Summary
We propose to adopt a new airworthiness directive (AD) for all The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD- 83), and DC-9-87 (MD-87) airplanes; and Model MD-88 airplanes. This proposed AD was prompted by a report of fatigue cracking in a rear spar lower cap of the horizontal stabilizer. This proposed AD would require repetitive inspections for cracking of the rear spar lower caps of the horizontal stabilizer, post-modification and post-repair inspections, and corrective actions if necessary. This proposed AD also provides an optional terminating fatigue life enhancement modification. We are proposing this AD to detect and correct fatigue cracking in the rear spar lower caps of the horizontal stabilizer, which, paired with cracking in adjacent areas, could adversely affect the structural integrity of the airplane.