Action
Final rule.
Summary
We are adopting a new airworthiness directive (AD) for MDHI Model MD900 helicopters with certain main rotor blade (MRB) retention bolts (bolts) installed. This AD requires a daily check of the position of each bolt, a daily check and a repetitive inspection for a gap in each bolt, and, if necessary, removing and inspecting the bolt for a crack and replacing any cracked bolt with an airworthy bolt. This AD was prompted by multiple reports of in-service bolt failures. The actions are intended to prevent failure of a bolt, which could lead to loss of MRB structural integrity and subsequent loss of control of the helicopter.