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Electric Aircraft Advances Showcased at CAFE Symposium

By Peter S. Lert


The CAFE Foundation’s fourth annual Electric Aircraft Symposium in Rohnert Park, California, showed evidence that electric propulsion continues to evolve. Several hundred participants gathered for a series of discussions and presentations on the issues surrounding electric aircraft (both fixed-wing and rotor). The gathering also addressed the overall role of electric-powered vehicles in the future energy picture which may have implications ranging far beyond those of aircraft alone.

In terms of electric aircraft technology, the impression was that progress during the last year had been incremental rather than revolutionary. New electric motor designs offer significant improvements in efficiency and power-to-weight ratio. On the battery front, the possibility of using nanomaterials will allow better energy densities (the amount of power a battery can store for a given weight), although at present such materials remain very expensive. It may also be possible to use nanomaterials in aircraft structures, both to improve overall weight and strength and to allow dual-use materials for actually utilizing structural elements as batteries. Even so, it would appear that for the next few years, pure electric aircraft – albeit entirely viable from a technological standpoint – won’t be particularly practical in basic transportation. The fact remains that for pure electric power to replace the internal combustion engine, we still need an approximate 20-fold increase in battery energy density.

Turbo-diesel engine
Although shown here directly connected to a propeller, this tiny turbo-diesel engine packs enough power-to-weight to be a viable powerplant for a hybrid electric aircraft.

The picture remains considerably more promising, however, for the realm of recreational aviation. A light two-place aircraft with a range of, say, 100 nautical miles is entirely feasible and even potentially practical with current technology; given that much recreational flying occurs within 50 nautical miles of the home airfield, it makes the electric airplane an attractive alternative. In addition, hybrid power begins to look quite attractive, possibly in an aircraft with an internal combustion engine for takeoff and climb and an electric motor for low-powered cruise flight.

As can be expected, many such designs are at least somewhat sailplane-like, because cruise efficiency depends to a large extent on high-aspect ratio and low-span loading to minimize induced drag.

 ”Just a few years ago, electric model aircraft were considered an impractical novelty,” said Ron Wagner, EAA manager of field relations and a symposium attendee. “Today, some say that about 90 percent of new model aircraft are electric powered. As new technologies develop, the same could happen within the full-scale aviation community. We live in exciting times.

“There is a groundswell of activity in the area of electric flight. Interest is high and EAA will play an important role by keeping its members informed about what is going on.”

One of the most dynamic presentations, one that spoke specifically to the homebuilt community, was that of Eva Hakansson from KillaCycle, the world’s fastest electric motorcycle. In very plain language she showed us how we all have the ability to enter this new area by using existing, off-the-shelf technology and homebuilding skills.

Among the attendees were several of the entrants for next year’s CAFE Foundation Green Flight Challenge. This will be a flight efficiency competition for aircraft that can average at least 100 mph on a 200-mile flight while achieving greater than 200 passenger miles per gallon (or equivalent use of electricity). The prize for the aircraft with the best performance will be $1.5 million. This is the largest prize ever offered for a general aviation competition. A $150,000 prize for best score by a biofueled aircraft is also offered. Learn more here.

The presenters – it’s reassuring to know that the people on the leading edge of this blossoming technology are willing to share their knowledge.

EAA will again highlight electric aircraft advances at EAA AirVenture Oshkosh this year with daily showcase flights, evening flight demos, and displays and forums in AirVenture’s Aviation Learning Center. For more on electric aircraft innovation at AirVenture, click here.

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