A heat exchange device to be positioned in an aircraft pylon and including a heat exchanger and an obturator to adopt a closed state where it prevents flow of air from flowing through the heat exchanger, and more- or less-permissive states where it allows flow of air to flow with a higher or lower flow rate. The obturator includes slats each including a pivot axis, the pivot axes of the various slats being mutually parallel and intersecting the direction of the flow of air, the slats being simultaneously mobile in rotation about their pivot axis between a closed position in which the slats are contiguous, which corresponds to the closed state of the obturator, and an open position in which the slats are spread apart, which corresponds to the permissive state of the obturator.