Uncrewed Systems Technology 047 l Aergility ATLIS l AI focus l Clevon 1 UGV l Geospatial insight l Intergeo 2022 report l AUSA 2022 report I Infinity fuel cell l BeeX A.IKANBILIS l Propellers focus I Phoenix Wings Orca

104 The result is akin to a real-world FEA map, with heat maps of propellers showing where composites are thicker or thinner, smoother or twisted, and accurate to around 0.005 mm. The maps can also be produced for very small propellers as well as very large ones, from diameters of around 5 cm up to 5 m. If 3D scans do not go deep enough for some suppliers, ultrasound machines can be an alternative. They are costly but they can be of critical help in unearthing visual subsurface data about the integrity of props, revealing bubbles in the resin system or areas where the layers of fibre have not connected together optimally. For even deeper analysis of propeller quality, some suppliers are contracting companies who X-ray props and rotors for the general aviation market. Ultrasonic scans only penetrate until they meet some resistance, in the form of an air bubble or similar. X-rays on the other hand provide views all the way through a propeller, although there is the trade- off here in the higher expense of the machinery and the necessary protection systems around the testing chamber. And for anyone seeking a more practical approach to validating propellers’ longevities, some companies are investigating the robustness of available composite and protection materials using ballistics testing, for example by firing flurries of particles at props, both with and without nickel-cobalt edge protection. The tests indicate that nickel-cobalt protection can safeguard propellers’ structural integrities and aerodynamic profiles enough to theoretically multiply their lifespans by a factor of 14, while increasing their weights by only around 10%. In practical terms, most propellers available these days will last until their UAV platforms crash, but with the prominence of professional-grade craft across defence, government and commercial work, a real increase in prop lifetimes from around 100 hours to more than 1000 will be vital to ensuring uncrewed systems are viewed (and certified) as high-end industry tools and vehicles. Also, more industry-standard physical tests – such as compression, stress rupture, fatigue and stress-corrosion testing – can be applied to propellers, while laser or blue-light scanners can December/January 2023 | Uncrewed Systems Technology Protective sheaths can easily be gauged by comparing how they perform compared with unprotected blades or other sheaths in penetrant or strike tests (Courtesy of Fichtner & Schicht) Ultrasound and X-ray scans enable checking of materials integrities inside prop blades (Courtesy of Mejzlik)