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 repetitive inspections to detect discrepancies of the diagonal brace lugs of the engine strut, and rework of the diagonal brace lugs, if necessary. That AD also provides an option to defer the rework for certain cases by accomplishing repetitive inspections and resealing the bushing. That AD also provides for an optional terminating modification for the repetitive inspections. This amendment adds a requirement to repetitively inspect a new area of the diagonal brace of the engine strut. For certain airplanes, this amendment also adds new repetitive inspections of the subject area and requires that certain previously required repetitive inspections be accomplished at reduced intervals. This amendment is prompted by reports of fatigue or stress corrosion cracking in new areas of the diagonal brace. The actions specified in this AD are intended to prevent such fatigue or stress corrosion cracking, which could result in failure of the strut and consequent separation of the engine from the airplane.