Wings that waggle "could cut aircraft emissions"

Aircraft wings that redirect air to waggle sideways could reduce airline fuel bills by 20%, according to research in the United Kingdom.

The new approach, which promises to cut mid-flight drag dramatically, uses tiny air-powered jets that redirect the air, making it flow sideways back and forward over the wing.

The jets work by the Helmholtz resonance principle: when air is forced into a cavity, the pressure increases and forces air out and sucks it back in again, causing an oscillation - the same phenomenon that happens when a person blows over a bottle.

Dr Duncan Lockerby, from the University of Warwick, who is leading the project, said: "This has come as a bit of a surprise to all of us in the aerodynamics community. It was discovered, essentially, by waggling a piece of wing from side to side in a wind tunnel.

"The truth is we are not exactly sure why this technology reduces drag, but with the pressure of climate change we can't afford to wait around to find out. So we are pushing ahead with prototypes and have a separate three-year project to look more carefully at the physics behind it."

The work is being funded by the UK's Engineering & Physical Sciences Research Council (EPSRC) and aircraft manufacturer Airbus.

Simon Crook, EPSRC aerospace manager, said: "This could help drastically reduce the environmental cost of flying. Research like this highlights the way UK scientists and engineers continue to make significant contributions to our lives."

The project, also part funded by EADS Innovation Works, is being carried out with scientists at Cardiff, Imperial, Sheffield, and Queen's University Belfast.

It is still at concept stage but it is hoped the new wings could be ready for trials as early as 2012. If successful, this technology could also have a major impact on the aerodynamic design and fuel consumption of cars, boats and trains.

The UK aviation industry has announced targets to reduce emissions per passenger kilometre by 50% by 2020. Part of these savings will be made from lighter aircraft as well as improvements in engines and fuel efficiencies, but drag friction is also a main factor in fuel consumption during flights.

Engineers have known for some time that tiny ridges - known as riblets, similar to those found on sharks' bodies - can reduce skin-friction drag by 5%. But the micro-jet system being developed by Dr Lockerby and his colleagues could reduce this drag by up to 40%.

The Engineering & Physical Sciences Research Council is the UK's main agency for funding research in its title's fields. It invests more than 740 million pounds a year in research and postgraduate training, to help the nation handle the next generation of technological change.

*Richard Levick, London Press Service.