Airworthiness Directives; Hartzell Propeller Inc. HC-A3V, HC-B3M, HC-B3T, HC-B4M, HC-B4T, and HC-B5M Series Propellers

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This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Hartzell Propeller Inc. (Hartzell) HC-A3V, HC-B3M, HC-B3T, HC-B4M, HC- B4T, and HC-B5M series propellers. This proposal would require hub replacement over a 10-year time period with a concurrent blade and blade clamp inspection. This proposal is prompted by reports of two propeller hub failures and one crack indication that occurred on Mitsubishi MU-2B-60 aircraft, the similarity of construction and load transfer paths between the Hartzell propeller models installed on the Mitsubishi MU-2 aircraft and Hartzell's 3-, 4-, and 5-bladed steel hub propeller models, several blade shank failures, and reports of cracks in blade clamps. The actions specified by the proposed AD are intended to prevent propeller hub, blade, or blade clamp failure, which can result in loss of aircraft control.