Summary
This document proposes the supersedure of 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 action would require 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 action also would require modification of the subject area, which would constitute terminating action for the repetitive inspection requirements. This proposal is prompted by additional reports of fatigue cracking in the subject area of these airplanes. The actions specified by the proposed 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.