What was found
WHILE UPON APPROACH, THE NLG FAILED TO EXTEND. AN EMERGENCY BLOW DOWN OF THE GEAR ALSO RESULTED IN THE FAILURE OF THE NLG TO EXTEND. A SECOND ATTEMPT OF EMERGENCY EXTENSION RESULTED IN ALL GEAR EXTENDING THE ACFT LANDED WITHOUT FURTHER INCIDENT. LANDING GEAR WAS PINNED AND SAFETIED IN THE DOWN AND LOCKED POSITION AND FERRIED FOR TROUBLESHOOTING AND REPAIR. UPON ARRIVAL, TECHS JACKED ACFT AND PERFORMED SEVERAL NORMAL AND EMERGENCY LANDING GEAR EXTENSIONS. THE NOSE LANDING GEAR FAILED TO EXTEND ON EACH ATTEMPT. TECHS REMOVED THE NLG UP-LOCK ACTUATOR AND FOUND THAT THE END YOKE JAM NUT SECURING THE LOCK RING TAB TO THE PISTON HAD BACKED OFF ALLOWING THE UP-LOCK ACTUATOR PISTON TO ROTATE. THE PISTON ROTATION