What was found
THE NLG WOULD NOT RETRACT AFTER TAKEOFF. THE GEAR WARNING HORN WAS ALSO ON. COMPLYING WITH ABNORMAL PROCEDURES WAS NO HELP. THE AIRCRAFT WAS RETURNED TO NGO WHERE IT LANDED WITHOUT INCIDENT. THE NLG RETRACT AND UNLOCK CYLINDERS WERE REMOVED AND REPLACED. LEAK AND OPERATIONAL CHECKS WERE GOOD. *S/D* SUPPLEMENT IS ISSUED TO REFLECT THE FACT THAT THE AIRCRAFT FERRIED TO NRT BEFORE THE NLG RETRACT AND UNLOCK CYLINDERS WERE REPLACED AS A PRECAUTIONARY MEASURE. THE NLG UNLOCK CYLINDER PART NUMBER IS: ACG73305501. IN ADDITION, THE PART TOTAL CYCLES SHOULD BE: 28, 893.