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

This amendment adopts a new airworthiness directive (AD) that is applicable to certain EMBRAER Model EMB-145 series airplanes. This action requires repetitive visual inspections to detect cracks in the firewall of the auxiliary power unit (APU), and repair, if necessary. This AD also requires installation of a visco-elastic damper blanket on the firewall, which constitutes terminating action for the repetitive inspection requirements. This amendment is prompted by reports indicating that cracks were found in the firewall of the APU due to vibration of the firewall. The actions specified in this AD are intended to prevent such cracking, which could result in reduced structural integrity of the fuselage and empennage in the event that a fire penetrates through the firewall of the APU.