Airworthiness Directives; The Boeing Company Airplanes

We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 777-200, -200LR, -300, -300ER, and 777F series airplanes. This AD was prompted by a report that during a test of the oxygen system, an operator found that the passenger oxygen masks did not properly flow oxygen, and that a loud noise occurred in the overhead area, which was caused by the flex line separating from the hard line due to a missing clamshell coupler. This AD requires, for certain airplanes, performing a detailed inspection of certain areas of the airplane oxygen system to ensure clamshell couplers are installed and fully latched, and corrective actions if necessary. For all airplanes, this AD requires performing and meeting the requirements of the low pressure leak test. We are issuing this AD to prevent the oxygen system flex line from separating from the hard line, which could cause an oxygen leak and a drop in the oxygen system pressure, resulting in improper flow of oxygen through the passenger masks and injury to passengers if emergency oxygen is needed.