What was found
LANDING GEAR COLLAPSED ON LANDING. AFTER AIRCRAFT WAS TOWED TO HANGAR AND PLACED ON JACKS, FOUND THE GEAR ACTUATOR JACKSCREW HAD BECOME SEPARATED FROM THE MOTOR/GEAR PORTION OF THE GEAR ACTUATOR. AFTER REMOVAL OF THE ACTUATOR FROM AIRCRAFT AND DISASSEMBLY, DISCOVERED THE DRIVE GEAR/JACKSCREW RETAINING NUT, P/N AN364-720C, HAD BACKED OFF THE THREADED SHAFT OF THE JACKSCREW ALLOWING THE JACKSCREW TO SEPARATE FROM THE DRIVE MECHANISM.