Geese show how to cut air-fuel use

Lessons from birds point to ways of saving aircraft carbon emissions, say scientists Scientists have proposed an unusual method for cutting aircraft fuel consumption - they want to fly jumbo jets in formation like geese.

The prospect of flotillas of airliners soaring across the sky in V-shaped flocks, like migrating birds, is startling. Nevertheless, research by aviation experts has shown it could lead to major reductions in aircraft fuel consumption.

The work follows research carried out almost 100 years ago by a German researcher, Carl Wieselsberger. In 1914, he published a paper in which he calculated that birds flying in V-formations use less energy to flap their wings than those on solo flights. Birds in flocks can therefore fly longer than those travelling on their own.

Wieselsberger showed that when a bird flaps its wings it creates a current known as upwash; essentially, air lifts up and rises round the tips of the wings as they flap. Other birds, flying in the first one's wake, experience an updraft, allowing them to fly further.

This idea is supported by observations by French scientists who studied great white pelicans trained to fly behind an aircraft. The team strapped instruments and transmitters to individual birds. These revealed the birds' heart rates went down when they were flying together, and also showed they were able to glide more often when they flew in formation.

"They fly in formation to save energy," said team leader Henri Weimerskirch.

Such experiments suggest that 25 large birds - such as pelicans or geese - flying in a V-shaped formation can travel 70 per cent further than solo birds.

Many of the great migratory journeys, some covering thousands of kilometres, made by birds would be impossible without the energy-saving effects of group flight, scientists say.

But aviation engineers have now taken these discoveries to their logical conclusion and have proposed that aircraft fly in V-shaped groups so they can benefit from similar energy-saving effects. This is the brainchild of researchers led by Professor Ilan Kroo, of Stanford University, California, who say airlines could make substantial cuts in the amount of aviation fuel they use.

In one calculation, the team envisaged three passenger jets leaving Los Angeles, Las Vegas and San Francisco airports en route to the east coast of the US. In the hypothetical exercise, the planes rendezvoused over Utah, then continued their journeys travelling in a V, with planes taking turns to lead the formation.

The group found the aircraft used 15 per cent less fuel and produced less carbon dioxide when flying in formation compared with solo performances.

Such an approach could make significant inroads into the amount of carbon dioxide pumped into the atmosphere by planes. The aviation industry is expected to become a major emitter of greenhouse gases over the next two decades, and airline chiefs are desperately looking for ways to cut fuel consumption. Formation flights could be the answer, says Kroo and his team.

However, critics say safety could be compromised by craft flying in tight formation, while co-ordinating schedules could become a headache. Kroo and his team say such difficulties can be overcome by more detailed work on the scheme.

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