A variable cycle propulsion
system for a supersonic
airplane, the
system comprising at least one engine having means for producing
exhaust gas and a gas exhaust
nozzle for generating thrust for supersonic flight speeds, and at least one separate auxiliary propulsion
assembly dissociated from said engine, having no
gas generator, and capable of generating thrust for
takeoff, landing, and subsonic flight speeds. The
system further comprises gas flow tapping means movable between a position in which they tap off at least a fraction of the
exhaust gas produced by said engine and feed it to said propulsion
assembly to enable it to generate thrust for
takeoff, landing, and subsonic cruising flight, and a position in which the gas produced by the engine is directed solely to the engine
nozzle for supersonic cruising flight.