What was found
ON APPROACH, CREW REPORTED NO LEFT MAIN GEAR DOWN LOCK INDICATION. PERFORMED GEAR WILL NOT EXTEND HYDRAULICALLY PROCEDURE, STILL NO DOWN LOCK INDICATION. TOWER FLYBY INDICATED GEAR SEEMED TO BE DOWN. ON LANDING LEFT MAIN GEAR COLLAPSED. GEAR SWING INDICATED NO MALFUNCTION OF LEFT MAIN GEAR ACTUATOR. FURTHER INSPECTION FOUND LEFT MAIN LANDING GEAR UPLOCK ACTUATOR RESTRICTING HYDRAULIC FLUID FLOW TO LEFT MAIN GEAR ACTUATOR. TEARDOWN REVEALED ONE INCORRECT SIZE SEQUENCE BALL INSTALLED, CAUSING INTERNAL RESTRICTION OF HYDRAULIC FLUID.