are in aerodynamic continuity the annular vein 10 has constant height perpendicularly to the longitudinal axis u03b4 according to the forms of fig5 to 7 the cross section of the ifs is no longer in aerodynamic continuity at the active mobile element 103 which penetrates the annular vein 10 consequently reducing the height of the latter this configuration is advantageous since it gives the possibility of having better operation of the turbine engine 6 with a strong dilution rate in the descent or cruising phase according to the forms of fig8 to 10 the transverse section of the ifs is no longer in aerodynamic continuity at the active mobile element 103 which penetrates the inside of the ifs 8 consequently increasing the height of the annular vein 10 this configuration is adapted to the operation of the fan in the case of a strong thrust at take off or during the ascent phase in altitude as illustrated in fig1 to 13 the active mobile elements 103 may drive the passive mobile elements 101 so as to keep an aerodynamic line thus in the case of fig1 the active mobile elements 103 penetrate the annular vein 10 consequently pushing back the.