What was found
WHILE CLEANING GREASE ON LT WING, A SUSPECTED CRACK WAS FOUND AT WS #226, EXTENDING FROM THE AFT EDGE 4 INCHES FORWARD ON BOTTOM SKIN. C/W W/O 287639. STOP DRILLED CRACK AT WS #226 AND APPLIED TAPE. PERFORMED HFEC INSP TO BONDED STIFFENER STRAP AT LT WING O.B FLAP LOWER SHROUD BETWEEN YW-209.019+YW-277.019 IAW NDT MAN, PART 6, 51-00-01-250-801. FOUND THE BONDED STIFFENER CRACKED. PERFORMED UT DISBOND CHECK IAW Q400 NDT PART 1, 51-00-04. NO DISBOND NOTED BETWEEN BONDED STRAP AND SHROUD SKIN. FABRICATED DOUBLER, REF Q400 REPAIR DRAWING 8/4-57-4888. INSTALLED ALL REPAIR PARTS AND SEALED AND PAINTED REPAIR PER T/C RD8/4-57-4888/1. RETURNED TO SERVICE.