Abstract: An engine has a shroud which surrounds one of a propfan and a propeller having blades. The shroud has a variable geometry. A direction of the air flow inside a duct of the shroud is reversible via an adjustment of the blades for the reversal of the thrust of the engine. A separately movable nozzle ring forms a rearward end of the shroud. The nozzle ring is axially displaceable to an extent such that its trailing edge forms wherein air flow is promoted around the end of the shroud.

Abstract: A construction is provided to aerodynamically affect a jet engine nacelle in its intake lip area primarily by forming and pivotally arranging flaps on a radially outer circumferential sector of the intake lip such that from a first extreme position, in which they are adapted to a cruise lip geometry, they can be moved into a second extreme position, in which they radially expand the outer contour of the intake lip while providing and exposing air blowoff ducts with their rear side, said ducts terminating at the outer wall of the nacelle at essentially a tangent therewith. Further air injection flaps are also provided in certain embodiments for forming air injection ducts through the intake lip walls during certain engine operating conditions.