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40 systems such as an airliner full of people to level E for the lowest level. The top level for unmanned craft is level B, as the criticality required for flight electronics whose failure or malfunction could involve loss of life. The development of software that complies with DO-178C is a costly process, one where the development organisation has to be certified by regulators. That means using a DO-178C process for an autopilot for a small, inexpensive UAV is not cost-effective. However, if there are issues of reliability in a delivery service for example, or the UAV is carrying an expensive camera – which can cost well over $100,000 for a hyperspectral or high-resolution Lidar unit – in hard-to-reach locations, then the higher software integrity levels may become more relevant. Some programming languages do not have the tools available to certify systems to the higher levels though, so that needs to be considered in the definition of the autopilot design. What developers have also done is certify a highly configurable system so that any performance can be achieved by setting the right parameters on the autopilot. That allows the autopilot to be used on any kind of aircraft as well as sea and ground vehicles by using the same hardware and software. In this way, DO-178C compliance remains valid as there is no software change. It does however lead to a larger, more complex and more costly implementation compared with a smaller autopilot dedicated to a particular platform. There is a research project in the European Commission’s ITEA programme to look at ways of achieving DO-178C compliance for UAVs in a more cost-effective fashion than is the case for manned aircraft. Hardware For hardware, the reliability standard is DO-254. This defines the design assurance guidance for airborne electronic hardware, and follows the same five-stage certification process as DO-178C. December/January 2018 | Unmanned Systems Technology Focus | Autopilots The development platform for an autopilot (Courtesy of Callen-Lenz) Environmental testing of autopilot boards (Courtesy of Micropilot) Development of software that complies with DO-178C is a costly process, and involves certification by the regulators