A B727-200 ON APCH AT 4000 FT REQUIRED EXCESSIVE TRIM TO MAINTAIN WINGS LEVEL CAUSED BY A DELAMINATED LEADING EDGE SURFACE.

Narrative

THE INCIDENT INVOLVED PARTIAL DELAMINATION OF THE LEADING EDGE FLAPS ON A B727-200 SERIES ACFT. THE FIRST INDICATION OF A PROB WAS ON FINAL APCH WHEN THE AUTOPLT BEGAN S-TURNING BACK AND FORTH ACROSS THE LOC. WHEN THE AUTOPLT WAS DISCONNECTED; I ENCOUNTERED UNUSUAL CTL FORCES THAT REQUIRED ABOUT 2 UNITS OF R RUDDER TRIM PLUS 20 DEGS R AILERON TO STAY WINGS LEVEL AND ON COURSE. ENGINES AND ALL FLT CTL POS INDICATIONS WERE READING NORMALLY. THE ACFT WAS NOT DIFFICULT TO CTL AND I MAINTAINED A STABLE FINAL. DUE TO LIGHT WINDS; A RELATIVELY HIGH (THOUGH IFR) CEILING; AND A CONCERN THAT CHANGING CONFIGN MIGHT CAUSE MORE PROBS; AND BECAUSE WE WERE ALREADY SET FOR FINAL APCH; I ELECTED TO CONTINUE TO LNDG. LNDG WAS SMOOTH; AND WE WROTE UP THE PROB. MAINT PERSONNEL MET US AT THE ARPT AND INDICATED NOTHING SEEMED IMMEDIATELY APPARENT. THEY HAD BEGUN FLT CTL CHKOUTS WHEN I LEFT THE ACFT; AFTER BRIEFING THE ONCOMING CREW. AFTER CREW REST; I HAD A CHANCE TO CALL MAINT BEFORE CONTINUING MY ROTATION. I WAS INFORMED THE PLANE WAS IN THE HANGAR WITH ABOUT 3/4 OF THE SURFACE OF A LEADING EDGE FLAP DELAMINATED AND SEPARATED FROM THE SUPPORTING STRUCTURE.