A DC9-50 HAD THE NOSE LNDG GEAR COLLAPSE ON LNDG DUE TO INCORRECT INSTALLATION OF INTERIM REPAIR HYD FLEX LINE INTERFERING WITH DOWN-LOCK MECHANISM.

Narrative

ON AUG/XX/96; AT THE START OF SHIFT #1; LEAD MECH WAS ASSIGNED TO THE 2 ACFT THAT WERE IN THE HANGAR FOR A SVC CHK AND A 'C' CHK. ACFT X WHICH WAS IN FOR A SVC CHK NEEDED TO BE FINISHED. ABCD; THE MGR ON DUTY INSTRUCTED ME TO REPLACE THE TEMPORARY FLEX LINE THAT WAS INSTALLED ON THE L STEERING ACTUATOR. I ASSIGNED A MECH TO SEE WHICH LINE NEEDED TO BE REPLACED. THE MECH LOOKED UP THE PART AND FOUND OUT THERE WERE NO REPLACEMENT PARTS IN SUPPLY. I NOTIFIED ABCD ABOUT THE SIT. ABCD INSTRUCTED US TO HAVE IT REMOVED SO HE COULD BENCH CHK IT ON THE TEST STAND. THE LEAK CHK WAS OK SO HE SAID TO PUT IT BACK ON THE AIRPLANE AND SEE IF IT LEAKS AGAIN. THE MECH HOOKED UP THE LINE AND IT STARTED LEAKING AGAIN. THE MECH AND I WENT UP TO SEE ABCD IN THE MGR'S OFFICE TO FIND OUT WHAT HE WANTED DONE NEXT. ABCD SAID TO TAKE OUT THE LINE AND RESECURE EVERYTHING. THE MECH ACCOMPLISHED THE RESECURING; BUT I DID NOT GET TO SEE THE FINAL CLOSE UP. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR WAS CONTACTED AND REVEALED THE FOLLOWING DETAILS. THE NOSE GEAR COLLAPSE WAS A DIRECT RESULT OF THE FLEXIBLE HOSE INSTALLED IN THE L NOSE GEAR STEERING CYLINDER HYD CIRCUIT. THE FLEXIBLE HOSE PREVENTED THE NOSE GEAR DOWN AND LOCK LINKAGE FROM GOING OVER-CTR THUS PREVENTING A DOWN AND LOCKED CONDITION. THE RPTR BELIEVES THE FLEXIBLE HOSE INSTALLED AS AN INTERIM REPAIR FOR A LEAKING SOLID TUBE WAS TOO LONG AND COULD NOT BE CLAMPED ADEQUATELY. CALLBACK CONVERSATION WITH ACN 343596 RPTR REVEALED THE FOLLOWING: THE NOSE GEAR COLLAPSE WAS CAUSED BY THE FLEXIBLE NOSE STEERING LINE INTERFERING WITH THE DOWN LOCK MECHANISM. THIS FLEXIBLE HYD HOSE WAS INSTALLED AS AN INTERIM REPAIR FOR A LEAKING HARD LINE. THE RPTR STATES HE MADE THE FIRST INSTALLATION OF THE HOSE. ON THE OVERNIGHT LAYOVER THE LINE WAS REMOVED WITH THE HARD LINE TUBING FOR A BENCH CHK. THE LINE BENCH CHKED OK; BUT LEAKED AGAIN ON THE AIRPLANE AND THE INTERIM REPAIR FLEXIBLE HOSE WAS REINSTALLED.