Twin wings will silence sonic boom

Aircraft that can fly faster than the speed of sound without generating a sonic boom could be developed from a design by a leading UK academic.

Aircraft that can fly faster than the speed of sound without generating a sonic boom could be developed from a design by a leading UK academic.

The supersonic biplane design could be used to build a new generation of business jets capable of supersonic flight even over land, as they do not generate the disturbing sonic boom.

The concept is based on a double flying wing design, and is the brainchild of Prof John Ffowcs Williams, master of Emmanuel College, Cambridge and a world expert in noise- reduction technology.

‘You need an aircraft that doesn’t disturb the air very much because disturbances cause resistance to motion, which produces the sonic boom,’ said Williams, who directed the Concorde noise panel in the 1960s and 1970s, and was prominent in the development of anti-sound, a concept now used to cut aircraft noise.

Sonic booms are caused by the shock waves produced by an aircraft moving through the air. But with a double flying wing design, if the aircraft’s two wings are positioned correctly, their respective waves can be made to destructively interfere with each other. This means the two waves effectively cancel each other out, and dramatically reduce the noise produced.

‘In addition the upper and lower surfaces of the wing assembly would be formed so that the airflow over them is straight and smooth. It would create no waves as it travelled, eliminating or at least minimising the sonic boom,’ said Williams.

It is sonic boom that prevents Concorde flying at supersonic speed over land, and has meant the aircraft’s only route is across the Atlantic from London and Paris to New York.

Williams’ design, which he first patented in 1986 but has not made public until now, could be used to develop a business jet able to fly from A to B faster than the speed of sound.

‘Markets only follow once a manufacturer has announced its intention to build an aircraft, but if you wanted to fly an aircraft as fast as the speed of sound without making a sonic boom, it would be very worthwhile,’ said Williams.

Aviation analysts believe the market for business jets is growing rapidly, with even Boeing now interested in the sector.

An aircraft capable of flying point-to-point at the speed of sound would be highly attractive, as long as the price was right, said one analyst. ‘On paper it could easily be justified, but it would have to be at a reasonable price.’

Williams was this week awarded the Sir Frank Whittle medal by the Royal Academy of Engineering, in recognition of his contribution to researching the properties of sound. Williams’ work into understanding and reducing the sound produced by Concorde helped to make the aircraft viable.

He also developed the Ffowcs Williams-Hawkings equation with his student David Hawkings. This describes how surfaces moving at high speed generate sound, and has dramatically reduced the noise from helicopter blades and jet engine fans.