Airworthiness Directives; McDonnell Douglas DC-9-10, -20, -30, -40, and -50 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain McDonnell Douglas DC-9-10, -20, -30, -40, and -50 series airplanes, that currently requires a one-time visual inspection to determine the modification status of the corners of the forward lower cargo doorjamb; low-frequency eddy current or X-ray inspections to detect cracks of the fuselage skin and doubler at all corners of the forward lower cargo doorjamb; various follow-on repetitive inspections; and modification, if necessary. This amendment retains those requirements but requires certain high-frequency, rather than low-frequency, eddy current inspections for certain conditions. The actions specified by this AD are intended to detect and correct cracking, which could result in rapid decompression of the fuselage and consequent reduced structural integrity of the airplane. This action is intended to address the identified unsafe condition.