Airworthiness Directives; Saab Model SAAB SF340A and SAAB 340B Series Airplanes

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Saab Model SAAB SF340A and SAAB 340B series airplanes. This action requires revising the Airplane Flight Manual (AFM) to require verification that the auto-ignition system is operational; to define icing conditions at higher ambient temperatures; and to provide the flight crew with limitations and procedures to aid in the avoidance of engine power interruptions. This amendment is prompted by a report of complete power loss of the left engine and power fluctuations on the right engine as a result of build up of ice and/or slush in the engine inlet and subsequent ingestion into the engines; the auto-ignition system of the left engine had failed, which prevented automatic restart of the engine following power interruption. The actions specified in this AD are intended to prevent failure of the auto-ignition system to re-light the engine in the event of power interruptions due to the ingestion of ice and/or slush into the engine, which could result in engine flameout and subsequent shutdown, and to provide the flight crew with guidance to aid in avoidance of such occurrences.