Airworthiness Directives; Boeing Model 727 Series Airplanes Modified in Accordance With Supplemental Type Certificate SA1444SO, SA1509SO, SA1543SO, or SA1896SO

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 727 series airplanes that have been converted from a passenger-to a cargo-carrying ("freighter") configuration, that requires, among other actions, installation of a fail-safe hinge, redesigned main deck cargo door warning and power control systems, and 9g crash barrier. This amendment is prompted by the FAA's determination that the main deck cargo door hinge is not fail-safe; that certain main deck cargo door control systems do not provide an adequate level of safety; and that the main deck cargo barrier is not structurally adequate during an emergency landing. The actions specified by this AD are intended to prevent structural failure of the main deck cargo door hinge or failure of the cargo door system, which could result in the loss or opening of the cargo door while the airplane is in flight, and consequent rapid decompression of the airplane, including possible loss of flight control or severe structural damage; and to prevent failure of the main deck cargo barrier during an emergency landing, which could injure occupants.