The founder of Bye Aerospace has written an IEEE Spectrum article about a 2-seat 3-hour trainer: “Cheaper, Lighter, Quieter: The Electrification of Flight Is at Hand”
I’m skeptical that this small company, founded in 2007, can do what has eluded Airbus and Pipistrel. But the editors of Spectrum are supposed to know stuff about electricity. So maybe this isn’t crazy.
It starts with a huge weight savings on the engine:
You rev the motor not with a throttle but a rheostat, and its high torque, available over a magnificently wide band of motor speeds, is conveyed to the propeller directly, with no power-sapping transmission. At 20 kilograms (45 pounds), the motor can be held in two hands, and it measures only 10 centimeters deep and 30 cm in diameter. An equivalent internal-combustion engine weighs about seven times as much and occupies some 120 by 90 by 90 cm.
Then there have been big improvements in batteries, supposedly, since 2007:
Bye Aerospace has worked with Panasonic and Dow Kokam; currently we use a battery pack composed of LG Chem’s 18650 lithium-ion batteries, so called because they’re 18 millimeters in diameter and 65 mm long, or a little larger than a standard AA battery. LG Chem’s cell has a record-breaking energy density of 260 watt-hours per kilogram, about 2.5 times as great as the batteries we had when we began working on electric aviation. Each cell also has a robust discharge capability, up to about 10 amperes. Our 330-kg battery pack easily allows normal flight, putting out a steady 18 to 25 kW and up to 80 kW during takeoff. The total energy storage capacity of the battery pack is 83 kWh.
A little fantasy doesn’t hurt:
Should something go wrong with the batteries in midflight, an alarm light flashes in the cockpit and the pilot can disconnect the batteries, either electronically or mechanically. If this happens, the pilot can then glide back to the airfield, which the plane will always be near, given that it is serving as a trainer.
This isn’t true even for pattern work at a typical busy training airport where the control tower might say “extend upwind two miles.”