Summary
This document proposes superseding four existing airworthiness directives (ADs) for the specified Bell model helicopters. Two of the existing ADs require an initial and repetitive inspection of certain part-numbered main rotor yokes installed on Bell Model 204B, 205A-1, and 212 helicopters. Two other existing ADs also establish a retirement life of 3,600 hours time-in-service (TIS) for certain part-numbered main rotor yokes installed on the Bell Model 204, 205 series, and 212 series helicopters. Those ADs were prompted by reports of cracks in the main rotor yoke (yoke). This action would retain the requirements of the existing ADs and would apply these inspections and retirement lives to additional part-numbered yokes. This action would also increase the inspection frequency for certain yokes installed on a Bell Model 205B or 212 helicopter and would require replacing any unairworthy yoke. This proposal is prompted by the need to expand the applicability to include yokes produced under a Parts Manufacturing Approval (PMA) whose design approval was based on identicality with the affected Bell yoke parts and a recent discovery of a cracked yoke. The actions specified by the proposed AD are intended to prevent cracking of a yoke, failure of the yoke, and subsequent loss of control of the helicopter.