^{Figure 1. Vienna Airport runways (source: flugspuren.at)}

Vienna Airport is the largest airport in Austria and acts as a hub for Austrian Airlines. In 2018 it served a total of 27 million people (representing annual growth of 10.84%) and managed over 240,000 aircraft movements. The airport has two runways that are able to operate with no restrictions in terms of aircraft size. The airport is surrounded mostly by rural areas, but there are a number of conurbations in the proximity of the airport, which are particularly relevant for the below-described case study.

Noise regulations

Noise is a significant issue for Vienna Airport. The airport has a range of noise management actions, as outlined on their dedicated noise management website https://flugspuren.at/, including continuous descent approaches and night flight restrictions and land-use planning interventions including insulation and ‘winter gardens’ for certain households. 

Additionally, local communities are involved in noise management matters through a Dialogue Forum. This Forum arose due to objections to the proposed construction of a third airport third runway. Communities felt they were not effectively consulted, resulting in mistrust between the airport and the surrounding population. A mediation process led to the change of the location of the proposed third runway (see Figure 1) (yet to be built), and the creation of the Dialogue Forum – a forum between communities’ representatives, relevant stakeholders and airport representatives, which ensures the established close working relationships to be maintained and that consultation with stakeholders would continue going forward.

^{Figure 2. Proposed new location of the third runway and additional infrastructure (Source: Vienna Airport)}

This case study describes the ongoing implementation of the curved approach on a flight path into Vienna Airport to avoid the conurbations of Aspern and Groß-Enzersdorf (communities in the vicinity of the airport). The case study considers aspects of noise-sharing, modelling, monitoring, trials and engagement processes linked to this one operational procedure. In essence, this case study concerns changes to an aircraft flight track in an attempt to reduce the number of people exposed to noise in a region, but at the potential trade-off of some residents being subjected to increased levels of noise. This is a common challenge for airports, that requires thorough processes of communication and engagement with residents to reach consensus on outcomes that are deemed to be acceptable by communities.

Objective

This case study looked that nuances of implementing a flight track change (in this case a curved approach), in terms of impacts on noise distribution on the ground, and communication and engagement with residents so as to build consensus on the optimal location of the flight track. It is an example of a thorough approach being taken by an airport, but has still been unable to reach consensus, owing to the sensitive nature of flight track modifications.  

Approach

Testing the curved approach and monitoring its data for over 2,5 years, while informing the surrounding communities about the process and the findings of the testing process, as well as canvassing their perspectives on potential implementation to try to find consensus.

1. The potential for a curved approach on this flight track was raised when the curved approach was suggested for the proposed third runway. Residents in areas north of the airport suggested that such a curved approach could help avoid overflights there too and requested that the airport investigate implementation;
2. The Dialogue Forum brought together the communities and relevant stakeholders to discuss the curved approach possibilities. The community of Groß-Enzersdorf (approximately 10,000 inhabitants) objected to the proposed changes as they were concerned that the curved approach would result in increased noise exposure above their community;
3. The Dialogue Forum created a curved approach Working Group to find an outcome that would be best suited for all communities. A key consideration of the group is not to transfer the burdens of noise onto others. Thus, proposed flight paths were assessed on their ability to fly over uninhabited areas with the aim of noise delivering newly exposed populations;
4. Through discussions in the Dialogue Forum, it was decided to commence trials to assess the impact of aircraft flying on the curved approach;
5. Noise monitoring terminals were placed symmetrically along the new trial flight route. Measurements were taken for over 2,5 years. A lengthy trial period was required as only a limited number of aircraft flying that route had the capacity to fly a curved approach. Additionally, appropriate direction and winds are also mandatory to perform the curved approach landing;
6. The results of these trials presented by the Dialogue Forum showed little change from noise exposure from the conventional straight-line approach to the runway;
7. Data were collected by an independent body from the airport (AustroControl) and presented directly to communities by them. This helped to assure the validity of the data and provide residents with the opportunity to ask questions and request additional data and modelling information. This is a good example of good engagement practice;
8. At the time of this case study, no changes had been approved as despite best efforts of the airport, the issue of moving the flight track remained highly contentious, due to the fact that there would be populations of both beneficiaries and people who would be made worse off by the flight track change. Local elections made the issue further difficult to approve at a political level.

This case study found out that the curved approach landing does not significantly change noise exposure at the communities (lower noise by 1,5 dB) and is very similar to noise generated by the conventional straight-line approach. The provision of full data and cooperation with Austro Control helped to build trust between the community and the airport, however, concerns were still held about exposing new residents to noise. The airport went to great efforts to build a robust dialogue with communities about the implementation of a curved approach. This is good practice in a number of ways. Firstly, the airport was open to listening to the community’s idea for the flight track in the first instance. Next, through its Dialogue Forum, the airport was in a position to actively engage with its communities to understand their needs, wants, and concerns from such a flight path. That the curved approach has not yet been implemented should not be seen as a failing, but rather it is evidence of the airport doing a good job at engaging with residents and not implementing a noise management action that might show a small benefit in terms of noise distribution numbers, but that would nonetheless be an unwanted change to many members of the community.

This case is an example of the complexities of noise sharing and how collaboration between stakeholders – including individual communities – is essential in ensuring that the optimal outcomes have been reached.