generated by the gas turbine engine the annular cowling structure 12 comprises a first front portion 20 called the fixed structure which includes a plurality of radial apertures 21 an annular reinforcing structure 22 commonly called the fore frame is mounted at the front 5 of the radial apertures 21 furthermore the annular structure 12 comprises at least a second portion 25 comprising displaceable shutters that close the radial apertures 21 in this embodiment the shutters 25 are pivotable and are called doors typically such shutters 25 are mounted on pivots 26 their pivoting motion merely being a rotation about these pivots 26 these shutters 25 also may be mounted on a set of linkage rods not shown the pivoting motion then being more complex but not affecting the present invention the front and rear parts of the shutter 25 are respectively denoted by 27 and 28 the shutter is driven into open and closed positions by control means 29 which in this instance includes a hydraulic linear actuator hinged at one end to the fixed structure 20 and at its other end to the shutter 25 the portions of the walls 13 and 14 are part of the fixed structure 20 and are referenced by 13a and 14a respectively the portions of the walls 13 and 14 belonging to the shutter 25 are denoted by 13b and 14b when the shutter 25 is in the closed mode the wall portions 13b and 14b are aligned with the wall portions 13a 14a at the fixed cowling structure 20 the annular structure 12 of the thrust reverser 10 also comprises locking systems 35 to keep the shutter 25 in its closed mode without resorting to the control means 29 these locking systems 35 typically are mounted between the front.