Tail-rotor cracking has prompted the FAA to issue an Airworthiness Directive for Bell helicopters. The AD affects approximately 400 Bells, including the 204B, 205A, 205A-1, 205B, 210, 212, 412, 412CF and 412EP. More than 380 of these machines are listed on the U.S. registry. The AD prescribes shortened inspection and maintenance intervals for the tail rotors on these helicopters.