Summary
This document proposes to supersede Airworthiness Directive (AD) 97-22-16, which applies to certain Raytheon Model 1900, 1900C, and 1900D airplanes. AD 97-22-16 currently requires you to replace the bearings on the vent blower assemblies with improved design bearings and install a thermal protection device for the vent blowers. That AD resulted from reports of vent blower assembly bearings seizing and locking the blower motor on several of the affected airplanes. This proposed AD is the result of reports that vent blower assemblies modified in accordance with AD 97-22-16 are still malfunctioning. This proposed AD would retain the actions required in AD 97-22-16 for certain vent blower assemblies and require you to incorporate further product improvement modifications on all affected vent blower assemblies. The actions specified by this proposed AD are intended to prevent smoke from entering the cockpit and cabin due to the current configuration of vent blower assemblies, whichcould result in the pilot becoming incapacitated or impairing her/his judgment. Such a condition could lead to the pilot not being able to make critical flight safety decisions and result in loss of control of the airplane.