Uncrewed Systems Technology 048 | Kodiak Driver | 5G focus | Tiburon USV | Skypersonic Skycopter and Skyrover | CES 2023 | Limbach L 2400 DX and L 550 EFG | NXInnovation NX 100 Enviro | Solar power focus | Protegimus Protection

82 W e previously featured German aero engine manufacturer Limbach in UST 17 (February/March 2018). In that article, the company detailed its 7 kg L 275 EF two-stroke boxer twin that produces 18 kW and is aimed squarely at the kind of 25 kg MTOW UAV that has become the mainstay of aerial data and surveillance providers. In the 5 years since then, Limbach has continued to expand its customer base and operations in the UAV sector. The growth and evolution of that market has prompted Limbach to focus on subsystem areas in its r&d that are centred on torque-to-weight ratio. The reasoning lies in the customer base. The kinds of uncrewed aircraft their end-users are working on show a growing proportion of large UAV configurations. One (undisclosed) user even makes an airship that integrates three, four-stroke fuel engines to provide a distributed and vectored thrust system. That trend towards bigger, heavier andmore power-hungry UAVs explains Limbach’s r&d focus on increasing torque. As aircraft get bigger, they needmore lift, which tends tomean increasing either the size or number of blades on each prop, so that it generates extra lift without needing higher revs. But a bigger or heavier prop requiresmore force to rotate it – in essence, its enginemust generatemore torque. The company’s engineers have paid significant attention to two of its models in particular in this respect. One is the L 550 EFG, a modular expansion of the L 275 EF boxer twin (the focus of the article in our February/March 2018 issue). It is essentially the same two- stroke but has the crankcase and shaft extended backwards to accommodate an additional cylinder pairing, making it a four-cylinder boxer. Rory Jackson finds out how this company is developing engines with higher torque to match the growing demand for it in the UAV industry February/March 2023 | Uncrewed Systems Technology it up Torque Most of Limbach’s r&d over the past 5 years has gone into its four-stroke engines, such as the L 2400 DX, its most powerful solution (Images courtesy of Limbach)