Airworthiness Directives; McDonnell Douglas Model DC-9-15F Airplanes Modified In Accordance With Supplemental Type Certificate (STC) SA1993SO; and Model DC-9-10, DC-9-20, DC-9-30, DC-9-40, and DC-9-50 Series Airplanes in All-Cargo Configuration, Equipped With a Main-Deck Cargo Door

The FAA is adopting a new airworthiness directive (AD) for the airplanes listed above. For certain airplanes, this AD requires inspecting to determine the airplane's cargo configuration, and reporting findings to the FAA. For airplanes modified in accordance with a certain STC or with a cargo configuration that deviates from the as-delivered configuration, this AD requires revising certain manuals and manual supplements to specify certain cargo limitations. This AD also requires relocating all cargo restraints on the main cargo deck. This AD is prompted by reports that deficiencies related to the cargo loading system may exist on all McDonnell Douglas Model DC-9-15F airplanes modified in accordance with STC SA1993SO. We are issuing this AD to ensure that cargo in the main cabin is adequately restrained and to prevent failure of components of the cargo loading system, failure of the floor structure, or shifting of cargo. Any of these conditions could cause cargo to exceed load distribution limits or cause damage to the fuselage or control cables, which could result in reduced controllability of the airplane.