On the development of the Anuloid, a disk-shaped VTOL aircraft for urban areas

This paper deals with the early development of the Anuloid, an innovative disk-shaped VTOL aircraft. The Anuloid concept is based on the following three main features: the use of a ducted fan powered by a turboshaft for the lift production to take-off and fly; the Coanda effect that is developed through the circular internal duct and the bottom portion of the aircraft to provide further lift and control capabilities; the adoption of a system of ducted fixed and swiveling radial and circumferential vanes for the anti-torque mechanism and the flight control. The early studies have been focused on the CFD analysis of the Coanda effect and of the control vanes; the flyability analysis of the aircraft in terms of static performances and static and dynamic stability; the preliminary structural design of the aircraft. The results show that the Coanda effect is stable in most of the flight phases, vertical flight has satisfactory flyability qualities, whereas horizontal flight shows dynamic instability, requiring the development of an automatic control system.