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54 us that Sullivan has recently supplied its first hybrid system, and as such is still exploring the possibilities of hybrid power for multi-rotor craft. Power4Flight’s Jim Newton explained that his US company is working in a three-way partnership with Currawong Engineering (Australia-based) and Cobra Aero (US-based) to develop a range of UAV engines. The team has developed the B29i (also known as Corvid-29), a 29 cc fuel-injected engine manufactured by Currawong, with an advanced engine calibration system developed by Power4Flight and a specially designed and manufactured low-noise exhaust by Cobra Aero. Thirty engines have been fielded and integrated into three different airframes. Newton said they also provide a 35 cc and a 50 cc engine, and have plans to expand their product range further. Newton also introduced us to Cobra Aero’s Sean Hilbert, whose company is the lead developer of the A33-N, a 33 cc air-cooled single-cylinder which, unusually for its market, will feature twin spark plugs and a variable exhaust system. The system shows excellent fuel efficiency and noise output for loitering mode he said. The exhaust power valve is either fully opened for maximum power or partially closes the exhaust port for less noise and greater fuel efficiency, such as when the UAV is loitering as opposed to taking off or climbing. It is used in conjunction with an exhaust bypass valve that avoids the use of the main noise attenuation route in the exhaust when maximum power is required. The 2.1 kW A33-N features CNC machine-finished transfer ports and uses proven Currawong fuel injection using an electrically driven positive displacement piston fuel pump to deliver fuel – initially gasoline – at around 3 bar to a solenoid- type injector. Currawong’s Gavin Brett noted that this system overcomes the fuel delivery issues that affect many small two-strokes used in UAV applications. There are more than 1000 Currawong fuel systems in the field, he said. Brett brought to our attention the development of hybrid propulsion systems for UAVs, combining internal combustion (IC) and electric power. Currawong is due to launch its hybrid solution for multi-rotor craft and a parallel hybrid solution for fixed-wing craft later in 2016 (along with other variations on these June/July 2016 | Unmanned Systems Technology Power4Flight is partnering with two other companies to develop a UAV engine range Aeryon demonstrated its Aeryon Live platform using a SkyRanger