27 May 2002

Through the sound barrier without a boom?

Supersonic aircraft might not be plagued by the problem of sonic boom if a radical design proposal by a Cambridge academic could be made to work. Professor John Ffowcs Williams, Master of Emmanuel College Cambridge, directed the Concorde Noise Panel in the 1960s and 70s. He now believes it is possible to build an aeroplane that could pass through the sound barrier without generating the characteristic and disturbing sonic boom, which prevents Concorde flying supersonic over land and severely limits its routes.

Professor Ffowcs Williams is a world expert in noise-reduction technology and was prominent in developing the concept of anti-sound now routinely used to silence some aircraft noises. He will receive the Royal Academy of Engineering Sir Frank Whittle Medal at the Academy Awards Dinner tonight (27 May) for his lifelong dedication to understanding the properties of sound, which has enabled huge innovation in international transport.

His concept for avoiding sonic booms was patented in 1986 but it involves a radically new aircraft configuration. "You need an aeroplane that doesn't disturb the air very much because disturbances cause resistance to motion, which produces the sonic boom," he explains. "I envisaged an aeroplane making destructively interfering waves, a double flying wing in fact, based on the disturbance-free biplane proposed by the influential German scientist Adolf Busemann. 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." Concorde is still the only supersonic passenger jet in service but many in the airline industry foresee a market for a supersonic business jet and minimising sonic boom could be crucial to its acceptance.

Professor Ffowcs Williams got involved in Concorde's development in 1964 when he was a Reader in the mathematics department at Imperial College. There was a real risk that Concorde would be too noisy to operate but the noise problem was poorly understood. "Strange things happened," he says. "The propulsive jet makes most of the noise, which increases with speed until at very high speeds it doesn't get any louder, so going faster may be better! We had to rethink the whole physics of the process."

Since then Professor Ffowcs Williams has made an enormous contribution to predicting and reducing sound, both in aircraft and submarines. With his student David Hawkings he developed the deceptively simple and elegant Ffowcs Williams-Hawkings equation describing how surfaces moving at high speed generate sound. This has helped to reduce dramatically the noise from helicopter blades and jet engine fans. A typical passenger plane is now 30 decibels quieter than its 1950s equivalent, even though planes have become much heavier since then.

Professor Ffowcs Williams is justly proud of his achievements - he was born in Wales in 1935, one of three boys. His mother died when he was five and he was sent to a Quaker school in North Yorkshire, despite speaking no English. He left school at 16 and served an engineering apprenticeship with Rolls-Royce and eventually won a scholarship to Southampton University. After working at the National Physical Laboratory and in the US he joined Imperial College, where he was ultimately appointed Rolls-Royce Professor of Theoretical Acoustics before moving to Cambridge University in 1972 as the first Rank Professor of Engineering. He founded a consultancy company in Cambridge, Topexpress Ltd, which pioneered active noise control.

ends

Notes for editors

1. The Royal Academy of Engineering Sir Frank Whittle Medal reflects the spirit of the late Sir Frank Whittle OM KBE CB FEng FRS, one of the most creative engineers of all time. British pioneer of the jet engine, he made an extraordinary contribution to society despite many difficulties.
   
   
2. This is only the second time that the Whittle Medal has been awarded - the first in 2001 went to the creator of the world-wide web, Professor Tim Berners-Lee OBE FREng FRS for his achievements in communication.
   
   
3. Frank Whittle was born in Coventry in 1907, the son of a skilful mechanic and inventor. From an early age he experimented in his father's factory and was fascinated by the fledgling aviation industry. He joined the RAF in 1923 as an apprentice. His talents were soon recognised and he qualified as a pilot at the RAF College, Cranwell, before reading Mechanical Sciences at the University of Cambridge. While at Cranwell he had developed a thesis on jet propulsion and patented his design in 1930, but officials at the Air Ministry dismissed his ideas as impractical. However, in 1936 he and some associates founded a company, Power Jets Ltd, to develop the theory. Despite political and financial adversity, Whittle's jet engine made its maiden flight on 15 May 1941, powering the purpose-built Gloster E28/39. By 1944 the engine was in service with the RAF. The technology quickly spread and has been fully exploited worldwide.
   
   
4. The Royal Academy of Engineering aims to pursue, encourage and maintain excellence across the whole field of engineering in order to promote the advancement of the science, art and practice of engineering for the benefit of the public. The Academy comprises the UK's most eminent engineers and is able to use their combined wealth of knowledge and experience to meet its objectives.
   

For more information please contact:

Jane Sutton at the Royal Academy of Engineering
tel: 020 7227 0536 (direct), mobile: 07989 513045, email: jane...@...org.uk

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