The FAA has published a final rule for certain MD model helicopters. This amendment -- scheduled to become effective today -- adopts a new Airworthiness Directive for the specified model helicopters modified with a Helicopter Technology Company, LLC, Supplemental Type Certificate (STC) No. SR09172RC, SR09074RC, or SR09184RC. This action requires recording on the component history card or equivalent record the number of torque events (TEs) on each main rotor blade. When a blade accumulates 13,720 TEs and 750 hours time-in-service (TIS), the AD requires inspecting both surfaces of the blade for a crack at specified intervals. If a crack is found, the AD also requires replacing the blade with an airworthy blade. Also, the AD establishes life limits for certain part-numbered blades. This proposal is prompted by several reports, including a recent report dated July 24, 2003, of blade cracks due to a high number of TEs per hour. The FAA claims the actions specified in this AD are intended to prevent fatigue cracking of the blade, blade failure, and subsequent loss of control of the helicopter.