66 With regulations in the EU aimed at curbing and eventually eliminating internal combustion engines in road vehicles, the future of European engines – and particularly the expertise and innovative capacity around them – is likely to lie not amidst the automotive industry but in the UAV industry. Two-strokes’ high power density make them ideal in the many military and commercial applications increasingly trusted to uncrewed aircraft. Moreover, the performance demands of customers in areas such as surveillance, rescue, reconnaissance and heavy industry has spurred huge advancements in their fuel efficiency, lifespan and vibration reduction. Hence, it is largely because of UAVs that there exists a range of small, high-quality two-strokes (outside of motorsport-type bikes) today, designed for running close to redline power for at least eight or nine hours, non-stop and at high altitude, without faults or failures. The Switzerland-based corporation of Suter Industries AG and CAE GmbH has been a particular success story in such engines since our last feature on them in 2020 (Issue 32). Some key areas of Suter’s technology and capabilities have changed dramatically from those we reported five years ago. Most glaringly, there are now four separate products making a family of Suter Industries engines, where only one existed in 2020, with all four being spark-ignited, boxer, twin two-strokes. The first engine, the TOA 288, is now well known and established in the wider UAV industry, being used as the power unit by successful UAV companies such as Dufour Aerospace (Issue 52) and Volansi (Issue 33). It is, as readers may recall, an air-cooled engine, weighing 8.9 kg and outputting 23.9 bhp (17.6 kW) at 6500 rpm – though in the six years since its launch, its TBO has been revised upwards through optimisations and endurance testing, from 250 hours to 500. Since productionising that engine, Suter has created the TOW 288, a watercooled version of the TOA 288, slightly heavier than its air-cooled predecessor at 10 kg, but producing 20 kW (27.2 hp) and 29.2 Nm at 6500 rpm, making it the higher power and torque solution. In an even bigger leap (in terms of the engineering undertaken), the company then created the HF TOA 288-SDI, an 8.6 kg, heavy fuel engine, based on the TOA 288 platform and still air-cooled. This engine runs on Jet-A1 as standard, with JP-5 and JP-8 also compatible, Rory Jackson visits this Swiss company at its headquarters to learn how it is building a new wave of spark-ignited, boxer, twin two-strokes for the UAV space Running the redline February/March 2025 | Uncrewed Systems Technology All four production engines are rating to service ceilings of 6100 m, and spark-ignited with capacitive discharge ignition systems and EFI
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