The European Union (EU) aeronautic industry is a world leader in its sector, and contributes to the EU economy with more than 500000 jobs and with a turnover of close to 140 B€. Regarding the production of civil aircraft, EU companies have, right now, about the 40% of the global market of short/medium range aircrafts. The competition in this huge market from new countries is starting to increase and hence, in order to maintain (or if possible increase) that portion of the global sales, it is necessary to being leaders in innovation and in product performance. The objective of the Clean Sky 2 program is to build a platform to potentiate the innovation in this important industry for the EU. Inside the Clean Sky 2 program there are 6 different technical areas called, three Integrated Technology Demonstrators (ITD) and three Innovative Aircraft Demonstrator Platform (IADP); the present proposal is focused in the Large Passenger Aircraft (LPA) IADP.
Fuel consumption is probably the most important factor in the civil aircraft industry, and almost all the innovations are focused in this subject, always without compromising the security. Lower fuel consumption not only means lower operating cost of the airlines, but also lower CO2 emissions. The challenge proposed in this program is to address technologies that could allow achieving a 20% in specific fuel consumption; it is expected that these innovations could be introduced in the aircraft with market entry between 2025 and 2030.
One of the most promising technologies that could allow achieving the aforementioned goal is the Counter Rotatory Open Rotor (CROR) engine, which could offer an improvement in fuel consumption in the range of 15% - 20% compared to the actual engines. The best position for the CROR engines is in the aircraft rear-end; this is due to the large diameter of those engines, and also to provide additional advantages such noise cabin reduction and passenger comfort. The location of the engine at the rear of the fuselage is a very important engineering challenge, since its integration implies several important changes of the aircraft structure. Some examples are the large pylon that has to be designed to support the structure that could induce vibration and fatigue in the rear of the fuselage, the modification of all the systems because of the new location, the modification of the aircraft centre of gravity...etc.
In addition of all this new issues that have to be addressed, there is a very important one which is the tolerance to the engine failure. In particular, the topic of this project is focused in blade release or an Uncontained Engine Rotor Failure (UERF); under these circumstances high energy debris could impact to the fuselage, causing large structural damages that could compromise the aircraft structure safety. The current proposal is focused in the development and maturation of innovative shielding solutions to sustain high and low energy debris associated with the engine failure.
There are two overarching objectives in this project. The first one is to validate the maturity level of different technologies and structural solutions, to protect the rear-end structure from different impacts associated to engine failure. To this end both real and virtual impact tests of debris associated with the engine failure will be performed on both simple panels and full-scale representative aircraft structures.
The second objective of this project is to advance in the development of virtual testing methodologies. The economic impact of performing real experimental tests for the aircraft companies is very high, and virtual testing could diminish the number of experimental test (and hence its economic impact), which ideally could be limited to the ones that allow the aircraft certification. Right now the virtual testing technique is widely used in static problems, but its application under dynamic (impact for instance) conditions is limited. This project will allow improving the virtual testing for impact problems, increasing the competitiveness of the EU aircraft companies.
One of the most critical challenges of such innovative engines mounted on the rear fuselage is safety, in accordance with the certification requirements in the case of failure. Damage to the airframe from a failed blade could potentially be catastrophic. High energy debris can be released and impact the aircraft at high speed, challenge the structure integrity and the safe continuation of flight and landing, endangering passenger’s life. Safety of crew and passengers is of highest importance, which is reflected in strict regulations and requirements of the aviation authorities that need to be met by the aircraft manufacturer.
The aviation regulatory agents have been engaged in discussions with airframe and engine manufacturers concerning regulations that would apply to new technology fuel efficient “open-rotor” engines. Existing regulations for the engines and airframe did not envision features of these engines that include eliminating the fan blade containment systems and including two rows of counter-rotating blades.
Therefore, the feasibility of using aircraft fuselage shielding needed to be investigated and this project deals in part with this lack of documentation regarding to certification specifications, acceptable means of compliance and guidance material (for use in the certification process).
All experience gained during the tasks carried out in the project will support the definition of an aeronautical product testing framework as part of the validation and certification process of the development of new technologies resulting from the integration of the advanced new engines and propulsion concepts, such as CROR, in new eco-efficient aircraft generation
