Airworthiness Directives; Boeing Model 747-100 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747-100 series airplanes, that currently requires repetitive inspections to detect cracking of the wing front spar web above engine numbers 2 and 3, and to detect cracked or broken fasteners in the web; and repair, if necessary. That AD also provides an optional terminating action for the repetitive inspections. This amendment requires various improved inspections. This amendment is prompted by a report indicating that the existing inspections do not adequately detect vertical cracks. The actions specified by this AD are intended to prevent fuel leakage onto an engine and a resultant fire due to cracked or broken fasteners in the wing front spar.