Airworthiness Directives; Eurocopter Deutschland GmbH Helicopters
We are adopting a new airworthiness directive (AD) that supersedes an existing Emergency Airworthiness Directive (EAD) for certain Eurocopter Deutschland GmbH (ECD) Model EC135 helicopters. The existing EAD, which was previously sent to all known U.S. owners and operators of ECD Model EC135 helicopters and not made generally effective by publication in the Federal Register, currently requires inspecting the ring frame between the rear structure tube (tailboom) and the tail rotor fenestron housing (fenestron housing) for a crack before the first flight of each day and replacing any cracked ring frame with an airworthy ring frame. Since we issued that EAD, we have determined that a pre-flight pilot check in conjunction with a recurring 25-hour inspection is sufficient for determining the airworthiness of the ring frame. Additionally, ECD has developed a modification that is terminating action for the requirements of that EAD. This superseding AD revises the inspection requirements of the EAD to allow an owner/operator to perform the pre-flight pilot check, adds a recurring inspection of the ring frame, and allows for installation of a ring frame reinforcement as an optional terminating action for the AD requirements. The actions are intended to detect a crack in the ring frame which could result in loss of the fenestron structure and subsequent loss of control of the helicopter.