What was found
DURING ROUTINE INSP, FOUND PART CRACKED. CHECKED (2) OTHER AC THAT HAPPENED TO BE IN SHOP, FOUND (1) OF THEM TO HAVE A SIMILAR CRACK. THIS SECTION OF BULKHEAD IS ATTACH STRUCTURE FOR LWR ATTACH ANGLE FOR IB FLAP DRIVE BELLCRANK. IT IS CURIOUS THAT THE FACTORY INSTALLED SOME EXTRA REINFORCEMENT STRUCTURE (A BRACKET) IN THIS POSITION IN LT WING. THERE ARE EVEN SOME "PILOT DRILL" (PD) HOLES DRILLED AT FACTORY IN RIB AND HEAVY ATTACH ANGLE ON THE AFFECTED RT SIDE. IT WOULD APPEAR THAT BOTH LT AND RT BELLCRANKS WOULD EXPERIENCE SAME FORE-AFT FORCES BY AIR LOADS ON FLAPS. SO WHY REINFORCE ONLY ONE SIDE? IT IS POSSIBLE THAT FACTORY ASSY LINE NEGLECTED TO INSTALL AN INTENDED SIMILAR REINFORCEMENT ON THE RT SIDE? (K)