Unmanned Systems Technology 023 I Milrem Multiscope I Wireless charging I Logistics insight I InterGeo, CUAV London & USA show reports I VideoRay Defender I OS Engines GR400U-FI I Ultrabeam Hydrographic Ultra-2 I IMUs

62 T he GF40U-FI is OS Engines’ first foray into the design and manufacture of an internal combustion engine for the burgeoning UAV market. This Japanese company specialises in precision engineering two- and four- stroke – and even rotary – engines for model applications. Its state-of-the-art facility produces a wide range of such units (see sidebar: Background) and it was thus well- equipped to move from the hobby market into the professional UAV world. Interestingly, going against contemporary trends, it chose to do so with a four- stroke of tiny displacement rather than a two-stroke equivalent. Although an equivalent two-stroke would be inherently simpler and smaller than this gasoline-fuelled 40 cc four- stroke single, the GF40U-FI is far less complex than a typical four-stroke. Importantly, it offers inherently less noise and vibration than a two-stroke of the same (2 kW or so) power output. Using fuel injection, pre-mix lubrication and air cooling developed in-house, it boasts impressive fuel consumption figures for a weight of only 3.32 kg including exhaust, electronics and generator. How does that compare to a two- stroke? Based on the lessons of a number of UAV two-strokes investigated by UST over the past 22 issues, it is fair to assume that an air-cooled, port injected, pre-mix lubricated single directly driving a propeller – and thus with an operating speed in the 3500-9000 rpm range – would require less than 35 cc to produce 2 kW. Thanks also to its simplicity, such a two-stroke engine can Ian Bamsey reports on this four-stroke UAV engine developed by a company better known for its model aero power plants Model of simplicity The GF40U-FI and associated electrical components. OS Engines develops its own ECU, generator and rectifier to optimise integration with the engine December/January 2019 | Unmanned Systems Technology