AD FAA-2018-0276

We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 747-100, -100B, -100B SUD, -200B, -200C, - 200F, -300, -400, -400D, 747SP, and 747SR, and 747-8 series airplanes. This AD was prompted by reports indicating that additional areas of Boeing Material Specification (BMS) 8-39 flexible urethane foam were found during an inspection required by a related AD. This AD requires inspecting for BMS 8-39 flexible urethane foam insulation in the floor panel assemblies and the power drive unit (PDU) cover assemblies, doing applicable on-condition actions, modifying certain dripshields, and replacing BMS 8-39 foam strips on certain dripshields with BMS 8-371 foam strips. We are issuing this AD to address the unsafe condition on these products.