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A tail assembly for a rotorcraft. The tail assembly is manufactured to include at least one transition structure provided in the tail assembly. The transition structure is longitudinally arranged between a longitudinal median boom portion and a tail fin. A power transmission shaft of the rotorcraft

A tail assembly for a rotorcraft. The tail assembly is manufactured to include at least one transition structure provided in the tail assembly. The transition structure is longitudinally arranged between a longitudinal median boom portion and a tail fin. A power transmission shaft of the rotorcraft extends at least partly externally above a longitudinal median boom portion of the tail assembly. The transition structure includes at an entering region a cut-out elevation step, where is made a passing through opening for the power transmission shaft.

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1. A method of manufacturing a tail assembly for a rotorcraft; the tail assembly including a power transmission shaft covered by at least one non-load bearing fairing and a load bearing structure defining, from fore to aft, a tail boom and a tail fin; the load bearing structure having a fore end and

1. A method of manufacturing a tail assembly for a rotorcraft; the tail assembly including a power transmission shaft covered by at least one non-load bearing fairing and a load bearing structure defining, from fore to aft, a tail boom and a tail fin; the load bearing structure having a fore end and a longitudinal median boom portion extending from the fore end towards the tail fin; the tail assembly comprising a power transmission shaft penetrating inside the tail fin by a passing through opening in the load bearing structure; the passing through opening positioned on a surface of the load bearing structure facing the fore end; wherein the method includes:a transition stage of providing the load bearing structure of the tail assembly with at least one transition structure that is longitudinally arranged between the longitudinal median boom portion and the tail fin; the non-load bearing fairing being detachably secured to the longitudinal median boom portion for allowing access to the power transmission shaft and being flush with a longitudinal part of the transition structure; at least one transverse section of the transition structure having an upwards dimension that is higher than an elevation junction dimension of the longitudinal median boom portion at a junction between the longitudinal median boom portion and the transition structure;a cut-out arrangement stage of providing the transition structure with at least one cut-out elevation step, the passing through opening being made in the cut-out elevation step, such that the power transmission shaft extends at least partly externally above the longitudinal median boom portion between the fore end and the cut-out elevation step, the power transmission shaft penetrating in the load bearing structure through the passing through opening;an upper location stage of determining a longitudinal distance shift at which an upper end of the cut-out elevation step is longitudinally shifted forwards relative to a leading edge of the tail fin; anda lower offset stage of defining a lower offset at which a lower end of the cut-out elevation step is longitudinally shifted forwards with respect to the upper end of the cut-out elevation step. 2. The method of manufacturing of claim 1, wherein a longitudinal dimension of the transition structure is comprised between 0.05 m and 0.4 m. 3. The method of manufacturing of claim 2, wherein the upper end of the cut-out elevation step is linked to a longitudinal part of the transition structure, the longitudinal part extending from the cut-out elevation step towards the leading edge of the tail fin. 4. The method of manufacturing of claim 1, wherein the method includes an angle affecting stage which consists in providing a front—downwards/rear—upwards cut-out angle according to which the cut-out elevation step is bent with respect to a transverse reference plane (PREF) that is parallel to a transverse direction of the tail assembly and orthogonal to a longitudinal direction of the tail assembly; the cut-out angle being comprised between 1 degree and 70 degrees. 5. The method of manufacturing of claim 1, wherein the method includes a reinforcement stage during which stage at least two reinforcement ribs are rigidly secured to the longitudinal median boom portion and to the cut-out elevation step, with the power transmission shaft extending between the ribs; the method including a stage of determining a lateral position of each reinforcement rib including a sideward spacing value between the power transmission shaft and the corresponding reinforcement rib. 6. A tail assembly for a rotorcraft, the tail assembly including a load bearing structure defining, from fore to aft, a tail boom and a tail fin; the load bearing structure having a fore end and a longitudinal median boom portion extending from the fore end towards the tail fin; the tail assembly comprising a power transmission shaft which penetrates inside the tail fin by a passing through opening in the load bearing structure; the passing through opening positioned on a surface of the load bearing structure facing the fore end; wherein the power transmission shaft is covered by at least one non-load bearing fairing; wherein the tail assembly includes: at least one transition structure provided in the tail assembly; the transition structure being longitudinally arranged between the longitudinal median boom portion and the tail fin; the non-load bearing fairing being detachably secured to the longitudinal median boom portion for allowing access to the power transmission shaft and being flush with a longitudinal part of the transition structure; at least one transverse section of the transition structure having an upwards dimension that is higher than an elevation junction dimension of the longitudinal median boom portion at a junction between the longitudinal median boom portion and the transition structure; at least one cut-out elevation step being arranged on the transition structure, the passing through opening being made in the cut-out elevation step, such that the power transmission shaft extends at least partly externally above the longitudinal median boom portion, between the fore end and the cut-out elevation step, the power transmission shaft penetrating in the load bearing structure through the passing through opening; the cut-out elevation step having an upper end which is longitudinally shifted forwards relative to a leading edge of the tail fin, the cut-out elevation step having a lower end which is longitudinally shifted forwards with respect to the upper end. 7. The tail assembly of claim 6, wherein the tail assembly includes an external tail rotor. 8. The tail assembly of claim 6, wherein the tail assembly includes a ducted tail rotor. 9. The tail assembly of claim 6, wherein the transition structure is at least partly a part of the longitudinal median boom portion. 10. The tail assembly of claim 6, wherein characterized in that the transition structure is at least partly a part of the tail fin. 11. The tail assembly of claim 6, wherein the cut-out elevation step is bent with respect to a transverse reference plane that is parallel to a transverse direction of the tail assembly and orthogonal to a longitudinal direction of the tail assembly by a front—downwards/rear—upwards cut-out angle; the cut-out angle being comprised between 1 degree and 70 degrees. 12. The tail assembly of claim 11, wherein the upper end is linked to a longitudinal part of the transition structure, the longitudinal part extending from the cut-out elevation step towards the leading edge of the tail fin. 13. The tail assembly of claim 6, wherein the non load-bearing fairing is shaped with a horseshoe section perpendicularly to the longitudinal direction of the rotorcraft, and wherein at least one of a fore edge and an aft edge of the non load-bearing fairing being slanted. 14. A rotorcraft, wherein the rotorcraft includes at least one tail assembly according to claim 6. 15. A rotorcraft, wherein the rotorcraft includes at least one tail assembly according to claim 7. 16. A rotorcraft, wherein the rotorcraft includes at least one tail assembly according to claim 8. 17. A rotorcraft tail assembly comprising: a load bearing structure having a tail boom with a longitudinal median boom portion, a tail fin, and a transition structure positioned longitudinally between and connecting the longitudinal median boom portion to the tail fin, wherein the transition structure has a cut-out elevation step and to a longitudinal part, the cut-out elevation step defining a passing through opening, wherein the cut-out elevation step has an upper end shifted longitudinally forward of a leading edge of the tail fin and a lower end shifted longitudinally forward of the upper end and connected to the longitudinal median boom portion at a junction, wherein the cut-out elevation step extends upwardly in elevation from the longitudinal median boom portion such that the transition structure has an upwards dimension that is higher than an elevation at the junction and such that the longitudinal part is offset in elevation from the longitudinal median boom portion, and wherein the longitudinal part of the transition structure extends longitudinally aftward from the upper end of the cutout elevation step to the leading edge of the tail fin;a power transmission shaft extending along the tail boom, the power transmission shaft extending longitudinally above the longitudinal median boom portion, through the passing through opening of the transition structure, and into an inside region of the tail fin; anda non-load bearing fairing detachably secured to the longitudinal median boom portion to cover the power transmission shaft and allow access to the power transmission shaft, the non-load bearing fairing extending from the transition structure towards a fore end of the tail boom, wherein an upper surface of the non-load bearing fairing is flush with the longitudinal part of the transition structure. 18. The rotorcraft tail assembly of claim 17 wherein the non-load bearing fairing has a horseshoe-shaped cross-section, a fore edge that is slanted top-front to down-rear, and a rear edge that is slanted down-front to top-rear, wherein a slant angle of the rear edge corresponds with an angle of the cut-out elevation step. 19. The rotorcraft tail assembly of claim 17 wherein the power transmission shaft is arranged in elevation between an upper surface of the longitudinal median boom portion and the non-load bearing fairing. 20. The rotorcraft tail assembly of claim 17 further comprising first and second reinforcement ribs, each rib connected to the cut-out elevation step and to an outer surface of the longitudinal median boom portion, each rib extending longitudinally from the cut-out elevation step towards a fore end of the tail boom, and wherein the power transmission shaft is positioned between the first and second reinforcement ribs.