UPPER AND LOWER FLANGES WEAR COMMON TO ROLLER CONTACT SURFACES. RECOMMENDED 06-SEP-2011 SERVICE LETTER MOS 51 737-SL-57-099 WING LEADING EDGE? SLAT DETENT ARM AND ROLLER ALIGNMENT (SUPERSEDED BY 51 737-SL-57-099 REV. A), RECOMMENDED 28-FEB-2012 SERVICE LETTER MOS 51 737-SL-57-099 REV. A WING LEAD