Airworthiness Directives; Bell Helicopter Textron Canada Helicopters

We are adopting an airworthiness directive (AD) superseding an existing airworthiness directive for Bell Helicopter Textron Canada (Bell) Model 407 and 427 helicopters. The existing AD requires inspecting certain hydraulic servo actuators (servo) to determine whether the shaft turns independently of the nut or the clevis assembly, and additional actions based upon the inspection's outcome. The AD also requires reidentifying the servo. Since we issued that AD, Bell has learned that additional servos may need repair or removal. This AD expands the scope of the current AD to include inspections for all servos, and requires that servos meeting inspection requirements be marked with the letter "V" after the part number on the data plate. The actions are intended to detect any loose or misaligned parts in the servo that could lead to failure of the servo and subsequent loss of helicopter control.