This aircraft’s first flight reflects a difference in strategy compared to most competitors
By Paul Brinkmann|November 28, 2023
Electra’s Goldfinch starts its flight test program
This story was updated with additional context about Electra’s approach to safety and innovation.
When Electra’s demonstrator aircraft, the hybrid-electric EL-2 Goldfinch, took off on its inaugural flight, there was a notable difference compared to first flights by most other companies working on electrification of aircraft.
Lead test pilot Cody Allee climbed aboard the two-seat aircraft. Other companies in the field have tended to fly their aircraft remotely from the ground, often numerous times, before putting a pilot aboard.
Having a person on the flight from Manassas Regional Airport ruled out a development approach in which lots of technical risk would have been accepted.
“It’s a business decision — are you willing to crash it to learn whatever you’re trying to find out on that first flight?” J.P. Stewart, Electra’s vice president and general manager, tells me. “You can’t take that trade when you have a person on the airplane.”
Electra invested more time in modeling, simulation and ground testing to be confident about the odds of success and safety of the Nov. 11 flight and the vigorous flight program to come.
The first flight was purely electric. Electra did not reveal the duration or range. On the second flight, Nov. 19, the hybrid electric powertrain was engaged, demonstrating the range-enhancing capability for the planned production versions. This flight lasted 23 minutes, with Allee taking the aircraft to an altitude of 3,200 feet and covering 30 miles [48 kilometers] over the Washington, D.C., suburbs, according to Electra.
Allee might have kept the aircraft up longer on the second flight, but temperatures near freezing that day resulted in the lithium-ion batteries getting too cold for optimum operation, an effect that was expected based on the ambient temperature, Stewart says. The demonstrator doesn’t have the full thermal management system that future versions will have, he says, particularly the ability to regulate the coolant.
“We’ve shown that our computer modeling, and the whole design, match pretty well. We thought that was true, but the rubber meets the road in a test like this,” he says.
As far as Electra knows, the Nov. 19 flight marked the first by a hybrid-electric, short takeoff and landing aircraft. The company calls the planned production version an “ultra-short takeoff and landing” aircraft, because the intent is for it to takeoff in as little as 150 feet [45 meters]. Such a short takeoff would be made possible by the multiple rotors (EL-2 has eight) positioned across the wing. These rotors will accelerate the air before it reaches the leading edge, augmenting the lift produced by the wing’s shape and the plane’s forward motion, in a “blown-lift” technique.
Regarding power, electricity on the EL-2 sometimes flows only from the turbogenerator in its nose, sometimes only from the battery, or sometimes from both, Stewart says. When and how the right balance between these sources is achieved is something the company intends to study in the ongoing flight test program. The turbogenerator reflects Electra’s business strategy, which is to expand from the small EL-2 Goldfinch to an eight-passenger production version that could be flown up to 500 miles [800 kilometers] without having to be recharged. By contrast, the purely electric aircraft in development have so far topped out at about 240 kilometers.
The longer range means Electra’s aircraft could replace today’s long car trips, which Stewart says amount to “one very promising market segment.”
NASA’s canceled X-57 all-electric plane would have tested a version of the blown-lift technique in flight, but the agency decided to end the project earlier this year without flying, partly due to problems with its electric motors.
Stewart says the aircraft share only very basic similarities.
“We blow the wing all the time, using all the rotors,” he says, whereas NASA had intended to turn off and stow some of the rotors after takeoff.
There also will be significant changes from the EL-2 to the as yet unnamed production version. The demonstrator has cables and pullies connected directly to the flight control surfaces whereas the production model will send electronic commands from the cockpit through software to the control surfaces, meaning it will be fly-by-wire.
Flying with mechanically controlled surfaces has shown that “you don’t need fancy fly-by-wire systems in order to make the airplane safe and flyable,” Stewart adds.
Future test flights will “drive into every detail of stability control and of aircraft performance” while the first two flights were designed to demonstrate “basic functionality of all of the systems, mostly that the hybrid system moves power through it as it should, and that temperatures stay within the ranges that they should” despite changes in altitude and range and outside temperatures, Stewart says.
