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38 Focus | Autopilots accommodate also influences the specification of the ground infrastructure, so the definition of the autopilot is key to an increasingly wide range of functions. For example, if an aircraft has a ‘perching’ function – where it hovers above a location to make a delivery or for wirelessly charging its battery – then that has to be accommodated in the autopilot, as it will depend on the aerodynamics of the craft to allow it to perch on the infrastructure. The requirements placed on an autopilot are also growing. These days, most unmanned aircraft can only be used when there is a visual line of sight and they are well away from restricted airspace. The advent of autonomous UAVs though is leading to changes in airspace regulation, both in North America and Europe, that will see operation beyond visual line of sight (BVLOS). This also applies to sea craft, which will be allowed to operate autonomously BVLOS. Instead of different types of restricted and non-restricted airspace and certification based on weight, the use of UAVs in the UK and Europe is moving to a risk-based approach. That impacts directly on the functionality and design of the autopilot. An open certification would be for a small UAV operating within line of site, as now. Specific certification would apply to the same UAV operating with a professional camera over people and BVLOS. It would also apply to a larger UAV used for lifting materials on a building site, for example. Then full certification would apply, as now, to a large UAV operating over people where serious harm could come to them if there was a problem such as the craft falling out of the sky. The next generation of autopilots will have to include the situational awareness for these different modes of operation, and developers will have to be aware of the types of certification the autopilot will have to support. That means the design of the autopilot is changing in a number of areas. It has to handle much larger BVLOS distances, with secure and reliable comms. It also has to have a level of integrity and reliability that matches the likely use of the craft. That can vary from a low level of integrity for a small UAV operating in unrestricted airspace with a small payload and waypoint settings, to large craft with autonomous operation that will enter controlled airspace and need to interact with air traffic control. There are very different requirements for the reliability of the hardware and the integrity of the software, and each has its own technology and manufacturing implications. The type of comms technology that is integrated with the autopilot is also key. These range from a point-to-point radio link to a ground control station, which can have a limited range through a cellular wireless (4G) link, to a mobile phone where handover between base stations will be required, all the way to a 4G link to a remote server in the cloud controlled from anywhere in the world. Software integrity The DO-178C standard (also called ED12 in Europe) is for onboard critical software development. To ensure compliance, a software team has to follow strict procedures for software development, aided with some dedicated software. Compliance involves software development and documentation, from requirements definition to software validation and testing. As part of the quality assurance, dedicated hardware is used for extensively testing the software so that evidence of the software’s reliability can be generated.   DO-178C has different levels of software criticality, called the Design Assurance Level (DAL). These range from level A for the most critical December/January 2018 | Unmanned Systems Technology Veronte embeds an HSPA+ cellular comms module into its autopilot together with an eSim card (Courtesy of Embention)