a nacelle of an aircraft 1 according to an exemplary embodiment as represented in fig1 , comprises in a manner known per se an outer structure 2 , termed ofs , which defines an annular flow duct 3 with a concentric inner structure 4 , termed ifs , surrounding the structure of the jet engine ( not shown ) to the rear of a fan ( 5 ). more precisely , this outer structure 2 is broken down into a front air inlet section 6 , a mid - section 7 intended to surround the fan 5 , and a rear section 8 generally formed by at least two half - shells . the inner structure 4 comprises an inner panel 10 which surrounds a downstream portion of the jet engine . as represented in fig2 and 3 , exhaust means 11 are provided in this inner panel 10 so that any untimely excess pressure occurring in the jet engine compartment is discharged into the annular duct 3 . these exhaust means 11 are preferably positioned at the front of the inner panel 10 so as to be situated as close as possible to the sensitive regions in which excess pressure may occur due to an explosion in the jet engine compartment . these exhaust means 11 comprise at least one excess pressure flap 12 equipped with a strut 13 . the excess pressure flap 12 is attached to the inner panel 10 , and is pivotably mounted about the latter via a set of hinges 9 . a nacelle according to an exemplary embodiment is represented more specifically in fig4 to 6 . the strut 13 of the excess pressure flap 12 comprises a cylindrical hollow casing 14 in which a rod 15 can slide . this casing 14 has an end 16 pivotably mounted about an axis 33 in a fastening plate 31 attached to the excess pressure flap 12 , and the rod 15 , extending the casing 14 , has an end 17 pivotably mounted in a fastening block 32 attached to the inner panel 10 of the inner structure 4 . more precisely , and as represented in fig5 and 6 , a locking finger 120 is housed in the casing 14 , and is arranged between the end 16 thereof and the rod 15 . more precisely , this locking finger 120 has a first end 121 pivotably mounted about the axis 33 in the region of the end 16 of the casing 14 , and a second end 123 housed in a cavity 124 formed in the rod 15 . furthermore , elastic return means are produced in the form of at least one compression spring 122 . the latter is arranged transversely to the locking finger 120 in the region of the end 16 of the casing 14 , and has a first end 125 bearing against the inner face of the lateral surface 30 of the casing 14 , and a second end 126 housed in a transverse blind bore 127 formed in the locking finger 120 . in this way , when the excess pressure flap 12 is in the closed position in the continuation of the inner panel 10 of the inner structure 4 , the casing 14 , the locking finger 120 and the rod 15 are coaxial to one another . on the other hand , in the event of untimely excess pressure in the jet engine compartment which is sufficient to cause the excess pressure flap 12 to open , the rod 15 is caused to slide in the casing 14 as represented in fig1 , and the second end 123 of the locking finger 120 is extracted from the cavity 124 of the rod 15 owing to the sliding of the latter into the deployed position . the compression spring 122 can then force the first end 121 of the locking finger 120 to pivot about said axis 33 , the effect of which is to longitudinally off - center the locking finger 120 with respect to the cavity 124 of the rod 15 . said rod will therefore be locked in the case of rearward return since the second end 123 of the locking finger 120 will no longer be positioned opposite the cavity 124 presented by the rod 15 . therefore , these locking means make it possible to lock the strut 13 in its spacing position which has been designed so as to ensure a minimum discharge flow rate to the outside in the event of untimely excess pressure . it should be noted that the lateral surface 30 of the casing 14 may have an opening 128 which , during maintenance operations on the ground , makes it possible to reach the locking finger 120 and to force it to pivot about its axis 33 in order to arrange it parallel to the casing 14 and to the rod 15 , thereby finally allowing a rearward return of the latter . moreover , detection means 129 are advantageously provided to allow the operator or operators to check instantaneously from the outside whether the exhaust means 11 have been actuated or not in flight . for that purpose , these detection means 129 comprise a control system whose activation is conditioned by the activation of the exhaust means 11 as represented schematically in fig7 . this control system will advantageously comprise a cam whose pivoting will be controlled by the opening of the excess pressure flap 12 . this cam will preferably be connected to a prestressed trigger which is connected to transmission means 130 attached to at least one external mechanical display member 131 . more precisely , the pivoting of the cam will cause the release of the prestress trigger , which as it is released will exert a pull on the transmission means advantageously produced in the form of a cable 130 , this pull causing the deployment of the mechanical member preferably produced in the form of a “ pop - out ” - type device 131 as represented in the deployed position in fig2 . although the disclosure has been described in connection with specific exemplary embodiments , it goes without saying that it is in no way limited thereto and that it comprises all the technical equivalents of the means described as well as the combinations thereof if they come within the scope of the disclsoure .