DENVER – The developer of the four-seat “Sun Flyer 4” reports that 10 deposits have been received for the electric airplane unveiled at EAA AirVenture Oshkosh 2017.
According to officials with Aero Electric Aircraft Corp. (AEAC), Spartan College of Aeronautics and Technology is the first flight school to hold a deposit for a Sun Flyer 4.
Academy of Aviation, with training operations in Farmingdale, Long Island, and White Plains, Westchester County Airport, New York, took the final delivery position for the Sun Flyer 4 in the “Oshkosh special.”
“Academy of Aviation believes in innovation and embraces change to provide a superior product and experience,” said Chris Richards, president. “The Sun Flyer will advance this next-gen cost-effective capability to a whole new level — this changes everything.”
The two-seat Sun Flyer, “Sun Flyer 2,” will be the first FAA-certified all-electric trainer aircraft under FAR Part 23. The new four-seat IFR-capable aircraft will closely follow the certification of the two-seat version, according to company officials.
Features of the Sun Flyer 4 include a 46-inch cabin width, 38-foot wing span, ballistic parachute recovery system, and a gross weight of 2,700 pounds, with 800 pounds of payload for pilot and passengers. The projected flight endurance is four hours.
“At $5 of electricity per flight hour and under $20 operating cost per flight hour, Sun Flyer 4 will run completely on batteries, resulting in operating costs that are five times lower than costs associated with similar combustion-engine aircraft such as a Cessna 182 or Cirrus SR-20,” said George Bye, CEO of Aero Electric Aircraft Corp. (AEAC). “The Sun Flyer family of aircraft use transformative electric technology that provides disruptive affordability.”
Spartan College, which holds 25 deposits for production Sun Flyer 2s, will develop a complete training syllabus for the Sun Flyer family of aircraft, including a special course for airframe and powerplant (A&P) technicians to receive specialized electric maintenance training.
The company recently posted this video of a ground test:
There may be some confusion in the some recent images of 2-seat “Sun Flyer” developmental prototype and older archive images of the “E1”. Note the recent power-on ground test images and video of the Sun Flyer prototype. The yellow, single-seat electric “E1” was experimental airplane we flew previously also appears occasionally in internet image searches and old press releases. Under a contract, now concluded, the “E1” helped us advance our research in electric aviation. We also flew it as part ‘quiet flight’ research with the National Park Service – from which a nice video was created.
Goerge,
I might be interest in one of these, however it’s very difficult to get logical performance information. With the stated specifications above of 2,700 pounds providing 800 pounds of payload for pilot and passengers means that the airframe is 1900 pounds. Nothing significantly different than my nearly 50 year old Cessna Cardinal. 4 hours of endurance is suggested, but not specified at what performance level.
While the aerodynamics are likely to be on par with any modern day aircraft, hence be possible of 125 – 150 knot cruise speed at 135hp / 100kW, the obvious variable is the energy storage capacity and density (mass/weight) of the battery. Electric powered airplanes won’t reivent physics, so we can calculate all this.
To go with the claimed “4 hours” endurance using my cruising data of 100kW / 135hp @ 125-150 knots would require a 400kWh battery (about 11 to 12 gallons of 100LL energy equivalent). That’s what is required to achieve the speeds that we have become accustomed to with 50 year old designs.
Today’s best lithium cells are around 300 wH/kg, which equate to a battery with about 250-ish per kg.(about 115 wH/lb).
So, a 400kWh battery with state of the art cells and the best battery packing is about 3500 pounds of battery. More than the gross weight of the plane.
So, what I imagine is what which is so common with aircraft advancement… big promises that always fall short. So, let’s look at what could be done with the available weights published:
With a total unladen weight of 1900 pounds, the actual airframe has to weigh something. If it were all battery, it could be about 200kWh with the very best modern day cells. That’s only two hours of 100kW energy cruising anyway. I’ll give you the benefit of the doubt, and suggest that you can stuff 100-150kWh in there.
100kWh = 900 pounds
150kWh = 1300 pounds
So, 1 to 1.5 hours at cruise speed while consuming 100kW (180hp @ 75% = 135hp)
Will battery capacity get more dense? Of course, with a 15-30% increase expected by 2025. But, we are quickly approaching the theoretical maximum of lithium architecture, according to the experts who actually produce those cells.
Is a new breakthrough technology guaranteed in the next 10-15 years? Maybe; perhaps solid state batteries succeed.
But, here’s what I want to be clear about. Nobody is cruising for 4 hours at 135hp (125-150 knots) in a 1900 pound electric airplane. Nobody.
And, nobody wants to cruise around at:
100kWh capacity battery / 4 hours = 25kW (34hp)
150kWh capacity battery / 4 hours = 37.5kWh (50hp)
Can you clear up these concerns?
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The second concern is how to charge the battery. My business is Electric Vehicle charging equipment, and I’m happy to collaborate for free to advance the cause.
Thanks,
Tony Williams
Airline Transport Pilot
San Diego, California USA
Tony,
Sorry, I didn’t see your comment until today. I’m happy to address your questions.
The first point is that maximum flight endurance is based on best endurance speed. For the Sun Flyer 2, that speed is 60 knots and 3.5 hours. Roughly the same as a DA-20 or Cessna 152. At higher speeds the energy consumption is greater, (for conservatism we do not calculate the additional benefit of regenerative energy derived through the propeller on descent or deceleration which is automatic – just like a hybrid Prius, through our motor-controller software).
Electric aviation is focused on flight training, where cost benefits are realized and slower traffic pattern speeds are typical. Take a look at some of the pilot reports published by some of the reviewer after flying the Pipistrel “ALPHA electro”. We can validate their figures somewhat from our research spanning the last 5-7 years. We have engineered, researched and flown a Cessna 172 we converted to electric propulsion, and also the work we did with the “E1” single-seat electric propulsion research aircraft.
The Sun Flyer 2, which is to be fully certified under the new FAR 23 is a larger, heavier aircraft than the Pipistrel advanced ultralight (Canada), or light sport (Australia) aircraft. Sun Flyer 2 is also significantly ruggedized for the primary flight training role, (not a long, x-country cruiser). At 1,900 lbs gross weight and a 46 inch-wide cabin it is a substantial and capable trainer which is designed to spend over 1/2 its time training student in the airport traffic pattern. We are using 83 kW-hr of the very latest LG MJ1 battery cells. This provides excellent energy and performance and access to the entire primary flight training syllabus with all of the low-ops cost electric propulsion benefits. As you point out, as battery energy density improves, so will the Sun Flyer capability.
If you’re looking for some higher speed x-country capability, you might take a look at the “Sun Flyer 4” instead of the Sun Flyer 2. The Sun Flyer 4, designed with additional batteries and 4-place size, it is a much better comparison to what you’re used to. Electric also does well at higher cruise altitudes, which translates to improved true airspeed and cross-country range – even if batteries still limit the endurance when compared to the longer legs with a conventional avgas-fueled airplane. I agree with you, long range at high speeds will remain the domain of conventional GA aircraft for at least the near future.
Tom Bowen, our chief engineer (formerly Mooney chief engineer), and Charlie Johnson, our president, (formerly the Cessna president and COO) are pretty careful and conservative when it comes to product analysis and performance predictions. Charlie’s motto, and ours, is “Under promise and over deliver.”
For the latest updates see: http://www.SunFlyer.com