Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Bell Helicopter Textron, Inc. Model 205A, 205A-1, 205B, 212, and 412 series helicopters. This proposal would require removal and replacement of a certain design main transmission lower planetary spider (spider) and would establish a 2,500 hours' time-in-service retirement life for the spider. This proposal is prompted by five failures of the spider that occurred during the manufacturer's fatigue tests. The actions specified by the proposed AD are intended to prevent fatigue failure of the spider, failure of the main transmission, and subsequent loss of control of the helicopter.