Boffins show off "silent" aircraft

OVER THE PAST FEW YEARS, Professor Ann Dowling from Cambridge University's Engineering department has managed to generate a great deal of press coverage of the joint UK/US project to design an airliner that doesn't scare the bejesus out of Heathrow flightpath residents at 5am every morning. Well now the design is approaching completion, or at least as complete as a proof of concept design can get, and details are due to be announced today at the Royal Aeronautical Society.

At the presentation, Prof. Dowling and her 40-strong team of researchers will be showing off the unique blended wing architecture that has been developed as a partnership between students at Cambridge and MIT, but also several commercial partners including Boeing and Rolls Royce.

The stealthy looking 215 seat SAX-40's main improvements over similar sized conventional airliners (such as the 757) is a claimed vast reduction in noise at low altitudes; read when it's buzzing your house near the landing strip. This is managed through a number of neat innovations:

• The fueslage is blended into the wing so that it generates lift too, improving efficiency.
• The three engines are mounted at the back, on top of the wing, so that noise is reflected upwards.
• It is possible to change the profile of the jet exhaust, allowing slower moving air during takeoff and landing for the same thrust.
• There are no slats or flaps which generate a huge proportion of the noise on landing, instead the wing has been shaped to provide lift at lower speeds.
• Likewise, the undercarriage has been optimised for low noise rather than maximum cargo space.

Reducing airline noise was the hot topic in aviation when the project was started around 3-4 years ago, as it would have allowed airlines to operate more flights over a longer period of the day without annoying nearby residents.

However, with the dramatic rise of the environmental lobby pushing for fewer, not more flights, the silent aircraft now finds itself in a very different commercial landscape. However, the reduction in noise reduces energy loss and gives better fuel consumption in return - up to 35% more in theory.

As with most research projects designed towards a specific goal, this isn't something that had any real thought given to the manufacturability. The complex, changing profile of the fuselage down the length of the plane, as opposed to today's almost identical tubular segments, produced in bulk and joined together like a worm, means the SAX-40 would be very difficult and expensive to make.

Prof. Dowling reckons that 2030 is a timescale in which the benefits of this project will be seen, however it is this hack's belief that it is more likely that some of the design features will be integrated into more conventional aircraft than there being any chance of our skies being filled with delta-winged airliners. Which is a shame, as it's a good looking aircraft, very much from the British school of design that includes Concorde and the V bombers of the 1960s. µ