Electra cites progress on short landings and takeoffs

Plans call for larger versions to rely on its 'blown lift' technology

This story has been updated to clarify the number of batteries in Electra’s demonstrator and planned production aircraft.

Pilot Cody Allee begins rolling the small yellow plane down a runway in Northern Virginia. At a distance of 50 meters and a speed of 75 kph, the aircraft leaps into the air, leaving the other 1,450 meters of the runway unused, as shown in a video of the May 16 test flight released by electric aircraft developer Electra.

This low-speed, short takeoff at Warrenton-Fauquier Airport demonstrated Electra’s blown-lift propulsion technique. Eight propellers accelerated air at the wing, where the portion flowing under it was deflected downward by the wing and its unusually large flaps to increase lift in an effect that Electra compares to thrust vectoring. The airflow over the wing stayed attached to the surface to ensure controllability.

The same video shows the two-seat demonstrator plane, EL-2 Goldfinch, landing in 46 meters, again with the aid of blown lift.

Through the ongoing tests, Electra wants to see just how little runway is needed, while proving the effectiveness of blown lift. The company says computer modeling shows that the effect should extend to larger versions of the aircraft, particularly a planned production model that would seat up to two pilots and nine passengers, which Electra says should also be able to take off and land within 46 meters.

The intent is for the aircraft fly into and from facilities too small for conventional airplanes, J.P. Stewart, Electra’s vice president and general manager, tells me. He compares the distance to the diameter of two adjacent helipads.

The company envisions developing a still-larger production version for civil and military applications: a 200-seat airliner.

“What really makes the short takeoffs and landings work is being able to fly slowly while maintaining control with the distributed electric propulsion on the wing,” Stewart says. “The idea, for example, is that the airplane may only be moving at 30 knots [55 kph], but the wing is actually seeing 60 knots [110 kph] of equivalent airspeed” because of the propellers blowing air at the wing.

Test flights also continue to provide information on the performance of the company’s hybrid-electric propulsion, which consists of eight motors and three power sources — a turbogenerator and two batteries. Plans call for the production version to have four batteries. The turbogenerator can either charge the batteries in flight or provide electricity directly to the motors. This configuration is designed to reduce fuel usage by 40% on a typical 160-kilometer flight, the company says.

Though not shown in the video, Allee has been flying the plane regularly to explore the limits of the design. The shortest takeoff was 46 meters, and the shortest landing distance was 35 meters.

“That is a very unusual thing for an airplane. Most airplanes would take off around 2,500 feet [760 meters],” Stewart says. “The plane is meeting our expectations, based on computer models, very closely. We’re very pleased.”

Another milestone achieved by the Goldfinch is flying very slowly without stalling. So far, the slowest speed in flight has been 24 knots [45 kph], whereas a typical Cessna 172 stall speed is about 40 knots [75 kph].

Stewart, a pilot, leads the test flight program at Electra. He’s been in a chase plane for the flights while Allee has been in Goldfinch’s cockpit.

The blown lift augments pressure effects on the wing — higher pressure on the bottom and lower on top. The air also is blown at the flaps and ailerons, which can be lowered to extend the width of the wing.

“The blown ailerons in particular are what provide additional controllability at low speed,” Stewart says.

Electra cites progress on short landings and takeoffs