The German Aerospace Center, Deutsches Zentrum für Luft und Raumfahrt (DLR), and aerospace research institute Bauhaus Luftfahrt are studying how to make electric commuter aircraft practical. The Cooperation for Commuter Research (CoCoRe) project is using the example of a 19-seat hybrid-electric commuter aircraft capable of flying from Mannheim to Berlin to learn more about the economics and environmental impact of the technology.
Electric aircraft have a number of advantages over conventional ones. Not only are they zero-emission, but they are mechanically simpler and easier to maintain. However, they also suffer from relying on very heavy batteries that hold much less energy than a tank of aviation fuel, resulting in much lower payloads and shorter ranges.
As a result, engineers are looking at how to work within the limitations of the technology and find the best niche to exploit. CoCoRe's brief is to look at prop-drive, 19-seater, commuter-class aircraft like the Dornier Do 228 and the Jetstream 31. These tend to operate on short-range routes, which are more suited to electric propulsion.
"According to our research, 56 percent of 19-seaters worldwide fly distances of less than 200 km (125 mi) and 83 percent fly less than 350 km (217 mi). This usage pattern means that the combination of fully electric flight enhanced by range extenders will prevent the majority of carbon dioxide emissions caused by commuter aircraft," says Annika Paul of Bauhaus Luftfahrt.
The study assumed a hybrid-electric aircraft with various modifications, like batteries installed over the landing gear nacelles for better takeoff and landing characteristics as well as ease of swapping out the batteries. These batteries, weighing in at two tonnes, give the aircraft a takeoff weight of 8.6 tonnes and a 200-km range, which is extended to 1,000 km (620 mi) through the use of supplemental gas turbines that the researchers say are important for safety reasons as well as allowing for longer flights.
According to the researchers, the flight range can be extended to over 400 km (250 mi) as batteries become more efficient, airframes become lighter, and multi-propeller designs become more advanced.
From an economic point of view, the CoCoRe project says that such hybrid-electric aircraft could find a niche in places like Canada, which have routes in remote areas with few passengers, or between medium-sized European cities, including Mannheim to Berlin, Bremen to Berlin and Münster to Leipzig.
The researchers also say technology advances to increase the number of charge-discharge cycles from around 1,000 and increases in carbon dioxide prices would also improve the economic prospects for electric aircraft.
Source: DLR