Development of the Aero Electric Sun Flyer solar-electric flight trainer continues, and the two-seat proof-of-concept prototype is on display this week at EAA AirVenture 2016 in Oshkosh, Wis. The all-composite airplane, which is powered by a 100-KW electric motor fed by LG lithium-ion batteries, is entering the next phase of ground and then flight testing, and it should fly in early fall. FAA certification in the primary category is expected in 2018, and plans are to obtain certification in additional countries.

“Five years ago we starting along this journey,” said Aero Electric CEO George Bye. The idea was to figure out how to revitalize general aviation using new technologies, and early on the company identified electric propulsion as a promising opportunity. Early tests involved an electric-powered Cessna 172, which was flown about 25 times. After initial flight testing of a German single-seat solar-electric design, Aero Electric developed the two-seat Sun Flyer as a technology platform ideally suited for the pilot training market. “Look at flight training, it’s such a critical area of general aviation,” Bye said. “Forecasts are for a huge requirement for new pilots.” Yet the fleet of training aircraft is aging and shrinking. 

The $249,000 Sun Flyer is designed for a maximum endurance of three hours, but for the training role will likely fly missions of about 1.3 to 1.5 hours. Recharging time for the airplane’s lithium-ion battery pack after a typical sortie should be 20 to 30 minutes using “supercharging” technology. Cost of energy for the Sun Flyer should be about $2 per flight hour, compared to the typical $50 per hour for gasoline for a piston-powered training airplane. The Sun Flyer will be equipped with photovoltaic cells on the wings, which will charge the batteries about 10 to 12 percent during flight and given enough time, fully while on the ground. A fleet of Sun Flyers could generate surplus electricity while parked during the day, allowing the operator to sell electricity to the grid at peak times, then the batteries could be charged at night when electricity costs go down. The prototype isn’t equipped with the solar cells. 

The Sun Flyer is equipped with an energy-available gauge, which will also predict available range. The batteries should last for three to five years, but as they are replaced, newer battery technology should result in improved performance, including longer duration and range. “Batteries are improving at about 10 percent per year,” Bye said. “We will see a vast expansion in utility. Four-seat and larger airplanes are coming because of these improvements in technology. Improvements and regular upgrades are part of the system of the Sun Flyer.”

Spartan College of Aeronautics has ordered 20 Sun Flyers, and the college will not only train pilots in the new airplane, but also teach mechanics how to maintain electric-powered aircraft. “We have agreed to collaborate to build a maintenance training program to help individuals service the Solar Flyer and similar electric aircraft as we roll through this revolution,” said Spartan president and CEO Peter Harris. Spartan currently operates 40 traditional training airplanes.