A feasibility study of micro air vehicles soaring tall buildings

Micro Air Vehicles (MAVs) are person-portable platforms, which due to their small size and corresponding manoeuvrability show great potential for surveillance in urban environments. Achieving useful endurance using on-board electric power plants remains challenging despite rapid advances in battery energy storage density. This paper examines experimentally the feasibility of using orographic ‘slope’ lift in urban built environments to enhance the operational capability of MAV platforms by increasing range and endurance. A representative building in an urban environment was selected for investigation. The flow-field velocity in the upwind region of a 1:100 scale model of this building was mapped in a wind-tunnel with a reproduced vertical velocity profile. The vertical velocity component was found to be in the order of 15%–50% of the mean wind velocity at building height. These results were compared with data measured on the full-size building and found to agree well. The sink-rate of a soaring MAV was measured through flight-testing and found to be less than the available vertical velocity component in the upstream flow field for average wind speeds which indicates that soaring is feasible, provided that controllability challenges in high-turbulence environments can be overcome.