Aircraft propulsion unit with a cooler installed at engine nacelle

The propulsion unit has an air vein (13) guiding pressurized air towards an air pipe (20) arranged between an outer wall (6) and an inner wall (60) of a nacelle (10). A cooler (14) has two surface cooling units (145, 146) i.e. fins, on its corresponding outer and inner faces (141, 142) that are arranged at the level of the outer wall of the nacelle and a wall (23) of the air pipe, respectively. The air pipe has an air inlet (21) that is arranged at the front of the nacelle to create an additional air inlet.