AD 2008-16-16 Amendment 39-15634

We are adopting a new airworthiness directive (AD) for BHTC Model 230 helicopters. This AD results from mandatory continuing airworthiness information (MCAI) issued by the aviation authority of Canada which indicates that the existing rigging procedures for the tail rotor pitch change mechanism have to be changed due to the possibility of parts interference. The cumulative effect of individual part tolerances resulting in the total assemblage of those parts being out of tolerance could result in the tail rotor yoke striking another part other than the flapping stop (parts interference) as cited in the MCAI. Also, the misalignment of the tail rotor counterweight bellcrank may result in higher tail rotor pedal forces and a higher pilot workload after failure of the No. 1 hydraulic system. Both parts interference and the misaligned counterweight bellcrank create an unsafe condition. This AD requires actions that are intended to address these unsafe conditions.