ATR Details Hybrid-Electric Study Option For EVO

First announced in May 2022, few specifics of the EVO have been revealed until now. Designed to have 20% lower CO2 emissions and 20% lower maintenance costs than the current ATR 42/72 family, the EVO is intended to run on 100% sustainable aviation fuel.

After several rounds of studies into propulsion options for the advanced variant, a “mildly hybridized” propulsion system combining electric motors and new thermal engine appears to be the “most likely” solution, says Daniel Cuchet, ATR's SVP of engineering and chief technical officer.

Commenting at the 2024 Congress of the International Council of the Aeronautical Sciences, Cuchet says that, judged against the current ATR 72-600 baseline, hybrid-electric propulsion appears to offer the most practical near-term solution to the 4-megawatt total power requirement. Insufficient battery power rules out an all-electric option, while a hybrid hydrogen propulsion system remains a longer-term possibility.

The hybrid-electric system would be capable of matching the current aircraft’s 72-passenger load and optimum 200 nm range, while still delivering 20% lower CO2 emissions. A hybrid hydrogen system would likely see passenger capacity reduced to fewer than 60 but would see emissions per passenger cut by 40%.

The preliminary parallel hybrid architecture is outlined with two battery packs providing a combined 300-500 kW, equal to a 10-20% power split with the thermal engines, depending on the mission phase. The packs will power electric motors mechanically linked to the propeller gearboxes. “That’s what we are discussing depending on mission phase,” says Cuchet, noting, “the integration and modification of that is quite a challenge.”

Electric power will be used to supplement the turboprop engine for takeoff in hot and high conditions and climb, providing around 10% of the overall power. In normal operations, ATR envisions electrical energy providing up to 20% of the power for the top-of-climb segment and initial cruise, with recharging from the thermal engines potentially occurring later in the cruise and during descent, as well as on the ground between flights.

The future ATR propulsion study work is partially supported by research done by the French civil aviation research council CORAC, as well as through technology maturation efforts underway as part of the European Union’s Clean Aviation public-private partnership.