Abstract: An array of chutes is permanently mounted within the flowpath of an exhaust nozzle of an aircraft jet engine for entraining and mixing ambient air with the exhaust gas so as to reduce the noise level of aircraft, particularly during take-off. In order to provide good engine performance during all modes of jet engine operation, a convergent-divergent flap assembly is arranged downstream from the chutes for controlling the nozzle throat and exit areas when the chutes are closed.

Abstract: A method is disclosed for discharging combustion gases from an engine powering an aircraft at subsonic and supersonic velocities. The engine includes a variable area exhaust nozzle having primary and secondary flaps defining a generally converging channel and exhaust channel, respectively, for the combustion gases. The method comprises the steps of contouring the secondary flaps to a first contour at a first position at a first value of a nozzle pressure ratio NPR across the converging and exhaust channels. The method further includes the step of contouring the secondary flaps to a second contour at a second position at a second value of NPR. In a preferred embodiment, the first contour is straight at low values of NPR and the second contour is generally concave for high values of NPR.

Abstract: An exhaust assembly is provided for a gas turbine engine effective for propelling an aircraft from takeoff through subsonic and supersonic velocity. The exhaust assembly is effective for receiving exhaust gases discharged from an outlet of a core engine of an aircraft gas turbine engine. The assembly includes a casing, a variable area converging-diverging nozzle attached to the casing and including a first throat and an outlet for channeling exhaust gases received from the core engine. A plurality of retractable chutes are disposed upstream of the nozzle outlet and are positionable in a deployed position forming a converging nozzle having a second throat with a flow area less than that of the first throat. Means are provided for channeling air along aft facing surfaces of the chutes into the CD nozzle for mixing with the exhaust gases when the chutes are disposed in the deployed position for reducing noise from the exhaust gases.

Abstract: A method is disclosed for discharging combustion gases from an engine powering an aircraft at subsonic and supersonic velocities. The engine includes a variable area exhaust nozzle having primary and secondary flaps defining a generally converging channel and exhaust channel, respectively, for the combustion gases. The method comprises the steps of contouring the secondary flaps to a first contour at a first position at a first value of a nozzle pressure ratio NPR across the converging and exhaust channels. The method further includes the step of contouring the secondary flaps to a second contour at a second position at a second value of NPR. In a preferred embodiment, the first contour is straight at low values of NPR and the second contour is generally concave for high values of NPR.