Airworthiness Directives; MD Helicopters, Inc. Model 369D, 369E, 369F, 369FF, 500N, and 600N Helicopters

This amendment supersedes an existing airworthiness directive (AD) for the MD Helicopters, Inc. (MDHI) Model 369A, H, HE, HM, HS, D, and E helicopters with a certain part-numbered main rotor blade (blade) and modified with a Helicopter Technology Company, LLC (HTC), Supplemental Type Certificate (STC) No. SR09172RC, SR09074RC, or SR09184RC. That AD currently requires recording on the component history card or equivalent record (record) each torque event (TE) on each blade, inspecting both surfaces of the blade, and replacing any cracked blade with an airworthy blade. Also, that AD establishes life limits for certain part-numbered blades. This amendment revises the model applicability, adds MDHI part-numbered blades, removes any reference to the life limits of the blades, changes the requirements for inspecting the blades, and revises the STC applicability. This amendment also provides that compliance with portions of certain documents constitutes alternative methods of compliance with portions of this AD, contains editorial changes for clarification, and makes some corrections. This amendment is prompted by additional reports of cracked blades and by the comments received in response to AD 2003-24- 01. The actions specified in this AD are intended to detect fatigue cracking of the blade to prevent blade failure and subsequent loss of control of the helicopter.