AD FAA-2013-0981

We are superseding Airworthiness Directive (AD) 97-11-07 and AD 99-18-23, which apply to all The Boeing Company Model MD-90-30 airplanes. AD 97-11-07 and AD 99-18-23 required revising the Airworthiness Limitations Section (ALS) of the Instructions for Continued Airworthiness to incorporate certain compliance times for principal structural element (PSE) inspections and replacement times for safe-life limited parts. This new AD also requires revising the maintenance or inspection program to incorporate a new PSE requirement for the rear spar caps of the horizontal stabilizer and its associated inspections, which would terminate certain inspections of the horizontal stabilizer rear spar. This AD was prompted by an analysis of data that identified a need to introduce a new PSE requirement for the rear spar caps of the horizontal stabilizer. We are issuing this AD to detect and correct fatigue cracking of PSEs and certain safe-life limited parts, which could adversely affect the structural integrity of the airplane.