Airworthiness Directives; Empresa Brasileira de Aeronautica, S.A. (EMBRAER) Model EMB-120 Series Airplanes

Resumo

This amendment adopts a new airworthiness directive (AD) that is applicable to all EMBRAER Model EMB-120 series airplanes. This action requires revising the FAA-approved Airplane Flight Manual (AFM) to limit the revolutions per minute (RPM) of the propeller during ground operation, and removing and installing a new placard. This AD also requires revising the FAA-approved maintenance program to limit the maximum RPM of the propeller during ground operations. This amendment is prompted by reports of failures of in-service propellers and subsequent testing, which revealed that operating the propeller at or near certain nominal propeller RPM produces high vibration stress. The actions specified in this AD are intended to limit exposure to high vibration stresses during ground operations under certain weather conditions; this situation could accelerate fatigue cracking if corrosion is present in the propeller, which could lead to the failure of the propeller and subsequent reduced controllability of the airplane.