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test rig should go wrong it would be hugely inconvenient to have to wait for a subcontractor’s engineer to arrive. We can just fabricate or retrieve a replacement part, and cycle the engine again in no time.” Guimbard adds, “Having our own test rigs has been critical for us to be able to cycle the engine in high over-temperature conditions, severe vibratory operations, and in all possible ways to comply with the EASA’s CS-E [Certification Specifications on Engines] requirements for test procedures.” The company is also working on a more powerful version of the turbo- generator, the TG-R90. This will weigh 64 kg without circuitry and other equipment, measure 1065 mm long and 412 mm wide, and produce a continuous output of 85 kW (up to a peak of 90 kW). As with Turbotech’s other systems, it will target a 3000-hour TBO and be able to run on any fuel, from kerosene to natural gas, biofuels and hydrogen. The TG-R90’s development began in early 2020. Ground tests of the first prototype are expected later this year, with flight tests starting in early 2021, in order to make the system commercially available in the autumn of 2022. “We anticipate very large electric aircraft being able to string multiple TG- R90s in parallel, to have flyable electric powerplants rated to 500 kW or more,” Fauvet says. “It’s simply not possible for companies to keep on building bigger and bigger electric aircraft they want using batteries alone; you’re looking at 20 t of batteries for the power that some of the designs out there are going to need,” he adds. “Turbo-generators are the missing link to the SWaP-optimised endurance needed for widespread eVTOL commuter vehicles, unmanned aerial refuelling tankers, autonomous air freight and so much more.” Turbotech TP-R90 and TG-R55 | Dossier The direct drive maximises the power from the generator; no gearbox is needed. It keeps the mechanics simple as well