Ideally, this moisture drains into bilge areas of the fuselage and then is vented overboard. However, if there are gaps between blankets, or if some blanket surface damage has occurred, water may drip into the cabin or accumulate in the insulation blanket itself. Wet-arcing has been cited as the cause of various operators' electrical problems. On one 737-300 that Boeing studied, the difference in weight between its existing insulation blankets and a set of new, drier ones was found to be approximately 80 pounds. These older, waterlogged blankets can increase operating costs due to added weight, reduce the blankets' insulating properties and create a breeding ground for bacteria and fungi.
Accumulated water can also exacerbate corrosion and decrease the service life of the airframe.
Damaged blankets with accumulated water need to be replaced with serviceable units. Remedies It is virtually impossible to eliminate moisture from aircraft cabins. However, based on extensive studies and testing, Boeing has determined that a number of maintenance and procedural steps can be taken to reduce potential damaging effects from cabin moisture. Boeing suggests that the best way to minimize condensation is to eliminate holes in insulation blankets, overlap them during installation and reduce gaps between blankets and aircraft structure. Unrestricted flow channels for water to drain should be assured and plastic bilge trays added in the lower section of the fuselage to prevent insulation blankets from coming into contact with draining water.