Summary
We propose to adopt a new airworthiness directive (AD) for all Model MD-90-30 airplanes. This proposed AD would require repetitive high frequency eddy current inspections for cracking on the hinge bearing lugs of the left and right sides of the center section ribs of the horizontal stabilizer, and related investigative and corrective actions if necessary. This proposed AD results from reports of cracks found on either the left or right (or in one case, both) sides of the center section ribs of the horizontal stabilizer. We are proposing this AD to detect and correct cracking in the hinge bearing lugs of the center section of the left and right ribs, which could result in failure of the hinge bearing lugs and consequent inability of the horizontal stabilizer to sustain the required loads.