European research for climate-friendly aviation

"With our contributions to technology and demonstrator platforms in Clean Sky 2 and now in Clean Aviation, we are playing a key role in shaping climate-friendly air transport in Europe," says DLR Divisional Board Member for Aeronautics Markus Fischer. "We are particularly involved in evaluating and analysing new aeronautics technologies and their potential, where DLR is a European leader." As part of the technology evaluation, referred to as the Technology Evaluator for Clean Sky 2, the impact of technological developments in aeronautics on the environment and climate is being comprehensively analysed.

"The overall conditions of the complex research projects in Clean Sky 2 required close coordination with the French aeronautics research organisation ONERA," adds Ulrich Herrmann, the DLR Coordinator for Clean Aviation and Clean Sky 2. "We have achieved a new degree of trust-based cooperation."

DLR has been involved in a total of 27 projects within the context of Clean Sky 2, some of which are worthy of a special mention:

The thermoplastic fuselage of tomorrow

The Multifunctional Fuselage Demonstrator (MFFD) is eight metres long and has a diameter of four metres. This aircraft component is made of thermoplastic CFRP. The prototype was manufactured as part of the Clean Sky 2 programme at DLR in Augsburg in order to test the innovative material and the new technologies for their readiness for use. This unique eight-metre-long fuselage section reduces the weight of the fuselage by approximately one tonne compared to conventional aluminium construction. The reduced weight and higher efficiency of the structure will enable lower energy consumption by future aircraft and therefore lower carbon dioxide emissions.

Next-generation helicopter

It flies faster, further and more efficiently than previous helicopters. It is the Rapid And Cost-Effective Rotorcraft (RACER) demonstrator. Back in 2017, Airbus presented the concept for the new high-speed helicopter with a box-wing design, which could reach speeds of up to 400 kilometres per hour and is intended to offer the best compromise between safety, cost effectiveness and sustainability with a 20 percent reduction in emissions of carbon dioxide, nitrogen oxides and noise. As part of Clean Sky 2, DLR researchers have worked with ONERA to design and evaluate the configurations for the helicopter and have also analysed and demonstrated the acoustic properties of the configuration. The RACER is not only faster, it is also quieter.

From flight test to virtual certification

The trend towards ever-larger engines for the various thrust classes requires a broad research approach to the complex gas turbine system, from the fan at the inlet to the complete compressor system, the combustion unit, the turbines and the exhaust. In the Transition project, DLR has developed, adapted, built and operated a realistic turbine test rig as part of Clean Sky 2 together with Rolls-Royce. The improvement of the measurement systems has been developed and their implementation has been pursued. This allows the further industrial application of the test rig to be planned. As part of the 2ShaftCompressor project, DLR worked with MTU Aero Engines in the Clean Sky 2 programme to create and implement an aero-mechanical design for an integrated compressor system consisting of a low-pressure compressor, a short and lightweight transition duct and a high-pressure compressor. The ambitious design targets for reducing fuel consumption will be validated by operating this test stand. These challenging tasks will be continued on a bilateral basis after the completion of the Clean Sky 2 programme

Extraction system can reduce energy consumption and emissions

A key driver for increasing the efficiency of new aircraft is the reduction of drag. The aerodynamic drag on the load-bearing surfaces can be reduced by hybrid laminarisation. Although this has long been known and physically understood, practical implementation in series production has been hindered by the complexity of the systems to date. In the HLFC-WIN project, DLR, together with Airbus and other industrial partners, has designed a fully integrated, production-ready laminarisation system as part of Clean Sky 2. This has been implemented in a ground-based demonstrator. The demonstrator combines the extraction system, the replaceable, variably perforated titanium skin of the wing leading edge, as well as the aircraft's high-lift and de-icing systems. The operation of these systems has been simulated on the ground and even demonstrated in the event of a bird strike. Manufacturing and operating costs have been estimated and operation in a fleet of aircraft has been assessed as economically viable.

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