Abstract: The invention is an exhaust duct system for an aircraft, the aircraft having at least one turboprop propulsion system mounted on the wing within a nacelle, the propulsion system having a circular shaped exhaust port generally aligned with the longitudinal axis of the aircraft. In detail, the invention includes a generally shallow S shaped duct having a longitudinal axis aligned with the longitudinal axis of the exhaust port. A duct includes a circular shaped inlet section, a rectangular exhaust port section and a transition section therebetween. The inlet has a larger diameter than the exhaust port of the propulsion system and is positioned there about. The inlet includes a plurality of flexible finger like members extending inward such that they are in slidable engagable with the external surface of the exhaust port.