Airworthiness Directives; The Boeing Company Airplanes

We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 747-200B, 747-300, and 747-400 series airplanes. This AD requires replacing certain low-pressure oxygen flex- hoses with new non-conductive low-pressure oxygen flex-hoses in the gaseous passenger oxygen system in airplanes equipped with therapeutic oxygen. This AD also requires a general visual inspection of the low- pressure passenger oxygen system to ensure there is minimum clearance of the oxygen system components from adjacent structure and systems. This AD was prompted by reports of low-pressure flex-hoses of the flightcrew oxygen system that burned through due to inadvertent electrical current from a short circuit. We are issuing this AD to address the unsafe condition on these products.