Airworthiness Directives; Boeing Model 747 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that requires repetitive high frequency eddy current inspections to find cracking of the bulkhead frame support at body station 2598 under the hinge support fittings of the horizontal stabilizer, and repair if cracking is found. These actions are necessary to find and fix fatigue cracking in the frame support, which could result in inability of the structure to carry horizontal stabilizer flight loads and reduced controllability of the horizontal stabilizer. This action is intended to address the identified unsafe condition.