What was found
DURING HEAVY CHECK, SOME RIVETS ATTACHING TO LOWER FRAME THROUGH THE EXTERNAL SKIN, NEAR NAC WL 94, HAVE POOR PITCH & EDGE DISTANCE. THERE IS A CRACK IN THE LOWER FRAME IN THIS AREA STARTING FROM A FASTENER HOLE GOING TO THE EDGE OF THE FRAME. MAINTENANCE REPAIR PER EO NR S54020 AND SAAB STATEMENT 72SDS1756 REV A DATED 9/13/99.