88 The UAV industry offers many types of aircraft configurations, from the tilt-wing system featured in our Dufour Aerospace digest (page 48) to tilt-rotors, multi-rotors, fixed-wing/quadrotor hybrids, tail-sitters, catapult-launched systems and so on. Each comes with its own scaling and integration considerations for powertrains. For UAVs sized for small, two-stroke IC engines for example, a catapult-launched UAV’s engine will suffer far higher g-forces and mechanical loads than other types, whereas a multirotor will undergo minimal g-forces but need very high electrical output and active thermal management. Systems integrators can therefore struggle to find their optimum powertrain configuration. Ideal figures for parameters such as the engine’s displacement, maximum continuous power output and weight can change depending on factors such as end-users’ MTOWs, mission CONOPS and the particulars of their airframe. Naturally, those factors might also need to be altered for each customer, which could then alter the engine’s safety, fuel efficiency and many other performance parameters or integration considerations. That can mean choosing between running a sub-optimal engine or finding a new engine supplier. Such a choice could be avoided however through modularity and commonality of engine parts. In theory, if an engine manufacturer offered common or easily interchanged components, UAV manufacturers and technicians could quickly reconfigure powertrains for different missions, instead of switching to an entirely different engine. One UAV engine developer, Sky Power, has taken this approach, which has been applied to four of its engines – the SP-110, 170, 210 and 275. These share ancillary components and commonalities across their designs, such that any UAV using one of them could be swapped for one of the others. “If the end-user isn’t 100% sure of their UAV’s MTOW, or of their other physical or performance parameters, or the exact kinds of missions they’ll be flying, we tell them to ‘go one engine bigger’,” says Karsten Schudt of Sky Power. “Most customers just consider dry engine weight, rather than wet weight, and go a little too small. That means they could spend most flight hours operating between 90% and 100% of the engine’s load, so fuel consumption goes up and their TBO goes down. “Picking an engine with a higher dry Rory Jackson finds out how this company is offering engines with common components to suit different UAV types The common good A commonality of engine parts can benefit UAV integrators and engine manufacturers alike, as Sky Power offers with its SP-110, 170, 210 (pictured) and 275 (Images courtesy of Sky Power) October/November 2023 | Uncrewed Systems Technology
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