Summary
We propose to adopt a new airworthiness directive (AD) for certain Lockheed Martin Corporation/Lockheed Martin Aeronautics Company Model L-1011 series airplanes. This proposed AD was prompted by reports of cracked rib cap castellations. This proposed AD would require repetitive inspections for castellation and skin clips cracked or damaged between stringers and cracked stringer clips of the wing box pylon back-up structure, and front spar to rear spar, repetitive inspections for cracking, damage, or failure of the pylon back-up torque box structure; repetitive inspections for cracking or damage of the wing box external areas at the drag brace aft wing fitting; and repetitive inspections of the outer surface of the wing upper and lower skins for cracks or damage along the rib attachment at the fastener holes and between the two rows of attachment; and corrective actions if necessary. We are proposing this AD to detect and correct cracked or damaged rib cap castellations, whichcould degrade the structural capabilities of the airplane.