Electra Starts Proving Blown Lift eSTOL Technology

Electra.aero’s EL-2 eSTOL demonstrator completed its first series of test flights between April and May, according to details about the flights released by the company last week. (Image: Electra.aero)

Electra.aero has completed the first test flights of its piloted blown-lift hybrid-electric short takeoff and landing (eSTOL) demonstrator aircraft, EL-2. According to a May 29 announcement, the Northern Virginia startup completed a series of test flights between April and May at Manassas Regional Airport and Warrenton-Fauquier Airport.

Established in 2020, Electra is developing a nine-passenger hybrid electric eSTOL aircraft with a 500-mile range and cruising speed of 200 mph. The company's website describes the fixed wing eSTOL as targeting ultra-short takeoffs, while estimating the aircraft will need an area of just 300 x 100 feet for takeoffs and landings.

The eSTOL Electra is developing is different from other electric vertical takeoff and landing (eVTOL) aircraft designs because it uses an electric propulsion technique known as blown lift. Details released by Electra about the future production version of their eSTOL describes blown lift as a variation of the way propellers are typically used for thrust.

The technology  section of Electra's website further describes how blown lift contributes to their aircraft's aerodynamic performance. While wings generate lift in traditionally designed aircraft, the concept of blown lift uses a distributed electric propulsion system to cause the propellers to also blow significant amounts of air over large wing flaps that deflect the air downwards.

"By blowing air over the wing and large flaps with an array of electric motors, our eSTOL multiplies the amount of lift the wing makes at very slow speeds. With this technique, we can take off and land at speeds as slow as 35 mph, which only takes a few vehicle lengths to achieve," the company notes on its website. "The key is in the accelerated airflow forming a thick jet sheet coming off of the trailing edge of the wing, making the wing act virtually larger than it physically is. In climb and cruise, we reduce blowing and stow the flaps for ultra-efficient operations."

The website further describes how Electra's hybrid-electric propulsion system combines a turbogenerator with battery packs to power the aircraft's electric motors. Electra's configuration includes a hybrid electric mode, "battery re-charge" mode, and an all-electric mode. Across these three modes, operators can charge the battery in-flight via the turbogenerator or re-charge on the ground. The turbogenerator is compatible with sustainable aviation fuel.

The two-seater EL-2 eSTOL demonstrator aircraft that completed a series of test flights between April and May is designed to show the full-scale of the company's distributed electric propulsion system. The longest flight completed during the campaign lasted 1 hour and 43 minutes, and the aircraft reached an altitude of 6,500 feet.

"The aircraft took off in less than 170 feet and landed in under 114 feet," Electra notes in their press release. "It flew as slowly as 25 kts on takeoff and landing. Data and insights gained from the flight test program will inform the design of Electra’s 9-passenger commercial eSTOL aircraft, with entry into commercial service under FAA Part 23 regulations targeted for 2028."