Airworthiness Directives; Jetstream Model ATP Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to all Jetstream Model ATP airplanes, that currently requires revising the Airplane Flight Manual (AFM) to prohibit flight in freezing precipitation conditions. This amendment adds a requirement to install modifications of the engine air intake system. This amendment is prompted by the development of modifications of the engine air intake system intended to permit operation of these airplanes in freezing precipitation conditions. The actions specified by this AD are intended to prevent engine power rollback in flight during freezing precipitation conditions.