A structure of a pneumatic installation in a tail zone of an aircraft includes an auxiliary power unit (1) for supply of pneumatic and electrical power, whose pneumatic power outlet is linked to a duct (2) which conventionally incorporates bends (7) and compensation elements (6) for thermal expansion and for compensation of the vibrations produced by the APU (1) in its functioning. The power outlet of the APU (1) is arranged in its front part in which is connected the duct consisting of a straight pipe (2a) inclined downwards toward the lower part of the aircraft in which compensation elements (6) for thermal expansion and for compensation of vibrations are inserted in order to reduce the length of the duct (2) and eliminate the bends, so that the pressure losses are considerably reduced.