The Ada 2005 task dispatching model includes new scheduling policies such as EDF and round robin, in addition to the traditional fixed priority dispatching, and allows mixing these policies into a hierarchy of schedulers. This hierarchical scheduling model is a very interesting solution that allows us to have in the same system the best properties of the three policies: the high performance of EDF, the predictability of fixed priorities, and the fair distribution of unused capacity provided by a round robin scheduler. The paper presents one of the first implementations of this hierarchical dispatching model, built with GNAT over MaRTE OS. An evaluation of the implementation is provided and examples of usage are shown.