is therefore not able to open at a given moment during the trajectory the electronic control device 4 will cause the rod 35 to retract from the pyrotechnic piston the first flap 7 a will open under the action of the centrifugal force the pin 36 thereafter comes out of the notch 37 freeing the second flap 7 b which can now also open the surface 29 moves away from the pin 38 thereby freeing the third flap 7 c which in turn opens freeing the fourth flap 7 d because only one locking device the pyrotechnic piston is employed the four flaps open practically simultaneously this results in a symmetry and reproducibility of the opening movement that avoids disturbances to the braking trajectory of the projectile the rotation of each flap is halted by its abutment heel 31 coming into contact with the tubular part 16 of the axial support 15 such an arrangement enables the angle of opening of the flaps to be controlled the arc length of the external profile 26 of each flap and the length of the different abutment heels are selected such that in the deployed position the free end 40 of each flap the end that is the furthest away from the pivot 19 presses on or lies opposite to a neighboring flap or else presses on or lies opposite to the lower plate 18 that forms a bearing surface integral with the fuse and.