is put into the lowest idling speed position by the crew said position being detected by the corresponding microswitch 25 26 this microswitch 25 26 then acts in such a way as to de energize the coil 14 15 of the corresponding magnetic coupler which then moves into the disengaged state thus in automatic operation only the throttle lever 1 2 corresponding to the healthy engine is coupled to the servomotor 32 which enables automatic control of the airplane with a single engine should the crew wish to disengage both levers 1 2 it can of course perform this disengaging by operating a fast disengaging switch provided on the handle of each of the levers 1 2 by means of the lever 34 the pilot can adjust the friction torque exerted on the rotary assembly and therefore the reaction power that the throttle levers 1 2 oppose to the pilot 39 s action in fact rotation of the lever 34 causes an axial displacement of the screw 36 and therefore a variation of the strain brought to bear between the lever 34 and the mobile assembly by means of the springs 37 there ensues a variation of the frictional forces brought to bear on the mobile assembly by the friction washers 38 39 it should be specified that the variation of frictional forces brought to bear by the washers 38 39 is due to the fact that the rotary assembly has a slight axial mobility as a result of which the strains brought to bear by the springs 37 on the annular element 4 have repercussions on the drive mechanism 7 and on the annular element 5 through the presence of the ball bearings.