Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to supersede an existing airworthiness directive (AD) for the Bell Model 407 helicopters. The existing AD currently requires preflight checking and repetitively inspecting for a crack in certain tailbooms that have been redesigned, replacing the tailboom if there is a crack, modifying and re-identifying certain tailbooms, installing an improved horizontal stabilizer assembly, and assigning a 5,000 hour time-in-service (TIS) limit. Since we issued that AD, we have received several additional reports of cracked tailboom skins. This proposed AD would retain the existing requirements and apply additional inspection requirements. The proposed actions are intended to prevent separation of the tailboom and subsequent loss of control of the helicopter.