62 for a European supercar manufacturer, offering better rigidity, a lighter crankshaft, and minimised vibration.” Elmer also has a ‘Kára’ design concept for a smaller turbocharged i4 drone engine for 80-150 hp output, weighing 35 kg all-up. The company’s engines have been spark-ignited to date, but Elmer is also closely familiar with compression ignition systems. Many of its high-level racing engines were built with maximum cylinder pressures equivalent to or exceeding that of diesel engines, and its team is capable of reviewing and customising appropriately for the necessary design differences in piston crowns, combustion chambers and thermal management systems. “The main technical advantage we have is that our billet design type is very cost-effective and quick to design,” Elmgren added. “As a core principle, we machine from billet for all our parts because that lets us use stronger aluminium alloys with very thin wall thicknesses, resulting in reduced weight and increased power and performance over cast components. It also allows very quick iterations and design changes, even during manufacturing.” Windracers displayed its ULTRA MK2, the latest and improved version of the fixed-wing aircraft we featured in Issue 43 (April/May 2022). “The most obvious change on the MK2 is its different engines: we’ve gone to a pair of Hirth two-stroke F23 engines, which give us a lot more power than our previous supplier,” said Stephen Krajewski. “While we’re watching developments with electric and hydrogen, we continued with combustion engines because they’re the practical choice for middle-mile air cargo based on cost and performance but also on carbon impact. “Windracers ULTRA is designed to work in remote locations in Africa and elsewhere where charging infrastructure is scarce, and batteries lack the energy density needed for long-range, heavy-lift flights. In these contexts, combustion offers a better balance of capability and operational sustainability – especially for humanitarian partners like Aviation Sans Frontières.” Meanwhile, the UAV’s tail boom has been redesigned as an inverted V-tail with increased outward extension, enabling more efficient weight with the same controllability (possibly more, pending further tests) as before. Its undercarriage has also been updated with larger wheels, springs and braking components for better overall robustness. “Technicians in remote locations need to be able to maintain and repair this UAV, so we’ve continued to opt for simplicity and standard parts, keeping and improving robustness of the tricycle undercarriage, as an example,” Krajewski added. “Overall though, these upgrades have increased the useful load capacity from 100 kg up to 150 kg, and we’ll also have some definite numbers in future as to by how much our 1000 km range has increased. “Carrying more means the UAV supports more use-cases, including using the drop doors to deliver freight by parachute, and we can integrate more sensing equipment onboard. The NORCE [Norwegian Arctic Survey] bought two Windracers ULTRA MK2s and are integrating an ice penetrating radar and antennas onboard both of them. We’re also working on permissions for a flight from the UK to Norway; that’ll be possibly the longest cross-border commercial UAV flight ever.” August/September 2025 | Uncrewed Systems Technology Elmer Aviation’s Thor engine is a 150 kg, 2000 hp, turbocharged, inline, four-cylinder four-stroke Windracers ULTRA MK2 features new engines from Hirth, an inverted V-tail and various other engineering improvements
RkJQdWJsaXNoZXIy MjI2Mzk4