Airworthiness Directives; McDonnell Douglas Model DC-9-10, -20, -30, -40, and -50 Series Airplanes and C-9 (Military) Airplanes

摘要

This amendment supersedes an existing airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-9-10, -20, -30, -40, and -50 series airplanes, that currently requires repetitive radiographic and ultrasonic or eddy current inspections, and modification of the upper cap of the front spar of the left and right engine pylons, if necessary. This amendment requires new, improved x- ray and eddy current inspections to detect cracks of the upper cap of the front spar of the left and right engine pylons, and repetitive inspections or corrective actions, if necessary. This amendment also requires modification of the subject area, which constitutes terminating action for the repetitive inspection requirements. This amendment is prompted by additional reports of fatigue cracking in the subject area of these airplanes. The actions specified by this AD are intended to prevent failure of the upper cap of the front spar of the engine pylons due to fatigue cracking, and consequent reduced structural integrity of the airplane.