Summary
This document revises an earlier proposed airworthiness directive (AD) that is applicable to all Aerospatiale Model ATR-42 and ATR-72 series airplanes. That proposal would have superseded an existing AD to prohibit operation of the airplane in certain icing conditions unless modifications are accomplished or alternative procedures and training are adopted, and to require restrictions on the use of the autopilot in certain conditions. That proposal also would have added requirements for modification of the deicing boots on the leading edge of the wing and various follow-on actions. That proposal was prompted by an FAA determination that, during flight in certain icing conditions, and with the airplane in a specific flight configuration, a ridge of ice can form on the wing and cause an interruption in the airflow over the ailerons, aileron deflection, and resultant lateral control forces. This action revises the originally proposed rule by removing certain limitations and procedures. The actions specified by this proposed AD are intended to prevent a roll upset from which the flight crew may be unable to recover.