eFlyer 2 completes first flight

AOPA first reported on the company's two-seat Sun Flyer prototype in 2016. The Sun Flyer 2, a modified light-sport aircraft used as proof of concept, completed its first flight in 2018. The program was renamed eFlyer in 2019. That year, Bye Aerospace reported nearly 300 orders for its electric aircraft and anticipated beginning eFlyer 2 deliveries in 2021. The company applied for an eFlyer 2 type certificate in 2018, and the FAA accepted its certification plans in 2023.

Flight schools make up the bulk of the company's customer base. About 80 percent of Bye Aerospace's paid, nonrefundable deposits have come from flight schools, CEO Rod Zastrow said, with some customers interested in purchasing a few aircraft and others considering much larger fleets. A typical training flight is expected to use half of the aircraft's available battery power, which would allow the airplane to be recharged in about 20 to 30 minutes.

Bye Aerospace is working with Electro.Aero, a company offering charging solutions, on a charging system that allows airplanes to connect to chargers plugged in at the edge of a ramp or hangar area rather than requiring equipment at every parking area. Special cables could reach aircraft parked as far as 100 feet away. One charger can charge two airplanes at once, and the company recommends one charger for every six airplanes.

Access to electricity is another challenge. Utility companies usually bring power only to the edge of an airport property, so airport operators or tenants must pay to extend it to hangars and aircraft parking areas. Bye said the cost of chargers and related equipment could be financed alongside aircraft purchases as capital expenses.

The eFlyer 2 is a clean-sheet design. Bye Aerospace learned from its earlier proof-of-concept aircraft that retrofitting an existing airframe came with weight and endurance limits because the aircraft had not been designed to carry large battery systems. The current eFlyer2 uses a lightweight composite structure, a 125-kilowatt (167-horsepower) electric motor, and a battery system with about 90 kilowatt-hours of capacity. It is also equipped with Garmin G500 TXi avionics.

Flight testing is still underway. The company expects the eFlyer 2 to perform most private, instrument, and commercial training flights, including practice-area work, maneuvers, and traffic-pattern operations. Zastrow said the company's projections call for about 1.5 to two hours of flight training time, plus a 30-minute VFR reserve. Those figures have not yet been demonstrated in flight testing.

The full scale eFlyer 2 prototype completed a six-minute test flight from Centennial Airport in Colorado on September 17 with Chief Test Pilot Elliot Seguin at the controls. Climb performance and power requirements were better than the company expected.

"We found ourselves with climb rates far exceeding what we thought we might have," Zastrow said. Power settings during the flight were also lower than the company had projected, and the aircraft had no maintenance write-ups. "We've got a lot more to learn, as all flight programs do," Zastrow said. "But we could not be off to a better start."

The company estimates operating costs at about $35 to $40 per flight hour, including electricity, maintenance, and battery replacements. Zastrow said many traditional training aircraft cost roughly $165 to $175 per hour, depending on fuel prices and other factors such as location. If those estimates hold up, operating costs could be up to 80 percent lower. "We used about $1 worth of electricity from just a pure energy cost perspective," Zastrow said.

Battery replacement would remain a recurring expense, but electric propulsion does not incur costs like oil changes and major engine overhauls.

Flight testing is also helping engineers refine the propeller. Finding the right propeller for an electric motor has proved more challenging than using one designed for a conventional trainer because the electric motors deliver power differently and are smaller than piston engines.

Bye is evaluating propeller sizes, blade angles, performance, and noise levels. The company expects the eFlyer 2 to be quieter than traditional piston trainers after takeoff, when power settings are reduced. Additional noise testing is planned, and propeller design could help lower noise levels even further.

The company has already begun certification work under FAR Part 23. Zastrow said the FAA previously agreed to the company's system-specific certification plans, functional hazard analyses, issue papers, and methods and means of compliance. They are now studying whether some of that work can be applied under the newer Part 22 framework associated with the Modernization of Special Airworthiness Certification rule. Bye is evaluating the newer pathway for potential time and cost savings while also considering international certification requirements. The Part 23 work could remain important for exporting the aircraft if other regulators do not adopt similar rules.

Engineers still need to evaluate the aircraft's endurance and high-altitude performance and continue making improvements before customer deliveries can begin. "We're going to do this safely, deliberately, and thoroughly test the aircraft," Zastrow said.