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

21 developed a few decades ago that exhibits very low thermal creep thanks to the absence of grain boundaries. Following the high-pressure turbine is a three-stage power turbine, which maximises the engine’s high-altitude efficiency. Biskupski notes that the engine could theoretically run on just one turbine stage being driven by the combustor, but having more than one enables it to capture the power coming out of the combustion chamber more efficiently, and thus produce more thrust relative to the emissions. “We use almost all the energy that the air stores; any more turbines and of course we wouldn’t be light enough,” he adds. “The high-pressure and power turbines also counter-rotate relative to each other, in order to extract a little more momentum from the air without adding metal, before the air leaves via two exhaust pipes at the front. “Those exhaust pipes and ports might look like really simple metal parts, but they were really carefully optimised in some special software we wrote, to streamline the metal along how the air wants to flow, and to make sure there are no separations in airflow that could cause losses.” Additive manufacturing On both ends of the engine are gearboxes designed for reducing the turbine input speeds to manageable outputs for propellers at the front and accessories such as generators at the rear. Biskupski notes here that additive manufacturing systems were critical to minimising the weight of the gearboxes while still transmitting the 1300 shp from the output shaft to the propeller. Indeed, 3D-printed metal parts can be found throughout the Catalyst, having been used heavily to minimise weight and optimise complex geometries. The swirlers, for example, were printed to achieve extremely close fidelity with the fluid dynamics simulated in GE’s CAD. “And having invested in lots of metal laser sintering machines, we’re also able to print many swirlers at the same time, as well as other parts such as gearboxes, fuel heaters and so on,” Biskupski says. FADEC Engine performance and power are managed and adjusted in the FADEC software, which has been written primarily to provide a flying experience similar to that of comparatively simple turbofans. A power management system generates operational targets for the control system, which in turn modulates blade pitch and fuel injection according to those targets and the engine’s operating points. It takes inputs from up to 27 sensors for data on power and environmental factors, with four digital data buses per control channel. All sensors and buses are dual redundant, and self-diagnostics are performed using the same sensors. “The FADEC hardware and software are developed according to the most important industry standards – DO-254 and DO-178C, with DAL A for both,” Biskupski adds. Conclusion With the first test flight and much of the core r&d having been completed, Biskupski and his team have set their sights on final validation trials for military and commercial certifications. Biskupski notes that the engine’s 2450 hours of testing so far include triple-redline condition trials, as prescribed by the FAA, without any burn-throughs or other problems, validating the work and quality targeted by him and his colleagues. Additional data is to be collected that will inform GE Aviation as to how the engine might be modified and customised to suit slightly different airframes and missions between customers – a key value proposition for the ever-changing, high- end UAV market. Unmanned Systems Technology | December/January 2022 Janek Biskupski was born in Warsaw, and attended primary school there before moving to Budapest, Hungary. After completing secondary school education at ELTE Apaczai Csere Janos, he went to study at the Helsinki University of Technology, achieving a (distinction-level) MSc in Machine Design in 1998. For the next two years he worked as a researcher at the university, with a particular focus on designing and improving commercial CAD/CAE solutions. Then, after a few years as an r&d consultant at Nextrom Oy, providing insight on machine design (including 3D CAE) for bearings, pneumatics and other systems, he joined GE Aviation as an engineer in 2003. He went on to become senior engineer in 2010 and principal engineer in 2013, contributing to numerous key projects in various ways. These include overseeing key compressor tests for the GE9X – touted as the world’s largest and most powerful commercial jet engine, which resulted in what was then the highest pressure-ratio compressor in the aviation world – and leading the systems integration on a new two-stage power turbine in the company’s HMAX demonstrator engine. He now lives and works again in Warsaw, and as principal engineer was responsible for defining GE Aviation’s design and analysis methodologies from the company’s Airfoils Center of Excellence. As Catalyst systems leader he is responsible for the new European engine development programme. Janek Biskupski