Today, there are around 3,000 commuter class aircraft in service worldwide, with only just over a dozen new 19-seaters being delivered each year in the civil sector in recent years. In its study, the DLR Institute of Airports and Transportation examined a configuration that, with a few modifications, is closely based on the 19-seater Do-228 and, in particular, Jetstream 31 aircraft models flying today. In their design, the researchers modified the landing gear nacelles, which were extended above the wings to accommodate quickly replaceable battery blocks. “This allows us to keep the weight of the comparatively heavy batteries exactly where it is most convenient on the aircraft during take-off and landing – directly above the landing gear. Empty batteries can thus be changed quickly and easily at an airport,” explains DLR project manager Wolfgang Grimme.
Limited by the weight of the batteries of 2 tons at a total take-off mass of 8.6 tons, the researchers assume in their concept a range of 200 kilometers, flown fully electrically. Depending on requirements, this can be extended to a range of more than 1000 kilometres using two range extenders in the form of a gas turbine that can be coupled and decoupled with the respective propeller. According to research by Bauhaus Luftfahrt, 56% of aircraft in this category worldwide typically fly distances of less than 200 kilometres and 83% fly less than 350 kilometres. “Therefore, a large part of the CO2 emissions in the field of commuter aircraft could already be avoided with the combination of fully electric flight and a comparatively small range extender,” explains Annika Paul of Bauhaus Luftfahrt.
The range extender is also decisive for the safety of such an electrified aircraft, since in an emergency, for example if a more distant alternative airport has to be approached in bad weather conditions, it provides the necessary additional range. The range extender thus also enables a longer fully electric flight, as the battery does not need to be used for reserves.
With future improvements in battery technology, a purely electric range of over 200 kilometres is also conceivable with the same battery weight. The development of new aircraft configurations, for example with numerous distributed electric propellers on the wings in combination with a modern, lighter aircraft design, would also extend the range of all-electric flight, although their development would be comparatively cost-intensive. In any case, fully electric flights of over 400 kilometres would be quite conceivable in the future.
In addition to analysing the technical possibilities, the researchers in the CoCoRe project also carried out a market analysis of possible fields of application for electric commuter aircraft. In addition to the widespread classical field of application as small feeder aircraft for remote regions with low passenger volumes, such as in Canada, the researchers also identified a need for medium-sized cities in Europe that have inadequate direct connections to large conurbations. For these cities, an economically viable regional air taxi service from smaller airports would be conceivable. Examples of such routes in Germany are Mannheim-Berlin, Bremen-Berlin or Münster-Leipzig. Economically challenging compared to conventional commuter aircraft for such scenarios are the short life span of about 1000 charging cycles of the batteries and the (still) comparatively low CO2 prices. If these factors increase in the future, the economic prospects of electric aircraft would also increase, according to the scientists’ considerations.