Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to supersede Airworthiness Directives (ADs) 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 currently require revising the Airworthiness Limitations Section (ALS) of the Instructions for Continued Airworthiness to incorporate certain compliance times for principal structural elements (PSE) inspections and replacement times for safe-life limited parts. Since we issued AD 97-11-07 and AD 99-18- 23, an analysis of data identified a need to introduce a new PSE requirement for the rear spar caps of the horizontal stabilizer. This proposed AD would require revising the maintenance or inspection program to incorporate the new PSE requirement and its associated inspections. We are proposing 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.