The FAA has published an amendment to an existing airworthiness directive for Bell Helicopter models 204B, 205A, 205A-1, 205B, 210, 212, 412, 412CF and 412EP. The action was prompted by three reports of blade tip weights being slung from the blades during flights causing significant vibration. The superseded AD requires replacing specified blades before further flight. This AD retains that requirement but adds additional blade part numbers and serial numbers.