The European Union has launched a new program to develop new and disruptive technologies for commercial aircraft programs that could enter service around 2035. Called Clean Aviation, the program was officially launched on December 1 and builds on the success of Clean Sky 1 and 2. EU targets technology breakthroughs with Clean Aviation. Like Clean Sky, Clean Aviation is part of the EU’s Horizon Europe program and is a private-public partnership to get aviation to climate neutrality in 2050. The European Commission supported Clean Sky with €2.6 billion in funding, with leading partners (the key European aerospace companies) contributing with the same amount. For Clean Aviation, the EC contributes €1.7 billion and private partners €2.4 billion. The objectives of Clean Sky 2, which was launched in 2014, were to increase aircraft fuel efficiency and reduce carbon dioxide (CO2), nitrogen oxide (NOx) emissions, and noise levels by 20 to 30 percent. The program looked at large and regional aircraft as well as rotorcraft. It has resulted in a list of technology programs for aircraft and engine configurations, aerodynamics, cockpit systems, and cabin design, new structures and production systems, and non-propulsive energy and control systems. Graphic showing the different areas to which Clean Sky 2 research has contributed. (Clean Aviation) Since Clean Sky 2, the European Union has raised its targets on emissions. Its Flightpath 2050 roadmap, which is directly related to the EU’s Green Deal program announced this summer, now targets a 75 percent reduction of CO2 emissions by 2050, 90 percent of NOX emissions, and a 65 percent reduction in noise. Clean Aviation focusses on three areas Clean Aviation will look at three areas: hybrid-electric regional aircraft, ultra-efficient short- and medium-haul range aircraft, and at disruptive technologies that are needed for hydrogen-based airliners. For regional aircraft with a range up to 1.000 kilometers, the target is a 50 percent fuel-burn reduction and 90 percent lower emissions. Until 2025, this program will look at ‘building blocks’ and various integration options, followed by a second phase to mature the concepts for fitting into a demonstrator aircraft. Technology not immediately ready could be further developed in the 2030s. Energy options include hybrid-electric, 100 percent drop-in fuels like sustainable aviation fuels (SAFs) or synthetic fuels, as well as hydrogen. For ultra-efficient short- and medium-haul range aircraft, the focus is on ultra-efficient, thermal energy-based propulsion systems using SAFs and/or e-fuels, as this is the only way to meet the range requirements. The target here is to get at least 30 percent better energy efficiency and 86 percent lower emissions by 2035. Phase 1 will look at top-level aircraft requirements and includes conceptual design and preliminary design characteristics, leading to a preferred aircraft configuration. “This will be based on holistic multidisciplinary numerical simulations, research and development of critical components, materials and processes, technologies and the associated integrated ground tests, such as high-Reynolds-number (flight condition) wind tunnel tests, functional bench tests (including virtual testing), and full-scale sub-component integration tests and flight tests”, says Clean Aviation. This graphic shows the timeframe for the different steps needed for the development of a short to medium-haul airliner. (Clean Aviation) The design will be translated into a digital aircraft platform “and the best combinations of phase 1 technologies for the target concept aircraft at mission and fleet-level will be assessed via a complementary technology and concept aircraft evaluation platform.” In phase 2, the best candidate technologies are selected for integration in large-scale components and a large-scale flying demonstrator program “to validate the performance of key technologies for the targeted aircraft at realistic sizes under operational conditions.” The timeframe is aggressive, with a decision now until 2035. Hydrogen needs to overcome many challenges The Clean Aviation program for hydrogen will look at the several technological challenges that need to be overcome before this fuel can be fully exploited as the one with the lowest emissions and biggest climate benefits. The key problems, as described by AirInsight in August, include the storage of the super-cold (-253 Celsius) liquid hydrogen in tanks and the effect it has on aircraft integration and structure. “In this light, Clean Aviation aims to mature and demonstrate all relevant systems ready to be integrated into future aircraft: liquid hydrogen storage onboard, fuel distribution system, fuel cell-based propulsion drive trains or direct combustion of hydrogen into turboprop or turbofan engines. This comprises the selection and validation of the most suitable concepts, materials, and designs to provide the required performance, lifetime, costs, and safety. Beyond that, the integration of these systems into the aircraft platform requires a deep understanding of operational, maintenance, and certification aspects.” The program sets no deadline for the development of these technologies, nor does it make any reference at all to 2035, the year that Airbus hopes to have its first hydrogen-based airliner ready. Airbus CEO Guillaume Faury said in September that while its ZEROe hydrogen roadmap is aggressive, he thinks that the airframer should be able to develop the necessary technologies in the next five years and aim for a program launch in 2027, resulting in entry into service around 2035. Not technology could be the roadblock, but more likely the regulatory approval of a hydrogen aircraft and the availability of the fluid, Faury said. Part of Clean Aviation is the creation of an Impact Monitoring Framework that monitors the progress of the participants towards achieving the program’s goals. “The second level of impact evaluation and assessment will be implemented through collaborative research projects carried out under the supervision of the European Commission, with the aim to contribute to the definition of future EU aviation policies, to support the EU position in ICAO, and to communicate the impact of EU aviation research and relevant policies.” On a third level, the EU will keep an eye on how Clean Aviation contributes to the overall objectives of the Horizon Europe project.
