Engine, such as a turbojet, modular with speed reducer

The present invention relates to an engine (1) in modular structure comprising a plurality of coaxial modules (A, B, C) with, at one end, a first module (A) comprising a power transmission shaft (3) and a speed reducer (7), the speed reducer comprising a drive means (8 and 9), said power transmission shaft being driven by a turbine shaft (2) integral with one (C) of said separate coaxial modules the first module via the speed reducer (7), characterized in that the turbine shaft is fixed to the drive means of the speed reducer (7) by an impeller nut (14), and that the speed reducer (7) is arranged so as to present a central opening allowing access to a tool for mounting / dismounting through said opening, the impeller nut (14) from said motor end.