From: Andy Soos, ENN
Published June 17, 2013 05:05 PM

Flying Thunder

Jets are quite loud especially if they fly over your home much less for those closer like passengers or those at an airport. When jet-powered passenger aircraft first went into service in the 1950s, their engines were as loud as rock bands. Times have changed, but public dismay over jet noise has not. EurActiv reports from the Paris Air Show. Today’s engines are on average 75% quieter than those produced at the dawn of the jet age. This is the result, manufacturers say, of steady technological improvements that along with more aerodynamic aircraft have reduced the nuisance of flying for passengers and those on the ground.

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Aircraft noise is noise pollution produced by any aircraft or its components, during various phases of a flight: on the ground while parked such as auxiliary power units, while taxiing, on run-up from propeller and jet exhaust, during take off, underneath and lateral to departure and arrival paths, over-flying while en route, or during landing.  Their sources include aerodynamic (wind) and engines.

Yet even if planes are quieter, the surge in air traffic means noise remains a political bombshell in Europe , which leads the world in noise-based flight restrictions.  What happens in Europe may affect the rest of the world in time.

The updated noise regulation, proposed by the European Commission in December 2011, reflect obligations under the International Civil Aviation Organization (ICAO) to create a balanced approach to noise pollution, including the use of quieter aircraft, improved airport planning and operational procedures that cut noise levels in the air as well as around airfields.

The aviation industry says it is doing its part through new engine technologies and future airplane designs that will make flying machines quieter than household appliances. Some of the newest aircraft engines coming on the market produce noise equivalent to a food mixer or coffee grinder, or about 85 decibels.  It used to be that jet engines were 120 or higher.

Boeing forecasts that the number of airplanes in service will double - from 20,310 in 2012 to 41,240 - by 2032. Airbus, Boeing’s chief rival for medium- and long-range passenger jets, also foresees a doubling of the world’s air fleet over 20 years.
 
"An airplane needs a certain amount of thrust and you can make the thrust by moving a lot of air slowly, or little bit of air very fast," Epstein,  vice president for technology and environment for Pratt & Whitney, explained in an interview. "The noise gets made by the speed of the air being moved. So from a noise point of view, you want to move as much air as you possible can as slowly as you possibly can. But the inside of the engines — all those compressors and turbines - want to turn really fast."

Among the futuristic designs that would reduce fuel consumption and noise are aircraft with V-shaped wings blinding into the fuselage, and engines mounted on top of the wings.

"Doing that actually shields the citizen on the ground from rather a lot of the engine noise," said Andrew Watt, head of environment at Eurocontrol, the Brussels-based civil-military air traffic management and safety organization.

Eurocontrol is also working to reduce noise through changes in landing patterns, so that aircraft spend less time cruising at lower altitudes before they begin their landing. This gliding approach from higher altitudes reduces fuel consumption and means people living along flight paths endure less noise since aircraft are at higher altitudes.

"On the approach, aerodynamic noise is actually quite significant, in particular once you deploy the control surfaces and you deploy the undercarriage," Watt said. "The aircraft is no longer as clean, as slippery as it was through the air, so that causes turbulence which generates the noise. So often times on the approach, it can be that the dominant factor is the fuselage noise and not that of the engines."

But those living in flight paths may be less convinced that their world is getting quieter.

In May, hundreds of anti-noise demonstrators mixed with travellers at Frankfurt’s airport and earlier this month similar protests were held in Berlin, where the much-delayed Brandenburg Willy Brandt Airport is nearly completion.

Europe already leads the world in imposing operating restrictions on cargo and passenger operations, limits that are viewed as bad for business in an industry with round-the-clock operations and customers across the world. Of the world’s 161 major airports with night flying limits or bans, 106 are in Europe.

For further information Europe Noise and Planes.

Low Flying Plane image via Wikipedia.

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