Airworthiness Directives; Boeing Model 747 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to all Boeing Model 747 series airplanes, that currently requires periodic inspections and cleaning of the drainage system cavity of the canted pressure deck, aft of the wing center section. This amendment adds new repetitive tests and inspections for discrepancies of the drainage system of the canted pressure deck; and corrective actions, if necessary. This amendment also terminates the requirements of the existing AD. The actions specified by this AD are intended to prevent ice accumulation on the lateral flight control cables and/or components due to water entering the wheel well of the landing gear and freezing, which could restrict or jam control cable movement, resulting in loss of controllability of the airplane. This action is intended to address the identified unsafe condition.