Unmanned Systems Technology 027 l Hummingbird XRP l Gimbals l UAVs insight l AUVSI report part 2 l O’Neill Power Systems NorEaster l Kratos Defense ATMA l Performance Monitoring l Kongsberg Maritime Sounder

Hummingbird XRP | Dossier 20-25 lb of thrust purely because of the ‘dirtiness’ of the duct itself.” That dirtiness is caused by the presence of the engine and alternator along with their mounting arms, which consist of four carbon fibre tubes, and the heat sink that draws heat away from the inverters and power supplies, even though its fins align with the airflow through the duct. The rotors in the duct are directly controlled by the power management system rather than the autopilot. This arrangement ensures that the speed of the central duct fans is controlled by cooling requirements as the priority rather than thrust. That is important if, for example, the Hummingbird is being used in ‘perch and stare’ mode, sitting on a hill or building with the external rotors turned off and the sensors operating on battery power. As the batteries discharge, the power management unit senses when they need recharging, and the hybrid system starts doing that, he says. During that process, the power management unit starts the central ducted fans and regulates their cooling effect by controlling their speed until the batteries are recharged, while the mission continues. Generating 13 kW of three-phase electrical power and converting it from AC to DC through an inverter means there is a lot of heat to get rid of. Although the power electronics manufacturers offered their own heat sinks and cooling fans, Bishop wanted a more efficient and lighter solution, so he designed a heat sink shaped to conform to the inside curvature of the main duct. Mounted in the power bay – one of eight electronics bays arranged around the top of the aircraft – the 8 x 6 in aluminium alloy heat sink dissipates heat from the power electronics through fine fins that protrude through a window in the upper duct into the airflow. Moulds, lay-up and 3D printing Reference Technologies also chose an external supplier to build the airframe. Adam Works, formerly Adam Aircraft, has built corporate jet airframes from carbon fibre-reinforced plastic (CFRP). Early on, Bishop invested heavily in tooling to make CFRP parts. For the original Hummingbird, with its 24 in diameter duct, all the tooling for the structural components was CNC-machined from aluminium billet, with a price tag to match – he says the moulds for the main duct alone cost more than $100,000. When construction of this early version began in 2015, Adam Works used wet lay-up techniques, manually applying resin to dry carbon fibre cloth before putting the parts into vacuum bags and curing them in a 400-600 F oven. With such expensive tooling, changes to the design were consequently also very expensive. “We made major