Abstract. The article discusses the vertical flight of a flapping wing aerial vehicle, which is also called an ornithopter. The robot is a chain of five links connected in series by active cylindrical hinges with the central link being the body and the remainder forming folding wings in pairs. The distinctive feature of this device is that the flaps of its wings imitate those of a seagull i.e. the device has a biological prototype. We construct a mathematical model of this device; much attention is given to the model of the interaction of the wings with the air environment and we determine the positions and velocities of points of application of the reduced aerodynamic forces to each of the links. Based on the results of numerical modelling of the vertical flight of the robot three modes of flight were established: ascent, hovering at a certain height and descent. The device can operate in these modes based on the oscillation parameters of the wings in particular flapping frequency and amplitude, the ratio of the amplitudes of two links and one wing and the shift of the equilibrium oscillation position of the wings relative to zero.