In the context of the fight against global warming, the public is demanding that the aviation industry becomes more environmentally friendly than ever before. However, although the most popular topic when talking about the relationship between aviation and environment is the greenhouse gas emissions, it is not the only relevant one. Noise exposure in airport surroundings is, at a local level, a very real issue that political entities, aviation authorities and airport operators have to deal with.

Since decades ago, an important element when developing new aircraft and engines has been the reduction of noise emissions directly from the source. Further improvements in this area, along with other preventive and corrective measures, will prevent noise impact to the communities around the airports from growing along with traffic increasing.

The Impact of Aircraft Noise

When assessing individual aircraft noise emissions, the most common unit of measurement are the Effective Perceived Noise Decibels (EPNdB). To certify a given aircraft and engine combination the EPNdB are measured experimentally at three points: approach, lateral and flyover:

Figure 1: Measurement points for aircraft EPNdB calculation

Source: ICAO

International Civil Aviation Organization (ICAO) Annex 16 – Volume I, dedicated to aircraft noise, has evolved in the last decades and has been pushing for reductions in cumulative EPNdB – the sum of approach, lateral and flyover EPNdB. Chapter 2, issued in 1973, set the first limits depending on the Maximum Take-Off Weight (MTOW) of the aircraft. After successive Chapters, released in 1977 and 2001, lowering the cumulative EPNdB limits, the ICAO Committee on Aviation Environment Protection (CAEP) proposed the new Chapter 14 in 2013, currently in place for aircraft submitted for certification on or after 31 December 2017.

Nowadays, typical aircraft range between 260 EPNdB and 290 EPNdB. The noisiest aircraft are those with four engines and the quietest ones the new generation narrow-bodies (A320neo, B737Max).

Figure 2: Evolution of EPNdB limits by MTOW set by ICAO Annex 16 Chapter and Cumulative EPNdB certified for typical regional, narrowbody, two-engine and four engine-wideboy jets

Source: ICAO and EASA

Fleet Evolution and Estimation of Impact in Terms of Lden

To comply with Annex 16, aircraft and engine manufacturers have been consistently reducing the cumulative EPNdB emitted by their equipment.

Figure 3: Evolution of EPNdB margins against Chapter 3 limits

Source: EASA

In the last CAEP, a panel of experts estimated that by 2030, on average, the aircraft noise margin against Chapter 3 limits for newly certified aircraft would be:

• Around 40 EPNdB for narrowbody jets, versus an average of 31 EPNdB for those certified in 2020
• Around 38 EPNdB for widebody jets, versus an average of 30 EPNdB in 2020
• Around 31 EPNdB for regional jets, versus an average of 23 EPNdB in 2020

These figures would provide important margins also against Chapter 14, but it should not be discarded that new Chapters will be introduced in Annex 16 during the next decade.

But, how do EPNdB reductions translate in terms of noise exposure at the airport? It is not possible to translate noise emissions from a single aircraft directly into noise exposure from a fleet of aircraft. However, software simulations help getting an insight of the potential impact of future improvements. At three airports with a share of 75%-80% of commercial operations served by aircraft of A320 and B737 families and varying shares of night operations and trajectories dispersion, 55 dB footprints (measured in Lden) shrank by:

• 11-15% when considering average models of the family used today instead of the oldest and noisiest ones.
• 19-35% when considering A320neo/B737MAX instead of the typical ones used today

Figure 5: Size of Lden 55 dB footprints under different narrowbody fleet scenarios at different airports

Source: ALG Analysis

How Can Airports Promote the Use of Less Noisy Aircraft?

During last years, many airports have developed a series of policies and practices that are integrated within larger noise management plans – which can also include operational improvements, insulation programs and community engagements activities. These policies and practices vary from one airport to another:

• London Heathrow applies variable landing charges, monitors noise using fixed devices to impose fines to those who breach limitations and actively works with the UK government, ICAO and Airport Council International (ACI) to improve aircraft noise certification standards.
• Frankfurt has two noise-related charges; one included in the landing and take-off charges and the noise abatement charge. These are set depending on various factors: actual noise measured, type of operation (Arrival/Departure), noise category of the aircraft, overnight stays at the airport, incentives for technological improvements (therefore contributing to the upgrade of the airlines’ fleet) and noise certificates.
• Madrid bans night-time operations of aircraft within the noisiest ICAO categories and applies noise charges that increase with the noise category. Additionally, noise charges are doubled for night operations.
• Barcelona imposes fines to any aircraft that exceeds certain noise limits, enforces a total noise quota per airline – dependant on the carrier’s fleet – and restricts operations of aircraft that comply marginally with their noise limits to certain hours of the day.
• Zurich encourages airlines to operate the quietest possible aircraft by charging variable rates according noise level emitted; all jet aircraft are assigned one of the defined five noise categories, each of which has a different charge rate. All revenue from noise charges is credited to the Airport of Zurich Noise Fund (AZNF) and is used only for specific noise mitigation / correction / prevention purposes.

These practices are expected to be introduced gradually in more airports throughout Europe and the world as operators and authorities become aware of the relevance of noise pollution for the local communities.

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About the authors
Javier Calvo Torrijos is a MSc in Space and Aeronautical Engineering and Senior Engagement Manager at ALG. jcalvo@alg-global.com
Jaime García-Almuzara Hernández is a MSc in Space and Aeronautical Engineering and Consultant at ALG. jgarciaalmuzara@alg-global.com
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