Airworthiness Directives; Bombardier Model DHC-8-102, -103, -106, -201, -202, -301, -311, and -315 Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Bombardier DHC-8-102, -103, -106, -201, - 202, -301, -311, and -315 airplanes, that currently requires inspections to detect breakage in the struts of the rear mount strut assemblies on the left and right engine nacelles, and replacement of any broken struts. The existing AD also requires eventual replacement of all currently installed struts with new and/or reworked struts, as terminating action for the inspections. The amendment requires new repetitive inspections of the strut assemblies for cracking of struts replaced per the existing AD, and replacement of any cracked strut with a new, machined strut. The amendment also changes the applicability of the existing AD by adding certain airplanes and removing certain other airplanes, and includes an optional terminating action for the repetitive inspections. The actions specified by this AD are intended to prevent failure of the engine rear mount struts, which could result in reduced structural integrity of the nacelle and engine support structure. This action is intended to address the identified unsafe conditions.