Airworthiness Directives; Airbus Industrie Model A300, A300-600, and A310 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Airbus Model A300, A300-600, and A310 series airplanes, that currently requires inspections to detect cracks in the lower spar axis of the nacelle pylon between ribs 9 and 10, and repair, if necessary. The existing AD also provides for optional modification of the pylon, which terminates the inspections for Model A300 and A310 series airplanes and increases the threshold and repetitive interval of the inspections for Model A300-600 series airplanes. This amendment reduces the inspection threshold and requires repetitive inspections following accomplishment of the optional modification for Model A310 series airplanes. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent fatigue cracking, which could result in reduced structural integrity of the lower spar of the pylon.