Summary
This document proposes to supersede priority letter airworthiness directive (AD) 90-02-23 by adopting a new AD applicable to Hartzell Propeller Inc. ( )HC-( )2Y( )-( ) propellers. Priority letter AD 90-02-23 currently requires repetitive visual inspections of propeller hubs for cracks using a 10X glass, and, if necessary, removal and replacement of cracked hubs with serviceable parts. This proposal would change the frequency and method of inspection by requiring initial and repetitive eddy current inspections (ECI) of the propeller hub fillet radius for cracks. In addition, this proposed AD would allow installation of an improved design propeller hub as terminating action to the repetitive ECI. This proposal is prompted by reports of cracked propeller hubs found in service after they had been inspected in accordance with the visual inspections required by the priority letter AD. The actions specified by the proposed AD are intended to improve the method for detecting propeller hub cracks, which can result in an inflight separation of propeller blades and damage to the aircraft.