Aircraft cargo Structure
Airframes converted to cargo configuration may have their passenger window transparencies removed and replaced by mechanically fastened sheet metal panels. Piercing and forced entry both remain restricted by the heavy construction zone around the window openings. Do aircraft that are purpose built as freighters still have the window frames or are they deleted to reduce weight and fabrication complexity? If windows frames and their surrounding substructure (skin doublers and triplers) are not installed, does the window belt skin sheet thickness remain the same or is it thinner? Thinner skins and the elimination of built-up or unit window frames and their surrounding substructure would positively affect maindeck piercing and forced entry considerations on freighter airframes.