THE PILOT WAS LANDING ON RUNWAY 4R, WHEN ACCORDING TO THE PILOT, HE WAS ESTABLISHED ON THE GLIDE SLOPE WHEN HE FELT A VIBRATION. HE REPORTED THAT THE FLYING CHARACTERISTICS DEGRADED AND HE MADE THE NECESSARY CORRECTION SUCCESSFULLY. THERE WERE NO INDICATIONS IN THE COCKPIT OF ANY FAILURE. THE AIRPLANE TOUCHED DOWN 2 MINUTES LATER AND TAXIED TO THE GATE WITHOUT ANY FURTHER INCIDENCE. INSPECTION OF THE AIRPLANE REVEALED SEPARATION OF THE NO. 2 FLAP VANE FROM THE RIGHT WING. FURTHER TESTING BY THE NTSB LAB REVEALED THE SEPARATION OCCURRED DUE TO STRESS CORROSION AND FATIGUE CRACKING THAT INITIATED AT THE LUG BORE.