vanes 2 each vane having top and bottom pivots 3 and 4 whose orientation is operated from the top by a linkage 5 located outside engine housing 6 a rotor 7 is formed by vanes 8 the bases of which are set into rotor disk 9 top pivot 3 turns in a bearing set in the upper ring of housing 6 one of the ends of a control rod or lever 10 is fixed to pivot 3 while the other end is fixed to link 11 for operating the ring of vanes the safety stop of the invention fig2 and 5 consists of at least one arm 14 including attachment means for becoming fixed to pivot 4 and stop elements 15 and 16 fixed to inner ring 13 to block the rotation of arm 14 in case the control mechanism e g 10 and 11 breaks according to the embodiment shown in fig2 and 4 the end of cylindrical pivot 4 at the vane root has at least one and preferentially two parallel flattened surfaces 17 pivot 4 is held within a bearing 12 consisting of a bushing of self lubricating material fixed within inner stator ring 13 of the compressor stage the radially inner surface 18 of this stator ring 13 is provided with a circumferentially extending notch 19 into which projects the end of pivot 4 particularly the.