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Aviation Transport

and one sign of this is an initiative called Clean Sky, a joint venture between the Commission and the industry that started in 2008 and is aimed at improving the environmental perfor- mance of aircraft.

The seven-year, €1.6B scheme is one of the largest and most comprehensive research projects the EU has ever undertaken and aims to green the aviation sector in line with targets set by the Advisory Council for Aeronautics Research in Europe (ACARE).

These require the industry to cut CO2 emis- sions by 50%, NOx emissions by 80% and external noise by 50%.

Clean Sky is looking at every aspect of aircraft design and operation to play its part in reducing environmental impacts. The ini- tiative comprises six Integrated Technology Demonstrators (ITDs), some covering differ- ent types of aircraft and others dealing with issues common to the entire industry. There is also a Technology Evaluator, which will examine the work of each ITD and assess its impacts on the lifecycle and operations of individual aircraft, on airports and on the global air traffic system.

“The big opportunity for Clean Sky is to demonstrate new technologies, either on the ground or in flight,” says Axel Krein, senior vice-president or research and technology at Airbus. “Large-scale demonstrations provide us with the information needed to manage the risk to introduce new technologies into an aircraft – demonstrations in real operational conditions.”

There are separate ITDs dealing specifically with green regional aircraft, smart fixed-wing aircraft (which focuses on larger planes) and green rotorcraft or helicopters. The cross- cutting ITDs look at Sustainable and Green Engines (SAGE), Eco-Design and Systems for Green Operation.

Rolls-Royce and Safran are leading one of the most important projects, the engines ITD. SAGE is examining new technology involving open rotor engines, which could bring up to 30% cuts in emissions and fuel consump- tion by removing the nacelle – the cover- ing that surrounds the turbine blades on jet engines. Removing the nacelle reduces weight and drag, which automatically improves fuel efficiency, while engine efficiency is further boosted because larger fan diameters are pos- sible. “Further improvements in propulsive efficiency can be gained for open rotor engines by using a second row of propeller blades

The initiative comprises six Integrated Technology Demonstrators, some covering different types of aircraft and others dealing with issues common to the entire industry

rotating in opposition to the front row to remove the spin from the column of air to give a more direct thrust,” says Rolls-Royce, which is leading research on designs for the Counter- Rotating Open Rotor (CROR) engine. “In the current economical and environ- mental context, efficiency and operating cost of aero engines have become major issues for airlines and airframers as well as for engine manufacturers,” says Eric Dautriat, the Brussels-based head of Clean Sky. It is hoped that the technology, which would see engines fitted at the rear of the aircraft rather than under the wing, could be applied to the next generation of single-aisle commercial aircraft, as well as future large regional aircraft.

“Rear-mounted open-rotor engines offer unrivalled environmental performance for short-haul flying due to their higher propul- sive efficiency,” says easyJet, the UK budget airline. “There are significant difficulties in fixing such a large engine under a wing of a narrow-body aircraft, making rear-mounting of the engines the optimum solution.” But there is a lot to do before open rotor jet engines become a common sight, principally in aerodynamics, in reducing the amount of noise they make and working out the best way to integrate them into the body of the aircraft. There are two strands to the Smart Fixed- Wing Aircraft ITD – improvements in wing technology and research on how to integrate new power plants such as the open rotor engine onto the airframe. The creation of a new “laminar” wing is, along with the open rotor engine, one of Clean Sky’s flagship projects and aims to reduce drag by up to 10%, increase fuel efficiency and cut emis- sions. Swedish aerospace group Saab is one of the lead partners, while the UK’s GKN Aerospace is also involved but the key player in the project is Airbus, which will help to bring together all the different elements that go into the new wing technology. The new wing will look significantly different to cur- rent designs – it will be much smoother, less curved and have a thinner and shorter leading edge, with much less sweep to it.

It is not just outside the aircraft that changes will be made. Clean Sky is exploring a num- ber of less visible improvements as well. The Eco-Design demonstrator is re-examining the entire life cycle of an aircraft “from drawing board to dismantling” with a view to making it greener. Much of the material that goes into aircraft is already recyclable, but the Eco- Design project hopes to increase still further the proportion that can be reused. The aim is to reduce the amount of raw material, energy and water used to make aircraft and to ensure

that as much as possible of what does go into a new plane is renewable, recyclable and safe. In the Green Operations

ITD, work is

going on to cut energy use on board planes by introducing all-electrical aircraft equipment and cutting the amount of heat produced by on-board functions. This includes attempts to phase out hydraulic and brake fluids and to use more electronic “fly-by-wire” systems. Green Operations also encompasses meas-

ures to improve energy management during flights using ‘green missions’ that take advan- tage of advances in IT to create more efficient climb, cruise and descent profiles taking into account factors such as noise parameters and weather conditions. Such missions include more fuel efficient take-off and landing pro- cedures such as green landing trajectories that allow planes to coast in to airports on continu- ous descents, complemented by smart ground operations that cut fuel consumption by using ground vehicles to tow vehicles to the runway. All of this work ties in with another col- laboration between the industry and Brussels, known as the Single European Sky – and SESAR, the Single European Sky ATM (Air Traffic Management) Research programme. The Single European Sky is an effort to sim- plify the EU’s airspace, which is controlled by 27 national authorities that have been reluc- tant to cede control of their airspace. It is estimated that flights in Europe are on average 49km longer than they need to be because they have to follow national bor- ders. Given that every minute of flying time saved cuts fuel consumption by an average

of 62l and CO2 emissions by 160kg, reform- ing ATM could have a significant impact on the industry. After years of delay, progress is now being made – three of the nine common airspace blocks that will form the founda- tion stones of the Single European Sky have recently been put in place. Perhaps inevitably given the involvement of the European Commission, Clean Sky has attracted complaints that it is overly bureau- cratic, but Dautriat says there was simply a huge amount to organise in the early stages of the initiative. Two years in, the first fruits of Clean Sky are beginning to ripen, he says. “We are producing the first pieces of hardware and we have had some initial flight tests.” The key to the success of Clean Sky will not be individual breakthroughs, but how all of the outcomes of the ITDs are integrated into producing a more sustainable aviation indus- try. “Clean Sky is one project, rather than a fragmentation of individual pieces,” says Krein. “From the beginning, Clean Sky has been designed towards one common headline: The greening of the air transport system.”

Sustainable Business | February 2011 | 25

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