This paper presents preliminary results of the modelling of an unconventional unmanned airship moving in an ideal fluid. We are studying here a quad-rotor flying wing. The airships are also governed by the aerodynamic forces that have to be modelled. An evaluation of the added masses of the airship's components is presented. A first dynamic modelling including the effect of the added masses is proposed. A control law based on the elaborated dynamic model was applied to this large flying object to evaluate its sensitivity when manoeuvring over an uploading area.