Airworthiness Directives; Empresa Brasileira de Aeronautica S.A. (EMBRAER) Model EMB-135 Airplanes and Model EMB-145, -145ER, -145MR, -145LR, -145XR, -145MP, and -145EP Airplanes

The FAA is superseding an existing airworthiness directive (AD), which applies to certain EMBRAER Model EMB-135 airplanes and Model EMB-145, -145ER, -145MR, -145LR, -145XR, -145MP, and -145EP airplanes. That AD currently requires revising the airplane flight manual (AFM) to prohibit in-flight auxiliary power unit (APU) starts, and installing a placard on or near the APU start/stop switch panel to provide such instructions to the flightcrew. This new AD adds an optional revision to the AFM that allows limited APU starts and adds a terminating action. This AD results from the airplane manufacturer developing modifications that revise or eliminate the need for restrictions to in-flight APU starts. We are issuing this AD to prevent flame backflow into the APU compartment through the eductor during in- flight APU starts, which could result in fire in the APU compartment.