Airworthiness Directives; MD Helicopters, Inc. Model MD900 Helicopters

This amendment supersedes an existing airworthiness directive (AD) for MD Helicopters, Inc. (MDHI) Model MD900 helicopters, that currently requires reducing the life limit of certain Notar fan system tension-torsion (TT) straps. That existing AD also requires, at a specified time interval, removing each affected TT strap from the helicopter, doing a visual and X-ray inspection, and replacing any unairworthy part before further flight. This amendment requires the same actions as the existing AD, but also requires revising the life limit on the component history card or equivalent record and doing repetitive visual and X-ray inspections, and removes reporting requirements. This amendment is prompted by two in-flight TT strap failures. The actions specified by this AD are intended to prevent failure of a TT strap, loss of directional control, and subsequent loss of control of the helicopter.