Aviation needs pilots, and training schools need an affordable way to offer training. The solution: The Sun Flyer from Aero Electric Aircraft Corp. (AEAC).
AEAC is planning to offer the first certified U.S.-sponsored, practical, all-electric airplane serving the aviation flight training markets. It unveiled the single-seat technology demonstrator for its next-generation solar-electric training aircraft at last year’s EAA AirVenture. It continues to perform initial R&D flight test operations while the first two-seat prototype Sun Flyer is being assembled.
AEAC was created primarily to bring the two-seat solar-electric Sun Flyer aircraft to the flight training market. AEAC intends to work with the FAA to fully certify the solar-electric aircraft. The company is targeting the replacement of tens of thousands of significantly aged legacy training aircraft by offering the Sun Flyer’s low operating cost, low aircraft unit cost, low noise and the complete elimination of aviation gasoline exhaust pollutants.
The AEAC management team includes Charlie Johnson, the former president of Cessna, and George Bye, CEO of Bye Aerospace and former leader of Javelin. The company is outsourcing engineering, marketing, legal and administration in order to maximize efficiencies and capitalize on the complementary talent from Bye Aero.
It has a strategic advisory council made up of experts from the industry including Pete Bunce, General Aviation Manufacturers Association (GAMA); Jack Pelton, Experimental Aircraft Association (EAA); and Austin Blue, president of Spectrum Aeronautical and CEO of SciFly.
“Our goal with Sun Flyer is to achieve lower operating costs and enhanced safety features for a flight training airplane by focusing on the benefits of solar-electric propulsion and durable composite construction,” Bye says. “We view Sun Flyer as a tremendous first step in bringing more efficient solar-electric propulsion to general aviation,” he claims.
Solar energy collection from solar cells affixed to the composite wing skin, produces electric power that is combined with Lithium-ion batteries to run the electric propulsion system, which directly drive the multi-blade composite propeller. Engine performance is controlled by an electronic control unit which ensures optimal use of the energy stored in the batteries. The electric design features reduced cooling drag compared to a conventionally powered aircraft and nose frontal area is reduced due to a smaller motor size and the required cooling intake. Propeller efficiency is improved due to the utilization of additional blade area when contrasted to an internal combustion engine aircraft.
Fuel cost for the solar electric Sun Flyer is $1 of electricity per flight hour, compared to $25 to $65 for leaded aviation fuel per flight hour for a typical trainer. Sun Flyer operating costs are projected to be $11 per flight hour – five times lower than the legacy trainer costs equipped with conventional internal combustion engines.
Four key design elements make the Sun Flyer’s low operating cost and performance possible:
• Light, efficient electric motor and controller are combined with Lithium-ion batteries. Battery packs can be swapped out with simple ease and efficiency;
• Supplemental energy through solar energy collection from extremely light weight solar cells affixed to the wing skin and re-gen propeller;
• Sleek, low drag fuselage with long-wing (high aspect ratio) advanced aerodynamics; and
• Very light, carbon composite aircraft structure.
The electric motor's throttle is very intuitive with one control lever. There is no need to adjust mixture richness and monitor cylinder head temperature as in aircraft with internal combustion engines. The throttle computer control unit is responsible for optimum motor operation, battery status, and the entire power system all necessary information is shown on digital display.
The unique Sun Flyer electric aircraft configuration is the result of multiple engineering team studies involving aerodynamics, aircraft characteristics, flight profiles, and available and adapted technologies. A solar electric propulsion system configuration includes:
Electric motor – With smaller motor size and little engine cooling area, there is more exposed propeller length for thrust. The electric motor efficiency (95 percent) combines with propeller efficiency (85 percent or more) to achieve higher propulsive efficiency over a combustion engine.
Energy storage unit (ESU) – An ESU is comprised of several battery packs. Within each pack are Lithium-ion batteries that are made up of many cells and a battery management unit (BMU). Electronics in the BMU monitor both safety and performance of individual cells. AEAC/Sun Flyer proposes to use multiple ESU systems to provide safety and redundancy.
Battery energy density has now improved to 275 Wh/Kg, and industry technical reports presented at the CAFÉ Foundation Electric Aircraft Symposium in early May 2015 suggested that 400 to 500 Wh/Kg will be produced soon.
Solar panels – The Sun Flyer’s wings will have thin film photo voltaic (TFPV), currently providing 24 percent and projected to be perhaps as much as 28 percent conversion efficiency and additional flight endurance. Industry experts are forecasting eventual conversion efficiencies of 35 percent and higher.
Regeneration – Electricity produced from solar TFPV depends on angle of the sun, time of year, and cloudiness. The high conversion efficiency of sunlight energy to electric energy will allow for a meaningful supplement to flight endurance.
The electric motors also serve as generators, so when the aircraft decelerates and/or descends the propeller can be used (much like a windmill) to convert energy to charge aircraft batteries. AEAC currently estimates 15 percent will be recovered for the Sun Flyer, per airport traffic pattern, through regeneration if the descent is flown at 60 knots and 400 feet per minute. Up to 25 percent may be recovered in higher speed and higher rates of descent. Recovery efficiency increases with aircraft speed.
The less complex electric system design makes it easier to maintain and repair. There are two moving parts vs. the hundreds of moving parts in an internal combustion engine.
“From a mechanics point of view, the amount of time spent on performing routine maintenance operations will be greatly diminished, given the reduced number of components involved with a solar-electric propulsion system,” Bye says.
The Flight Training Schools
Spartan College of Aeronautics and Technology has signed a training program development and deposit agreement to help develop a complete training system for Sun Flyer, and has reserved the first 20 Sun Flyer delivery positions. Independence Aviation has signed a deposit agreement for an early delivery position on a Sun Flyer training system.
“Our training school customers are to be commended for their innovative spirit and forward-thinking strategy,” Bye says.
“We are impressed by George Bye’s vision and welcome the opportunity to work with him and his team to explore a new training paradigm,” Peter H. Harris, CEO of Spartan College of Aeronautics and Technology, says. “It aligns perfectly with Spartan’s long history of innovation in education. The Sun Flyer is a natural ally in Spartan’s quest to offer the best and most accessible flight training program.”
“The Sun Flyer’s promise to reduce dramatically the costs of maintenance and fuel for training aircraft is a game changer,” says Ryan Goertzen, president of Spartan College of Aeronautics and Technology. “This more efficient aircraft will open up the market to a broader audience who will be able to afford to pursue their dream of becoming a professional pilot.”