Issue 41 Unmanned Systems Technology December/January 2022 PteroDynamics X-P4 l Sense & avoid l 4Front Robotics Cricket l Autonomous transport l NWFC-1500 fuel cell l DroneX report l OceanScout I Composites I DSEI 2021 report

36 T here is increasing acknowledgement in the industry that implementing sense & avoid (SAA) systems for unmanned aircraft requires an ecosystem rather than a point technology. There is no ‘silver bullet’ solution for SAA, and its implementation depends on the specifics of the operation and the environment. The SAA system in an aircraft – whether it is optical via a camera sensor, radar or Lidar, or a radio signal beacon such as ADS-B – increasingly has to be integrated with a local air traffic management (ATM) system, which needs a reliable radio link. The increasing use of UAVs for local delivery services is driving the requirement for BVLOS operation, where SAA is essential. But that highlights the role of the local environment for SAA systems, as the delivery services might be required to operate in particular, predefined corridors of airspace. Other UAVs might need to operate in general but restricted airspace. Airspace is also defined by its type, depending on where it is and its function. Control zones are a controlled airspace extending upwards from the surface of the Earth to a specified limit. Control areas are above controlled areas and offer protection for aircraft entering and leaving airports. Airways meanwhile provide connections between control areas and across national boundaries. Prohibited, restricted and danger areas are used when it is also necessary to warn or restrict aircraft from certain areas for safety reasons, and these can be permanent or temporary. Temporary restrictions are a major problem for SAA systems. While they should be identified and included in a flight plan, there may be situations where other aircraft do not follow an expected path in order to avoid such zones and so increase the risk of a collision. There are also various categories that need to be considered in SAA implementations: • Cooperative aircraft are any other airspace user who is able to provide, either actively or upon interrogation, their position, speed, altitude and heading as a minimum, but may also include their planned route and destination • Non-cooperative aircraft are any other airspace user that is not a cooperative aircraft • There can be obstacles that are either man made or natural, and there is the terrain, including the local sea level where appropriate • Weather can also affect the safe operation of the aircraft. Many sensors have been developed over the years to support SAA in cooperative aircraft, but these have had Advances in sense & avoid imaging sensors and algorithms have yet to make them suitable for small UAVs, prompting a shift to ground-based systems. Nick Flaherty reports Preparing the ground December/January 2022 | Unmanned Systems Technology Sense & avoid definitions (Courtesy of the Civil Aviation Authority)