Airworthiness Directives; Boeing Model 747 Series Airplanes

This amendment adopts a new airworthiness directive (AD) that is applicable to all Boeing Model 747 series airplanes. This action requires repetitive inspections for cracking of the upper skin of the horizontal stabilizer center section and the rear spar upper chord, and repair, if necessary. This action is necessary to find and fix such cracking, which could lead to reduced structural capability of the horizontal stabilizer center section, and result in loss of controllability of the airplane. This action is intended to address the identified unsafe condition.