Uncrewed Systems Technology 043 l Auve Tech Iseauto taxi l Charging focus l Advanced Navigation Hydrus l UGVs insight l MVVS 116 l Windracers ULTRA l CES 2022 show report l ECUs focus I Distant Imagery

84 Digest | Windracers ULTRA UAV families was avoided primarily because of their high purchase costs, expensive spare parts and short periods between scheduled maintenance. The engines selected for the ULTRA are Vanguards, from US supplier Briggs & Stratton. They are made in very high volumes and therefore benefit from the economics of mass production. They have excellent reliability, and include fuel injection and a sophisticated engine management system. Before being installed in the ULTRA though, a lot of modifications are made to them to reduce their mass and remove any unnecessary parts such as cooling fans and baffles. The engines include electric starters to enable remote shutdown and restart. This has safety benefits and allows fully automated remote operation. Each engine is equipped with an alternator to provide two independent sources of electric power. A sophisticated power management and isolation system allows continued operation should one of them fail. Even if the other alternator fails, the aircraft has enough battery capacity to allow more than an hour of continued operation. Flight control As outlined earlier, a ‘zero points of failure’ (ZPOF) philosophy is adhered to by the ULTRA design team, and this presented some considerable challenges regarding the avionics and flight control systems. High-end autopilot systems used in large civil aircraft manufacturers use triple-redundant, certified hardware and software, which provides very high integrity flight control. This architecture nevertheless has at least one inherent single point of failure in that it needs an ‘arbitrator’, which sits above the three redundant systems. The arbitrator’s function is to monitor the autopilot’s health and pass control to one of the back-up systems should anomalous behaviour be detected in the primary flight control system. Despite the sophistication of such certified flight control systems, however, some major vulnerabilities remain. For example, there have been several recent fatal incidents involving large civil passenger aircraft that were caused by the failure of flight control sensors such as air data and angle-of-incidence devices. Certified flight control systems are extremely complex, costly and uneconomic for UAV applications. The challenge facing the Windracers design team therefore was to find an affordable but nevertheless extremely robust flight control solution. An entirely new architecture has been developed by DA in response to this challenge. The architecture has now been patented, allowing ZPOF flight control systems to be realised. Unlike certified airliner flight control systems, the architecture is not only robust to flight control unit failures but also sensor failures. This has been achieved by developing the concept of ‘resources’ and a multiple redundant triple-layer ‘masterless’ flight control system that allows the user to ‘plug and play’ any number of sensors and flight controllers. April/May 2022 | Unmanned Systems Technology Load testing of the UAV’s primary structure An example of an actuate node, a core building block of the DA Masterless Architecture, providing up to two servo actuator outputs at 75 W/10 A each