Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 767-200, -300, -300F, and -400ER series airplanes. This proposed AD was prompted by reports of cracked and corroded nuts on an outboard flap support rib. This proposed AD would require, for certain airplanes, repetitive inspections of the cap seal for damaged sealant on nuts common to certain outboard flap support ribs, related investigative and corrective actions if necessary, and replacement of all fasteners in the support ribs, which terminates the repetitive inspections. For certain other airplanes, this proposed AD would require repetitive inspections of the cap seal for damaged sealant on nuts common to certain outboard flap support ribs, related investigative and corrective actions if necessary, and if necessary, a detailed inspection to determine the nut type installed in the outboard flap support rib and corrective actions; for these airplanes, this proposed AD provides optional replacement of all fasteners in the support ribs, which would terminate the repetitive inspections. We are proposing this AD to detect and correct cracked and corroded nuts and bolts and the installation of incorrect nuts on certain outboard flap support ribs, which could lead to additional nut and bolt damage in the joint, and result in loss of an outboard flap, and adversely affect continued safe flight and landing of the airplane.