Aircraft wings that change their shape in flight can help to protect the environment

Aircraft wings that change their shape in flight can help to protect the environment. Simulation of a flex module. Credit: © Fraunhofer IFAM

A top priority for any airline is to conserve as much fuel as possible -- and this helps to protect the environment. The EU project SARISTU aims to reduce kerosene consumption by six percent, and integrating flexible landing devices into aircraft wings is one step towards that target. Researchers will be showcasing this concept alongside other prototypes at the ILA Berlin Air Show from May 20-25.

Airport congestion has reached staggering levels as some 2.2 billion people a year take to the skies for business or pleasure. As their numbers grow and more jets add to pollution in the atmosphere, the drawbacks to the popularity of flying become obvious. This has encouraged airlines, aircraft manufacturers and researchers to pull together to reduce airliners' kerosene consumption and contribute to protecting the environment. One effort in this direction is the EU's SARISTU project, short for Smart Intelligent Aircraft Structures.

Landing flaps that change their shape

While birds are able to position their feathers to suit the airflow, aircraft wing components have so far only been rigid. As the name suggests, landing flaps at the trailing edge of the wing are extended for landing. This flap, too, is rigid, its movement being limited to rotation around an axis. This is set to change in the SARISTU project. "Landing flaps should one day be able to adjust to the air flow and so enhance the aerodynamics of the aircraft," explains Martin Schüller, researcher at the Fraunhofer Institute for Electronic Nano Systems ENAS in Chemnitz. A mechanism that alters the landing flap's shape to dynamically accommodate the airflow has already been developed by the consortium partners. Algorithms to control the required shape modifications in flight were programmed by ENAS, in collaboration with colleagues from the Italian Aerospace Research Center (CIRA) and the University of Naples.

The mechanism that allows the landing flap to change shape can only function if the skin of the landing flap can be stretched as it moves, a problem tackled by researchers from the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Bremen. "We've come up with a silicon skin with alternate rigid and soft zones," reveals Andreas Lühring from Fraunhofer IFAM. "There are five hard and three soft zones, enclosed within a silicon skin cover extending over the top."

The mechanism sits underneath the soft zones, the areas that are most distended. While the novel design is noteworthy, it is the material itself that stands out, since the flexible parts are made of elastomeric foam that retain their elasticity even at temperatures ranging from minus 55 to 80 degrees Celsius.

Four 90-centimeter-long prototypes -- two of which feature skin segments -- are already undergoing testing. Does the mechanism work? Are the forces being transferred correctly? These are questions for upcoming tests in the wind tunnel. Scientists will be showcasing the prototype at the ILA Berlin Air Show from May 20 -- 25.

Maneuverable wingtips

A single improvement won't be enough to cut kerosene consumption by six percent. Since a variety of measures are needed, scientists from Fraunhofer IFAM are participating in a second subproject focusing on the wingtip. Here the SARISTU consortium has developed a tab that forms part of the wing tip and changes shape during flight to keep air resistance as low as possible. Any gap between the flap and the fixed aircraft wing would cancel out any positive effect. "This led us to develop an elastic connecting element, and this work already covers everything from the chemical makeup to the process technology and manufacture of the component," says Lühring. Like the landing tab, this component retains its elasticity at temperatures ranging from minus 55 to 80 degrees Celsius, and it easily copes with the high wind speeds involved. Researchers will be showcasing the prototype at the ILA Berlin Air Show.

Funding

This project has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 284562.

Source: Fraunhofer-Gesellschaft

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The Composite plane life cycle assessment shows lighter planes are the future

Boeing Dreamliner 787. Credit: Image courtesy of University of Sheffield

A global fleet of composite planes could reduce carbon emissions by up to 15 per cent, but the lighter planes alone will not enable the aviation industry to meet its emissions targets, according to new research.

The study, by the Universities of Sheffield, Cambridge and University College London, is the first to carry out a comprehensive life cycle assessment (LCA) of a composite plane, such as the Boeing Dreamliner 787 or Airbus 350, and extrapolate the results to the global fleet.
The LCA covers manufacture, use and disposal, using publicly available information on the Boeing Dreamliner 787 fuselage and from the supply chain -- such as the energy usage of the robots that construct the planes. The study compares the results to the traditional -- and heavier -- aluminium planes.

Emissions during the manufacture of composite planes are over double those of aluminium planes. But because the lighter aircraft use significantly less fuel, these increased emissions are offset after just a few international flights. Over its lifetime, a composite plane creates up to 20 per cent fewer CO2 emissions than its aluminium equivalent.

Professor in Advanced Materials Technologies at the University of Sheffield, Alma Hodzic, said: "This study shows that the fuel consumption savings with composites far outweigh the increased environmental impact from their manufacture. Despite ongoing debates within the industry, the environmental and financial savings from composites mean that these materials offer a much better solution."

The researchers fed the data from the LCA into a wider transport model to gauge the impact on CO2 emissions as composite planes are introduced into the global fleet over the next 25 years, taking into account other factors including population, economic prosperity, oil prices and speed of adoption of the new technology.

The study -- published in the International Journal of Life Cycle Assessment -- estimated that by 2050, composite planes could reduce emissions from the global fleet by 14-15 per cent relative to a fleet that maintains its existing aluminium-based configuration.

Professor in Energy and Transport at UCL, Andreas Schäfer, explains: "The overall emissions reduction for the global fleet is lower than the reduction for an individual plane, partly, because by 2050, not all the fleet will be of composite construction. New planes entering the fleet before 2020 could still be in use by 2050, but the faster the uptake of this technology, the greater the environmental benefits will be."

Dr Lynette Dray from the University of Cambridge added: "Given that global air traffic is projected to increase four-fold between now and 2050, changing the materials used could avoid 500 million tonnes of CO2 emissions in 2050 alone, a value that roughly corresponds to current emission levels."

Professor Hodzic commented: "The industry target is to halve CO2 emissions for all aircrafts by 2020 and while composites will contribute to this, it cannot be achieved by the introduction of lighter composite planes alone. However, our findings show that composites -- alongside other technology and efficiency measures -- should be part of the picture."

Source: University of Sheffield

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