Noise

Aviation operations inevitably involve a degree of noise for neighbouring communities. The Zurich Airport Group is aware of this and is taking numerous measures to minimise adverse impacts.

Relevance

Where noise arises and how loud it is perceived to be depends on a variety of interrelated factors. One key factor is the orientation of runways and flight paths, which depend on the nature of the terrain and the prevailing weather conditions. Another is the flight timetables of airlines, with the aircraft fleets they deploy being a further major factor. Urban development, too, cannot be disregarded as in recent decades this has brought ever more residents into areas affected by noise in Zurich. Another key factor are advances in engine technology. However, this is in the hands of the airlines and can only be indirectly influenced by airports (through noise charge incentives for example).

Noise is less of an issue for the company's majority-owned subsidiaries in Brazil and Chile where the volume of air traffic is much lower. Moreover, most take-offs and landings in Brazil are over the sea, while the airports in Chile are sited well away from large conurbations.

Approach and progress

Communication with local residents

The company is aware that aviation noise can be perceived as a nuisance and that there is a growing need for information and action. Transparent information and dialogue with residents are vital. It has therefore reported on the measures it has taken and provided updates on noise statistics and flight operations for many years already. For instance, the number of take-offs and landings at Zurich, broken down by runways and flight paths, is reported on the company's website each day. Residents affected by aircraft noise can call or e-mail Flughafen Zürich AG directly with any queries or concerns and staff from the Noise Management department will respond to specific questions.

Besides individuals, a number of bodies including adjacent municipalities, the Canton of Zurich and other neighbouring cantons, districts across the border in Germany and a variety of agencies and citizens organisations concerned with air traffic noise make representations to Zurich Airport. The company maintains a regular dialogue with these groups too. Exchanges are more frequent ahead of changes affecting take-off and landing operations.

In the year under review, fewer enquiries and complaints were received compared with the previous year. The most frequent reason was the inbound flights from the south in the evening hours and regular aircraft delays after 11 p.m. (see Noise statistics).

Noise exposure is less of an issue in Brazil and Chile. In Brazil, the environmental licence of an airport is subject to the obligation to set up an easily accessible digital hotline for noise complaints and to submit reports on these to the authorities. The airports in Florianópolis, Vitória and Macaé provide channels to report complaints on all matters, but especially for noise. See the Business ethics section for more information.

Noise monitoring

Two years after flight movements hit their lowest point in 2020 as a result of the Covid-19 pandemic, although take-offs and landings increased again during the reporting year, numbers were still lower than in 2019. Accordingly, for the second year in a row all monitoring stations registered more aircraft noise than the previous year, both during the day and at night.

The diagram above shows changes in exposure to aircraft noise at Zurich Airport over time. 2019 was chosen as the last benchmark year with a normal level of flight operations prior to the pandemic as the noise contours for 2022 are only available from the middle of the year. Comparing noise contours from the past, especially up until 2004 and then again from 2017, shows a fall in noise exposure despite steady or increasing amounts of air traffic. This can be attributed to technical advances in aircraft design resulting in lower noise emissions.

Flight path monitoring

Take-off routes from Zurich Airport were configured to avoid low overflights of densely populated areas wherever possible. The Noise Management department monitors all departures from Zurich Airport for adherence to the prescribed flight paths. These are mandatory during daytime at least up to an altitude of 5000 feet (approximately 1500 metres above sea level) and at night up to flight level 80 (approximately 8000 feet or 2500 metres above sea level). Compliance with these noise-optimised flight paths is monitored with the aid of the Airport Track And Noise Monitoring System (ATANOMS).

An aircraft may only deviate from the prescribed flight path if there is good reason to do so, for instance to avoid storm clouds or following instructions from an air traffic controller. If there is no legitimate reason, an investigation is triggered, and the pilot in question will be asked to submit a statement in writing. These investigations often also involve interviews with representatives of the airlines. If the investigators are not satisfied, the matter may be referred to FOCA. This constant monitoring encourages the airlines to optimise the take-off phase at all times.

As in the previous year, instructions from air traffic control were the most frequent legitimate reason cited for flight path deviations. 138 (2021: 89) investigations into unjustified deviations were launched and 39 (2021: 13) interviews with chief pilots were conducted.

Night flights and special authorisations

Residents in the Zurich region perceive night-time flights to be particularly intrusive. In particular, noise between 11 p.m. and 11:30 p.m. often gives rise to complaints. This period is used to work off the backlog of delays built up over the day. Together with the airlines and ground handling agents, Flughafen Zürich AG has taken steps to reduce the number of flights during this period. Measures include optimising operational processes, increasing noise surcharges and prioritising long-haul flights scheduled to take off around 10:40 p.m. and 10:45 p.m. Analyses carried out prior to the pandemic indicate that the measures taken have helped improve the situation.

Night flights (between 10 p.m. and 6 a.m.) accounted for only 4.7% (2021: 3.5%) of flight movements in 2022. Special authorisations were issued for a total of 241 flights (2021: 75 flights) during the night-time curfew period (11:30 p.m. to 6 a.m.). Such night flights are only authorised when there are justifiable grounds (see Noise statistics).

Use of the noise protection hangar

In the first nine months of the year, a total of 147 engine ground tests had to be conducted outside the noise protection hangar owing to the damage. From October to December, 81 engine tests were conducted in the recommissioned noise protection hangar. Throughout 2022, a total of 228 engine ground tests thus took place (2021: 377). Between 7 p.m. and 7 a.m. only 36 engine tests (16% of all engine tests) were conducted, most of these in the noise protection hangar from October onwards.

Because of the necessary monitoring equipment, the noise level can only be determined in the noise protection hangar. From October to December, when the noise protection hangar was being used again, the permitted noise level was never exceeded. According to figures provided by the aircraft maintenance companies, 893 idle tests were performed on the apron and on the stands. 285 of these were run at night (between 10 p.m. and 6 a.m.).

Noise charges and Airport Zurich Noise Fund

Levying noise-related charges gives airlines a financial incentive to operate the quietest possible aircraft on their Zurich routes. All jet aircraft are assigned to one of five noise categories, each of which has a different charge rate based on the time of take-off and landing. In addition, rates for night-time flights are charged and vary according to noise category and the specific take-off or landing time.

Until the end of 2020, all income from noise charges was credited to the Airport Zurich Noise Fund (AZNF). AZNF funds are used primarily to cover the costs of noise mitigation measures, in particular the sound insulation programme, and the costs of meeting compensation claims for noise and overflying. As the law currently stands, the AZNF has sufficient assets to cover the known future costs for these purposes. Since then, therefore, revenue from aircraft noise charges has been reallocated to the “Aviation” segment. Further details about AZNF can be found in note 20, Airport Zurich Noise Fund.

A total of CHF 12.1 million in revenue was generated from aircraft noise charges in 2022. Of this, CHF 5.1 million were from standard charges applicable to all 24 hours, and CHF 7.0 million were from surcharges levied during shoulder periods and at night (9 p.m. to 7 a.m.). The surcharges were last adjusted in 2019.

Sound insulation

As the airport's operator, Flughafen Zürich AG is obliged to pay the costs of sound insulation measures in properties in the communities around Zurich Airport that are exposed to excessive aircraft noise. As its main measure, the company plans to install sound-insulating windows in at least 200 properties a year between 2022 and 2026, or alternatively reimburse homeowners. In the year under review, this target was met with 206 properties (properties with their own number).

In addition, in areas where night-time noise exposure limits are exceeded, the company is offering owners the option of installing automatic window-closing systems or sound-absorbing ventilators. Owners of properties with noise-sensitive rooms which are located within a clearly defined perimeter, and which were not subject to any obligation to install sound insulation during construction or conversion, are eligible to benefit from these passive noise mitigation measures. Property owners who have already taken the initiative of fitting sound-insulating windows themselves are reimbursed by Flughafen Zürich AG.

From 1999 through 2022, approximately CHF 300 million was spent on sound insulation measures in around 5560 buildings. Of CHF 11.3 million expenditure in 2022, CHF 0.7 million was spent on project planning, CHF 8.5 million on refurbishments and CHF 2.1 million on reimbursements. This expenditure was funded entirely by the AZNF.

Flughafen Zürich AG's south-side sound insulation concept is designed to prevent local residents being awoken by early-morning inbound flights from the south. At the request of owners, the company will install automated window-closing systems or sound-absorbing ventilators in bedrooms in the areas affected. After phase 1 was completed, on 19 January 2021 FOCA published its decision on phase 2 of the south-side sound insulation concept with a larger perimeter. Following an objection raised by a neighbouring community which seeks to have the perimeter extended to include the whole municipality, the court case is still to be heard by the Swiss Federal Administrative Court.

As part of the completed phase 1 of the south-side sound insulation concept, around 1100 window-closing systems and 900 sound-absorbing ventilators were installed in bedrooms between the middle of 2016 and spring 2018. The total costs amounted to around CHF 3 million.

Noise compensation (formal expropriations)

As air traffic noise can affect the value of a property, the company is faced with around 20,100 claims for compensation from property owners around Zurich Airport. The compensation claims were submitted at the time the airport was privatised and following the imposition by Germany of restrictions on flight approaches over its territory. Any new claims may now only be submitted if there are substantial changes to flight operations; as a result no further claims have been submitted to Flughafen Zürich AG since then. Of the compensation claims received, as at the end of 2022 over 14,871 (74%) had been concluded, with CHF 86.6 million being paid in noise compensation. All noise compensation claims are paid from the Airport Zurich Noise Fund (AZNF).

As there are very few provisions regarding noise compensation or direct overflights in federal legislation, every open question of law must first be tested in the relevant courts. Legal test cases are being conducted in the interests of processing outstanding claims efficiently. They are helpful both for clarifying open questions of law and for obtaining legal rulings regarding the specific situation in the various airport regions.

Noise statistics for Zurich Airport