Summary
This document proposes to adopt a new airworthiness directive (AD) that would apply to certain Raytheon Aircraft Company (Raytheon) Models 1900, 1900C, and 1900D airplanes (formerly referred to as Beech Models 1900, 1900C, and 1900D airplanes). The proposed AD would require fabricating and installing a placard that restricts the use of the forward and aft vent blower assemblies to only the ``OFF'' or ``HIGH'' position. The proposed AD would also require 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 proposed modification would eliminate the need for the placard. The proposed AD is the result of vent blower assembly bearings seizing and locking the blower motor on several of the affected airplanes. The actions specified by the proposed 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.