What was found
MCN - MAJOR REPAIR - DURING C-17 CHECK A .25 INCH CRACK WAS FOUND ON SKIN AT LOWER ROW OF FASTENER HOLES STR 4 LT BS 387. MAINTENANCE CUTOUT CRACKED SKIN AT STR 4 LT, BS 387; PERFORMED A HFEC INSPECTION OF CUTOUT TO VERIFY NO CRACKS EXIST; FABRICATED A DOUBLER, A FILLER, 2 EACH INTERNAL DOUBLERS, AND A TAPERED FILLER; INSTALLED REPAIR PARTS IAW B737-300 SRM 53-00-01 PG 355 FIG 228.