An accident caused by the loss of a tail-rotor blade prompted the FAA to issue an emergency airworthiness directive (AD) for the MD 369 series. The agency said it reviewed MD Helicopter service bulletins affecting tail rotor blades in operation with a machining defect, and the AD is requiring inspections before further flight. Bores of the tail-rotor blade root fittings should be checked. Operators should replace each blade assembly that does not have a smooth radius.