Summary
This document proposes to revise an existing airworthiness directive (AD), applicable to Sensenich Propeller Manufacturing Company Inc. Models M76EMM, M7EMMS, 76EM8, and 76EM8S() metal propellers, that currently restricts operators from continuously operating the propeller at engine speeds from 2,150 to 2,350 revolutions per minute (RPM). This action would remove propellers installed on certain additional Textron Lycoming O-360 series reciprocating engines with solid crankshafts from this requirement, and update the referenced Sensenich Propeller Company Inc. service bulletin to the latest revision. Reworking of all affected propeller models remains a requirement of the proposed AD, regardless of engine installation. This proposal is prompted by inquiries concerning tachometer red arc restrictions on certain Textron Lycoming O-360 series reciprocating engines with solid crankshafts. The actions specified by the proposed AD are intended to prevent propeller blade tip fatigue failure, which can result in loss of control of the aircraft.