Airworthiness Directives; Jetstream Model ATP Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to all British Aerospace Model ATP series airplanes, that currently requires inspections to detect cracking of the aft end of the wing rib boom angles on the left and right engine, and repair or replacement of the wing rib boom angle assemblies, if necessary. That AD was prompted by the detection of cracks in the engine outboard rib boom angles at the main landing gear (MLG) actuator attachment point. The actions specified by that AD are intended to prevent structural failure of the actuator attachment point, which could lead to collapse of the MLG. This amendment limits the applicability of the rule to only a certain number of airplanes; revises the initial inspection threshold, depending on whether or not certain modifications have been accomplished on the boom angles; and requires that modified boom angles be installed whenever replacement is necessary.