Vertiflite May/June 2021

Horizon Aircraft

draw air into the aluminum generator housing. The air’s path is designed to push it through a guide vane, cooling the stator and rotor, before it exits through the gaps between the enclosure’s fins. Turbotech is currently developing and testing this technology with 55 kW (TG-R55) and 90 kW (TG-R90) power-class generators. The TG-R55 turbogenerator weighs 121 lb (55 kg) and provides 55 kW of continuous power. The turbine, equipment and fuel make up a high-power-density electric machine that weighs 254 lb (115 kg), yet carries the same energy density as 2,200 lb (1,000 kg) of lithium-ion batteries. Used in conjunction with battery power, it can provide up to 10 times more range than an all-electric aircraft. It consumes an economical 4–6 gallons (15–22 liters) of Jet-A1 fuel per hour at cruise. Turbotech says its turbogenerator can burn Jet-A1, diesel or biofuels, and may also be adapted to run on hydrogen for emissions-free flight. Turbotech notes that several turbogenerators can be installed in parallel, enabling an increase in continuous power supply, with two TG-R90s providing 180 kW, three providing 270 kW, etc. “This architecture will allow [us] to improve safety thanks to redundancy, and optimize fuel consumption in running only the exact number of turbogenerators needed at their best power ratio,” Turbotech stated. Both TG-R55 and TG-R90 are running on test bench this year, and are available for sale as prototypes. Turbotech has also been testing its TP-R90, which is a regenerative turboprop engine. The turbine and heat exchanger are used for both the turbogenerator and the turboprop: for one it drives an electrical generator, for the other, it drives a gearbox and a propeller.

The Horizon X5 is planned to use the latest high-performance Corvette L5 engine. (Horizon) Many eVTOL designs rely on hybrid-propulsion as a result of the limited power density of current battery technology. Lindsay, Ontario, Canada-based Horizon Aircraft had previous experience with adapting the General Motors Corvette engine for use on a 1946 Republic Seabee seaplane. Horizon is planning to use the Corvette’s gasoline-powered LS V8 engine with a smaller battery system for extended range beyond what a pure electric configuration would allow. Horizon announced in February that it was being acquired by Texas-based Astro Aerospace to help fund its Cavorite X5 five-seat eVTOL (see “Electric VTOL News,” Vertiflite , March/April 2021). In March, Horizon announced that it had completed 200 test flights of the 1/6th-scale demonstrator.