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Making aircraft cleaner, more efficient, and better

Increased numbers of European flights will necessarily increase the environmental impact of air travel. The European Commission has been active in finding ways to minimise environmental impact since the Second Framework Programme, back in 1989.

Daniel Chiron chaired a meeting...
Making aircraft cleaner, more efficient, and better
Increased numbers of European flights will necessarily increase the environmental impact of air travel. The European Commission has been active in finding ways to minimise environmental impact since the Second Framework Programme, back in 1989.

Daniel Chiron chaired a meeting of some of the leading lights in increasing the efficiency and reducing the environmental impact of aircraft during the Aerodays 2006 exhibition and conference, held on 19-21 June, in Vienna. 'Environmental issues are of growing concern,' he said. 'And not just recently, but at the start of FP2 in 1989, projects addressed environmental issues. But now the number of issues has risen - the reduction in emissions of nitrogen oxide, carbon dioxide and noise. ACARE set out in its Vision 2020 report that there should be a 50 per cent reduction in CO2 and a reduction in noise by a factor of two,' he said.

Several projects target this problem but through a variety of means. Modern aircraft are of staggering complexity, but the essential pathways for minimising environmental impact rest on the efficiency of the engines, and therefore the fuel that drives them, and the efficiency of the aircraft itself.

While this statement may appear obvious, there are in reality thousands of modifications that can be made to an aircraft to improve its performance and efficiency. Unfortunately, some modifications will actually work to decrease performance in other areas, so that compromises must be made.

Nick Peacock, research and technology programme executive for Rolls Royce, a partner in many of the ongoing research projects said, 'Design is all about compromise. The [Airbus] A380 was said to have been 'compromised' to make it quieter. Is there a trade-off between emissions and noise? Absolutely, but we need to try and keep both at the lowest levels. We develop the technology - it is up to others to decide how to implement the technology,' he said.

Peacock's specific projects are in the economic design of jet engines. 'Since 1990, we have reduced the fuel needed in aircraft by 24 per cent. But, as air traffic is growing faster, the environmental impact is actually getting worse,' he said.

The ACARE Vision 2020 targets see drastic cuts in emissions and noise. 'These are brave goals that have been set. We realised that to achieve these types of efficiencies, we need a step-change in technology. The targets are really significant, and must be supported by national governments, the EU etc. But, we need rather more radical solutions, in engines, airframes and air traffic management,' he said.

Rolls Royce has developed a vision, with technologies looking forward to the next five, 10 and 20 years. Existing products are adapted to test possible improvements. The five-year, near term project, ANTLE, funded under Fifth Framework Programme (FP5), uses 19 partners to tweak individual parts of the engine for greater efficiencies. 'We rely heavily on Universities to do our thinking for us,' said Peacock. The ANTLE engine was fired successfully in 2005, and many of the technologies will filter down into the next generation engines.

The engine is the perhaps the most important aircraft feature, giving the aircraft sufficient speed to gain lift, and consuming kerosene. As Nick Peacock describes, the jet engine is in need of a step-change to achieve greater efficiencies. However, it is by no means the aircraft's only feature capable of giving greater efficiencies. Many of the aircraft's systems run on technology that may have been cutting-edge when developed, but are considered to be old or simply environmentally unsound today.

The Power Optimised Aircraft (POA) Technology Platform envisages an aeroplane which replaces much of the current hydraulic and other technology with electric-only technology. Lester Faleiro is Research and Technology Officer from Leibherr-Aerospace, a project coordinator, and explains the original idea, 'To reduce weight, which reduces consumption, and therefore fuel. We are changing systems to electrical systems, which are more efficient.'

'The aircraft runs systems using a mechanical gearbox or fuel power. We are trying to move all the systems over to electric systems, from fuel pumps, to electric bearings. Hydraulic and bearings oils are very environmentally unfriendly. The new Boeing 787 will be much more electric, and the Airbus A380 is also going beyond the current use,' he said.

While it is easy to think of an aircraft as a cohesive whole, when broken down into its separate systems, each with different technologies, the aircraft displays a bewildering variety of systems. With all of these systems replaced with electrical systems, the POA project can deliver economy savings. Objectives look to reduce peak non-propulsive power by 25 per cent, fuel consumption by 5 per cent, as well as reductions in peripheral costs, such as maintenance, production and increased reliability.

Ironically, all these objectives can already be achieved, but with one startling additional fact: 'The POA design is actually heavier than the traditional aircraft, but still more fuel efficient. It does not seem right, but holistically, it works,' said Faleiro. Car owners may query the safety of an all electric aircraft, given that electrical malfunctions on the road are so common. 'Safety is a driver, not a constraint,' he said. 'In traditional systems, for example the landing gear, there is triple redundancy - this means three failsafes used. With electrical systems we have more redundancy than before, and so more safety,' he said.

AWIATOR is another Technology Platform project funded under FP5, with 23 partners from the EU and Israel and due to complete in mid-2007. AWIATOR examines only the wing, and how energy savings can be made. The wing is the oldest and most adapted part of the aircraft, as it is what enables flight to take place. However, there are still a vast number of adjustments and improvements that can be made to this most essential of components.

Separate work programmes look at issues such as managing turbulence and vortices, load control, the design of specific wing parts to reduce both noise and fuel consumption, spoiler design, wing lengths and wingtips. Jens König from Airbus Deutschland is the project manager for interdisciplinary projects for AWIATOR. '45 flight test hours have been scheduled for between July and December 2006 on an Airbus A340. But, the A340 is already an old aircraft, but these technologies will be developed for future aircraft use,' he said.

Mr König pointed out that many of the work programmes have been SME-led, and the Technology Platform approach has drawn universities into the process, which will in turn further develop the chain of innovation. However, he also believes there could be a step-change needed, citing the Joint Technology Initiative CLEAN SKY as a possible starting point.

Moving to the noise the aircraft makes, the SILENCE(R) Technology Platform aims to develop technologies to reduce the absolute amount of noise the aircraft makes. 'We have been testing 35 large prototypes,' said Eugène Kors from Snecma, the project coordinator. 'Some solutions are applicable to different aircraft. We now have 14 different platforms identified, to see which ones fit each aircraft the best,' he said.

The project's aim is to reduce by 10 decibels (db) the noise aircraft make by 2016. The project focuses mainly on the landing gear, engines and lift devices. As in the ANTLE project, the number of tweaks and adjustments that can be made to an engine are numerous, and the engines would seem to be the most obvious source of noise. Not so, says Mr Kors, '50 per cent of the noise produced on take off and landing by the aircraft is due to the landing gear,' he said. Designs from several sub-groups have been tested in wind tunnels and on flying prototypes.

Many of the innovations, such as redesigned inlet valves, have already made noise reductions without any noticeable reduction in performance. Other technologies, such as single panels for the jet intake, have been adopted on newer aircraft, such as the A380. Prototypes have shown sound improvements from redesigned exhausts and exhaust plugs.

Active technologies, such as on the inlet fans show a great deal of promise, as do 'scarfed' inlets for engine housings. Active technologies play an additional role in the ARTIMA project, which uses 'smart' technologies to find new methods of improving performance and making diagnostic tests.

Gregorio Kawiecki is the head of research and development (R&D) at Gamesa Desarrollos Aeronáuticos. To explain how smart substances are used in aircraft, Mr Kawiecki painted a picture of what exactly smart substances are. 'A smart substance has special properties. It can change its shape in response to external fields, like magnetic or electric stimuli.'

Mr Kawiecki explained that common rock salt, as you would find in the kitchen, has the properties of a smart substance. 'If you pass an electric current through the substance, then it grows slightly. To pass the current through the other way, it shrinks. Now, imagine a brick of this smart substance attached to a table. If I make the brick expand or contract, it will cause the table to bend. Now imagine I pass the current through for just a second, the sudden expansion will cause a shock-wave.'

Both these properties have been found to be extremely useful in both making aircraft more efficient and in finding flaws in aircraft structures. If the smart material is attached to a part of the aircraft that vibrates, the material could be used to actively dampen the vibration. Because vibrations create inefficiency through drag or other effects, this alone could prove an energy-saver. 'We can produce a 10 per cent reduction in wing vibration through a piezo-electric device,' said an enthusiastic Mr Kawiecki.

The second property - the sudden shock - can be used to find imperfections in metal parts. Sensors can be arranged to find, in the same way as in sonar or radar, how the shockwave reflections behave. If there are imperfections in the reflections, then there are imperfections in the component. Mr Kawiecki explained that the damage detection technology has been shown to identify grades of imperfection.

In the longer term, these two uses of a very simple technology could be used to instantly detect any damage or aircraft flaw, both in construction and in flight, to make flying safer, and reduce vibrations and therefore increase fuel efficiency. The technology in ARTIMA was found to be ready and inexpensive - always a plus for new technologies. In their tests, Mr Kawiecki found that, 'the components used to make the shockwave cost as little as nine euros,' he said.

New developments in construction will also make components, especially larger components and panels, far easier to manufacture. The AGEFORM project, funded under FP5, is a process for moulding metal, especially aluminium-lithium alloys, with very high precision. Project coordinator from ALCAN, Frank Eberl explained that the vacuum process gave new hope for the metallurgic industry, as stronger and more flexible alloys are constantly in development, meaning that the metal aircraft have a good many miles left in it. The process developed could see drastic reductions in production and development time and therefore massive cost savings.

The ageforming process gives brings alloy moulding to a very high level of precision, but projects such as INCA have investigated how to find imperfections in apparently perfect pieces. A rare project, funded under FP5, the project sought partners in the US and Canada, 'but we wanted a European basis for this technology,' explained Dr Sönke Seebacher from Airbus, who coordinated the project. 'INCA is an SME-oriented project, to show technical results for new technical processes for both manufacturing and maintenance,' he said.

The team investigated thermography, shearography, new eddy current probes, x-rays, resonance techniques and data fusion, amongst other exotically-named processes. However, perhaps the key process is laser ultrasound, which can examine in great detail the integrity of curved objects. This component required input from the Canadian team that invented the process and US companies that already use the technique commercially.

Money from the Framework Programme can be used in a wide variety of sectors. Such is the complexity of the modern aeronautics industry that many projects can only be achieved collaboratively, requiring precise, often unique engineering expertise to achieve efficiencies. Such projects are the bread-and-butter of the Framework Programme - to use collaboration to find practical solutions to problems, and bring them to market. All of the schemes listed above aim to make air transport cheaper, lighter, more efficient, more comfortable, cleaner and more than any of these - safer, not just for the European aeronautics industry but for Europe's economy, and so for us all.

Source: CORDIS News attendance at 'Aerodays' event in Vienna, Austria

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