Airworthiness Directives; Empresa Brasileira de Aeronautica S.A. (EMBRAER) Model EMB-135 and -145 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain EMBRAER Model EMB-135 and -145 series airplanes, that currently requires determining whether a defective auxiliary power unit (APU) exhaust silencer is installed on the airplane; and corrective actions if necessary. For certain airplanes, this amendment requires modification of the APU exhaust silencer, and reidentification of the part number for the APU exhaust silencer once the modification is accomplished. For certain other airplanes, this amendment requires repetitive inspections to determine the structural integrity of the APU exhaust silencer; corrective actions, if necessary; eventual modification of the APU exhaust silencer, which terminates the repetitive inspections; and reidentification of the part number for the APU exhaust silencer once the modification is accomplished. This amendment also adds airplanes to the applicability of the existing AD. The actions specified by this AD are intended to prevent separation of the aft baffle assembly from the APU exhaust silencer and consequent separation of the assembly from the airplane, which could cause damage to other airplanes during takeoff and landing operations, or injury to people on the ground. This action is intended to address the identified unsafe condition.