Method and apparatus for suppressing the noise of a fan-jet engine

Claim 1

In a jet propulsion plant having a fan-jet engine, the combination comprising: a tubular housing disposed in spaced relation around the aft section of the casing of said engine, fan air of said engine flowing through the space between said housing and said casing; a thrust nozzle fixedly attached to the aft end of said housing and extending rearwardly from said casing, said nozzle being formed with corrugations which extend longitudinally thereof and gradually increase in depth in the downstream direction so as to form on said nozzle a plurality of lobes having radially extending sidewalls. a plurality of vanes pivotally mounted in pairs on said sidewalls at the aft end thereof, said vanes being movable between a retracted position wherein they extend longitudinally of said sidewalls and a deployed position wherein they extend laterally from opposite sides of said sidewalls and respectively intercept ambient air flowing through the spaces between said lobes and exhaust gas and fan air flowing through said lobes; and means operatively associated with said jet propulsion plant for synchronously moving said vanes between said retracted and deployed positions thereof.