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Aircraft noise is one of the biggest issues facing the aerospace industry
Wednesday 30 May 2007
With continued airport expansion and the huge growth in regional airport traffic, aircraft noise has become a major issue for airlines, airport operators and the government alike. The pressure is on to find quieter aircraft solutions, especially as these would also result in greater fuel efficiency, helping to reduce aviation's much criticised carbon footprint.
There are two main reasons for the noise that aircraft produce:
* The fans and high speed propulsive jet in the aircraft engines.
* Aerodynamic noise from the airframe, which comes from turbulent airflow passing over the fuselage, wings and landing gear.
So, what can aerospace engineers do to help? One team of engineers from the University of Cambridge and the Massachusetts Institute of Technology (MIT) has been leading the way. In November 2006, they unveiled the results of their extensive research, the SAX-40, a futuristic-looking passenger airliner concept for 2030 featuring some exciting design solutions including:
* A blended fuselage of the body and wings of the aircraft to reduce the aerodynamic noise over the aircraft.
* Using the aircraft as a shield to engine noise by placing engines above the body of the aircraft instead of beneath the wings, reflecting noise waves upwards.
* Sound insulation of the engines. (Engines were also re-designed to include variable-size jet nozzles, to allow slower jet propulsion during take off and climb leading to low noise.)
There are several technological challenges to overcome before the SAX-40 could be ready for 2030. Professor Ann Dowling, the British team leader explains, "The SAX-40 is very much a work in progress; composite structures are increasingly used in traditional 'tube-and-wing' aircraft, so it is feasible that strong enough composites for this design will exist in the future. Boeing's X48B design was our starting point; they have been working on blended-wing designs for decades. The SAX-40 design is different, in particular due to the 'chin' underneath its body which moves the lift on the centre-body forward and allowed us to use a more recognisable wing design, also resulting in better pitch control. We are meeting NASA soon to discuss the next stage. There are also five PhD students from the team at Cambridge still looking to improve noise estimates and work on further details of the design."
Some of the outcomes from the project research may even be developed for existing aircraft in the nearer future. Rolls-Royce worked closely with the team, involving their young engineers in the process as well. As Angel Gallo, a Rolls-Royce graduate trainee involved in the project says, " When I started work at Rolls-Royce, I didn't think I would have the chance to work on a new engine concept. But that is exactly what we are doing!"
* The Silent Aircraft Initiative www.silentaircraft.org
* Boeing www.boeing.com/phantom
* NASA www.nasa.gov
DEDICATION PAYS OFF: ANDREW FINE, YOUNG ENGINEER WITH AN INTEREST IN AIRCRAFT NOISE AND ACOUSTICS
I've always loved airplanes and wanted to be able to design them. However, I didn't do so well at A-level and couldn't get into my chosen courses. The University of the West of England was very supportive and offered me a place on their engineering foundation degree. I came top in the foundation year and was offered a place on their BEng aerospace systems engineering.
I worked part time in a hi-fi store where I got to design acoustic systems and became interested in taking my knowledge further. Getting a RAeS Centennial Scholarship allowed me to reduce my part-time hours and concentrate on my dissertation, examining noise generated by wing-flap gaps. I managed to get a first-class degree and applied to Cranfield University to spend more time studying aerodynamics and aircraft acoustics. For my thesis, I will investigate rotary blade noise on helicopters, flap-gap noise, slat-gap noise and landing gear noise.
I am working with amazing people and some of the most sophisticated technology around. I've also proved that you don't need to be an " A-grade" student to succeed - all you need is determination.
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