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The landing approach for fixed-wing small unmanned air vehicles (SUAVs) in complex environments such as urban canyons, wooded areas, or any other obscured terrain is challenging due to the limited distance available for conventional glide slope descents. Alternative approach methods, such as deep stall and spin techniques, are beneficial for such environments but are less conventional and would benefit from further qualitative and quantitative understanding to improve their implementation. Flight tests of such techniques, with a representative remotely piloted vehicle, have been carried out for this purpose and the results are presented in this paper. Trajectories and flight data for a range of approach techniques are presented and conclusions are drawn as to the potential benefits and issues of using such techniques for SUAV landings. In particular, the stability of the vehicle on entry to a deep stall was noticeably improved through the use of symmetric inboard flaps (crow brakes). Spiral descent profiles investigated, including spin descents, produced faster descent rates and further reduced landing space requirements. However, sufficient control authority was maintainable in a spiral stall descent, whereas it was compromised in a full spin.

In many applications it is advantageous to simulate the relative motion of two bodies in a laboratory environment. This permits the testing of sensors and systems critical to the safety of equipment and personnel with reduced risk, and facilitates stage-gate management of large projects to mitigate financial risks. The University of Bristol is collaborating with Cobham Mission Equipment to develop a large-scale facility for relative motion simulation, primarily for the purpose of testing automated air-to-air refuelling systems. The facility incorporates two 6DOF articulated robotic arms whose motion is dictated by real-time numerical simulations of the physical environment. Sensors on the robot-mounted equipment feed back into the numerical simulation to perform closed loop simulations with real hardware. This paper discusses the development of the facility and the different approaches considered for achieving real-time control of the robotic hardware. It then goes on to focus on aspects of the control topologies and motion optimisation which are used to maximise the performance of the facility. The current capabilities are demonstrated with respect to an aerial refuelling exercise and future challenges are explored.

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