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Hybrid-Electric Aircraft are Moving Swiftly from Concept to Commercial Reality

March 19, 2024

Several hybrid-electric aircraft are nearing commercial production, perhaps changing the economics of regional, short-haul, and air taxi services. Here's a look at what makes these unique, and eminently practical, aircraft tick.

Lee Goldberg

Related To: Electronic Design

What you’ll learn:

Hybrid-electric aircraft combine the best of electrical and conventional propulsion systems, enabling today's battery technologies to do most of the "heavy lifting" in smaller commercial aircraft.
Based on successful tests of prototypes, hybrid-electric aircraft promise to dramatically reduce the fuel consumption and operating costs of air taxi, air charter, and regional air carrier services.
Several manufacturers are expected to bring hybrid-electric passenger aircraft to market by 2025.

Though all-electric airliners may be a decade or more away, several hybrid-electric aircraft are nearing commercial production. And they may have a shot at changing the economics of regional, short-haul, and air taxi services.

These aircraft, whose electric propulsion units are powered primarily by batteries, also carry an onboard generator to provide supplemental power for takeoff and serve as inflight range extenders. The reduced battery weight makes operation feasible using today's storage technologies while reducing fuel consumption anywhere between 50% and 80%.

Two of the leaders in the commercialization of hybrid aircraft are Surf Air Mobility Inc. and Electra.aero Inc. (“Electra”). They have joined forces to use Electra’s hybrid-electric short takeoff and landing (eSTOL) to make affordable, sustainable, and easily accessible regional air travel to many of the United States' nearly 5,000 public use airports (Fig. 1).

1. After successful flights of an 80% scale prototype, Electra is tooling up for a pre-production version of its 9-passenger, 200-mph hybrid-electric aircraft with an anticipated range of 500 miles.

The 9-passenger, 200-mph production aircraft, based on a successfully tested prototype, will enable Surf Air to provide economical on-demand air mobility services. The 90-unit pre-order from Surf Air adds to 2,000+ aircraft pre-orders and options already placed by over 35 key operators.

Electra's eSTOL is designed to fill a gap in transportation between 50 to 500 miles, bringing air service to thousands of communities where air travel today isn’t a practical or affordable option. It does this using a combination of hybrid-electric propulsion and a "blown lift" short take-off and landing (STOL) system. The blown-lift system consists of series of electrically driven propellers distributed across an aircraft's wing with specialized flaps that enable it to capture the propwash and translate it into lift (Fig. 2).

2. A blown-lift system consists of a series of electrically driven propellers distributed across the wing. The cross section of the wing shown here illustrates the motor placement, as well as the different hinge locations for the inboard flap (left) and outboard aileron (right).

Because it uses a relatively conventional (simple) motor and wing structure to generate its lift, the system can deliver many of the advantages of vertical take-off (VTOL) systems at much higher efficiencies and a fraction of their cost and complexity.

An 80% scale, a technology demonstrator equipped with Electra's blown-lift STOL system has proven the basic feasibility of its technologies. As shown in the video above, the technology demonstrator took to the skies for the first time for an all-electric test flight on November 11, 2023, and a hybrid-electric flight launched on November 19. Based on initial tests of its prototype, Electra estimates its production craft will be able to safely operate from airfields as short as 300 feet.

Development of a prototype of the production aircraft is underway. The production prototype's batteries will be supplemented by a 600 kW electric turbogenerator propulsion system, manufactured by Safran Helicopter Engines, which will provide enhanced power for takeoff and serve as a range extender.

Surf Air Mobility has been operating a large fleet of conventional turboprop planes to deliver commuter aviation and air charter services for over 10 years and is now looking to electrify the majority of their fleet. In addition to Electra's aircraft, Surf's new fleet will include up to 150 units of an electrified version of Cessna's rugged Grand Caravan cargo plane, developed in partnership with Textron Aviation (Fig. 3).

3. Surf Air is working with Textron Aviation to produce up to 150 hybrid-electric versions of its Cessna Grand Caravan cargo/commuter workhorse.

Stay tuned to Electronic Design's Power technology channel for an upcoming feature that takes deep dive into the technologies behind hybrid-electric aircraft and a gives you close-up look at some of the aircraft expected to enter the market in the next two to three years.

Reference

Christopher B. Courtin, R. John Hansman, Mark Drela, “Flight Test Results of A Subscale Super-STOL Aircraft,” MIT International Center for Air Transportation (ICAT) January, 2020, Report No. ICAT-2020-01.

About the Author

Lee Goldberg | Contributing Editor

Lee Goldberg is a self-identified “Recovering Engineer,” Maker/Hacker, Green-Tech Maven, Aviator, Gadfly, and Geek Dad. He spent the first 18 years of his career helping design microprocessors, embedded systems, renewable energy applications, and the occasional interplanetary spacecraft. After trading his ‘scope and soldering iron for a keyboard and a second career as a tech journalist, he’s spent the next two decades at several print and online engineering publications.

Lee’s current focus is power electronics, especially the technologies involved with energy efficiency, energy management, and renewable energy. This dovetails with his coverage of sustainable technologies and various environmental and social issues within the engineering community that he began in 1996. Lee also covers 3D printers, open-source hardware, and other Maker/Hacker technologies.

Lee holds a BSEE in Electrical Engineering from Thomas Edison College, and participated in a colloquium on technology, society, and the environment at Goddard College’s Institute for Social Ecology. His book, “Green Electronics/Green Bottom Line - A Commonsense Guide To Environmentally Responsible Engineering and Management,” was published by Newnes Press.

Lee, his wife Catherine, and his daughter Anwyn currently reside in the outskirts of Princeton N.J., where they masquerade as a typical suburban family.

Lee also writes the regular PowerBites series.