What was found
(CAN) DURING ANNUAL INSPECTION THE HORIZONTAL STAB FAIRING SCREW HOLES FOUND TO BE DRILLED THROUGH THE RIVETS ATTCHING THE SKIN TO THE CLOSING RIBS OF BOTH HORIZONTALSTABS. HOLES WERE LOCATED ON THE LOWER SURFACES ONLY. 7 OF 19 RIVETS WERE DRILL ED ON THE PORT STAB AND 5 OF 19 RIVETS WERE DRILLED ON THE STBD STAB. THE HOLES WERE DRILLED AT TIME OF AIRCRAFT MANUFACTURE. AIR TRACTOR HAS BEEN NOTIIFIED BY MAINTENANCE PLANNING.