Powered Wind Tunnel Test of DEP Blown Wing Aircraft

Electra is developing a hybrid-electric ultra-short takeoff and landing (eSTOL) aircraft for commercial advanced air mobility markets which also offers strong dual-use capabilities for defense missions. ElectraÆs commercial product aircraft leverages distributed electric propulsion and blown lift to efficiently transport seven to nine passengers (1,800 lbs of payload) up to 500 nautical miles with takeoff ground rolls of only 150 feet. Electra is planning a commercial entry into service date of 2026 under FAA Part 23 regulations. As a risk reduction milestone to reaching the product, Electra is currently building a 2-seat, 3,000-lb gross weight hybrid-electric STOL technology demonstrator aircraft (ōTD-2ö), which is expected to achieve first flight inĀ2023. A blown wing ¢ the strong aeropropulsive interaction between the slipstream of many electrically driven propellers and the aircraft wing / flap system ¢ is the key enabler of the ultra-STOL field performance described here (i.e., less than 300 feet). Blowing increases wing lift by effectively increasing flap size (the ōjet flapö effect) and increasing the stall angle of attack. This jet flap effect is particularly strong in distributed electric propulsion (DEP) aircraft because the propellers are relatively small. This blown wing concept enables low takeoff and landing speeds and augments low speed precision flight control of the aircraft; both of which contribute to the ability of eSTOL aircraft to operate from highly constrained ground footprints. To best leverage blown wing DEP while maintaining currently accepted safety margins, accurate modeling of the wing-propeller interactions is critical; as is understanding how key limiting parameters (e.g., the stall angle of attack) vary with blowing. Computational estimates can be made using CFD tools, but since DEP technology is new, there is no validation data for these complex flows with representative propeller sizes. Thus, the result accuracy is difficult to validate, especially for predicting flow separation. Electra proposes to conduct a wind tunnel test of a representative blown wing with distributed electric propulsion which will produce an aero database that can be used to validate innovative design tools of other novel electric aircraft concepts ¢ including eVTOL, eSTOL, eCTOL, or any aircraft configuration with significant interaction between distributed propellers and aerodynamics surfaces. It is planned as a powered half-aircraft model in a university-scale wind tunnel. This test will advance the current state of the art in understanding the opportunities and limits of powered high lift concepts.