Airworthiness Directives; Raytheon Aircraft Company Models 1900, 1900C, and 1900D Airplanes

This amendment adopts a new airworthiness directive (AD) that applies to certain Raytheon Aircraft Company (Raytheon) Models 1900, 1900C, and 1900D airplanes (formerly referred to as Beech Models 1900, 1900C, and 1900D airplanes). This AD requires fabricating and installing a placard that restricts the use of the forward and aft vent blower assemblies to only the ``OFF'' or ``HIGH'' position. This AD also requires incorporating a modification that would replace the bearings on the vent blower assemblies with improved design bearings, and provide thermal protection for the vent blowers, as applicable. Incorporating the modification will eliminate the need for the placard. The AD results from reports of vent blower assembly bearings seizing and locking the blower motor on several of the affected airplanes. The actions specified by this AD are intended to prevent the vent blower assembly bearings from seizing, which could result in smoke emanating from the insulating material covering the electrical wiring and entering the airplane cabin.