Regional air mobility startup Electra is teaming under a NASA contract with researchers at the University of Southern California (USC) to mature blown lift technologies for electric short-takeoff-and-landing (eSTOL) aircraft.
Blown lift aircraft use wing flaps to deflect the propeller slipstream, which increases lift, both by turning the propeller jet and by suppressing the separation of airflow over the wing and flaps. The use of distributed electric propulsion enhances the effect, as it allows the use of many small propellers that can spread the blown lift over the entire wing. The small jets they produce increase blowing effectiveness and allow the use of a mechanically simple, single-slotted flap.
Electra, which recently unveiled plans to develop a hybrid-electric eSTOL aircraft with blown lift, will work with a team led by Alejandra Uranga, an assistant professor of aerospace and engineering at USC’s Viterbi School of Engineering. Uranga was previously the technology lead at the Massachusetts Institute of Technology (MIT) for the D8, a “double-bubble” low-emissions, low-noise aircraft concept jointly studied with Aurora Flight Sciences, Pratt & Whitney and NASA.
“Even the best CFD [computational fluid dynamics]-based blown lift and distributed electric propulsion models today lack validation against full-scale vehicles for these unique configurations,” Uranga says. “Current computational methods can predict some limited blown lift flow fields in three dimensions, but the large eSTOL design space compared to conventional aircraft means that fast, trusted, low-order methods are needed to rapidly evaluate design choices. This contract will help us develop those methods.”
Electra, which was founded in 2020 by John Langford, the founder and former CEO of Aurora, aims to develop a family of eSTOL regional aircraft. The first of these will be designed to fly with a pilot and seven passengers up to 500 mi. with takeoff and landing distances of less than 150 ft. The aircraft will be able to take off and land at speeds of less than 30 mph and cruise at 200 mph. This will enable the fixed-gear aircraft to operate from rooftops, parking lots and football pitches, Electra says.
The company is building a subscale, 3,000-lb. demonstrator aircraft to validate powered-lift eSTOL using hybrid-electric propulsion. The test aircraft will carry two people, take off and land in distances of less than 150 ft. and use a 150-kW hybrid-electric turbogenerator to power eight electric motors and charge a custom battery system during flight. Electra declines to specify which engine will be used in the turbogenerator, saying only that it is an “existing commercial off-the-shelf turbine used in aerospace applications.”
Electra adds that the demonstrator, which is due to begin test flights later this year, is “similar to a Cessna 172/182 in size/weight but has significantly better takeoff performance.”
“We are also helping them to better define the trade-offs and optimize the aircraft,” Uranga adds. This work is part of a complementary Electra-funded project.
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