Airworthiness Directives; MT-Propeller Entwicklung GMBH Models MTV-9-B-C and MTV-3-B-C Propellers

This amendment supersedes an existing airworthiness directive (AD), that is applicable to MT-Propeller Entwicklung GMBH Models MTV-9- B-C and MTV-3-B-C propellers. That AD currently requires initial and repetitive inspections of Torx head blade root lag screws that are used on certain serial number (SN) propellers and replacement of all lag screws on the propeller if any screws are found broken or with insufficient torque. In addition, that AD currently requires the replacement of certain part number (P/N) Torx head blade root lag screws with improved, hexagonal head blade root lag screws. This amendment requires the expansion of the applicability from certain SN propellers to all propellers with certain SN blades that may contain the suspect Torx head blade root lag screws. This amendment is prompted by FAA awareness that a propeller hub of an affected propeller could be changed, thereby changing the propeller serial number, creating a propeller that is not listed in the AD and that has affected blades and lag screws. The actions specified by this AD are intended to prevent failure of the blade root lag screw, which could result in propeller blade separation and loss of control of the airplane.