Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 747-400, 747-400D, 747-400F, 747-8F, and 747-8 series airplanes. This proposed AD was prompted by reports of very high temperatures, up to 67 degrees Celsius (152 degrees Fahrenheit), near the floor in the aft lower lobe cargo compartment. This proposed AD would require installing an additional zone temperature sensor (ZTS) in the aft cargo compartment. For certain airplanes, the proposed AD would first require installing tape and replacing the markers in the bulk cargo compartment, unless terminated by the early installation of the ZTS. We are proposing this AD to prevent overheating of the aft lower lobe cargo compartment, where, if temperature sensitive cargo is present, the release of flammable vapors could result in a fire or explosion if exposed to an ignition source.