Integral fuel tanks are formed within the aircraft structure by sealing compartments like wing sections during manufacture. Internal diaphragms both divide the wing into a number of tanks, and also prevent ‘surge’, external or internal pipes connect the tanks to the fuel system.
A number of methods are used for sealing the structure, including the use of sealant as a ‘faying compound’ between mating surfaces and the use of ‘filleting compound’ at the edges. The interior of the tank is then further protected by flexible sealant coatings, which may be applied by spreading, brushing or spraying. All the above methods may be used to seal the tank which may also be accompanied by special paint schemes, which are designed to minimize microbiological attack. A suitable number of large access panels, hand holds and tank connections, are included within the structure. The access panels are normally made fuel tight by using seals and sealant at the mating surfaces.