the bypass turbine engine shown by each of fig1 , 2 and 3 , comprises a hollow nacelle 1 of longitudinal axis l - l provided , at the front , with an air inlet 2 , and , at the rear , with an air outlet 3 . said hollow nacelle 1 internally bears a fairing 4 , preferably at least partially coated with acoustic attenuation coatings 5 intended to reduce the internal noise of said turbine engine . a central hot stream generator 6 comprising , in the known way , low - pressure and high - pressure compressors , a combustion chamber and low - pressure and high - pressure turbines , and generating the axial hot stream 7 of said turbine engine ; a fan 8 positioned axially in front of said central generator 6 and generating the annular cold stream 9 of said turbine engine ; and an inner fairing 10 surrounding said central generator 6 and forming , between itself and the casing 11 of this generator , an intermediate chamber 12 of annular cross section surrounding said generator , the rear part 10 r of said fairing forming the outer wall of the jet pipe 16 for said hot stream 7 . the inner fairing 10 and the fairing 4 , external to it , between them form a fan duct 13 of annular cross section surrounding the central generator 6 and through which the cold stream 9 flows . formed between the inner fairing 10 and the central generator 6 are , at the front , an annular air intake slot 14 , and , at the rear , an annular air discharge slot 15 . thus , the intermediate chamber 12 can be swept by a ventilation current f bled from the cold stream 9 at the front slot 14 and discharged at the boundary between said hot stream 7 and said cold stream 9 at the rear slot 15 , this ventilation current f being used to regulate the temperature of the central generator 6 . furthermore , in the usual way , the nacelle 1 is supported by a wing 17 of the aircraft ( this wing is depicted in part ) via a suspension pylon 18 . in the known turbine engine illustrated in fig1 , a precooler 19 is provided , this being positioned in the upper part of the fan duct 13 in the cold stream 9 . this precooler 19 is fed with a current of hot air 20 , from the central generator 6 , via a duct 21 on which there is a hot air regulating valve 22 . the cooled hot air 23 generated by the precooler 19 is dispatched to the user equipment ( not depicted ) via a duct 24 which passes through the suspension pylon 18 and which may be fitted with a regulating valve 25 . thus , in this known layout , some of the cold stream is bled off by the precooler 19 to cool the current of hot air 20 and to generate the cooled hot air current 23 and this also results in said precooler forming a current of heated cold air ( not depicted ) corresponding to said bled - off portion of the cold stream . this current of heated cold air is discharged to the outside , in any known way not depicted in fig1 , and generally causes an increase in drag . it will be readily understood therefore that the presence of the precooler 19 in the fan duct 13 and the discharging of the heated cold air are detrimental to the performance of the known engine illustrated in fig1 . in the nacelle 1 . 1 , according to the present invention and depicted in fig2 , we find all of the elements 2 to 18 and 20 to 25 described with reference to fig1 . however , in this nacelle 1 . 1 , the precooler 19 has been replaced by a precooler 30 positioned inside the intermediate chamber 12 in thermal contact with the rear part 10 r of the fairing 10 . the precooler 30 has a shape of annular cross section about the axis l - l and extends over the entire periphery of this rear part 10 r . in addition , the precooler 30 forms an intermediate passage 26 , of annular cross section , about the axis l - l between itself and the central generator 6 , said intermediate passage 26 opening to the rear via said annular air discharge slot 15 . further , in the nacelle 1 . 1 of fig2 there is , forward of the precooler 30 , an air intake 27 provided with shut - off means 28 and passing through said fairing 10 . when open , the air intake 27 is able to bleed a current of cooling air 29 from said cold flow 9 . thus , on the outside , the precooler 30 is cooled by the cold stream 9 leaving the fan duct 13 and sweeping over the rear part 10 r of the inner fairing 10 whereas , on the inside , when the air intake 27 is open , it is additionally cooled by said current of cooling air 29 passing through the intermediate passage 26 and exiting via the slot 15 . the precooler 30 has an inlet 31 connected to the duct 21 supplying the hot air current 20 and an outlet 32 connected to the duct 24 carrying the cooled hot air 23 . fig3 , which shows all the elements of fig2 , additionally shows the existence , in the nacelle 1 . 2 according to the invention of a bypass duct 33 mounted in parallel with the precooler 30 , connecting its inlet 31 and its outlet 32 and provided with a valve 34 . thus , if necessary , hot air can be routed directly from the inlet 31 to the outlet 32 , thereby bypassing the precooler 30 . fig4 depicts an embodiment of the air intake 27 with its shutter 28 ( but without the means of actuating the latter ). positioned in the chamber 12 on the casing 11 of the generator 6 are vanes 29 a for setting the current of cooling air 29 in rotation about the axis l - l . the exemplary embodiment of the precooler 30 which is illustrated by fig5 to 11 is structurally incorporated into said rear part 10 r of the inner fairing 10 . as can be seen in fig5 to 7 , said rear part 10 r comprises an inner wall 35 and an outer wall 36 which are parallel and spaced apart from one another by a space 37 in the form of an annular gap . positioned in this space is a framework 38 ( fig6 ) or 39 ( fig7 ) secured to said inner and outer walls 35 and 36 and delimiting curved ducts 40 which subdivide the space 37 . the ducts 40 are transverse to the axis l - l of the nacelle and are distributed along said rear part 10 r . a distribution pipe 41 connected to the hot air inlet 31 and able to distribute said hot air ( see arrows 42 ) within said space 37 ( and therefore into the ducts 40 ) along the entire rear part 10 r and transversely thereto ; and a collection pipe 43 connected to the cooled hot air outlet 32 and able to collect said air ( see arrows 44 ) passing through said space 37 through the ducts 40 , along the length of the rear part 10 r . as illustrated in fig8 to 11 , the cross section of the pipes 41 and 43 decreases from the front rearward , while the reverse is true of the distribution orifices 45 and the collection orifices 46 with which they are respectively provided .