RANGE. MAINTENANCE INVESTIGATED AND FOUND THAT THE LH PITCH TRIM ACTUATOR WAS BOUND UP AND WOULD NOT ROTATE. THE ACTUATOR WAS REMOVED AND DISASSEMBLED IAW THE KODIAK 100 AMM CH. 2731.5.10 AND DAHER FIELD SERVICE INSTRUCTION FSI-184 PITCH TRIM TAB ACTUATOR MAINTENANCE. THE RAMS AND RAM HOUSINGS WERE REMOVED AND WERE FOUND TO BE ADEQUATELY GREASED (GREASING WAS RECORDED A YEAR PRIOR) AND NOT THE CAUSE OF THE PROBLEM. FSI-184 DOESN'T GIVE FURTHER DISASSEMBLY INSTRUCTIONS. HOWEVER, THE OTHER HALF OF THE ACTUATOR WAS DISASSEMBLED TO GIVE ACCESS TO THE GEARBOX. DESPITE SOME GREASE STILL REMAINING, THE DRIVE GEAR AND THE TWO DRIVEN GEARS FOR THE JACKSCREWS WERE HEAVILY CORRODED. THE RUST IN THE GEAR TEETH WAS CAUSING THE ACTUATOR TO JAM. THE OTHER OTHER ACTUATOR (RH) WAS DISASSEMBLED AND INSPECTED AND FOUND TO HAVE VERY LITTLE CORROSION. IT WAS COMPLETELY GREASED ON THE INSIDE AND ON THE JACKSCREW THREADS AS DIRECTED BY FSI-184 ITCH TRIM TAB ACTUATOR MAINTENANCE AND REINSTALLED ON THE AIRCRAFT. THE FAILED ACTUATOR WAS REPLACED WITH A NEW COMPONENT. THIS IS A SAFETY OF FLIGHT ISSUE. IT IS POSSIBLE FOR THE PITCH TRIM SYSTEM TO BE SOMEWHAT OPERATIONAL (BUT STIFFLY). ONCE THE AIRCRAFT IS FLYING THE AIR LOADS ON THE TRIM TAB CAN RESIST AN INTERNALLY CORRODED ACTUATOR FROM TURNING COMPLETELY. IF THE PILOT CHOOSES TO USE ELECTRIC TRIM AND NOT MANUALLY TRIM IMMEDIATELY AFTER TAKEOFF, HE/SHE MAY NOT NOTICE THAT THE TRIM IS NOT MOVING UNTIL THE AIRLOADS INCREASE TO THE POINT THAT THE PILOT HAS DIFFICULTY HOLDING THE ELEVATOR CONTROL. EVEN THEN, DUE TO THE AIR LOADS, THE PITCH TRIM THAT MIGHT HAVE WORKED ON THE GROUND, NO LONGER IS MOVEABLE IN FLIGHT. WE ARE AWARE OF A FATAL ACCIDENT WITH ANOTHER OPERATOR OVERSEAS THAT OUR ORGANIZATION INVESTIGATED AND FOUND THAT ONE OR BOTH OF THE TRIM ACTUATORS FAILING IN THIS WAY CONTRIBUTED TO THE ACCIDENT. IT WAS DUE TO THIS ACCIDENT THAT QUEST/DAHER ISSUED FSI-184 AND REVISED THE AMM TO INCLUDE A TEST TO DETERMINE SERVICEABILITY OF THE PITCH TRIM SYSTEM. HOWEVER, WE FEEL THEY DID NOT GO FAR ENOUGH TO INCLUDE INSPECTION AND LUBRICATION OF THE INTERNAL GEARBOX.