2019-SW-042-AD; Bell Helicopter Textron Canada Limited Model 429 helicopters, to Require Inspecting a Certain Part-Numbered Curvic Coupling for Proper Engagement and Depending on the Inspection Results, Inspecting for Play, Inspecting the Curvic Coupling Teeth, Inspecting the Flapping Bearing Teeth, Replacing Parts, Performing a Rigging Check, and Reporting Information. 2019-SW-042-AD