To provide the subject device having an excellent characteristic at the time of direct propulsion and thrust inversion.

Each movable member 6, 7 is supported by turning shaft 12 secured to a fixed structure, and composed of an outer pannel 6 and an inner pannel 7. The outer pannel 6 is turned by the action of a jack 13 fixed on a main cover 10 and assures an aerodynamic contour of the cover 10 at the time of direct propulsion while the inner pannel 7 is at a superposed position below the outer pannel 6 at the time of direct operation and can slide on the extension of the outer pannel 6 by surely deviating the flux of inverted flow at the time of thrust inversion.