A B757-200 ON APCH WHEN FLAPS EXTENDED GOT LEADING EDGE SLAT WARNING. FOUND TORQUE TUBE AT #4 SLAT DISCONNECTED. LAST DOCUMENTED SLAT WORK ACCOMPLISHED IN EXCESS OF 30 DAYS.

Narrative

TORQUE TUBES WERE SEPARATED TO DO PYLON MODIFICATION. AFTER PYLON MODIFICATION WAS DONE; TORQUE TUBES WERE REATTACHED AND SAFETIED. PANELS WERE REMOVED FOR INSPECTION. PANELS THEN REINSTALLED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED 2 MAJOR PROJECTS WERE WORKING AT THE SAME TIME. PYLON STRUCTURAL MODIFICATION WHICH REQUIRED DISCONNECTING THE #4 LEADING EDGE SLAT TORQUE TUBE FOR PYLON ACCESS. THE OTHER JOB WAS LEADING EDGE SLAT ADJUSTMENT AND RIGGING. AFTER COMPLETION OF THE PYLON MODIFICATION THE TORQUE TUBE WAS CONNECTED AND 2 FASTENERS INSTALLED WITH SELF-LOCKING NUTS AND SAFETY WIRED. THE LEADING EDGE ACCESS PANELS WERE INSTALLED AND THE JOB CLOSED UP. THE PYLON MODIFICATION REQUIRED INSPECTION INCLUDING THE TORQUE TUBE CONNECTION AND THIS REQUIRED OPENING UP THE ACCESS PANELS AGAIN. INSPECTION WAS COMPLETED AND THE ACCESS PANELS WERE INSTALLED AND THE JOB CLOSED UP. AT COMPLETION OF THE SLAT ADJUSTMENT AND SLAT RIGGING THE JOB HAD TO BE INSPECTED AND THE ACCESS PANELS WERE OPENED INCLUDING #4 SLAT AND THE TORQUE TUBES AND COUPLINGS WERE AGAIN INSPECTED FOR A SECOND TIME. AN OP CHK OF THE LEADING EDGE SLATS WAS ACCOMPLISHED PRIOR TO RETURNING THE AIRPLANE TO SVC. THIS AIRPLANE FLEW FOR MORE THAN 30 DAYS WHEN ON LNDG WITH FLAPS EXTENDED THEY HAD A SLAT WARNING. THE TECHNICIAN WORKING THE RPT FOUND THE #4 TORQUE TUBE DISCONNECTED. FIRST RPT NO HARDWARE WAS FOUND BUT A SECOND CHK FOUND BOTH COUPLING BOLTS. AN INVESTIGATION BY THE COMPANY AND THE FAA WAS HELD AND ACFT DOCUMENTATION REVEALED NO WORK ACCOMPLISHED IN THE #4 SLAT AREA SINCE RELEASE. THE ONLY LOGICAL EXPLANATION COULD BE THE COUPLING BOLTS WERE INSTALLED AND MAYBE SELF LOCKING NUTS WERE ATTACHED FINGER TIGHT AND THE BOLTS HAD ENOUGH INTERFERENCE FIT TO REMAIN IN THE COUPLING HOLES. THIS JOB WAS INSPECTED TWICE! SUPPLEMENTAL INFO FROM ACN 710752: SLAT TORQUE TUBE WAS DISCONNECTED FOR PYLON MODIFICATION. TORQUE TUBE WAS RECONNECTED AFTER PYLON MODIFICATION WAS COMPLETED. LEADING EDGE PANEL WAS INSTALLED. HAD TO REMOVE PANEL FOR INSPECTION TO LOOK AT RECONNECTED TORQUE TUBE. INSPECTION GAVE OK TO CLOSE REINSTALLED PANEL. CALLBACK CONVERSATION WITH RPTR ACN 710752 REVEALED THE FOLLOWING INFO: THE RPTR STATED THE SLAT TORQUE TUBE WAS DISCONNECTED FOR THE PYLON MODIFICATION. AFTER THE PYLON MODIFICATION WAS COMPLETED THE TORQUE TUBE WAS CONNECTED WITH FASTENERS AND SAFETY WIRED. THE LEADING EDGE ACCESS PANEL WAS INSTALLED BUT HAD TO BE REMOVED FOR INSPECTION TO LOOK AT THE TORQUE TUBE CONNECTION. INSPECTION GAVE THE OK TO CLOSE UP THE ACCESS PANEL. AFTER THE CLOSE UP THE ACCESS PANEL IT HAD TO BE OPENED UP AGAIN DUE TO THE LEADING EDGE SLAT ADJUSTMENT AND RIGGING PROJECT COMPLETION. A SECOND INSPECTION WAS ACCOMPLISHED ON THE TORQUE COUPLINGS; FASTENERS AND SAFETY WIRING. A HEARING WAS HELD AFTER THE FINDING OF THE DISCONNECTED TORQUE TUBE AND WITH TWO INSPECTION SIGNOFFS AND ONE OP CHK OF THE SLATS IT'S HARD TO BELIEVE THIS SLIPPED THROUGH THE CRACKS. AFTER THE HEARING A MAINT MGR WENT TO A B757 IN THE DOCK AND HAD MAINT REMOVE #4 SLAT TORQUE TUBE COUPLING FASTENERS AND THE SLATS OPERATED. WITHIN 30 MINS OF OP THE TORQUE TUBE DISCONNECTED.