S - CENTER WING BOX- FRONT SPAR SHEAR FITTING - INSPECTION. REPAIR AND PREVENTIVE MODIFICATION. SERVICE BULLETIN MOS RECOMMENDED SB 737-57-1310 WINGS - CENTER WING - WING SPARS- FORWARD TRUNNION SUPPORT FITTING- FUSE PIN BORES - INSPECTION SUPERSEDED FOR CORROSION (SUPERSEDED BY SB 737-57-1310 RN. SERVICE BULLETIN MOS - I