Airworthiness Directives; Eurocopter Deutschland GMBH Model MBB- BK 117 Helicopters

This amendment supersedes an existing emergency priority letter airworthiness directive (AD), applicable to Eurocopter Deutschland GMBH (ECD) Model MBB-BK 117 helicopters, that currently requires, before further flight, creating a component log card or equivalent record and determining the age and number of flights on the tension-torsion (TT) strap. The AD also requires inspecting and removing, as necessary, certain unairworthy TT straps. This amendment requires the same actions as the emergency priority letter AD but clarifies the compliance requirements specified in the emergency priority letter AD. This amendment is prompted by an accident in which a main rotor blade (blade) separated from a helicopter due to fatigue failure of a TT strap. The actions specified by this AD are intended to prevent failure of a TT strap, loss of a blade, and subsequent loss of control of the helicopter.