Cutting carbon emissions is one side of the environmental focus for airlines and all those who contribute to the manufacturing of an aircraft, but there is another environmental factor less known but equally important – noise reduction.
From the technology side of noise reduction, manufacturers have developed engines and improved aerodynamics which have managed to reduce noise by 75% since the first commercial jet aircraft took to the skies in the 1950’s, and the trend continues with each aircraft developed and built. Self imposed targets such as those of Rolls-Royce – aiming to reduce perceived aircraft noise by 50% – illustrate an industry dedicated to a cause, an incredibly important cause which airlines and manufacturers have been helped extensively in by air traffic researchers.
Two recent developments by airberlin and Brussels International Airport have helped to proliferate silent skies; in the ‘Required Navigation Performance with Authorisation Required’ (RNP-AR) procedure of airberlin, and Continuous Descent Operations employed at Brussels Airport.
airberlin has been developing its noise cutting technology with its Boeing fleet at Innsbruck Airport, Austria, and are looking to exploit it across Germany. The RNP-AR project is part of Complex Heterogeneous Air Traffic (HETEREX), a joint research project aiming to create conditions for curved approaches, takeoff and landings. Curving the flight path of an aircraft is a truly great capacity to have for two reasons: firstly, the flight path is made more efficient thereby using less fuel, and secondly, heavily populated areas can be avoided, reducing emissions and noise in public residencies.
Similar practices have been the talk of the skies in and around Brussels International Airport, as Belgocontrol, Brussels Airlines, and the airport have jointly developed an environmentally friendly landing technique using less fuel and creating less noise. Belgium’s air space resembles a beehive of weaving activity due to its proximity to major airports such as Schiphol, Amsterdam, and Charles de Gaulle, Paris, as well as frequent traffic coming from a handful of German airports. The density of air traffic in the region has meant that testing has involved 9% of aircraft since 2010, equating to 3,000 flights. In order to achieve reductions in emissions and noise, the ‘Continuous Descent Operation’ (CDO) directs approaching aircraft to descend according to a continuous vertical profile as supposed to the stair-step profile traditionally employed. Continuous descent occurs over a 70km – 15 km distance from the airport, the same area over which reductions in noise were experienced. The University of Leuven found reductions of 2 dB(A) for medium haul aircraft and 3 dB(A) for long haul aircraft beyond 15km from the airport. Furthermore, the technique reduced fuel burn on average by 50kg for medium aircraft and 100kg for long haul aircraft.
Reducing the environmental impact of aircraft reaches further than just carbon emissions. Efforts to silence aircraft, according to these sterling examples, come hand in hand with reducing carbon emissions. Smoothing out flight paths looks to be a win for efficiency and silencing the skies.