109 of the fuselage, with radiators for easy cooling via the air rush under the fuselage’s wings. These placements also enable unobstructed connection to the four motors: one sits at each of the box wing’s two upper corners, with the other two integrated roughly two-thirds of the way down the lower sides. “The last important part is our communications set-up, because you can buy the best radio in the world and get nothing out of it if your antenna setup is wrong,” Fainveits says. “You need both good quality and good placement of your antennas. So we install our comms antennas for C2 and payload data streaming under the fuselage, pointing downwards at an angle, while the GNSS antennas point upwards at an angle.” Composite matters These subsystems integrate across a body largely made from external fairings of fibreglass-Kevlar composite, sandwiching Herex honeycomb foam in places for an increased strength-toweight ratio. “We previously made the 007 mostly from carbon-Kevlar, but we found, through some users’ work in ISR that carbon may be too reflective for defence work – it’s very easily detected by any radio wave-based technology – so the 025 is fully radio-transparent,” Fainveits explains. “There’s some minimal use of carbon tubes, but not enough to present a significant radar signature.” The composite and Herex honeycomb combination was key to achieving FIXAR’s weight goals (not exceeding 25 kg for regulatory approval) without sacrificing structural strength. Before entering series production, the company built eight full-size 025 units, each made using a different supplier’s composites and manufacturing methods. These were then benchtested for mechanical load handling by methods such as installing masses across their wings and bodies to analyse for wing flexing, vibration and similar undesirable properties. “From those results, we shortlisted the best three units, flight-tested them, and the one that performed the best became the unit which we put into series production,” Fainveits says. “Its materials come from companies in Germany and the Czech Republic who we can’t name. That’s a trade secret for now, given how much time and work went into finding the best materials, as is the glue used for bonding the composite fairings together, since it was a real struggle finding one that gave the best balance between strength and flexibility, allowing the body to bend just a little bit to distribute the heavier loads. “But we’ve historically found the bestquality materials come from Germany, with the Czech suppliers’ quality arguably becoming even better now. We also tested some Chinese materials, and while their prices were great, we found the quality wasn’t quite there yet.” Optimising aerodynamics Most of the modelling and simulations for informing the first scale prototype were performed in Matlab Simulink, particularly to enable FIXAR’s preferred hardware in-the-loop approach for developing the software logic and aerodynamics in tandem with one another. These tasks were implemented in collaboration with the Riga Technical University, to which FIXAR is partnered. The company then advanced to windtunnel tests (at its labs) to develop and optimise the built models’ designs. “We didn’t use Simulink at all during the practical development phases; everything there was established, traditional methodology, like analysing smoke movements around the scale model in the wind tunnel to optimise aerodynamics, and we also used such approaches to calibrate the airspeed sensors,” Fainveits says. “We also built some specialised, automated test stands with tension sensors and servo motors to estimate the optimal AoA at which the rotors ought to be angled for this aircraft. From those, we measured lift and drag forces, with the servos changing the angles of the propulsion sets to see how each angle might change the aerodynamic efficiency.” Given the plethora of payload hard points across the 025’s airframe, one of the biggest challenges in making the 025 function effectively was ensuring that, no matter the selection and arrangement of payloads integrated, the aircraft would fly with a consistent level of stability and hence controllability. Uncrewed Systems Technology | February/March 2025 A Lidar from LightWare enables real-time surface-tracking and autonomous altitude adjustment to the MOCA (minimal obstacles clearance altitude) – key inputs for the 025’s adaptive autonomy in flight
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