210 cc. It is air-cooled and naturally aspirated, and lubricated on 2% twostroke oil pre-mixed with its fuel; its crankshaft runs in four ball bearings. The engine can also be fitted with a starter/ generator. Greenjets attended Xponential for the first time to exhibit and discuss its shrouded electric turbofan thrusters for UAV applications, in particular its first product the ipm5, which generates 5 kg of thrust. “If you look across the UAV industry and its electric propulsion systems, it’s effectively all e-motors and propellers, but problems with propellers include the safety concerns of their exposed blades, and the noise from them and their tip speeds,” commented Darren James. “Our propulsors are designed and optimised to be safe and quiet, as well as efficient. Fixed-pitch propellers are great for producing thrust at one condition, but our solution does so over a much wider speed range, with the duct, static structures and fan all optimised for thrust generation from take-off to cruise.” The ipm5 weighs 750 g and is 200 mm in diameter. The company was spun out from Blue Bear Systems Research in 2022, with its staff coming largely from Rolls-Royce, Cosworth and other organisations with extensive experience and capabilities in CFD and turbomachinery. “That experience went into the fine-tuning of geometric tolerances, materials and control of this solution, along with the larger products we have in development,” James added. We caught up with Sagetech to discuss its transponder systems and the progress of its TCAS and ACAS programmes. “The primary solutions we’re showcasing are our MXS civil transponder, which was TSO-authorised in May 2022, and our MX12B, which is the military variant of that transponder,” said Rudy Johnson. “The MX12B has the same hardware footprint as the MXS – 190 g – and is DoD AIMS-approved for Mode 5 IFF functionality. Such is its small size that the encryption device can’t fit inside the housing. Normally you’d put that inside the transponder enclosure, but the MX12B’s enclosure is about the same size as the encryption system, so instead it just connects to it via a cable harness.” The company also continues to build on its transponders to develop its collision avoidance and detect & avoid systems, in line with upcoming standards such as ACAS Xu for large fixed-wing systems, ACAS Xr for rotorcraft and ACAS SXu for small aircraft with MTOWs below 55 lb operating at altitudes of less than 500 ft. “Our ACAS Xu and Xr-compliant systems are now being test flown and evaluated by some key customers to help us iterate and evolve them into mature products,” Johnson added. In its pursuit to supply ever greater quantities and customised variations of its propellers, Mejzlik has adopted a new hot-pressing approach in its manufacturing of prepreg carbon composite props. “Until now, we used wet layups, but hot-pressing prepreg carbon gives us faster turnaround times and multiplies our production capacities,” explained Ambroz Both. “Where previously we could produce some hundreds of propellers per month, now we can make 2000 in the same time, and finish each batch in 2 weeks. “A hot press contains a mould which gives you the exact same geometric layout across every part of every blade. That, plus using prepared, prepreg material, ensures you get really good consistency between 83 Uncrewed Systems Technology | August/September 2023 Sagetech’s MXS transponder Mejzlik’s hot press machine in use
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