Sun Flyer 2 On The Road To Certification
As Battery Technologies Evolve, George Bye Explains How Those Advances Positively Impact The Electric Aviation
By Anthony J. Liberatore
Aero-News Network Propwash – Issue 224/18 08.17.18
Sun Flyer 2 made quite a splash at AirVenture 2017, and Bye Aerospace was back at Oshkosh this year to provide an update on the electric-powered airplane.
Sun Flyer 2 was test flown on April 10th, 2018. George Bye of Bye Aerospace told the media at AirVenture that the prototype was based on the Aeron Lightning, but a great deal of further work has gone into designing a production aircraft that meets their specific design goals. This work, including preliminary design reviews and meetings with the FAA, has culminated in Bye Aerospace deciding to Certify the Sun Flyer 2 under the new FAR 23 Sub Part 1. They expect this certification to be completed in 2 years. The production aircraft will have a longer wingspan, added winglets, and L/D that is greater than 20. In regards to power, Bye noted the production motor will be supplied by Siemens, and a Siemens motor is currently being installed in the prototype. This motor, with a 90KW peak and a 70KW continuous rating, will have no traditional engine noise, no av-gas, and no C02 emissions. Additional benefits will be no vibration, which translates into more comfort, less fatigue for the instructor and student, as well as less fatigue on the aircraft’s structure. With a noise signature about 30db less than its reciprocating counterpart, the power management process will more akin to Turbine power management during the flight. Regarding performance, Bye Aerospace showed CFD models denoting airflow over the aircraft as the design team is designing both the wing washout and rudder to make spin entry extremely difficult for a non-spinning student experience. Bye also discussed anticipated performance numbers for the production Sun Flyer 2: a maximum range of 3.5 hrs, with a 135 kt cruising speed, and a 1000 fpm climb at a cost of $3 /hr of electricity. Bye also stated, “the performance capability of electric is surpassing conventional aircraft that are flying today, and we are almost on par with endurance of 3.5 hrs. That includes a VFR reserve that includes a battery depth of charge reserve.”
Bye discussed a host of topics in this briefing, and he even gave a shout out to his fantastic team members, including chief engineer Tom Bowen and Senior Counsel John Knudsen. Also discussed was the Sun Flyer 4, the four seat follow up to the Sun Flyer 2. This project is no secret to the press or to the general public, and Bye talked about some of its anticipated performance numbers including four hours of range and 150 kts cruising speed with a gross weight of 2700 lbs. One interesting characteristic Bye shared was that the 4 will have 800 lbs of payload utility which compares quite favorably to its piston powered brethren, especially when they are at full fuel load.
The charging time of the Sun Flyer 2 depends on a number of variables, the primary one being the charger type. With a Supercharger type electrical charger, the Sun flyer 2 can be charged in as little as 20 minutes. Other types of chargers can take two, four, or up to eight hours. About the EP Systems battery that the Sun Flyer is equipped with, Bye said, we flew the EP systems battery pack the that was designed for the NASA X-57’s systems project on our aircraft first and NASA is delighted. Bye believes that with the operating cost being 1/6th of a comparable piston powered aircraft, the revolution away from the internal combustion engine to electric has begun. It may be so disruptive that conventional powered aircraft can’t compete, especially in the training arena. When ANN asked Bye about the future of battery advancements, specifically the solid-state battery revolution that transportation industries are on the cusp of, Bye exclaimed “I Love it, I love it.” He referred again to the new FAR 23 Sub Part 1 certification, and revealed that both the Siemens motor and the EP Systems battery pack will be TSO’d. “What that means,” Bye continued, “is Siemens will maintain the motors, EP Systems will be maintaining the battery packs and under that TSO when a new battery system comes out, we literally trade the state of the art for the next generation so you go from a 3.5 hr airplane to a 4.5 hr or 5 hr airplane with that TSO approach, I love it.” Excited about this possibility of range enhancement, he concluded, that these new battery packs are coming up, “I love that, it makes our airplane better, but by having the TSO, my swap, the battery configuration and voltage to my system need to stay the same, but the cells get better! Awesome.”