Due to the ongoing efforts to improve efficiency of aircraft, Diamond Aircraft and Siemens AG are developing a hybrid-electric aircraft. There goal is for that aircraft to have better fuel performance and reduced noise impact compared to light piston airplanes.
Their current prototype is a modified Diamond DA40, originally a four seat single engine piston aircraft. The prototype has a one diesel engine mounted in the nose, used as a generator, and two electric motors. Each electric motor drives a propeller, mounted on both sides of the fuselage, forward of the wing. This gives it a funny, nose-heavy appearance. The diesel generator provides 110 kW of power and charges two 12kWh batteries mounted in the rear passenger compartment.
The project began in 2013, and the first test flight was October 31, 2018. The test flight was 20 minutes long and took place in Wiener Neustadt, Austria. During the flight, the aircraft performed its three modes of operation. The first is its charging mode; the generator is running and charges the batteries, while the batteries provide power to the electric motors. The second is generator only operation; the generator power goes directly to the motors, without any use of the batteries. The third is fully electric flight in which the aircraft is flown solely on power from the batteries and the generator is off. The prototype is able to cruise at 130 knots, fly for 30 minutes fully electric, and five hours with operation of the generator.
Hopefully these developments in electric aircraft will propel its usefulness in general and commercial aviation in the future.
https://www.flyingmag.com/diamond-da40-hybrid-electric-prototype-flies