Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model DC-9-80 series airplanes and Model MD-88 airplanes. This proposal would require visual/dye penetrant and ultrasonic inspections to detect cracks in the vertical leg of the rear spar lower cap of the wings, and various follow-on actions. This proposal is prompted by reports that, due to improper torque tightening of the attach studs of the flap hinge fitting, fatigue cracks were found in the vertical leg of the rear spar lower cap of the wing. The actions specified by the proposed AD are intended to prevent such fatigue cracking, which, if not detected and corrected in a timely manner, could result in loss of the spar cap, and consequent damage to the spar cap web and adjacent wing skin structure; this condition could lead to reduced structural integrity of the wing.