Clean Sky, the European Union’s ?1.6 billion ($1.9 billion) aeronautical research program, is aiming to have several demonstrators running on the ground or flying in 2014-2015. At the first Clean Sky conference, held June 18 in Brussels, project leaders said that after a slow start in 2008-2009 the joint technology initiative (JTI) is gathering speed.
The Clean Sky team is striving to offer timely solutions to make the next generation of aircraft more environmentally friendly. In their view, it would be a mistake to work on brilliant technologies that would be available too late. The public-private partnership is to end in 2017, by which time the European Commission and the industry will have each spent £800 million ($950 million), in cash and in kind, respectively.
The project is structured around six integrated technology demonstrators (ITDs) focused on the following topics:
• more efficient engines;
• a “smart” fixed-wing aircraft with reduced drag and advanced engine integration;
• regional aircraft;
• on-board systems and optimized flight paths; and
• ecological design for a lower environmental impact over the aircraft lifecycle.
In addition, there will be an “evaluator” phase to assess the impact of the technologies using simulation. The technologies are to be brought to at least technology readiness level six, which corresponds to demonstration in operational conditions.
500 Members Eventually
The JTI has gathered 78 member companies and organizations such as universities and research centers–12 have “leader” status and 64 are “associates.” The Clean Sky joint undertaking, now staffed with 20, plans to launch four calls for R&D proposals each year until 2012, which
is expected to bring more small- and medium-sized enterprises (SMEs) on board, with the total number of external partners eventually reaching 500. Collectively, the SMEs are supposed to contribute about 25 percent of the total work, said executive director Eric Dautriat.
In the field of engines, both Snecma Safran and Rolls-Royce are studying contra-rotating open rotor powerplants. Safran is working on a direct drive version, while Rolls-Royce is working on a geared engine. Still to be defined is how the choice will be made between the two options when the time comes to prepare an engine for flight-testing on an Airbus A340-600 test bed in 2015.
Meanwhile, one of the toughest challenges will be to cut noise. One concept involves minimizing the interaction between the two rows of blades possibly by altering the sizes of the blades. At the Clean Sky conference, Safran exhibited a mockup of an engine in a configuration in which the blades in the first row are longer than those in the second row.
Safran and Rolls-Royce representatives told AIN that they still do not understand all the potential risks with open rotors, adding that ground or flight-testing will likely reveal any problems.
The engineering teams do acknowledge that a lot has to be done in aircraft-engine integration with regard to acoustic, vibratory and aerodynamic aspects. Other engine demonstrators are being studied in the ITD phase of Clean Sky, including two- and three-shaft turbofans and a helicopter turboshaft.
Besides Safran and Rolls-Royce, other engine specialists–including MTU, Avio, ITP and Volvo Aero–are working on the sustainable and green engine (SAGE) ITD. The goals for this project are to cut carbon dioxide (CO2) emissions by 20 percent, nitrous oxides (NOx) by 60 percent and noise by 20 EPNdB.
Work in the smart fixed-wing aircraft ITD is being lead by Airbus and Saab. Their main aim is to cut wing drag by 25 percent for which they plan to use laminarity, either natural or induced through aspiration of the wing structure.
Plans call for a high-speed demonstration of this technology on an A340-300 in 2014. In parallel, either an Airbus A320 or a Dassault Falcon business jet is to be selected as a low-speed demonstrator test bed this year. According to Airbus research and technology expert Gareth Williams, this work will deal with the high-lift devices associated with the low-drag wing concept. The “smart wing structure concept” with a manufacturing solution is due to be ready in December 2011.
The “green regional aircraft” (GRC) ITD is led by Alenia and EADS-CASA. One major focus is on an all-electric architecture. Vito Perrupato, Alenia’s chief technical officer for the Clean Sky project, told AIN that if the environment control system (ECS) and flight controls, for example, were to change to being electrically driven, energy management would play a key role. To avoid the need for electric generators to be huge, the power management system would have to be able to disengage non-priority systems, such as the ECS, should power demand be at a temporary peak.
Tests are planned for electromechanic actuators (EMAs) that would replace hydraulic actuators for control surface power. EMAs will be tried at the component level, though, without being integrated in a full fly-by-wire and power-by-wire system. The GRC ITD’s targets are to cut CO2 emissions by 10 to 20 percent and noise by 10 dB. The envisioned configurations for this work are a 92-passenger turboprop and a 130-passenger aircraft powered by turbofans or open rotors.
Some ITDs are intended to have cross-over functions. In “Eco-design,” for example, research engineers will look for ways to reduce the scrap rates for raw materials in production.
The “technology evaluator” ITD will help to determine how effective Clean Sky’s technologies are. This simulation tool will be able to assess their impact at, for example, the airport level, comparing a given day of operations with and without these technologies. The first release of the technology evaluator is pegged for next year.
The Clean Sky conference took place more than two years after the JTI was born in February 2008. Explaining the delay, Dautriat said that more work to get to this point was necessary than had been anticipated. He told AIN that budgets are now in full swing and research activity is almost at cruise speed, with the first preliminary design reviews set to take place this year.