Many aeronautical systems are designed in consideration of Fluid dynamics, heat transfer and mechanical phenomena. The numerical simulation is now widely involved in the design. Today, existing tools and methodologies have reached a good maturity to analyse them separately. However, the real objective is to consider the behaviour of the systems with these coupled phenomena. Very disparate methodologies have been implemented to take this into account. Today, many methodologies imply to do the CFD simulations first, extract conditioning for heat transfer and export temperature fields for mechanical modelling. For that kind of modelling, each discipline has its own mesh, allowing exchange with other disciplines by interpolation of data.Some methodologies also exist for the coupling of (CFD + heat transfer).Before CFD democratization, quite many methodologies with thermal model taking into account enthalpy equilibrium have been developed and are today used for the design of many aeronautic systems. The tools solve thermal model + 1D fluid network.The objective to enhance the performance of the systems implies to reach a better accuracy by directly coupling Fluid dynamics and heat transfer; the aim is also to consider the transient behaviour.New methodologies emerge today; however, some difficulties remain, among them are : non coincident meshing that require efficient communication approach, coincident meshing that induce thermal models bigger than necessary, methodologies that are developed for steady simulation but not for transient simulations (which are still missing in industrial process of development).Considering these constraints, an approach for aerothermal coupling has been developed, ensuring a compromise between specificity of meshing for each discipline, ensuring continuity with today methodologies of thermal model taking into account enthalpic equilibrium, preserving compatibity with future CFD technologies (meshing, …).The application of this methodology on a validation case allowed accessing to transient behaviour without running still costly full transient CFD simulations.The methodology is also applied on a turbine casing.