Aerodynamic interference aspects on full helicopter configurations in view of assessing the potential of noise reduction are considered. The investigation is based on numerical tools of varying complexity and code-to-code comparisons over a range of different flight conditions in correlation to foreseen wind tunnel tests in the DNW on the BO105 scaled model. This work aims at evaluating the different codes as well as at defining the appropriate context for codes-to-test comparison. The main bulk of results concerns the pre-test activity while some selective comparisons of post-test simulations with measurements support the discussion as well as the conclusions of this exercise.