Airworthiness Directives; Boeing Model 747 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires inspections to detect cracking of the front spar web of the wing, and corrective action if necessary. This amendment adds one airplane to the applicability, changes certain compliance times, adds certain new requirements, and provides an optional modification. This action is necessary to detect and correct fatigue cracking of the front spar web, which could result in fuel leaking onto an engine and a consequent fire. This action is intended to address the identified unsafe condition.