Summary
This document revises an earlier proposed airworthiness directive (AD) for Bell Helicopter Textron, A Division of Textron Canada (Bell), Model 407 helicopters, that would have required preflight checking and repetitively inspecting for a crack in certain tailbooms that have not been redesigned and replacing the tailboom if a crack is found. That proposal was prompted by cracking discovered in other areas of certain tailbooms and introduction of a redesigned tailboom with a chemically milled skin, which does not require the current inspections. This action revises the proposed rule by correcting the model applicability, increasing the area of inspection for certain tailbooms, requiring modification of certain tailbooms, and establishing life limits for certain tailbooms. The actions specified by this proposed AD are intended to prevent separation of the tailboom and subsequent loss of control of the helicopter.